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    //! Implementation of configuration for various sources.
    //!
    //! This module will parse the various `source.*` TOML configuration keys into a
    //! structure usable by Cargo itself. Currently this is primarily used to map
    //! sources to one another via the `replace-with` key in `.cargo/config`.

    use crate::core::{GitReference, PackageId, SourceId};
    use crate::sources::source::Source;
    use crate::sources::{ReplacedSource, CRATES_IO_REGISTRY};
    use crate::util::context::{self, ConfigRelativePath, OptValue};
    use crate::util::errors::CargoResult;
    use crate::util::{GlobalContext, IntoUrl};
    use anyhow::{bail, Context as _};
    use std::collections::{HashMap, HashSet};
    use tracing::debug;
    use url::Url;

    /// Represents the entire [`[source]` replacement table][1] in Cargo configuration.
    ///
    /// [1]: https://doc.rust-lang.org/nightly/cargo/reference/config.html#source
    #[derive(Clone)]
    pub struct SourceConfigMap<'gctx> {
        /// Mapping of source name to the toml configuration.
        cfgs: HashMap<String, SourceConfig>,
        /// Mapping of [`SourceId`] to the source name.
        id2name: HashMap<SourceId, String>,
        gctx: &'gctx GlobalContext,
    }

    /// Definition of a source in a config file.
    #[derive(Debug, serde::Deserialize)]
    #[serde(rename_all = "kebab-case")]
    struct SourceConfigDef {
        /// Indicates this source should be replaced with another of the given name.
        replace_with: OptValue<String>,
        /// A directory source.
        directory: Option<ConfigRelativePath>,
        /// A registry source. Value is a URL.
        registry: OptValue<String>,
        /// A local registry source.
        local_registry: Option<ConfigRelativePath>,
        /// A git source. Value is a URL.
        git: OptValue<String>,
        /// The git branch.
        branch: OptValue<String>,
        /// The git tag.
        tag: OptValue<String>,
        /// The git revision.
        rev: OptValue<String>,
    }

    /// Configuration for a particular source, found in TOML looking like:
    ///
    /// ```toml
    /// [source.crates-io]
    /// registry = 'https://github.com/rust-lang/crates.io-index'
    /// replace-with = 'foo'    # optional
    /// ```
    #[derive(Clone)]
    struct SourceConfig {
        /// `SourceId` this source corresponds to, inferred from the various
        /// defined keys in the configuration.
        id: SourceId,

        /// Whether or not this source is replaced with another.
        ///
        /// This field is a tuple of `(name, location)` where `location` is where
        /// this configuration key was defined (such as the `.cargo/config` path
        /// or the environment variable name).
        replace_with: Option<(String, String)>,
    }

    impl<'gctx> SourceConfigMap<'gctx> {
        /// Like [`SourceConfigMap::empty`] but includes sources from source
        /// replacement configurations.
        pub fn new(gctx: &'gctx GlobalContext) -> CargoResult<SourceConfigMap<'gctx>> {
            let mut base = SourceConfigMap::empty(gctx)?;
            let sources: Option<HashMap<String, SourceConfigDef>> = gctx.get("source")?;
            if let Some(sources) = sources {
                for (key, value) in sources.into_iter() {
                    base.add_config(key, value)?;
                }
            }
            Ok(base)
        }

        /// Creates the default set of sources that doesn't take `[source]`
        /// replacement into account.
        pub fn empty(gctx: &'gctx GlobalContext) -> CargoResult<SourceConfigMap<'gctx>> {
            let mut base = SourceConfigMap {
                cfgs: HashMap::new(),
                id2name: HashMap::new(),
                gctx,
            };
            base.add(
                CRATES_IO_REGISTRY,
                SourceConfig {
                    id: SourceId::crates_io(gctx)?,
                    replace_with: None,
                },
            )?;
            if SourceId::crates_io_is_sparse(gctx)? {
                base.add(
                    CRATES_IO_REGISTRY,
                    SourceConfig {
                        id: SourceId::crates_io_maybe_sparse_http(gctx)?,
                        replace_with: None,
                    },
                )?;
            }
            if let Ok(url) = gctx.get_env("__CARGO_TEST_CRATES_IO_URL_DO_NOT_USE_THIS") {
                base.add(
                    CRATES_IO_REGISTRY,
                    SourceConfig {
                        id: SourceId::for_alt_registry(&url.parse()?, CRATES_IO_REGISTRY)?,
                        replace_with: None,
                    },
                )?;
            }
            Ok(base)
        }

        /// Returns the [`GlobalContext`] this source config map is associated with.
        pub fn gctx(&self) -> &'gctx GlobalContext {
            self.gctx
        }

        /// Gets the [`Source`] for a given [`SourceId`].
        ///
        /// * `yanked_whitelist` --- Packages allowed to be used, even if they are yanked.
        pub fn load(
            &self,
            id: SourceId,
            yanked_whitelist: &HashSet<PackageId>,
        ) -> CargoResult<Box<dyn Source + 'gctx>> {
            debug!("loading: {}", id);

            let Some(mut name) = self.id2name.get(&id) else {
                return id.load(self.gctx, yanked_whitelist);
            };
            let mut cfg_loc = "";
            let orig_name = name;
            let new_id = loop {
                let Some(cfg) = self.cfgs.get(name) else {
                    // Attempt to interpret the source name as an alt registry name
                    if let Ok(alt_id) = SourceId::alt_registry(self.gctx, name) {
                        debug!("following pointer to registry {}", name);
                        break alt_id.with_precise_from(id);
                    }
                    bail!(
                        "could not find a configured source with the \
                         name `{}` when attempting to lookup `{}` \
                         (configuration in `{}`)",
                        name,
                        orig_name,
                        cfg_loc
                    );
                };
                match &cfg.replace_with {
                    Some((s, c)) => {
                        name = s;
                        cfg_loc = c;
                    }
                    None if id == cfg.id => return id.load(self.gctx, yanked_whitelist),
                    None => {
                        break cfg.id.with_precise_from(id);
                    }
                }
                debug!("following pointer to {}", name);
                if name == orig_name {
                    bail!(
                        "detected a cycle of `replace-with` sources, the source \
                         `{}` is eventually replaced with itself \
                         (configuration in `{}`)",
                        name,
                        cfg_loc
                    )
                }
            };

            let new_src = new_id.load(
                self.gctx,
                &yanked_whitelist
                    .iter()
                    .map(|p| p.map_source(id, new_id))
                    .collect(),
            )?;
            let old_src = id.load(self.gctx, yanked_whitelist)?;
            if !new_src.supports_checksums() && old_src.supports_checksums() {
                bail!(
                    "\
    cannot replace `{orig}` with `{name}`, the source `{orig}` supports \
    checksums, but `{name}` does not

    a lock file compatible with `{orig}` cannot be generated in this situation
    ",
                    orig = orig_name,
                    name = name
                );
            }

            if old_src.requires_precise() && !id.has_precise() {
                bail!(
                    "\
    the source {orig} requires a lock file to be present first before it can be
    used against vendored source code

    remove the source replacement configuration, generate a lock file, and then
    restore the source replacement configuration to continue the build
    ",
                    orig = orig_name
                );
            }

            Ok(Box::new(ReplacedSource::new(id, new_id, new_src)))
        }

        /// Adds a source config with an associated name.
        fn add(&mut self, name: &str, cfg: SourceConfig) -> CargoResult<()> {
            if let Some(old_name) = self.id2name.insert(cfg.id, name.to_string()) {
                // The user is allowed to redefine the built-in crates-io
                // definition from `empty()`.
                if name != CRATES_IO_REGISTRY {
                    bail!(
                        "source `{}` defines source {}, but that source is already defined by `{}`\n\
                         note: Sources are not allowed to be defined multiple times.",
                        name,
                        cfg.id,
                        old_name
                    );
                }
            }
            self.cfgs.insert(name.to_string(), cfg);
            Ok(())
        }

        /// Adds a source config from TOML definition.
        fn add_config(&mut self, name: String, def: SourceConfigDef) -> CargoResult<()> {
            let mut srcs = Vec::new();
            if let Some(registry) = def.registry {
                let url = url(&registry, &format!("source.{}.registry", name))?;
                srcs.push(SourceId::for_source_replacement_registry(&url, &name)?);
            }
            if let Some(local_registry) = def.local_registry {
                let path = local_registry.resolve_path(self.gctx);
                srcs.push(SourceId::for_local_registry(&path)?);
            }
            if let Some(directory) = def.directory {
                let path = directory.resolve_path(self.gctx);
                srcs.push(SourceId::for_directory(&path)?);
            }
            if let Some(git) = def.git {
                let url = url(&git, &format!("source.{}.git", name))?;
                let reference = match def.branch {
                    Some(b) => GitReference::Branch(b.val),
                    None => match def.tag {
                        Some(b) => GitReference::Tag(b.val),
                        None => match def.rev {
                            Some(b) => GitReference::Rev(b.val),
                            None => GitReference::DefaultBranch,
                        },
                    },
                };
                srcs.push(SourceId::for_git(&url, reference)?);
            } else {
                let check_not_set = |key, v: OptValue<String>| {
                    if let Some(val) = v {
                        bail!(
                            "source definition `source.{}` specifies `{}`, \
                             but that requires a `git` key to be specified (in {})",
                            name,
                            key,
                            val.definition
                        );
                    }
                    Ok(())
                };
                check_not_set("branch", def.branch)?;
                check_not_set("tag", def.tag)?;
                check_not_set("rev", def.rev)?;
            }
            if name == CRATES_IO_REGISTRY && srcs.is_empty() {
                srcs.push(SourceId::crates_io_maybe_sparse_http(self.gctx)?);
            }

            match srcs.len() {
                0 => bail!(
                    "no source location specified for `source.{}`, need \
                     `registry`, `local-registry`, `directory`, or `git` defined",
                    name
                ),
                1 => {}
                _ => bail!(
                    "more than one source location specified for `source.{}`",
                    name
                ),
            }
            let src = srcs[0];

            let replace_with = def
                .replace_with
                .map(|val| (val.val, val.definition.to_string()));

            self.add(
                &name,
                SourceConfig {
                    id: src,
                    replace_with,
                },
            )?;

            return Ok(());

            fn url(val: &context::Value<String>, key: &str) -> CargoResult<Url> {
                let url = val.val.into_url().with_context(|| {
                    format!(
                        "configuration key `{}` specified an invalid \
                         URL (in {})",
                        key, val.definition
                    )
                })?;

                Ok(url)
            }
        }
    }