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    //! Cargo's config system.
    //!
    //! The `Config` object contains general information about the environment,
    //! and provides access to Cargo's configuration files.
    //!
    //! ## Config value API
    //!
    //! The primary API for fetching user-defined config values is the
    //! `Config::get` method. It uses `serde` to translate config values to a
    //! target type.
    //!
    //! There are a variety of helper types for deserializing some common formats:
    //!
    //! - `value::Value`: This type provides access to the location where the
    //!   config value was defined.
    //! - `ConfigRelativePath`: For a path that is relative to where it is
    //!   defined.
    //! - `PathAndArgs`: Similar to `ConfigRelativePath`, but also supports a list
    //!   of arguments, useful for programs to execute.
    //! - `StringList`: Get a value that is either a list or a whitespace split
    //!   string.
    //!
    //! ## Map key recommendations
    //!
    //! Handling tables that have arbitrary keys can be tricky, particularly if it
    //! should support environment variables. In general, if possible, the caller
    //! should pass the full key path into the `get()` method so that the config
    //! deserializer can properly handle environment variables (which need to be
    //! uppercased, and dashes converted to underscores).
    //!
    //! A good example is the `[target]` table. The code will request
    //! `target.$TRIPLE` and the config system can then appropriately fetch
    //! environment variables like `CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER`.
    //! Conversely, it is not possible do the same thing for the `cfg()` target
    //! tables (because Cargo must fetch all of them), so those do not support
    //! environment variables.
    //!
    //! Try to avoid keys that are a prefix of another with a dash/underscore. For
    //! example `build.target` and `build.target-dir`. This is OK if these are not
    //! structs/maps, but if it is a struct or map, then it will not be able to
    //! read the environment variable due to ambiguity. (See `ConfigMapAccess` for
    //! more details.)
    //!
    //! ## Internal API
    //!
    //! Internally config values are stored with the `ConfigValue` type after they
    //! have been loaded from disk. This is similar to the `toml::Value` type, but
    //! includes the definition location. The `get()` method uses serde to
    //! translate from `ConfigValue` and environment variables to the caller's
    //! desired type.

    use std::borrow::Cow;
    use std::cell::{RefCell, RefMut};
    use std::collections::hash_map::Entry::{Occupied, Vacant};
    use std::collections::{HashMap, HashSet};
    use std::env;
    use std::ffi::{OsStr, OsString};
    use std::fmt;
    use std::fs::{self, File};
    use std::io::prelude::*;
    use std::io::{self, SeekFrom};
    use std::mem;
    use std::path::{Path, PathBuf};
    use std::str::FromStr;
    use std::sync::Once;
    use std::time::Instant;

    use self::ConfigValue as CV;
    use crate::core::compiler::rustdoc::RustdocExternMap;
    use crate::core::shell::Verbosity;
    use crate::core::{features, CliUnstable, Shell, SourceId, Workspace, WorkspaceRootConfig};
    use crate::ops::{self, RegistryCredentialConfig};
    use crate::util::auth::Secret;
    use crate::util::errors::CargoResult;
    use crate::util::CanonicalUrl;
    use crate::util::{internal, toml as cargo_toml};
    use crate::util::{try_canonicalize, validate_package_name};
    use crate::util::{FileLock, Filesystem, IntoUrl, IntoUrlWithBase, Rustc};
    use anyhow::{anyhow, bail, format_err, Context as _};
    use cargo_util::paths;
    use curl::easy::Easy;
    use lazycell::LazyCell;
    use serde::de::IntoDeserializer as _;
    use serde::Deserialize;
    use toml_edit::Item;
    use url::Url;

    mod de;
    use de::Deserializer;

    mod value;
    pub use value::{Definition, OptValue, Value};

    mod key;
    pub use key::ConfigKey;

    mod path;
    pub use path::{ConfigRelativePath, PathAndArgs};

    mod target;
    pub use target::{TargetCfgConfig, TargetConfig};

    mod environment;
    use environment::Env;

    // Helper macro for creating typed access methods.
    macro_rules! get_value_typed {
        ($name:ident, $ty:ty, $variant:ident, $expected:expr) => {
            /// Low-level private method for getting a config value as an OptValue.
            fn $name(&self, key: &ConfigKey) -> Result<OptValue<$ty>, ConfigError> {
                let cv = self.get_cv(key)?;
                let env = self.get_config_env::<$ty>(key)?;
                match (cv, env) {
                    (Some(CV::$variant(val, definition)), Some(env)) => {
                        if definition.is_higher_priority(&env.definition) {
                            Ok(Some(Value { val, definition }))
                        } else {
                            Ok(Some(env))
                        }
                    }
                    (Some(CV::$variant(val, definition)), None) => Ok(Some(Value { val, definition })),
                    (Some(cv), _) => Err(ConfigError::expected(key, $expected, &cv)),
                    (None, Some(env)) => Ok(Some(env)),
                    (None, None) => Ok(None),
                }
            }
        };
    }

    /// Indicates why a config value is being loaded.
    #[derive(Clone, Copy, Debug)]
    enum WhyLoad {
        /// Loaded due to a request from the global cli arg `--config`
        ///
        /// Indirect configs loaded via [`config-include`] are also seen as from cli args,
        /// if the initial config is being loaded from cli.
        ///
        /// [`config-include`]: https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#config-include
        Cli,
        /// Loaded due to config file discovery.
        FileDiscovery,
    }

    /// A previously generated authentication token and the data needed to determine if it can be reused.
    #[derive(Debug)]
    pub struct CredentialCacheValue {
        /// If the command line was used to override the token then it must always be reused,
        /// even if reading the configuration files would lead to a different value.
        pub from_commandline: bool,
        /// If nothing depends on which endpoint is being hit, then we can reuse the token
        /// for any future request even if some of the requests involve mutations.
        pub independent_of_endpoint: bool,
        pub token_value: Secret<String>,
    }

    /// Configuration information for cargo. This is not specific to a build, it is information
    /// relating to cargo itself.
    #[derive(Debug)]
    pub struct Config {
        /// The location of the user's Cargo home directory. OS-dependent.
        home_path: Filesystem,
        /// Information about how to write messages to the shell
        shell: RefCell<Shell>,
        /// A collection of configuration options
        values: LazyCell<HashMap<String, ConfigValue>>,
        /// A collection of configuration options from the credentials file
        credential_values: LazyCell<HashMap<String, ConfigValue>>,
        /// CLI config values, passed in via `configure`.
        cli_config: Option<Vec<String>>,
        /// The current working directory of cargo
        cwd: PathBuf,
        /// Directory where config file searching should stop (inclusive).
        search_stop_path: Option<PathBuf>,
        /// The location of the cargo executable (path to current process)
        cargo_exe: LazyCell<PathBuf>,
        /// The location of the rustdoc executable
        rustdoc: LazyCell<PathBuf>,
        /// Whether we are printing extra verbose messages
        extra_verbose: bool,
        /// `frozen` is the same as `locked`, but additionally will not access the
        /// network to determine if the lock file is out-of-date.
        frozen: bool,
        /// `locked` is set if we should not update lock files. If the lock file
        /// is missing, or needs to be updated, an error is produced.
        locked: bool,
        /// `offline` is set if we should never access the network, but otherwise
        /// continue operating if possible.
        offline: bool,
        /// A global static IPC control mechanism (used for managing parallel builds)
        jobserver: Option<jobserver::Client>,
        /// Cli flags of the form "-Z something" merged with config file values
        unstable_flags: CliUnstable,
        /// Cli flags of the form "-Z something"
        unstable_flags_cli: Option<Vec<String>>,
        /// A handle on curl easy mode for http calls
        easy: LazyCell<RefCell<Easy>>,
        /// Cache of the `SourceId` for crates.io
        crates_io_source_id: LazyCell<SourceId>,
        /// If false, don't cache `rustc --version --verbose` invocations
        cache_rustc_info: bool,
        /// Creation time of this config, used to output the total build time
        creation_time: Instant,
        /// Target Directory via resolved Cli parameter
        target_dir: Option<Filesystem>,
        /// Environment variable snapshot.
        env: Env,
        /// Tracks which sources have been updated to avoid multiple updates.
        updated_sources: LazyCell<RefCell<HashSet<SourceId>>>,
        /// Cache of credentials from configuration or credential providers.
        /// Maps from url to credential value.
        credential_cache: LazyCell<RefCell<HashMap<CanonicalUrl, CredentialCacheValue>>>,
        /// Lock, if held, of the global package cache along with the number of
        /// acquisitions so far.
        package_cache_lock: RefCell<Option<(Option<FileLock>, usize)>>,
        /// Cached configuration parsed by Cargo
        http_config: LazyCell<CargoHttpConfig>,
        future_incompat_config: LazyCell<CargoFutureIncompatConfig>,
        net_config: LazyCell<CargoNetConfig>,
        build_config: LazyCell<CargoBuildConfig>,
        target_cfgs: LazyCell<Vec<(String, TargetCfgConfig)>>,
        doc_extern_map: LazyCell<RustdocExternMap>,
        progress_config: ProgressConfig,
        env_config: LazyCell<EnvConfig>,
        /// This should be false if:
        /// - this is an artifact of the rustc distribution process for "stable" or for "beta"
        /// - this is an `#[test]` that does not opt in with `enable_nightly_features`
        /// - this is an integration test that uses `ProcessBuilder`
        ///      that does not opt in with `masquerade_as_nightly_cargo`
        /// This should be true if:
        /// - this is an artifact of the rustc distribution process for "nightly"
        /// - this is being used in the rustc distribution process internally
        /// - this is a cargo executable that was built from source
        /// - this is an `#[test]` that called `enable_nightly_features`
        /// - this is an integration test that uses `ProcessBuilder`
        ///       that called `masquerade_as_nightly_cargo`
        /// It's public to allow tests use nightly features.
        /// NOTE: this should be set before `configure()`. If calling this from an integration test,
        /// consider using `ConfigBuilder::enable_nightly_features` instead.
        pub nightly_features_allowed: bool,
        /// WorkspaceRootConfigs that have been found
        pub ws_roots: RefCell<HashMap<PathBuf, WorkspaceRootConfig>>,
    }

    impl Config {
        /// Creates a new config instance.
        ///
        /// This is typically used for tests or other special cases. `default` is
        /// preferred otherwise.
        ///
        /// This does only minimal initialization. In particular, it does not load
        /// any config files from disk. Those will be loaded lazily as-needed.
        pub fn new(shell: Shell, cwd: PathBuf, homedir: PathBuf) -> Config {
            static mut GLOBAL_JOBSERVER: *mut jobserver::Client = 0 as *mut _;
            static INIT: Once = Once::new();

            // This should be called early on in the process, so in theory the
            // unsafety is ok here. (taken ownership of random fds)
            INIT.call_once(|| unsafe {
                if let Some(client) = jobserver::Client::from_env() {
                    GLOBAL_JOBSERVER = Box::into_raw(Box::new(client));
                }
            });

            let env = Env::new();

            let cache_key = "CARGO_CACHE_RUSTC_INFO";
            let cache_rustc_info = match env.get_env_os(cache_key) {
                Some(cache) => cache != "0",
                _ => true,
            };

            Config {
                home_path: Filesystem::new(homedir),
                shell: RefCell::new(shell),
                cwd,
                search_stop_path: None,
                values: LazyCell::new(),
                credential_values: LazyCell::new(),
                cli_config: None,
                cargo_exe: LazyCell::new(),
                rustdoc: LazyCell::new(),
                extra_verbose: false,
                frozen: false,
                locked: false,
                offline: false,
                jobserver: unsafe {
                    if GLOBAL_JOBSERVER.is_null() {
                        None
                    } else {
                        Some((*GLOBAL_JOBSERVER).clone())
                    }
                },
                unstable_flags: CliUnstable::default(),
                unstable_flags_cli: None,
                easy: LazyCell::new(),
                crates_io_source_id: LazyCell::new(),
                cache_rustc_info,
                creation_time: Instant::now(),
                target_dir: None,
                env,
                updated_sources: LazyCell::new(),
                credential_cache: LazyCell::new(),
                package_cache_lock: RefCell::new(None),
                http_config: LazyCell::new(),
                future_incompat_config: LazyCell::new(),
                net_config: LazyCell::new(),
                build_config: LazyCell::new(),
                target_cfgs: LazyCell::new(),
                doc_extern_map: LazyCell::new(),
                progress_config: ProgressConfig::default(),
                env_config: LazyCell::new(),
                nightly_features_allowed: matches!(&*features::channel(), "nightly" | "dev"),
                ws_roots: RefCell::new(HashMap::new()),
            }
        }

        /// Creates a new Config instance, with all default settings.
        ///
        /// This does only minimal initialization. In particular, it does not load
        /// any config files from disk. Those will be loaded lazily as-needed.
        pub fn default() -> CargoResult<Config> {
            let shell = Shell::new();
            let cwd = env::current_dir()
                .with_context(|| "couldn't get the current directory of the process")?;
            let homedir = homedir(&cwd).ok_or_else(|| {
                anyhow!(
                    "Cargo couldn't find your home directory. \
                     This probably means that $HOME was not set."
                )
            })?;
            Ok(Config::new(shell, cwd, homedir))
        }

        /// Gets the user's Cargo home directory (OS-dependent).
        pub fn home(&self) -> &Filesystem {
            &self.home_path
        }

        /// Returns a path to display to the user with the location of their home
        /// config file (to only be used for displaying a diagnostics suggestion,
        /// such as recommending where to add a config value).
        pub fn diagnostic_home_config(&self) -> String {
            let home = self.home_path.as_path_unlocked();
            let path = match self.get_file_path(home, "config", false) {
                Ok(Some(existing_path)) => existing_path,
                _ => home.join("config.toml"),
            };
            path.to_string_lossy().to_string()
        }

        /// Gets the Cargo Git directory (`<cargo_home>/git`).
        pub fn git_path(&self) -> Filesystem {
            self.home_path.join("git")
        }

        /// Gets the Cargo base directory for all registry information (`<cargo_home>/registry`).
        pub fn registry_base_path(&self) -> Filesystem {
            self.home_path.join("registry")
        }

        /// Gets the Cargo registry index directory (`<cargo_home>/registry/index`).
        pub fn registry_index_path(&self) -> Filesystem {
            self.registry_base_path().join("index")
        }

        /// Gets the Cargo registry cache directory (`<cargo_home>/registry/path`).
        pub fn registry_cache_path(&self) -> Filesystem {
            self.registry_base_path().join("cache")
        }

        /// Gets the Cargo registry source directory (`<cargo_home>/registry/src`).
        pub fn registry_source_path(&self) -> Filesystem {
            self.registry_base_path().join("src")
        }

        /// Gets the default Cargo registry.
        pub fn default_registry(&self) -> CargoResult<Option<String>> {
            Ok(self
                .get_string("registry.default")?
                .map(|registry| registry.val))
        }

        /// Gets a reference to the shell, e.g., for writing error messages.
        pub fn shell(&self) -> RefMut<'_, Shell> {
            self.shell.borrow_mut()
        }

        /// Gets the path to the `rustdoc` executable.
        pub fn rustdoc(&self) -> CargoResult<&Path> {
            self.rustdoc
                .try_borrow_with(|| Ok(self.get_tool(Tool::Rustdoc, &self.build_config()?.rustdoc)))
                .map(AsRef::as_ref)
        }

        /// Gets the path to the `rustc` executable.
        pub fn load_global_rustc(&self, ws: Option<&Workspace<'_>>) -> CargoResult<Rustc> {
            let cache_location = ws.map(|ws| {
                ws.target_dir()
                    .join(".rustc_info.json")
                    .into_path_unlocked()
            });
            let wrapper = self.maybe_get_tool("rustc_wrapper", &self.build_config()?.rustc_wrapper);
            let rustc_workspace_wrapper = self.maybe_get_tool(
                "rustc_workspace_wrapper",
                &self.build_config()?.rustc_workspace_wrapper,
            );

            Rustc::new(
                self.get_tool(Tool::Rustc, &self.build_config()?.rustc),
                wrapper,
                rustc_workspace_wrapper,
                &self
                    .home()
                    .join("bin")
                    .join("rustc")
                    .into_path_unlocked()
                    .with_extension(env::consts::EXE_EXTENSION),
                if self.cache_rustc_info {
                    cache_location
                } else {
                    None
                },
                self,
            )
        }

        /// Gets the path to the `cargo` executable.
        pub fn cargo_exe(&self) -> CargoResult<&Path> {
            self.cargo_exe
                .try_borrow_with(|| {
                    let from_env = || -> CargoResult<PathBuf> {
                        // Try re-using the `cargo` set in the environment already. This allows
                        // commands that use Cargo as a library to inherit (via `cargo <subcommand>`)
                        // or set (by setting `$CARGO`) a correct path to `cargo` when the current exe
                        // is not actually cargo (e.g., `cargo-*` binaries, Valgrind, `ld.so`, etc.).
                        let exe = try_canonicalize(
                            self.get_env_os(crate::CARGO_ENV)
                                .map(PathBuf::from)
                                .ok_or_else(|| anyhow!("$CARGO not set"))?,
                        )?;
                        Ok(exe)
                    };

                    fn from_current_exe() -> CargoResult<PathBuf> {
                        // Try fetching the path to `cargo` using `env::current_exe()`.
                        // The method varies per operating system and might fail; in particular,
                        // it depends on `/proc` being mounted on Linux, and some environments
                        // (like containers or chroots) may not have that available.
                        let exe = try_canonicalize(env::current_exe()?)?;
                        Ok(exe)
                    }

                    fn from_argv() -> CargoResult<PathBuf> {
                        // Grab `argv[0]` and attempt to resolve it to an absolute path.
                        // If `argv[0]` has one component, it must have come from a `PATH` lookup,
                        // so probe `PATH` in that case.
                        // Otherwise, it has multiple components and is either:
                        // - a relative path (e.g., `./cargo`, `target/debug/cargo`), or
                        // - an absolute path (e.g., `/usr/local/bin/cargo`).
                        // In either case, `Path::canonicalize` will return the full absolute path
                        // to the target if it exists.
                        let argv0 = env::args_os()
                            .map(PathBuf::from)
                            .next()
                            .ok_or_else(|| anyhow!("no argv[0]"))?;
                        paths::resolve_executable(&argv0)
                    }

                    let exe = from_env()
                        .or_else(|_| from_current_exe())
                        .or_else(|_| from_argv())
                        .with_context(|| "couldn't get the path to cargo executable")?;
                    Ok(exe)
                })
                .map(AsRef::as_ref)
        }

        /// Which package sources have been updated, used to ensure it is only done once.
        pub fn updated_sources(&self) -> RefMut<'_, HashSet<SourceId>> {
            self.updated_sources
                .borrow_with(|| RefCell::new(HashSet::new()))
                .borrow_mut()
        }

        /// Cached credentials from credential providers or configuration.
        pub fn credential_cache(&self) -> RefMut<'_, HashMap<CanonicalUrl, CredentialCacheValue>> {
            self.credential_cache
                .borrow_with(|| RefCell::new(HashMap::new()))
                .borrow_mut()
        }

        /// Gets all config values from disk.
        ///
        /// This will lazy-load the values as necessary. Callers are responsible
        /// for checking environment variables. Callers outside of the `config`
        /// module should avoid using this.
        pub fn values(&self) -> CargoResult<&HashMap<String, ConfigValue>> {
            self.values.try_borrow_with(|| self.load_values())
        }

        /// Gets a mutable copy of the on-disk config values.
        ///
        /// This requires the config values to already have been loaded. This
        /// currently only exists for `cargo vendor` to remove the `source`
        /// entries. This doesn't respect environment variables. You should avoid
        /// using this if possible.
        pub fn values_mut(&mut self) -> CargoResult<&mut HashMap<String, ConfigValue>> {
            let _ = self.values()?;
            Ok(self
                .values
                .borrow_mut()
                .expect("already loaded config values"))
        }

        // Note: this is used by RLS, not Cargo.
        pub fn set_values(&self, values: HashMap<String, ConfigValue>) -> CargoResult<()> {
            if self.values.borrow().is_some() {
                bail!("config values already found")
            }
            match self.values.fill(values) {
                Ok(()) => Ok(()),
                Err(_) => bail!("could not fill values"),
            }
        }

        /// Sets the path where ancestor config file searching will stop. The
        /// given path is included, but its ancestors are not.
        pub fn set_search_stop_path<P: Into<PathBuf>>(&mut self, path: P) {
            let path = path.into();
            debug_assert!(self.cwd.starts_with(&path));
            self.search_stop_path = Some(path);
        }

        /// Reloads on-disk configuration values, starting at the given path and
        /// walking up its ancestors.
        pub fn reload_rooted_at<P: AsRef<Path>>(&mut self, path: P) -> CargoResult<()> {
            let values = self.load_values_from(path.as_ref())?;
            self.values.replace(values);
            self.merge_cli_args()?;
            self.load_unstable_flags_from_config()?;
            Ok(())
        }

        /// The current working directory.
        pub fn cwd(&self) -> &Path {
            &self.cwd
        }

        /// The `target` output directory to use.
        ///
        /// Returns `None` if the user has not chosen an explicit directory.
        ///
        /// Callers should prefer `Workspace::target_dir` instead.
        pub fn target_dir(&self) -> CargoResult<Option<Filesystem>> {
            if let Some(dir) = &self.target_dir {
                Ok(Some(dir.clone()))
            } else if let Some(dir) = self.get_env_os("CARGO_TARGET_DIR") {
                // Check if the CARGO_TARGET_DIR environment variable is set to an empty string.
                if dir.is_empty() {
                    bail!(
                        "the target directory is set to an empty string in the \
                         `CARGO_TARGET_DIR` environment variable"
                    )
                }

                Ok(Some(Filesystem::new(self.cwd.join(dir))))
            } else if let Some(val) = &self.build_config()?.target_dir {
                let path = val.resolve_path(self);

                // Check if the target directory is set to an empty string in the config.toml file.
                if val.raw_value().is_empty() {
                    bail!(
                        "the target directory is set to an empty string in {}",
                        val.value().definition
                    )
                }

                Ok(Some(Filesystem::new(path)))
            } else {
                Ok(None)
            }
        }

        /// Get a configuration value by key.
        ///
        /// This does NOT look at environment variables. See `get_cv_with_env` for
        /// a variant that supports environment variables.
        fn get_cv(&self, key: &ConfigKey) -> CargoResult<Option<ConfigValue>> {
            if let Some(vals) = self.credential_values.borrow() {
                let val = self.get_cv_helper(key, vals)?;
                if val.is_some() {
                    return Ok(val);
                }
            }
            self.get_cv_helper(key, self.values()?)
        }

        fn get_cv_helper(
            &self,
            key: &ConfigKey,
            vals: &HashMap<String, ConfigValue>,
        ) -> CargoResult<Option<ConfigValue>> {
            log::trace!("get cv {:?}", key);
            if key.is_root() {
                // Returning the entire root table (for example `cargo config get`
                // with no key). The definition here shouldn't matter.
                return Ok(Some(CV::Table(
                    vals.clone(),
                    Definition::Path(PathBuf::new()),
                )));
            }
            let mut parts = key.parts().enumerate();
            let mut val = match vals.get(parts.next().unwrap().1) {
                Some(val) => val,
                None => return Ok(None),
            };
            for (i, part) in parts {
                match val {
                    CV::Table(map, _) => {
                        val = match map.get(part) {
                            Some(val) => val,
                            None => return Ok(None),
                        }
                    }
                    CV::Integer(_, def)
                    | CV::String(_, def)
                    | CV::List(_, def)
                    | CV::Boolean(_, def) => {
                        let mut key_so_far = ConfigKey::new();
                        for part in key.parts().take(i) {
                            key_so_far.push(part);
                        }
                        bail!(
                            "expected table for configuration key `{}`, \
                             but found {} in {}",
                            key_so_far,
                            val.desc(),
                            def
                        )
                    }
                }
            }
            Ok(Some(val.clone()))
        }

        /// This is a helper for getting a CV from a file or env var.
        pub(crate) fn get_cv_with_env(&self, key: &ConfigKey) -> CargoResult<Option<CV>> {
            // Determine if value comes from env, cli, or file, and merge env if
            // possible.
            let cv = self.get_cv(key)?;
            if key.is_root() {
                // Root table can't have env value.
                return Ok(cv);
            }
            let env = self.env.get_str(key.as_env_key());
            let env_def = Definition::Environment(key.as_env_key().to_string());
            let use_env = match (&cv, env) {
                // Lists are always merged.
                (Some(CV::List(..)), Some(_)) => true,
                (Some(cv), Some(_)) => env_def.is_higher_priority(cv.definition()),
                (None, Some(_)) => true,
                _ => false,
            };

            if !use_env {
                return Ok(cv);
            }

            // Future note: If you ever need to deserialize a non-self describing
            // map type, this should implement a starts_with check (similar to how
            // ConfigMapAccess does).
            let env = env.unwrap();
            if env == "true" {
                Ok(Some(CV::Boolean(true, env_def)))
            } else if env == "false" {
                Ok(Some(CV::Boolean(false, env_def)))
            } else if let Ok(i) = env.parse::<i64>() {
                Ok(Some(CV::Integer(i, env_def)))
            } else if self.cli_unstable().advanced_env && env.starts_with('[') && env.ends_with(']') {
                match cv {
                    Some(CV::List(mut cv_list, cv_def)) => {
                        // Merge with config file.
                        self.get_env_list(key, &mut cv_list)?;
                        Ok(Some(CV::List(cv_list, cv_def)))
                    }
                    Some(cv) => {
                        // This can't assume StringList or UnmergedStringList.
                        // Return an error, which is the behavior of merging
                        // multiple config.toml files with the same scenario.
                        bail!(
                            "unable to merge array env for config `{}`\n\
                            file: {:?}\n\
                            env: {}",
                            key,
                            cv,
                            env
                        );
                    }
                    None => {
                        let mut cv_list = Vec::new();
                        self.get_env_list(key, &mut cv_list)?;
                        Ok(Some(CV::List(cv_list, env_def)))
                    }
                }
            } else {
                // Try to merge if possible.
                match cv {
                    Some(CV::List(mut cv_list, cv_def)) => {
                        // Merge with config file.
                        self.get_env_list(key, &mut cv_list)?;
                        Ok(Some(CV::List(cv_list, cv_def)))
                    }
                    _ => {
                        // Note: CV::Table merging is not implemented, as env
                        // vars do not support table values. In the future, we
                        // could check for `{}`, and interpret it as TOML if
                        // that seems useful.
                        Ok(Some(CV::String(env.to_string(), env_def)))
                    }
                }
            }
        }

        /// Helper primarily for testing.
        pub fn set_env(&mut self, env: HashMap<String, String>) {
            self.env = Env::from_map(env);
        }

        /// Returns all environment variables as an iterator,
        /// keeping only entries where both the key and value are valid UTF-8.
        pub(crate) fn env(&self) -> impl Iterator<Item = (&str, &str)> {
            self.env.iter_str()
        }

        /// Returns all environment variable keys, filtering out keys that are not valid UTF-8.
        fn env_keys(&self) -> impl Iterator<Item = &str> {
            self.env.keys_str()
        }

        fn get_config_env<T>(&self, key: &ConfigKey) -> Result<OptValue<T>, ConfigError>
        where
            T: FromStr,
            <T as FromStr>::Err: fmt::Display,
        {
            match self.env.get_str(key.as_env_key()) {
                Some(value) => {
                    let definition = Definition::Environment(key.as_env_key().to_string());
                    Ok(Some(Value {
                        val: value
                            .parse()
                            .map_err(|e| ConfigError::new(format!("{}", e), definition.clone()))?,
                        definition,
                    }))
                }
                None => {
                    self.check_environment_key_case_mismatch(key);
                    Ok(None)
                }
            }
        }

        /// Get the value of environment variable `key` through the `Config` snapshot.
        ///
        /// This can be used similarly to `std::env::var`.
        pub fn get_env(&self, key: impl AsRef<OsStr>) -> CargoResult<String> {
            self.env.get_env(key)
        }

        /// Get the value of environment variable `key` through the `Config` snapshot.
        ///
        /// This can be used similarly to `std::env::var_os`.
        pub fn get_env_os(&self, key: impl AsRef<OsStr>) -> Option<OsString> {
            self.env.get_env_os(key)
        }

        /// Check if the [`Config`] contains a given [`ConfigKey`].
        ///
        /// See `ConfigMapAccess` for a description of `env_prefix_ok`.
        fn has_key(&self, key: &ConfigKey, env_prefix_ok: bool) -> CargoResult<bool> {
            if self.env.contains_key(key.as_env_key()) {
                return Ok(true);
            }
            if env_prefix_ok {
                let env_prefix = format!("{}_", key.as_env_key());
                if self.env_keys().any(|k| k.starts_with(&env_prefix)) {
                    return Ok(true);
                }
            }
            if self.get_cv(key)?.is_some() {
                return Ok(true);
            }
            self.check_environment_key_case_mismatch(key);

            Ok(false)
        }

        fn check_environment_key_case_mismatch(&self, key: &ConfigKey) {
            if let Some(env_key) = self.env.get_normalized(key.as_env_key()) {
                let _ = self.shell().warn(format!(
                    "Environment variables are expected to use uppercase letters and underscores, \
                    the variable `{}` will be ignored and have no effect",
                    env_key
                ));
            }
        }

        /// Get a string config value.
        ///
        /// See `get` for more details.
        pub fn get_string(&self, key: &str) -> CargoResult<OptValue<String>> {
            self.get::<Option<Value<String>>>(key)
        }

        /// Get a config value that is expected to be a path.
        ///
        /// This returns a relative path if the value does not contain any
        /// directory separators. See `ConfigRelativePath::resolve_program` for
        /// more details.
        pub fn get_path(&self, key: &str) -> CargoResult<OptValue<PathBuf>> {
            self.get::<Option<Value<ConfigRelativePath>>>(key).map(|v| {
                v.map(|v| Value {
                    val: v.val.resolve_program(self),
                    definition: v.definition,
                })
            })
        }

        fn string_to_path(&self, value: &str, definition: &Definition) -> PathBuf {
            let is_path = value.contains('/') || (cfg!(windows) && value.contains('\\'));
            if is_path {
                definition.root(self).join(value)
            } else {
                // A pathless name.
                PathBuf::from(value)
            }
        }

        /// Get a list of strings.
        ///
        /// DO NOT USE outside of the config module. `pub` will be removed in the
        /// future.
        ///
        /// NOTE: this does **not** support environment variables. Use `get` instead
        /// if you want that.
        pub fn get_list(&self, key: &str) -> CargoResult<OptValue<Vec<(String, Definition)>>> {
            let key = ConfigKey::from_str(key);
            self._get_list(&key)
        }

        fn _get_list(&self, key: &ConfigKey) -> CargoResult<OptValue<Vec<(String, Definition)>>> {
            match self.get_cv(key)? {
                Some(CV::List(val, definition)) => Ok(Some(Value { val, definition })),
                Some(val) => self.expected("list", key, &val),
                None => Ok(None),
            }
        }

        /// Helper for StringList type to get something that is a string or list.
        fn get_list_or_string(
            &self,
            key: &ConfigKey,
            merge: bool,
        ) -> CargoResult<Vec<(String, Definition)>> {
            let mut res = Vec::new();

            if !merge {
                self.get_env_list(key, &mut res)?;

                if !res.is_empty() {
                    return Ok(res);
                }
            }

            match self.get_cv(key)? {
                Some(CV::List(val, _def)) => res.extend(val),
                Some(CV::String(val, def)) => {
                    let split_vs = val.split_whitespace().map(|s| (s.to_string(), def.clone()));
                    res.extend(split_vs);
                }
                Some(val) => {
                    return self.expected("string or array of strings", key, &val);
                }
                None => {}
            }

            self.get_env_list(key, &mut res)?;

            Ok(res)
        }

        /// Internal method for getting an environment variable as a list.
        fn get_env_list(
            &self,
            key: &ConfigKey,
            output: &mut Vec<(String, Definition)>,
        ) -> CargoResult<()> {
            let env_val = match self.env.get_str(key.as_env_key()) {
                Some(v) => v,
                None => {
                    self.check_environment_key_case_mismatch(key);
                    return Ok(());
                }
            };

            let def = Definition::Environment(key.as_env_key().to_string());
            if self.cli_unstable().advanced_env && env_val.starts_with('[') && env_val.ends_with(']') {
                // Parse an environment string as a TOML array.
                let toml_v = toml::Value::deserialize(toml::de::ValueDeserializer::new(&env_val))
                    .map_err(|e| {
                        ConfigError::new(format!("could not parse TOML list: {}", e), def.clone())
                    })?;
                let values = toml_v.as_array().expect("env var was not array");
                for value in values {
                    // TODO: support other types.
                    let s = value.as_str().ok_or_else(|| {
                        ConfigError::new(
                            format!("expected string, found {}", value.type_str()),
                            def.clone(),
                        )
                    })?;
                    output.push((s.to_string(), def.clone()));
                }
            } else {
                output.extend(
                    env_val
                        .split_whitespace()
                        .map(|s| (s.to_string(), def.clone())),
                );
            }
            Ok(())
        }

        /// Low-level method for getting a config value as an `OptValue<HashMap<String, CV>>`.
        ///
        /// NOTE: This does not read from env. The caller is responsible for that.
        fn get_table(&self, key: &ConfigKey) -> CargoResult<OptValue<HashMap<String, CV>>> {
            match self.get_cv(key)? {
                Some(CV::Table(val, definition)) => Ok(Some(Value { val, definition })),
                Some(val) => self.expected("table", key, &val),
                None => Ok(None),
            }
        }

        get_value_typed! {get_integer, i64, Integer, "an integer"}
        get_value_typed! {get_bool, bool, Boolean, "true/false"}
        get_value_typed! {get_string_priv, String, String, "a string"}

        /// Generate an error when the given value is the wrong type.
        fn expected<T>(&self, ty: &str, key: &ConfigKey, val: &CV) -> CargoResult<T> {
            val.expected(ty, &key.to_string())
                .map_err(|e| anyhow!("invalid configuration for key `{}`\n{}", key, e))
        }

        /// Update the Config instance based on settings typically passed in on
        /// the command-line.
        ///
        /// This may also load the config from disk if it hasn't already been
        /// loaded.
        pub fn configure(
            &mut self,
            verbose: u32,
            quiet: bool,
            color: Option<&str>,
            frozen: bool,
            locked: bool,
            offline: bool,
            target_dir: &Option<PathBuf>,
            unstable_flags: &[String],
            cli_config: &[String],
        ) -> CargoResult<()> {
            for warning in self
                .unstable_flags
                .parse(unstable_flags, self.nightly_features_allowed)?
            {
                self.shell().warn(warning)?;
            }
            if !unstable_flags.is_empty() {
                // store a copy of the cli flags separately for `load_unstable_flags_from_config`
                // (we might also need it again for `reload_rooted_at`)
                self.unstable_flags_cli = Some(unstable_flags.to_vec());
            }
            if !cli_config.is_empty() {
                self.cli_config = Some(cli_config.iter().map(|s| s.to_string()).collect());
                self.merge_cli_args()?;
            }
            if self.unstable_flags.config_include {
                // If the config was already loaded (like when fetching the
                // `[alias]` table), it was loaded with includes disabled because
                // the `unstable_flags` hadn't been set up, yet. Any values
                // fetched before this step will not process includes, but that
                // should be fine (`[alias]` is one of the only things loaded
                // before configure). This can be removed when stabilized.
                self.reload_rooted_at(self.cwd.clone())?;
            }
            let extra_verbose = verbose >= 2;
            let verbose = verbose != 0;

            // Ignore errors in the configuration files. We don't want basic
            // commands like `cargo version` to error out due to config file
            // problems.
            let term = self.get::<TermConfig>("term").unwrap_or_default();

            let color = color.or_else(|| term.color.as_deref());

            // The command line takes precedence over configuration.
            let verbosity = match (verbose, quiet) {
                (true, true) => bail!("cannot set both --verbose and --quiet"),
                (true, false) => Verbosity::Verbose,
                (false, true) => Verbosity::Quiet,
                (false, false) => match (term.verbose, term.quiet) {
                    (Some(true), Some(true)) => {
                        bail!("cannot set both `term.verbose` and `term.quiet`")
                    }
                    (Some(true), _) => Verbosity::Verbose,
                    (_, Some(true)) => Verbosity::Quiet,
                    _ => Verbosity::Normal,
                },
            };

            let cli_target_dir = target_dir.as_ref().map(|dir| Filesystem::new(dir.clone()));

            self.shell().set_verbosity(verbosity);
            self.shell().set_color_choice(color)?;
            self.progress_config = term.progress.unwrap_or_default();
            self.extra_verbose = extra_verbose;
            self.frozen = frozen;
            self.locked = locked;
            self.offline = offline
                || self
                    .net_config()
                    .ok()
                    .and_then(|n| n.offline)
                    .unwrap_or(false);
            self.target_dir = cli_target_dir;

            self.load_unstable_flags_from_config()?;

            Ok(())
        }

        fn load_unstable_flags_from_config(&mut self) -> CargoResult<()> {
            // If nightly features are enabled, allow setting Z-flags from config
            // using the `unstable` table. Ignore that block otherwise.
            if self.nightly_features_allowed {
                self.unstable_flags = self
                    .get::<Option<CliUnstable>>("unstable")?
                    .unwrap_or_default();
                if let Some(unstable_flags_cli) = &self.unstable_flags_cli {
                    // NB. It's not ideal to parse these twice, but doing it again here
                    //     allows the CLI to override config files for both enabling
                    //     and disabling, and doing it up top allows CLI Zflags to
                    //     control config parsing behavior.
                    self.unstable_flags.parse(unstable_flags_cli, true)?;
                }
            }

            Ok(())
        }

        pub fn cli_unstable(&self) -> &CliUnstable {
            &self.unstable_flags
        }

        pub fn extra_verbose(&self) -> bool {
            self.extra_verbose
        }

        pub fn network_allowed(&self) -> bool {
            !self.frozen() && !self.offline()
        }

        pub fn offline(&self) -> bool {
            self.offline
        }

        pub fn frozen(&self) -> bool {
            self.frozen
        }

        pub fn locked(&self) -> bool {
            self.locked
        }

        pub fn lock_update_allowed(&self) -> bool {
            !self.frozen && !self.locked
        }

        /// Loads configuration from the filesystem.
        pub fn load_values(&self) -> CargoResult<HashMap<String, ConfigValue>> {
            self.load_values_from(&self.cwd)
        }

        /// Like [`load_values`](Config::load_values) but without merging config values.
        ///
        /// This is primarily crafted for `cargo config` command.
        pub(crate) fn load_values_unmerged(&self) -> CargoResult<Vec<ConfigValue>> {
            let mut result = Vec::new();
            let mut seen = HashSet::new();
            let home = self.home_path.clone().into_path_unlocked();
            self.walk_tree(&self.cwd, &home, |path| {
                let mut cv = self._load_file(path, &mut seen, false, WhyLoad::FileDiscovery)?;
                if self.cli_unstable().config_include {
                    self.load_unmerged_include(&mut cv, &mut seen, &mut result)?;
                }
                result.push(cv);
                Ok(())
            })
            .with_context(|| "could not load Cargo configuration")?;
            Ok(result)
        }

        /// Like [`load_includes`](Config::load_includes) but without merging config values.
        ///
        /// This is primarily crafted for `cargo config` command.
        fn load_unmerged_include(
            &self,
            cv: &mut CV,
            seen: &mut HashSet<PathBuf>,
            output: &mut Vec<CV>,
        ) -> CargoResult<()> {
            let includes = self.include_paths(cv, false)?;
            for (path, abs_path, def) in includes {
                let mut cv = self
                    ._load_file(&abs_path, seen, false, WhyLoad::FileDiscovery)
                    .with_context(|| {
                        format!("failed to load config include `{}` from `{}`", path, def)
                    })?;
                self.load_unmerged_include(&mut cv, seen, output)?;
                output.push(cv);
            }
            Ok(())
        }

        /// Start a config file discovery from a path and merges all config values found.
        fn load_values_from(&self, path: &Path) -> CargoResult<HashMap<String, ConfigValue>> {
            // This definition path is ignored, this is just a temporary container
            // representing the entire file.
            let mut cfg = CV::Table(HashMap::new(), Definition::Path(PathBuf::from(".")));
            let home = self.home_path.clone().into_path_unlocked();

            self.walk_tree(path, &home, |path| {
                let value = self.load_file(path)?;
                cfg.merge(value, false).with_context(|| {
                    format!("failed to merge configuration at `{}`", path.display())
                })?;
                Ok(())
            })
            .with_context(|| "could not load Cargo configuration")?;

            match cfg {
                CV::Table(map, _) => Ok(map),
                _ => unreachable!(),
            }
        }

        /// Loads a config value from a path.
        ///
        /// This is used during config file discovery.
        fn load_file(&self, path: &Path) -> CargoResult<ConfigValue> {
            self._load_file(path, &mut HashSet::new(), true, WhyLoad::FileDiscovery)
        }

        /// Loads a config value from a path with options.
        ///
        /// This is actual implementation of loading a config value from a path.
        ///
        /// * `includes` determines whether to load configs from [`config-include`].
        /// * `seen` is used to check for cyclic includes.
        /// * `why_load` tells why a config is being loaded.
        ///
        /// [`config-include`]: https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#config-include
        fn _load_file(
            &self,
            path: &Path,
            seen: &mut HashSet<PathBuf>,
            includes: bool,
            why_load: WhyLoad,
        ) -> CargoResult<ConfigValue> {
            if !seen.insert(path.to_path_buf()) {
                bail!(
                    "config `include` cycle detected with path `{}`",
                    path.display()
                );
            }
            let contents = fs::read_to_string(path)
                .with_context(|| format!("failed to read configuration file `{}`", path.display()))?;
            let toml = cargo_toml::parse_document(&contents, path, self).with_context(|| {
                format!("could not parse TOML configuration in `{}`", path.display())
            })?;
            let def = match why_load {
                WhyLoad::Cli => Definition::Cli(Some(path.into())),
                WhyLoad::FileDiscovery => Definition::Path(path.into()),
            };
            let value = CV::from_toml(def, toml::Value::Table(toml)).with_context(|| {
                format!(
                    "failed to load TOML configuration from `{}`",
                    path.display()
                )
            })?;
            if includes {
                self.load_includes(value, seen, why_load)
            } else {
                Ok(value)
            }
        }

        /// Load any `include` files listed in the given `value`.
        ///
        /// Returns `value` with the given include files merged into it.
        ///
        /// * `seen` is used to check for cyclic includes.
        /// * `why_load` tells why a config is being loaded.
        fn load_includes(
            &self,
            mut value: CV,
            seen: &mut HashSet<PathBuf>,
            why_load: WhyLoad,
        ) -> CargoResult<CV> {
            // Get the list of files to load.
            let includes = self.include_paths(&mut value, true)?;
            // Check unstable.
            if !self.cli_unstable().config_include {
                return Ok(value);
            }
            // Accumulate all values here.
            let mut root = CV::Table(HashMap::new(), value.definition().clone());
            for (path, abs_path, def) in includes {
                self._load_file(&abs_path, seen, true, why_load)
                    .and_then(|include| root.merge(include, true))
                    .with_context(|| {
                        format!("failed to load config include `{}` from `{}`", path, def)
                    })?;
            }
            root.merge(value, true)?;
            Ok(root)
        }

        /// Converts the `include` config value to a list of absolute paths.
        fn include_paths(
            &self,
            cv: &mut CV,
            remove: bool,
        ) -> CargoResult<Vec<(String, PathBuf, Definition)>> {
            let abs = |path: &str, def: &Definition| -> (String, PathBuf, Definition) {
                let abs_path = match def {
                    Definition::Path(p) | Definition::Cli(Some(p)) => p.parent().unwrap().join(&path),
                    Definition::Environment(_) | Definition::Cli(None) => self.cwd().join(&path),
                };
                (path.to_string(), abs_path, def.clone())
            };
            let table = match cv {
                CV::Table(table, _def) => table,
                _ => unreachable!(),
            };
            let owned;
            let include = if remove {
                owned = table.remove("include");
                owned.as_ref()
            } else {
                table.get("include")
            };
            let includes = match include {
                Some(CV::String(s, def)) => {
                    vec![abs(s, def)]
                }
                Some(CV::List(list, _def)) => list.iter().map(|(s, def)| abs(s, def)).collect(),
                Some(other) => bail!(
                    "`include` expected a string or list, but found {} in `{}`",
                    other.desc(),
                    other.definition()
                ),
                None => {
                    return Ok(Vec::new());
                }
            };
            Ok(includes)
        }

        /// Parses the CLI config args and returns them as a table.
        pub(crate) fn cli_args_as_table(&self) -> CargoResult<ConfigValue> {
            let mut loaded_args = CV::Table(HashMap::new(), Definition::Cli(None));
            let cli_args = match &self.cli_config {
                Some(cli_args) => cli_args,
                None => return Ok(loaded_args),
            };
            let mut seen = HashSet::new();
            for arg in cli_args {
                let arg_as_path = self.cwd.join(arg);
                let tmp_table = if !arg.is_empty() && arg_as_path.exists() {
                    // --config path_to_file
                    let str_path = arg_as_path
                        .to_str()
                        .ok_or_else(|| {
                            anyhow::format_err!("config path {:?} is not utf-8", arg_as_path)
                        })?
                        .to_string();
                    self._load_file(&self.cwd().join(&str_path), &mut seen, true, WhyLoad::Cli)
                        .with_context(|| format!("failed to load config from `{}`", str_path))?
                } else {
                    // We only want to allow "dotted key" (see https://toml.io/en/v1.0.0#keys)
                    // expressions followed by a value that's not an "inline table"
                    // (https://toml.io/en/v1.0.0#inline-table). Easiest way to check for that is to
                    // parse the value as a toml_edit::Document, and check that the (single)
                    // inner-most table is set via dotted keys.
                    let doc: toml_edit::Document = arg.parse().with_context(|| {
                        format!("failed to parse value from --config argument `{arg}` as a dotted key expression")
                    })?;
                    fn non_empty_decor(d: &toml_edit::Decor) -> bool {
                        d.prefix()
                            .map_or(false, |p| !p.as_str().unwrap_or_default().trim().is_empty())
                            || d.suffix()
                                .map_or(false, |s| !s.as_str().unwrap_or_default().trim().is_empty())
                    }
                    let ok = {
                        let mut got_to_value = false;
                        let mut table = doc.as_table();
                        let mut is_root = true;
                        while table.is_dotted() || is_root {
                            is_root = false;
                            if table.len() != 1 {
                                break;
                            }
                            let (k, n) = table.iter().next().expect("len() == 1 above");
                            match n {
                                Item::Table(nt) => {
                                    if table.key_decor(k).map_or(false, non_empty_decor)
                                        || non_empty_decor(nt.decor())
                                    {
                                        bail!(
                                            "--config argument `{arg}` \
                                                includes non-whitespace decoration"
                                        )
                                    }
                                    table = nt;
                                }
                                Item::Value(v) if v.is_inline_table() => {
                                    bail!(
                                        "--config argument `{arg}` \
                                        sets a value to an inline table, which is not accepted"
                                    );
                                }
                                Item::Value(v) => {
                                    if non_empty_decor(v.decor()) {
                                        bail!(
                                            "--config argument `{arg}` \
                                                includes non-whitespace decoration"
                                        )
                                    }
                                    got_to_value = true;
                                    break;
                                }
                                Item::ArrayOfTables(_) => {
                                    bail!(
                                        "--config argument `{arg}` \
                                        sets a value to an array of tables, which is not accepted"
                                    );
                                }

                                Item::None => {
                                    bail!("--config argument `{arg}` doesn't provide a value")
                                }
                            }
                        }
                        got_to_value
                    };
                    if !ok {
                        bail!(
                            "--config argument `{arg}` was not a TOML dotted key expression (such as `build.jobs = 2`)"
                        );
                    }

                    let toml_v: toml::Value = toml::Value::deserialize(doc.into_deserializer())
                        .with_context(|| {
                            format!("failed to parse value from --config argument `{arg}`")
                        })?;

                    if toml_v
                        .get("registry")
                        .and_then(|v| v.as_table())
                        .and_then(|t| t.get("token"))
                        .is_some()
                    {
                        bail!("registry.token cannot be set through --config for security reasons");
                    } else if let Some((k, _)) = toml_v
                        .get("registries")
                        .and_then(|v| v.as_table())
                        .and_then(|t| t.iter().find(|(_, v)| v.get("token").is_some()))
                    {
                        bail!(
                            "registries.{}.token cannot be set through --config for security reasons",
                            k
                        );
                    }

                    if toml_v
                        .get("registry")
                        .and_then(|v| v.as_table())
                        .and_then(|t| t.get("secret-key"))
                        .is_some()
                    {
                        bail!(
                            "registry.secret-key cannot be set through --config for security reasons"
                        );
                    } else if let Some((k, _)) = toml_v
                        .get("registries")
                        .and_then(|v| v.as_table())
                        .and_then(|t| t.iter().find(|(_, v)| v.get("secret-key").is_some()))
                    {
                        bail!(
                            "registries.{}.secret-key cannot be set through --config for security reasons",
                            k
                        );
                    }

                    CV::from_toml(Definition::Cli(None), toml_v)
                        .with_context(|| format!("failed to convert --config argument `{arg}`"))?
                };
                let tmp_table = self
                    .load_includes(tmp_table, &mut HashSet::new(), WhyLoad::Cli)
                    .with_context(|| "failed to load --config include".to_string())?;
                loaded_args
                    .merge(tmp_table, true)
                    .with_context(|| format!("failed to merge --config argument `{arg}`"))?;
            }
            Ok(loaded_args)
        }

        /// Add config arguments passed on the command line.
        fn merge_cli_args(&mut self) -> CargoResult<()> {
            let loaded_map = match self.cli_args_as_table()? {
                CV::Table(table, _def) => table,
                _ => unreachable!(),
            };
            let values = self.values_mut()?;
            for (key, value) in loaded_map.into_iter() {
                match values.entry(key) {
                    Vacant(entry) => {
                        entry.insert(value);
                    }
                    Occupied(mut entry) => entry.get_mut().merge(value, true).with_context(|| {
                        format!(
                            "failed to merge --config key `{}` into `{}`",
                            entry.key(),
                            entry.get().definition(),
                        )
                    })?,
                };
            }
            Ok(())
        }

        /// The purpose of this function is to aid in the transition to using
        /// .toml extensions on Cargo's config files, which were historically not used.
        /// Both 'config.toml' and 'credentials.toml' should be valid with or without extension.
        /// When both exist, we want to prefer the one without an extension for
        /// backwards compatibility, but warn the user appropriately.
        fn get_file_path(
            &self,
            dir: &Path,
            filename_without_extension: &str,
            warn: bool,
        ) -> CargoResult<Option<PathBuf>> {
            let possible = dir.join(filename_without_extension);
            let possible_with_extension = dir.join(format!("{}.toml", filename_without_extension));

            if possible.exists() {
                if warn && possible_with_extension.exists() {
                    // We don't want to print a warning if the version
                    // without the extension is just a symlink to the version
                    // WITH an extension, which people may want to do to
                    // support multiple Cargo versions at once and not
                    // get a warning.
                    let skip_warning = if let Ok(target_path) = fs::read_link(&possible) {
                        target_path == possible_with_extension
                    } else {
                        false
                    };

                    if !skip_warning {
                        self.shell().warn(format!(
                            "Both `{}` and `{}` exist. Using `{}`",
                            possible.display(),
                            possible_with_extension.display(),
                            possible.display()
                        ))?;
                    }
                }

                Ok(Some(possible))
            } else if possible_with_extension.exists() {
                Ok(Some(possible_with_extension))
            } else {
                Ok(None)
            }
        }

        fn walk_tree<F>(&self, pwd: &Path, home: &Path, mut walk: F) -> CargoResult<()>
        where
            F: FnMut(&Path) -> CargoResult<()>,
        {
            let mut stash: HashSet<PathBuf> = HashSet::new();

            for current in paths::ancestors(pwd, self.search_stop_path.as_deref()) {
                if let Some(path) = self.get_file_path(&current.join(".cargo"), "config", true)? {
                    walk(&path)?;
                    stash.insert(path);
                }
            }

            // Once we're done, also be sure to walk the home directory even if it's not
            // in our history to be sure we pick up that standard location for
            // information.
            if let Some(path) = self.get_file_path(home, "config", true)? {
                if !stash.contains(&path) {
                    walk(&path)?;
                }
            }

            Ok(())
        }

        /// Gets the index for a registry.
        pub fn get_registry_index(&self, registry: &str) -> CargoResult<Url> {
            validate_package_name(registry, "registry name", "")?;
            if let Some(index) = self.get_string(&format!("registries.{}.index", registry))? {
                self.resolve_registry_index(&index).with_context(|| {
                    format!(
                        "invalid index URL for registry `{}` defined in {}",
                        registry, index.definition
                    )
                })
            } else {
                bail!("no index found for registry: `{}`", registry);
            }
        }

        /// Returns an error if `registry.index` is set.
        pub fn check_registry_index_not_set(&self) -> CargoResult<()> {
            if self.get_string("registry.index")?.is_some() {
                bail!(
                    "the `registry.index` config value is no longer supported\n\
                    Use `[source]` replacement to alter the default index for crates.io."
                );
            }
            Ok(())
        }

        fn resolve_registry_index(&self, index: &Value<String>) -> CargoResult<Url> {
            // This handles relative file: URLs, relative to the config definition.
            let base = index
                .definition
                .root(self)
                .join("truncated-by-url_with_base");
            // Parse val to check it is a URL, not a relative path without a protocol.
            let _parsed = index.val.into_url()?;
            let url = index.val.into_url_with_base(Some(&*base))?;
            if url.password().is_some() {
                bail!("registry URLs may not contain passwords");
            }
            Ok(url)
        }

        /// Loads credentials config from the credentials file, if present.
        ///
        /// The credentials are loaded into a separate field to enable them
        /// to be lazy-loaded after the main configuration has been loaded,
        /// without requiring `mut` access to the `Config`.
        ///
        /// If the credentials are already loaded, this function does nothing.
        pub fn load_credentials(&self) -> CargoResult<()> {
            if self.credential_values.filled() {
                return Ok(());
            }

            let home_path = self.home_path.clone().into_path_unlocked();
            let credentials = match self.get_file_path(&home_path, "credentials", true)? {
                Some(credentials) => credentials,
                None => return Ok(()),
            };

            let mut value = self.load_file(&credentials)?;
            // Backwards compatibility for old `.cargo/credentials` layout.
            {
                let (value_map, def) = match value {
                    CV::Table(ref mut value, ref def) => (value, def),
                    _ => unreachable!(),
                };

                if let Some(token) = value_map.remove("token") {
                    if let Vacant(entry) = value_map.entry("registry".into()) {
                        let map = HashMap::from([("token".into(), token)]);
                        let table = CV::Table(map, def.clone());
                        entry.insert(table);
                    }
                }
            }

            let mut credential_values = HashMap::new();
            if let CV::Table(map, _) = value {
                let base_map = self.values()?;
                for (k, v) in map {
                    let entry = match base_map.get(&k) {
                        Some(base_entry) => {
                            let mut entry = base_entry.clone();
                            entry.merge(v, true)?;
                            entry
                        }
                        None => v,
                    };
                    credential_values.insert(k, entry);
                }
            }
            self.credential_values
                .fill(credential_values)
                .expect("was not filled at beginning of the function");
            Ok(())
        }

        /// Looks for a path for `tool` in an environment variable or the given config, and returns
        /// `None` if it's not present.
        fn maybe_get_tool(
            &self,
            tool: &str,
            from_config: &Option<ConfigRelativePath>,
        ) -> Option<PathBuf> {
            let var = tool.to_uppercase();

            match self.get_env_os(&var).as_ref().and_then(|s| s.to_str()) {
                Some(tool_path) => {
                    let maybe_relative = tool_path.contains('/') || tool_path.contains('\\');
                    let path = if maybe_relative {
                        self.cwd.join(tool_path)
                    } else {
                        PathBuf::from(tool_path)
                    };
                    Some(path)
                }

                None => from_config.as_ref().map(|p| p.resolve_program(self)),
            }
        }

        /// Returns the path for the given tool.
        ///
        /// This will look for the tool in the following order:
        ///
        /// 1. From an environment variable matching the tool name (such as `RUSTC`).
        /// 2. From the given config value (which is usually something like `build.rustc`).
        /// 3. Finds the tool in the PATH environment variable.
        ///
        /// This is intended for tools that are rustup proxies. If you need to get
        /// a tool that is not a rustup proxy, use `maybe_get_tool` instead.
        fn get_tool(&self, tool: Tool, from_config: &Option<ConfigRelativePath>) -> PathBuf {
            let tool_str = tool.as_str();
            self.maybe_get_tool(tool_str, from_config)
                .or_else(|| {
                    // This is an optimization to circumvent the rustup proxies
                    // which can have a significant performance hit. The goal here
                    // is to determine if calling `rustc` from PATH would end up
                    // calling the proxies.
                    //
                    // This is somewhat cautious trying to determine if it is safe
                    // to circumvent rustup, because there are some situations
                    // where users may do things like modify PATH, call cargo
                    // directly, use a custom rustup toolchain link without a
                    // cargo executable, etc. However, there is still some risk
                    // this may make the wrong decision in unusual circumstances.
                    //
                    // First, we must be running under rustup in the first place.
                    let toolchain = self.get_env_os("RUSTUP_TOOLCHAIN")?;
                    // This currently does not support toolchain paths.
                    // This also enforces UTF-8.
                    if toolchain.to_str()?.contains(&['/', '\\']) {
                        return None;
                    }
                    // If the tool on PATH is the same as `rustup` on path, then
                    // there is pretty good evidence that it will be a proxy.
                    let tool_resolved = paths::resolve_executable(Path::new(tool_str)).ok()?;
                    let rustup_resolved = paths::resolve_executable(Path::new("rustup")).ok()?;
                    let tool_meta = tool_resolved.metadata().ok()?;
                    let rustup_meta = rustup_resolved.metadata().ok()?;
                    // This works on the assumption that rustup and its proxies
                    // use hard links to a single binary. If rustup ever changes
                    // that setup, then I think the worst consequence is that this
                    // optimization will not work, and it will take the slow path.
                    if tool_meta.len() != rustup_meta.len() {
                        return None;
                    }
                    // Try to find the tool in rustup's toolchain directory.
                    let tool_exe = Path::new(tool_str).with_extension(env::consts::EXE_EXTENSION);
                    let toolchain_exe = home::rustup_home()
                        .ok()?
                        .join("toolchains")
                        .join(&toolchain)
                        .join("bin")
                        .join(&tool_exe);
                    toolchain_exe.exists().then_some(toolchain_exe)
                })
                .unwrap_or_else(|| PathBuf::from(tool_str))
        }

        pub fn jobserver_from_env(&self) -> Option<&jobserver::Client> {
            self.jobserver.as_ref()
        }

        pub fn http(&self) -> CargoResult<&RefCell<Easy>> {
            let http = self
                .easy
                .try_borrow_with(|| ops::http_handle(self).map(RefCell::new))?;
            {
                let mut http = http.borrow_mut();
                http.reset();
                let timeout = ops::configure_http_handle(self, &mut http)?;
                timeout.configure(&mut http)?;
            }
            Ok(http)
        }

        pub fn http_config(&self) -> CargoResult<&CargoHttpConfig> {
            self.http_config.try_borrow_with(|| {
                let mut http = self.get::<CargoHttpConfig>("http")?;
                let curl_v = curl::Version::get();
                disables_multiplexing_for_bad_curl(curl_v.version(), &mut http, self);
                Ok(http)
            })
        }

        pub fn future_incompat_config(&self) -> CargoResult<&CargoFutureIncompatConfig> {
            self.future_incompat_config
                .try_borrow_with(|| self.get::<CargoFutureIncompatConfig>("future-incompat-report"))
        }

        pub fn net_config(&self) -> CargoResult<&CargoNetConfig> {
            self.net_config
                .try_borrow_with(|| self.get::<CargoNetConfig>("net"))
        }

        pub fn build_config(&self) -> CargoResult<&CargoBuildConfig> {
            self.build_config
                .try_borrow_with(|| self.get::<CargoBuildConfig>("build"))
        }

        pub fn progress_config(&self) -> &ProgressConfig {
            &self.progress_config
        }

        pub fn env_config(&self) -> CargoResult<&EnvConfig> {
            let env_config = self
                .env_config
                .try_borrow_with(|| self.get::<EnvConfig>("env"))?;

            // Reasons for disallowing these values:
            //
            // - CARGO_HOME: The initial call to cargo does not honor this value
            //   from the [env] table. Recursive calls to cargo would use the new
            //   value, possibly behaving differently from the outer cargo.
            //
            // - RUSTUP_HOME and RUSTUP_TOOLCHAIN: Under normal usage with rustup,
            //   this will have no effect because the rustup proxy sets
            //   RUSTUP_HOME and RUSTUP_TOOLCHAIN, and that would override the
            //   [env] table. If the outer cargo is executed directly
            //   circumventing the rustup proxy, then this would affect calls to
            //   rustc (assuming that is a proxy), which could potentially cause
            //   problems with cargo and rustc being from different toolchains. We
            //   consider this to be not a use case we would like to support,
            //   since it will likely cause problems or lead to confusion.
            for disallowed in &["CARGO_HOME", "RUSTUP_HOME", "RUSTUP_TOOLCHAIN"] {
                if env_config.contains_key(*disallowed) {
                    bail!(
                        "setting the `{disallowed}` environment variable is not supported \
                        in the `[env]` configuration table"
                    );
                }
            }

            Ok(env_config)
        }

        /// This is used to validate the `term` table has valid syntax.
        ///
        /// This is necessary because loading the term settings happens very
        /// early, and in some situations (like `cargo version`) we don't want to
        /// fail if there are problems with the config file.
        pub fn validate_term_config(&self) -> CargoResult<()> {
            drop(self.get::<TermConfig>("term")?);
            Ok(())
        }

        /// Returns a list of [target.'cfg()'] tables.
        ///
        /// The list is sorted by the table name.
        pub fn target_cfgs(&self) -> CargoResult<&Vec<(String, TargetCfgConfig)>> {
            self.target_cfgs
                .try_borrow_with(|| target::load_target_cfgs(self))
        }

        pub fn doc_extern_map(&self) -> CargoResult<&RustdocExternMap> {
            // Note: This does not support environment variables. The `Unit`
            // fundamentally does not have access to the registry name, so there is
            // nothing to query. Plumbing the name into SourceId is quite challenging.
            self.doc_extern_map
                .try_borrow_with(|| self.get::<RustdocExternMap>("doc.extern-map"))
        }

        /// Returns true if the `[target]` table should be applied to host targets.
        pub fn target_applies_to_host(&self) -> CargoResult<bool> {
            target::get_target_applies_to_host(self)
        }

        /// Returns the `[host]` table definition for the given target triple.
        pub fn host_cfg_triple(&self, target: &str) -> CargoResult<TargetConfig> {
            target::load_host_triple(self, target)
        }

        /// Returns the `[target]` table definition for the given target triple.
        pub fn target_cfg_triple(&self, target: &str) -> CargoResult<TargetConfig> {
            target::load_target_triple(self, target)
        }

        pub fn crates_io_source_id<F>(&self, f: F) -> CargoResult<SourceId>
        where
            F: FnMut() -> CargoResult<SourceId>,
        {
            Ok(*(self.crates_io_source_id.try_borrow_with(f)?))
        }

        pub fn creation_time(&self) -> Instant {
            self.creation_time
        }

        /// Retrieves a config variable.
        ///
        /// This supports most serde `Deserialize` types. Examples:
        ///
        /// ```rust,ignore
        /// let v: Option<u32> = config.get("some.nested.key")?;
        /// let v: Option<MyStruct> = config.get("some.key")?;
        /// let v: Option<HashMap<String, MyStruct>> = config.get("foo")?;
        /// ```
        ///
        /// The key may be a dotted key, but this does NOT support TOML key
        /// quoting. Avoid key components that may have dots. For example,
        /// `foo.'a.b'.bar" does not work if you try to fetch `foo.'a.b'". You can
        /// fetch `foo` if it is a map, though.
        pub fn get<'de, T: serde::de::Deserialize<'de>>(&self, key: &str) -> CargoResult<T> {
            let d = Deserializer {
                config: self,
                key: ConfigKey::from_str(key),
                env_prefix_ok: true,
            };
            T::deserialize(d).map_err(|e| e.into())
        }

        pub fn assert_package_cache_locked<'a>(&self, f: &'a Filesystem) -> &'a Path {
            let ret = f.as_path_unlocked();
            assert!(
                self.package_cache_lock.borrow().is_some(),
                "package cache lock is not currently held, Cargo forgot to call \
                 `acquire_package_cache_lock` before we got to this stack frame",
            );
            assert!(ret.starts_with(self.home_path.as_path_unlocked()));
            ret
        }

        /// Acquires an exclusive lock on the global "package cache"
        ///
        /// This lock is global per-process and can be acquired recursively. An RAII
        /// structure is returned to release the lock, and if this process
        /// abnormally terminates the lock is also released.
        pub fn acquire_package_cache_lock(&self) -> CargoResult<PackageCacheLock<'_>> {
            let mut slot = self.package_cache_lock.borrow_mut();
            match *slot {
                // We've already acquired the lock in this process, so simply bump
                // the count and continue.
                Some((_, ref mut cnt)) => {
                    *cnt += 1;
                }
                None => {
                    let path = ".package-cache";
                    let desc = "package cache";

                    // First, attempt to open an exclusive lock which is in general
                    // the purpose of this lock!
                    //
                    // If that fails because of a readonly filesystem or a
                    // permission error, though, then we don't really want to fail
                    // just because of this. All files that this lock protects are
                    // in subfolders, so they're assumed by Cargo to also be
                    // readonly or have invalid permissions for us to write to. If
                    // that's the case, then we don't really need to grab a lock in
                    // the first place here.
                    //
                    // Despite this we attempt to grab a readonly lock. This means
                    // that if our read-only folder is shared read-write with
                    // someone else on the system we should synchronize with them,
                    // but if we can't even do that then we did our best and we just
                    // keep on chugging elsewhere.
                    match self.home_path.open_rw(path, self, desc) {
                        Ok(lock) => *slot = Some((Some(lock), 1)),
                        Err(e) => {
                            if maybe_readonly(&e) {
                                let lock = self.home_path.open_ro(path, self, desc).ok();
                                *slot = Some((lock, 1));
                                return Ok(PackageCacheLock(self));
                            }

                            Err(e).with_context(|| "failed to acquire package cache lock")?;
                        }
                    }
                }
            }
            return Ok(PackageCacheLock(self));

            fn maybe_readonly(err: &anyhow::Error) -> bool {
                err.chain().any(|err| {
                    if let Some(io) = err.downcast_ref::<io::Error>() {
                        if io.kind() == io::ErrorKind::PermissionDenied {
                            return true;
                        }

                        #[cfg(unix)]
                        return io.raw_os_error() == Some(libc::EROFS);
                    }

                    false
                })
            }
        }

        pub fn release_package_cache_lock(&self) {}
    }

    /// Internal error for serde errors.
    #[derive(Debug)]
    pub struct ConfigError {
        error: anyhow::Error,
        definition: Option<Definition>,
    }

    impl ConfigError {
        fn new(message: String, definition: Definition) -> ConfigError {
            ConfigError {
                error: anyhow::Error::msg(message),
                definition: Some(definition),
            }
        }

        fn expected(key: &ConfigKey, expected: &str, found: &ConfigValue) -> ConfigError {
            ConfigError {
                error: anyhow!(
                    "`{}` expected {}, but found a {}",
                    key,
                    expected,
                    found.desc()
                ),
                definition: Some(found.definition().clone()),
            }
        }

        fn missing(key: &ConfigKey) -> ConfigError {
            ConfigError {
                error: anyhow!("missing config key `{}`", key),
                definition: None,
            }
        }

        fn with_key_context(self, key: &ConfigKey, definition: Definition) -> ConfigError {
            ConfigError {
                error: anyhow::Error::from(self)
                    .context(format!("could not load config key `{}`", key)),
                definition: Some(definition),
            }
        }
    }

    impl std::error::Error for ConfigError {
        fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
            self.error.source()
        }
    }

    impl fmt::Display for ConfigError {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            if let Some(definition) = &self.definition {
                write!(f, "error in {}: {}", definition, self.error)
            } else {
                self.error.fmt(f)
            }
        }
    }

    impl serde::de::Error for ConfigError {
        fn custom<T: fmt::Display>(msg: T) -> Self {
            ConfigError {
                error: anyhow::Error::msg(msg.to_string()),
                definition: None,
            }
        }
    }

    impl From<anyhow::Error> for ConfigError {
        fn from(error: anyhow::Error) -> Self {
            ConfigError {
                error,
                definition: None,
            }
        }
    }

    #[derive(Eq, PartialEq, Clone)]
    pub enum ConfigValue {
        Integer(i64, Definition),
        String(String, Definition),
        List(Vec<(String, Definition)>, Definition),
        Table(HashMap<String, ConfigValue>, Definition),
        Boolean(bool, Definition),
    }

    impl fmt::Debug for ConfigValue {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            match self {
                CV::Integer(i, def) => write!(f, "{} (from {})", i, def),
                CV::Boolean(b, def) => write!(f, "{} (from {})", b, def),
                CV::String(s, def) => write!(f, "{} (from {})", s, def),
                CV::List(list, def) => {
                    write!(f, "[")?;
                    for (i, (s, def)) in list.iter().enumerate() {
                        if i > 0 {
                            write!(f, ", ")?;
                        }
                        write!(f, "{} (from {})", s, def)?;
                    }
                    write!(f, "] (from {})", def)
                }
                CV::Table(table, _) => write!(f, "{:?}", table),
            }
        }
    }

    impl ConfigValue {
        fn from_toml(def: Definition, toml: toml::Value) -> CargoResult<ConfigValue> {
            match toml {
                toml::Value::String(val) => Ok(CV::String(val, def)),
                toml::Value::Boolean(b) => Ok(CV::Boolean(b, def)),
                toml::Value::Integer(i) => Ok(CV::Integer(i, def)),
                toml::Value::Array(val) => Ok(CV::List(
                    val.into_iter()
                        .map(|toml| match toml {
                            toml::Value::String(val) => Ok((val, def.clone())),
                            v => bail!("expected string but found {} in list", v.type_str()),
                        })
                        .collect::<CargoResult<_>>()?,
                    def,
                )),
                toml::Value::Table(val) => Ok(CV::Table(
                    val.into_iter()
                        .map(|(key, value)| {
                            let value = CV::from_toml(def.clone(), value)
                                .with_context(|| format!("failed to parse key `{}`", key))?;
                            Ok((key, value))
                        })
                        .collect::<CargoResult<_>>()?,
                    def,
                )),
                v => bail!(
                    "found TOML configuration value of unknown type `{}`",
                    v.type_str()
                ),
            }
        }

        fn into_toml(self) -> toml::Value {
            match self {
                CV::Boolean(s, _) => toml::Value::Boolean(s),
                CV::String(s, _) => toml::Value::String(s),
                CV::Integer(i, _) => toml::Value::Integer(i),
                CV::List(l, _) => {
                    toml::Value::Array(l.into_iter().map(|(s, _)| toml::Value::String(s)).collect())
                }
                CV::Table(l, _) => {
                    toml::Value::Table(l.into_iter().map(|(k, v)| (k, v.into_toml())).collect())
                }
            }
        }

        /// Merge the given value into self.
        ///
        /// If `force` is true, primitive (non-container) types will override existing values.
        /// If false, the original will be kept and the new value ignored.
        ///
        /// Container types (tables and arrays) are merged with existing values.
        ///
        /// Container and non-container types cannot be mixed.
        fn merge(&mut self, from: ConfigValue, force: bool) -> CargoResult<()> {
            match (self, from) {
                (&mut CV::List(ref mut old, _), CV::List(ref mut new, _)) => {
                    old.extend(mem::take(new).into_iter());
                }
                (&mut CV::Table(ref mut old, _), CV::Table(ref mut new, _)) => {
                    for (key, value) in mem::take(new) {
                        match old.entry(key.clone()) {
                            Occupied(mut entry) => {
                                let new_def = value.definition().clone();
                                let entry = entry.get_mut();
                                entry.merge(value, force).with_context(|| {
                                    format!(
                                        "failed to merge key `{}` between \
                                         {} and {}",
                                        key,
                                        entry.definition(),
                                        new_def,
                                    )
                                })?;
                            }
                            Vacant(entry) => {
                                entry.insert(value);
                            }
                        };
                    }
                }
                // Allow switching types except for tables or arrays.
                (expected @ &mut CV::List(_, _), found)
                | (expected @ &mut CV::Table(_, _), found)
                | (expected, found @ CV::List(_, _))
                | (expected, found @ CV::Table(_, _)) => {
                    return Err(anyhow!(
                        "failed to merge config value from `{}` into `{}`: expected {}, but found {}",
                        found.definition(),
                        expected.definition(),
                        expected.desc(),
                        found.desc()
                    ));
                }
                (old, mut new) => {
                    if force || new.definition().is_higher_priority(old.definition()) {
                        mem::swap(old, &mut new);
                    }
                }
            }

            Ok(())
        }

        pub fn i64(&self, key: &str) -> CargoResult<(i64, &Definition)> {
            match self {
                CV::Integer(i, def) => Ok((*i, def)),
                _ => self.expected("integer", key),
            }
        }

        pub fn string(&self, key: &str) -> CargoResult<(&str, &Definition)> {
            match self {
                CV::String(s, def) => Ok((s, def)),
                _ => self.expected("string", key),
            }
        }

        pub fn table(&self, key: &str) -> CargoResult<(&HashMap<String, ConfigValue>, &Definition)> {
            match self {
                CV::Table(table, def) => Ok((table, def)),
                _ => self.expected("table", key),
            }
        }

        pub fn list(&self, key: &str) -> CargoResult<&[(String, Definition)]> {
            match self {
                CV::List(list, _) => Ok(list),
                _ => self.expected("list", key),
            }
        }

        pub fn boolean(&self, key: &str) -> CargoResult<(bool, &Definition)> {
            match self {
                CV::Boolean(b, def) => Ok((*b, def)),
                _ => self.expected("bool", key),
            }
        }

        pub fn desc(&self) -> &'static str {
            match *self {
                CV::Table(..) => "table",
                CV::List(..) => "array",
                CV::String(..) => "string",
                CV::Boolean(..) => "boolean",
                CV::Integer(..) => "integer",
            }
        }

        pub fn definition(&self) -> &Definition {
            match self {
                CV::Boolean(_, def)
                | CV::Integer(_, def)
                | CV::String(_, def)
                | CV::List(_, def)
                | CV::Table(_, def) => def,
            }
        }

        fn expected<T>(&self, wanted: &str, key: &str) -> CargoResult<T> {
            bail!(
                "expected a {}, but found a {} for `{}` in {}",
                wanted,
                self.desc(),
                key,
                self.definition()
            )
        }
    }

    pub fn homedir(cwd: &Path) -> Option<PathBuf> {
        ::home::cargo_home_with_cwd(cwd).ok()
    }

    pub fn save_credentials(
        cfg: &Config,
        token: Option<RegistryCredentialConfig>,
        registry: &SourceId,
    ) -> CargoResult<()> {
        let registry = if registry.is_crates_io() {
            None
        } else {
            let name = registry
                .alt_registry_key()
                .ok_or_else(|| internal("can't save credentials for anonymous registry"))?;
            Some(name)
        };

        // If 'credentials' exists, write to that for backward compatibility reasons.
        // Otherwise write to 'credentials.toml'. There's no need to print the
        // warning here, because it would already be printed at load time.
        let home_path = cfg.home_path.clone().into_path_unlocked();
        let filename = match cfg.get_file_path(&home_path, "credentials", false)? {
            Some(path) => match path.file_name() {
                Some(filename) => Path::new(filename).to_owned(),
                None => Path::new("credentials.toml").to_owned(),
            },
            None => Path::new("credentials.toml").to_owned(),
        };

        let mut file = {
            cfg.home_path.create_dir()?;
            cfg.home_path
                .open_rw(filename, cfg, "credentials' config file")?
        };

        let mut contents = String::new();
        file.read_to_string(&mut contents).with_context(|| {
            format!(
                "failed to read configuration file `{}`",
                file.path().display()
            )
        })?;

        let mut toml = cargo_toml::parse_document(&contents, file.path(), cfg)?;

        // Move the old token location to the new one.
        if let Some(token) = toml.remove("token") {
            let map = HashMap::from([("token".to_string(), token)]);
            toml.insert("registry".into(), map.into());
        }

        if let Some(token) = token {
            // login

            let path_def = Definition::Path(file.path().to_path_buf());
            let (key, mut value) = match token {
                RegistryCredentialConfig::Token(token) => {
                    // login with token

                    let key = "token".to_string();
                    let value = ConfigValue::String(token.expose(), path_def.clone());
                    let map = HashMap::from([(key, value)]);
                    let table = CV::Table(map, path_def.clone());

                    if let Some(registry) = registry {
                        let map = HashMap::from([(registry.to_string(), table)]);
                        ("registries".into(), CV::Table(map, path_def.clone()))
                    } else {
                        ("registry".into(), table)
                    }
                }
                RegistryCredentialConfig::AsymmetricKey((secret_key, key_subject)) => {
                    // login with key

                    let key = "secret-key".to_string();
                    let value = ConfigValue::String(secret_key.expose(), path_def.clone());
                    let mut map = HashMap::from([(key, value)]);
                    if let Some(key_subject) = key_subject {
                        let key = "secret-key-subject".to_string();
                        let value = ConfigValue::String(key_subject, path_def.clone());
                        map.insert(key, value);
                    }
                    let table = CV::Table(map, path_def.clone());

                    if let Some(registry) = registry {
                        let map = HashMap::from([(registry.to_string(), table)]);
                        ("registries".into(), CV::Table(map, path_def.clone()))
                    } else {
                        ("registry".into(), table)
                    }
                }
                _ => unreachable!(),
            };

            if registry.is_some() {
                if let Some(table) = toml.remove("registries") {
                    let v = CV::from_toml(path_def, table)?;
                    value.merge(v, false)?;
                }
            }
            toml.insert(key, value.into_toml());
        } else {
            // logout
            if let Some(registry) = registry {
                if let Some(registries) = toml.get_mut("registries") {
                    if let Some(reg) = registries.get_mut(registry) {
                        let rtable = reg.as_table_mut().ok_or_else(|| {
                            format_err!("expected `[registries.{}]` to be a table", registry)
                        })?;
                        rtable.remove("token");
                        rtable.remove("secret-key");
                        rtable.remove("secret-key-subject");
                    }
                }
            } else if let Some(registry) = toml.get_mut("registry") {
                let reg_table = registry
                    .as_table_mut()
                    .ok_or_else(|| format_err!("expected `[registry]` to be a table"))?;
                reg_table.remove("token");
                reg_table.remove("secret-key");
                reg_table.remove("secret-key-subject");
            }
        }

        let contents = toml.to_string();
        file.seek(SeekFrom::Start(0))?;
        file.write_all(contents.as_bytes())
            .with_context(|| format!("failed to write to `{}`", file.path().display()))?;
        file.file().set_len(contents.len() as u64)?;
        set_permissions(file.file(), 0o600)
            .with_context(|| format!("failed to set permissions of `{}`", file.path().display()))?;

        return Ok(());

        #[cfg(unix)]
        fn set_permissions(file: &File, mode: u32) -> CargoResult<()> {
            use std::os::unix::fs::PermissionsExt;

            let mut perms = file.metadata()?.permissions();
            perms.set_mode(mode);
            file.set_permissions(perms)?;
            Ok(())
        }

        #[cfg(not(unix))]
        #[allow(unused)]
        fn set_permissions(file: &File, mode: u32) -> CargoResult<()> {
            Ok(())
        }
    }

    pub struct PackageCacheLock<'a>(&'a Config);

    impl Drop for PackageCacheLock<'_> {
        fn drop(&mut self) {
            let mut slot = self.0.package_cache_lock.borrow_mut();
            let (_, cnt) = slot.as_mut().unwrap();
            *cnt -= 1;
            if *cnt == 0 {
                *slot = None;
            }
        }
    }

    #[derive(Debug, Default, Deserialize, PartialEq)]
    #[serde(rename_all = "kebab-case")]
    pub struct CargoHttpConfig {
        pub proxy: Option<String>,
        pub low_speed_limit: Option<u32>,
        pub timeout: Option<u64>,
        pub cainfo: Option<ConfigRelativePath>,
        pub check_revoke: Option<bool>,
        pub user_agent: Option<String>,
        pub debug: Option<bool>,
        pub multiplexing: Option<bool>,
        pub ssl_version: Option<SslVersionConfig>,
    }

    #[derive(Debug, Default, Deserialize, PartialEq)]
    #[serde(rename_all = "kebab-case")]
    pub struct CargoFutureIncompatConfig {
        frequency: Option<CargoFutureIncompatFrequencyConfig>,
    }

    #[derive(Debug, Default, Deserialize, PartialEq)]
    #[serde(rename_all = "kebab-case")]
    pub enum CargoFutureIncompatFrequencyConfig {
        #[default]
        Always,
        Never,
    }

    impl CargoFutureIncompatConfig {
        pub fn should_display_message(&self) -> bool {
            use CargoFutureIncompatFrequencyConfig::*;

            let frequency = self.frequency.as_ref().unwrap_or(&Always);
            match frequency {
                Always => true,
                Never => false,
            }
        }
    }

    /// Configuration for `ssl-version` in `http` section
    /// There are two ways to configure:
    ///
    /// ```text
    /// [http]
    /// ssl-version = "tlsv1.3"
    /// ```
    ///
    /// ```text
    /// [http]
    /// ssl-version.min = "tlsv1.2"
    /// ssl-version.max = "tlsv1.3"
    /// ```
    #[derive(Clone, Debug, Deserialize, PartialEq)]
    #[serde(untagged)]
    pub enum SslVersionConfig {
        Single(String),
        Range(SslVersionConfigRange),
    }

    #[derive(Clone, Debug, Deserialize, PartialEq)]
    pub struct SslVersionConfigRange {
        pub min: Option<String>,
        pub max: Option<String>,
    }

    #[derive(Debug, Deserialize)]
    #[serde(rename_all = "kebab-case")]
    pub struct CargoNetConfig {
        pub retry: Option<u32>,
        pub offline: Option<bool>,
        pub git_fetch_with_cli: Option<bool>,
        pub ssh: Option<CargoSshConfig>,
    }

    #[derive(Debug, Deserialize)]
    #[serde(rename_all = "kebab-case")]
    pub struct CargoSshConfig {
        pub known_hosts: Option<Vec<Value<String>>>,
    }

    #[derive(Debug, Deserialize)]
    #[serde(rename_all = "kebab-case")]
    pub struct CargoBuildConfig {
        // deprecated, but preserved for compatibility
        pub pipelining: Option<bool>,
        pub dep_info_basedir: Option<ConfigRelativePath>,
        pub target_dir: Option<ConfigRelativePath>,
        pub incremental: Option<bool>,
        pub target: Option<BuildTargetConfig>,
        pub jobs: Option<i32>,
        pub rustflags: Option<StringList>,
        pub rustdocflags: Option<StringList>,
        pub rustc_wrapper: Option<ConfigRelativePath>,
        pub rustc_workspace_wrapper: Option<ConfigRelativePath>,
        pub rustc: Option<ConfigRelativePath>,
        pub rustdoc: Option<ConfigRelativePath>,
        pub out_dir: Option<ConfigRelativePath>,
    }

    /// Configuration for `build.target`.
    ///
    /// Accepts in the following forms:
    ///
    /// ```toml
    /// target = "a"
    /// target = ["a"]
    /// target = ["a", "b"]
    /// ```
    #[derive(Debug, Deserialize)]
    #[serde(transparent)]
    pub struct BuildTargetConfig {
        inner: Value<BuildTargetConfigInner>,
    }

    #[derive(Debug, Deserialize)]
    #[serde(untagged)]
    enum BuildTargetConfigInner {
        One(String),
        Many(Vec<String>),
    }

    impl BuildTargetConfig {
        /// Gets values of `build.target` as a list of strings.
        pub fn values(&self, config: &Config) -> CargoResult<Vec<String>> {
            let map = |s: &String| {
                if s.ends_with(".json") {
                    // Path to a target specification file (in JSON).
                    // <https://doc.rust-lang.org/rustc/targets/custom.html>
                    self.inner
                        .definition
                        .root(config)
                        .join(s)
                        .to_str()
                        .expect("must be utf-8 in toml")
                        .to_string()
                } else {
                    // A string. Probably a target triple.
                    s.to_string()
                }
            };
            let values = match &self.inner.val {
                BuildTargetConfigInner::One(s) => vec![map(s)],
                BuildTargetConfigInner::Many(v) => v.iter().map(map).collect(),
            };
            Ok(values)
        }
    }

    #[derive(Deserialize, Default)]
    struct TermConfig {
        verbose: Option<bool>,
        quiet: Option<bool>,
        color: Option<String>,
        #[serde(default)]
        #[serde(deserialize_with = "progress_or_string")]
        progress: Option<ProgressConfig>,
    }

    #[derive(Debug, Default, Deserialize)]
    pub struct ProgressConfig {
        pub when: ProgressWhen,
        pub width: Option<usize>,
    }

    #[derive(Debug, Default, Deserialize)]
    #[serde(rename_all = "lowercase")]
    pub enum ProgressWhen {
        #[default]
        Auto,
        Never,
        Always,
    }

    fn progress_or_string<'de, D>(deserializer: D) -> Result<Option<ProgressConfig>, D::Error>
    where
        D: serde::de::Deserializer<'de>,
    {
        struct ProgressVisitor;

        impl<'de> serde::de::Visitor<'de> for ProgressVisitor {
            type Value = Option<ProgressConfig>;

            fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
                formatter.write_str("a string (\"auto\" or \"never\") or a table")
            }

            fn visit_str<E>(self, s: &str) -> Result<Self::Value, E>
            where
                E: serde::de::Error,
            {
                match s {
                    "auto" => Ok(Some(ProgressConfig {
                        when: ProgressWhen::Auto,
                        width: None,
                    })),
                    "never" => Ok(Some(ProgressConfig {
                        when: ProgressWhen::Never,
                        width: None,
                    })),
                    "always" => Err(E::custom("\"always\" progress requires a `width` key")),
                    _ => Err(E::unknown_variant(s, &["auto", "never"])),
                }
            }

            fn visit_none<E>(self) -> Result<Self::Value, E>
            where
                E: serde::de::Error,
            {
                Ok(None)
            }

            fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
            where
                D: serde::de::Deserializer<'de>,
            {
                let pc = ProgressConfig::deserialize(deserializer)?;
                if let ProgressConfig {
                    when: ProgressWhen::Always,
                    width: None,
                } = pc
                {
                    return Err(serde::de::Error::custom(
                        "\"always\" progress requires a `width` key",
                    ));
                }
                Ok(Some(pc))
            }
        }

        deserializer.deserialize_option(ProgressVisitor)
    }

    #[derive(Debug, Deserialize)]
    #[serde(untagged)]
    enum EnvConfigValueInner {
        Simple(String),
        WithOptions {
            value: String,
            #[serde(default)]
            force: bool,
            #[serde(default)]
            relative: bool,
        },
    }

    #[derive(Debug, Deserialize)]
    #[serde(transparent)]
    pub struct EnvConfigValue {
        inner: Value<EnvConfigValueInner>,
    }

    impl EnvConfigValue {
        pub fn is_force(&self) -> bool {
            match self.inner.val {
                EnvConfigValueInner::Simple(_) => false,
                EnvConfigValueInner::WithOptions { force, .. } => force,
            }
        }

        pub fn resolve<'a>(&'a self, config: &Config) -> Cow<'a, OsStr> {
            match self.inner.val {
                EnvConfigValueInner::Simple(ref s) => Cow::Borrowed(OsStr::new(s.as_str())),
                EnvConfigValueInner::WithOptions {
                    ref value,
                    relative,
                    ..
                } => {
                    if relative {
                        let p = self.inner.definition.root(config).join(&value);
                        Cow::Owned(p.into_os_string())
                    } else {
                        Cow::Borrowed(OsStr::new(value.as_str()))
                    }
                }
            }
        }
    }

    pub type EnvConfig = HashMap<String, EnvConfigValue>;

    /// A type to deserialize a list of strings from a toml file.
    ///
    /// Supports deserializing either a whitespace-separated list of arguments in a
    /// single string or a string list itself. For example these deserialize to
    /// equivalent values:
    ///
    /// ```toml
    /// a = 'a b c'
    /// b = ['a', 'b', 'c']
    /// ```
    #[derive(Debug, Deserialize, Clone)]
    pub struct StringList(Vec<String>);

    impl StringList {
        pub fn as_slice(&self) -> &[String] {
            &self.0
        }
    }

    /// StringList automatically merges config values with environment values,
    /// this instead follows the precedence rules, so that eg. a string list found
    /// in the environment will be used instead of one in a config file.
    ///
    /// This is currently only used by `PathAndArgs`
    #[derive(Debug, Deserialize)]
    pub struct UnmergedStringList(Vec<String>);

    #[macro_export]
    macro_rules! __shell_print {
        ($config:expr, $which:ident, $newline:literal, $($arg:tt)*) => ({
            let mut shell = $config.shell();
            let out = shell.$which();
            drop(out.write_fmt(format_args!($($arg)*)));
            if $newline {
                drop(out.write_all(b"\n"));
            }
        });
    }

    #[macro_export]
    macro_rules! drop_println {
        ($config:expr) => ( $crate::drop_print!($config, "\n") );
        ($config:expr, $($arg:tt)*) => (
            $crate::__shell_print!($config, out, true, $($arg)*)
        );
    }

    #[macro_export]
    macro_rules! drop_eprintln {
        ($config:expr) => ( $crate::drop_eprint!($config, "\n") );
        ($config:expr, $($arg:tt)*) => (
            $crate::__shell_print!($config, err, true, $($arg)*)
        );
    }

    #[macro_export]
    macro_rules! drop_print {
        ($config:expr, $($arg:tt)*) => (
            $crate::__shell_print!($config, out, false, $($arg)*)
        );
    }

    #[macro_export]
    macro_rules! drop_eprint {
        ($config:expr, $($arg:tt)*) => (
            $crate::__shell_print!($config, err, false, $($arg)*)
        );
    }

    enum Tool {
        Rustc,
        Rustdoc,
    }

    impl Tool {
        fn as_str(&self) -> &str {
            match self {
                Tool::Rustc => "rustc",
                Tool::Rustdoc => "rustdoc",
            }
        }
    }

    /// Disable HTTP/2 multiplexing for some broken versions of libcurl.
    ///
    /// In certain versions of libcurl when proxy is in use with HTTP/2
    /// multiplexing, connections will continue stacking up. This was
    /// fixed in libcurl 8.0.0 in curl/curl@821f6e2a89de8aec1c7da3c0f381b92b2b801efc
    ///
    /// However, Cargo can still link against old system libcurl if it is from a
    /// custom built one or on macOS. For those cases, multiplexing needs to be
    /// disabled when those versions are detected.
    fn disables_multiplexing_for_bad_curl(
        curl_version: &str,
        http: &mut CargoHttpConfig,
        config: &Config,
    ) {
        use crate::util::network;

        if network::proxy::http_proxy_exists(http, config) && http.multiplexing.is_none() {
            let bad_curl_versions = ["7.87.0", "7.88.0", "7.88.1"];
            if bad_curl_versions
                .iter()
                .any(|v| curl_version.starts_with(v))
            {
                log::info!("disabling multiplexing with proxy, curl version is {curl_version}");
                http.multiplexing = Some(false);
            }
        }
    }

    #[cfg(test)]
    mod tests {
        use super::disables_multiplexing_for_bad_curl;
        use super::CargoHttpConfig;
        use super::Config;
        use super::Shell;

        #[test]
        fn disables_multiplexing() {
            let mut config = Config::new(Shell::new(), "".into(), "".into());
            config.set_search_stop_path(std::path::PathBuf::new());
            config.set_env(Default::default());

            let mut http = CargoHttpConfig::default();
            http.proxy = Some("127.0.0.1:3128".into());
            disables_multiplexing_for_bad_curl("7.88.1", &mut http, &config);
            assert_eq!(http.multiplexing, Some(false));

            let cases = [
                (None, None, "7.87.0", None),
                (None, None, "7.88.0", None),
                (None, None, "7.88.1", None),
                (None, None, "8.0.0", None),
                (Some("".into()), None, "7.87.0", Some(false)),
                (Some("".into()), None, "7.88.0", Some(false)),
                (Some("".into()), None, "7.88.1", Some(false)),
                (Some("".into()), None, "8.0.0", None),
                (Some("".into()), Some(false), "7.87.0", Some(false)),
                (Some("".into()), Some(false), "7.88.0", Some(false)),
                (Some("".into()), Some(false), "7.88.1", Some(false)),
                (Some("".into()), Some(false), "8.0.0", Some(false)),
            ];

            for (proxy, multiplexing, curl_v, result) in cases {
                let mut http = CargoHttpConfig {
                    multiplexing,
                    proxy,
                    ..Default::default()
                };
                disables_multiplexing_for_bad_curl(curl_v, &mut http, &config);
                assert_eq!(http.multiplexing, result);
            }
        }
    }