#
cargo/ops/cargo_compile/
mod.rs

    1//! The entry point for starting the compilation process for commands like
    2//! `build`, `test`, `doc`, `rustc`, etc.
    3//!
    4//! The [`compile`] function will do all the work to compile a workspace. A
    5//! rough outline is:
    6//!
    7//! 1. Resolve the dependency graph (see [`ops::resolve`]).
    8//! 2. Download any packages needed (see [`PackageSet`]).
    9//! 3. Generate a list of top-level "units" of work for the targets the user
    10//!   requested on the command-line. Each [`Unit`] corresponds to a compiler
    11//!   invocation. This is done in this module ([`UnitGenerator::generate_root_units`]).
    12//! 4. Starting from the root [`Unit`]s, generate the [`UnitGraph`] by walking the dependency graph
    13//!   from the resolver.  See also [`unit_dependencies`].
    14//! 5. Construct the [`BuildContext`] with all of the information collected so
    15//!   far. This is the end of the "front end" of compilation.
    16//! 6. Create a [`BuildRunner`] which coordinates the compilation process
    17//!   and will perform the following steps:
    18//!     1. Prepare the `target` directory (see [`Layout`]).
    19//!     2. Create a [`JobQueue`]. The queue checks the
    20//!       fingerprint of each `Unit` to determine if it should run or be
    21//!       skipped.
    22//!     3. Execute the queue via [`drain_the_queue`]. Each leaf in the queue's dependency graph is
    23//!        executed, and then removed from the graph when finished. This repeats until the queue is
    24//!        empty.  Note that this is the only point in cargo that currently uses threads.
    25//! 7. The result of the compilation is stored in the [`Compilation`] struct. This can be used for
    26//!    various things, such as running tests after the compilation  has finished.
    27//!
    28//! **Note**: "target" inside this module generally refers to ["Cargo Target"],
    29//! which corresponds to artifact that will be built in a package. Not to be
    30//! confused with target-triple or target architecture.
    31//!
    32//! [`unit_dependencies`]: crate::core::compiler::unit_dependencies
    33//! [`Layout`]: crate::core::compiler::Layout
    34//! [`JobQueue`]: crate::core::compiler::job_queue
    35//! [`drain_the_queue`]: crate::core::compiler::job_queue
    36//! ["Cargo Target"]: https://doc.rust-lang.org/nightly/cargo/reference/cargo-targets.html
    37
    38use std::collections::{HashMap, HashSet};
    39use std::hash::{Hash, Hasher};
    40use std::sync::Arc;
    41
    42use crate::core::compiler::unit_dependencies::build_unit_dependencies;
    43use crate::core::compiler::unit_graph::{self, UnitDep, UnitGraph};
    44use crate::core::compiler::UserIntent;
    45use crate::core::compiler::{apply_env_config, standard_lib, CrateType, TargetInfo};
    46use crate::core::compiler::{BuildConfig, BuildContext, BuildRunner, Compilation};
    47use crate::core::compiler::{CompileKind, CompileTarget, RustcTargetData, Unit};
    48use crate::core::compiler::{DefaultExecutor, Executor, UnitInterner};
    49use crate::core::profiles::Profiles;
    50use crate::core::resolver::features::{self, CliFeatures, FeaturesFor};
    51use crate::core::resolver::{HasDevUnits, Resolve};
    52use crate::core::{PackageId, PackageSet, SourceId, TargetKind, Workspace};
    53use crate::drop_println;
    54use crate::ops;
    55use crate::ops::resolve::WorkspaceResolve;
    56use crate::util::context::{GlobalContext, WarningHandling};
    57use crate::util::interning::InternedString;
    58use crate::util::{CargoResult, StableHasher};
    59
    60mod compile_filter;
    61pub use compile_filter::{CompileFilter, FilterRule, LibRule};
    62
    63mod unit_generator;
    64use unit_generator::UnitGenerator;
    65
    66mod packages;
    67
    68pub use packages::Packages;
    69
    70/// Contains information about how a package should be compiled.
    71///
    72/// Note on distinction between `CompileOptions` and [`BuildConfig`]:
    73/// `BuildConfig` contains values that need to be retained after
    74/// [`BuildContext`] is created. The other fields are no longer necessary. Think
    75/// of it as `CompileOptions` are high-level settings requested on the
    76/// command-line, and `BuildConfig` are low-level settings for actually
    77/// driving `rustc`.
    78#[derive(Debug, Clone)]
    79pub struct CompileOptions {
    80    /// Configuration information for a rustc build
    81    pub build_config: BuildConfig,
    82    /// Feature flags requested by the user.
    83    pub cli_features: CliFeatures,
    84    /// A set of packages to build.
    85    pub spec: Packages,
    86    /// Filter to apply to the root package to select which targets will be
    87    /// built.
    88    pub filter: CompileFilter,
    89    /// Extra arguments to be passed to rustdoc (single target only)
    90    pub target_rustdoc_args: Option<Vec<String>>,
    91    /// The specified target will be compiled with all the available arguments,
    92    /// note that this only accounts for the *final* invocation of rustc
    93    pub target_rustc_args: Option<Vec<String>>,
    94    /// Crate types to be passed to rustc (single target only)
    95    pub target_rustc_crate_types: Option<Vec<String>>,
    96    /// Whether the `--document-private-items` flags was specified and should
    97    /// be forwarded to `rustdoc`.
    98    pub rustdoc_document_private_items: bool,
    99    /// Whether the build process should check the minimum Rust version
    100    /// defined in the cargo metadata for a crate.
    101    pub honor_rust_version: Option<bool>,
    102}
    103
    104impl CompileOptions {
    105    pub fn new(gctx: &GlobalContext, intent: UserIntent) -> CargoResult<CompileOptions> {
    106        let jobs = None;
    107        let keep_going = false;
    108        Ok(CompileOptions {
    109            build_config: BuildConfig::new(gctx, jobs, keep_going, &[], intent)?,
    110            cli_features: CliFeatures::new_all(false),
    111            spec: ops::Packages::Packages(Vec::new()),
    112            filter: CompileFilter::Default {
    113                required_features_filterable: false,
    114            },
    115            target_rustdoc_args: None,
    116            target_rustc_args: None,
    117            target_rustc_crate_types: None,
    118            rustdoc_document_private_items: false,
    119            honor_rust_version: None,
    120        })
    121    }
    122}
    123
    124/// Compiles!
    125///
    126/// This uses the [`DefaultExecutor`]. To use a custom [`Executor`], see [`compile_with_exec`].
    127pub fn compile<'a>(ws: &Workspace<'a>, options: &CompileOptions) -> CargoResult<Compilation<'a>> {
    128    let exec: Arc<dyn Executor> = Arc::new(DefaultExecutor);
    129    compile_with_exec(ws, options, &exec)
    130}
    131
    132/// Like [`compile`] but allows specifying a custom [`Executor`]
    133/// that will be able to intercept build calls and add custom logic.
    134///
    135/// [`compile`] uses [`DefaultExecutor`] which just passes calls through.
    136pub fn compile_with_exec<'a>(
    137    ws: &Workspace<'a>,
    138    options: &CompileOptions,
    139    exec: &Arc<dyn Executor>,
    140) -> CargoResult<Compilation<'a>> {
    141    ws.emit_warnings()?;
    142    let compilation = compile_ws(ws, options, exec)?;
    143    if ws.gctx().warning_handling()? == WarningHandling::Deny && compilation.warning_count > 0 {
    144        anyhow::bail!("warnings are denied by `build.warnings` configuration")
    145    }
    146    Ok(compilation)
    147}
    148
    149/// Like [`compile_with_exec`] but without warnings from manifest parsing.
    150#[tracing::instrument(skip_all)]
    151pub fn compile_ws<'a>(
    152    ws: &Workspace<'a>,
    153    options: &CompileOptions,
    154    exec: &Arc<dyn Executor>,
    155) -> CargoResult<Compilation<'a>> {
    156    let interner = UnitInterner::new();
    157    let bcx = create_bcx(ws, options, &interner)?;
    158    if options.build_config.unit_graph {
    159        unit_graph::emit_serialized_unit_graph(&bcx.roots, &bcx.unit_graph, ws.gctx())?;
    160        return Compilation::new(&bcx);
    161    }
    162    crate::core::gc::auto_gc(bcx.gctx);
    163    let build_runner = BuildRunner::new(&bcx)?;
    164    if options.build_config.dry_run {
    165        build_runner.dry_run()
    166    } else {
    167        build_runner.compile(exec)
    168    }
    169}
    170
    171/// Executes `rustc --print <VALUE>`.
    172///
    173/// * `print_opt_value` is the VALUE passed through.
    174pub fn print<'a>(
    175    ws: &Workspace<'a>,
    176    options: &CompileOptions,
    177    print_opt_value: &str,
    178) -> CargoResult<()> {
    179    let CompileOptions {
    180        ref build_config,
    181        ref target_rustc_args,
    182        ..
    183    } = *options;
    184    let gctx = ws.gctx();
    185    let rustc = gctx.load_global_rustc(Some(ws))?;
    186    for (index, kind) in build_config.requested_kinds.iter().enumerate() {
    187        if index != 0 {
    188            drop_println!(gctx);
    189        }
    190        let target_info = TargetInfo::new(gctx, &build_config.requested_kinds, &rustc, *kind)?;
    191        let mut process = rustc.process();
    192        apply_env_config(gctx, &mut process)?;
    193        process.args(&target_info.rustflags);
    194        if let Some(args) = target_rustc_args {
    195            process.args(args);
    196        }
    197        if let CompileKind::Target(t) = kind {
    198            process.arg("--target").arg(t.rustc_target());
    199        }
    200        process.arg("--print").arg(print_opt_value);
    201        process.exec()?;
    202    }
    203    Ok(())
    204}
    205
    206/// Prepares all required information for the actual compilation.
    207///
    208/// For how it works and what data it collects,
    209/// please see the [module-level documentation](self).
    210#[tracing::instrument(skip_all)]
    211pub fn create_bcx<'a, 'gctx>(
    212    ws: &'a Workspace<'gctx>,
    213    options: &'a CompileOptions,
    214    interner: &'a UnitInterner,
    215) -> CargoResult<BuildContext<'a, 'gctx>> {
    216    let CompileOptions {
    217        ref build_config,
    218        ref spec,
    219        ref cli_features,
    220        ref filter,
    221        ref target_rustdoc_args,
    222        ref target_rustc_args,
    223        ref target_rustc_crate_types,
    224        rustdoc_document_private_items,
    225        honor_rust_version,
    226    } = *options;
    227    let gctx = ws.gctx();
    228
    229    // Perform some pre-flight validation.
    230    match build_config.intent {
    231        UserIntent::Test | UserIntent::Build | UserIntent::Check { .. } | UserIntent::Bench => {
    232            if ws.gctx().get_env("RUST_FLAGS").is_ok() {
    233                gctx.shell().warn(
    234                    "Cargo does not read `RUST_FLAGS` environment variable. Did you mean `RUSTFLAGS`?",
    235                )?;
    236            }
    237        }
    238        UserIntent::Doc { .. } | UserIntent::Doctest => {
    239            if ws.gctx().get_env("RUSTDOC_FLAGS").is_ok() {
    240                gctx.shell().warn(
    241                    "Cargo does not read `RUSTDOC_FLAGS` environment variable. Did you mean `RUSTDOCFLAGS`?"
    242                )?;
    243            }
    244        }
    245    }
    246    gctx.validate_term_config()?;
    247
    248    let mut target_data = RustcTargetData::new(ws, &build_config.requested_kinds)?;
    249
    250    let specs = spec.to_package_id_specs(ws)?;
    251    let has_dev_units = {
    252        // Rustdoc itself doesn't need dev-dependencies. But to scrape examples from packages in the
    253        // workspace, if any of those packages need dev-dependencies, then we need include dev-dependencies
    254        // to scrape those packages.
    255        let any_pkg_has_scrape_enabled = ws
    256            .members_with_features(&specs, cli_features)?
    257            .iter()
    258            .any(|(pkg, _)| {
    259                pkg.targets()
    260                    .iter()
    261                    .any(|target| target.is_example() && target.doc_scrape_examples().is_enabled())
    262            });
    263
    264        if filter.need_dev_deps(build_config.intent)
    265            || (build_config.intent.is_doc() && any_pkg_has_scrape_enabled)
    266        {
    267            HasDevUnits::Yes
    268        } else {
    269            HasDevUnits::No
    270        }
    271    };
    272    let dry_run = false;
    273    let resolve = ops::resolve_ws_with_opts(
    274        ws,
    275        &mut target_data,
    276        &build_config.requested_kinds,
    277        cli_features,
    278        &specs,
    279        has_dev_units,
    280        crate::core::resolver::features::ForceAllTargets::No,
    281        dry_run,
    282    )?;
    283    let WorkspaceResolve {
    284        mut pkg_set,
    285        workspace_resolve,
    286        targeted_resolve: resolve,
    287        resolved_features,
    288    } = resolve;
    289
    290    let std_resolve_features = if let Some(crates) = &gctx.cli_unstable().build_std {
    291        let (std_package_set, std_resolve, std_features) = standard_lib::resolve_std(
    292            ws,
    293            &mut target_data,
    294            &build_config,
    295            crates,
    296            &build_config.requested_kinds,
    297        )?;
    298        pkg_set.add_set(std_package_set);
    299        Some((std_resolve, std_features))
    300    } else {
    301        None
    302    };
    303
    304    // Find the packages in the resolver that the user wants to build (those
    305    // passed in with `-p` or the defaults from the workspace), and convert
    306    // Vec<PackageIdSpec> to a Vec<PackageId>.
    307    let to_build_ids = resolve.specs_to_ids(&specs)?;
    308    // Now get the `Package` for each `PackageId`. This may trigger a download
    309    // if the user specified `-p` for a dependency that is not downloaded.
    310    // Dependencies will be downloaded during build_unit_dependencies.
    311    let mut to_builds = pkg_set.get_many(to_build_ids)?;
    312
    313    // The ordering here affects some error messages coming out of cargo, so
    314    // let's be test and CLI friendly by always printing in the same order if
    315    // there's an error.
    316    to_builds.sort_by_key(|p| p.package_id());
    317
    318    for pkg in to_builds.iter() {
    319        pkg.manifest().print_teapot(gctx);
    320
    321        if build_config.intent.is_any_test()
    322            && !ws.is_member(pkg)
    323            && pkg.dependencies().iter().any(|dep| !dep.is_transitive())
    324        {
    325            anyhow::bail!(
    326                "package `{}` cannot be tested because it requires dev-dependencies \
    327                 and is not a member of the workspace",
    328                pkg.name()
    329            );
    330        }
    331    }
    332
    333    let (extra_args, extra_args_name) = match (target_rustc_args, target_rustdoc_args) {
    334        (Some(args), _) => (Some(args.clone()), "rustc"),
    335        (_, Some(args)) => (Some(args.clone()), "rustdoc"),
    336        _ => (None, ""),
    337    };
    338
    339    if extra_args.is_some() && to_builds.len() != 1 {
    340        panic!(
    341            "`{}` should not accept multiple `-p` flags",
    342            extra_args_name
    343        );
    344    }
    345
    346    let profiles = Profiles::new(ws, build_config.requested_profile)?;
    347    profiles.validate_packages(
    348        ws.profiles(),
    349        &mut gctx.shell(),
    350        workspace_resolve.as_ref().unwrap_or(&resolve),
    351    )?;
    352
    353    // If `--target` has not been specified, then the unit graph is built
    354    // assuming `--target $HOST` was specified. See
    355    // `rebuild_unit_graph_shared` for more on why this is done.
    356    let explicit_host_kind = CompileKind::Target(CompileTarget::new(&target_data.rustc.host)?);
    357    let explicit_host_kinds: Vec<_> = build_config
    358        .requested_kinds
    359        .iter()
    360        .map(|kind| match kind {
    361            CompileKind::Host => explicit_host_kind,
    362            CompileKind::Target(t) => CompileKind::Target(*t),
    363        })
    364        .collect();
    365
    366    // Passing `build_config.requested_kinds` instead of
    367    // `explicit_host_kinds` here so that `generate_root_units` can do
    368    // its own special handling of `CompileKind::Host`. It will
    369    // internally replace the host kind by the `explicit_host_kind`
    370    // before setting as a unit.
    371    let generator = UnitGenerator {
    372        ws,
    373        packages: &to_builds,
    374        spec,
    375        target_data: &target_data,
    376        filter,
    377        requested_kinds: &build_config.requested_kinds,
    378        explicit_host_kind,
    379        intent: build_config.intent,
    380        resolve: &resolve,
    381        workspace_resolve: &workspace_resolve,
    382        resolved_features: &resolved_features,
    383        package_set: &pkg_set,
    384        profiles: &profiles,
    385        interner,
    386        has_dev_units,
    387    };
    388    let mut units = generator.generate_root_units()?;
    389
    390    if let Some(args) = target_rustc_crate_types {
    391        override_rustc_crate_types(&mut units, args, interner)?;
    392    }
    393
    394    let should_scrape = build_config.intent.is_doc() && gctx.cli_unstable().rustdoc_scrape_examples;
    395    let mut scrape_units = if should_scrape {
    396        generator.generate_scrape_units(&units)?
    397    } else {
    398        Vec::new()
    399    };
    400
    401    let std_roots = if let Some(crates) = gctx.cli_unstable().build_std.as_ref() {
    402        let (std_resolve, std_features) = std_resolve_features.as_ref().unwrap();
    403        standard_lib::generate_std_roots(
    404            &crates,
    405            &units,
    406            std_resolve,
    407            std_features,
    408            &explicit_host_kinds,
    409            &pkg_set,
    410            interner,
    411            &profiles,
    412            &target_data,
    413        )?
    414    } else {
    415        Default::default()
    416    };
    417
    418    let mut unit_graph = build_unit_dependencies(
    419        ws,
    420        &pkg_set,
    421        &resolve,
    422        &resolved_features,
    423        std_resolve_features.as_ref(),
    424        &units,
    425        &scrape_units,
    426        &std_roots,
    427        build_config.intent,
    428        &target_data,
    429        &profiles,
    430        interner,
    431    )?;
    432
    433    // TODO: In theory, Cargo should also dedupe the roots, but I'm uncertain
    434    // what heuristics to use in that case.
    435    if build_config.intent.wants_deps_docs() {
    436        remove_duplicate_doc(build_config, &units, &mut unit_graph);
    437    }
    438
    439    let host_kind_requested = build_config
    440        .requested_kinds
    441        .iter()
    442        .any(CompileKind::is_host);
    443    // Rebuild the unit graph, replacing the explicit host targets with
    444    // CompileKind::Host, removing `artifact_target_for_features` and merging any dependencies
    445    // shared with build and artifact dependencies.
    446    (units, scrape_units, unit_graph) = rebuild_unit_graph_shared(
    447        interner,
    448        unit_graph,
    449        &units,
    450        &scrape_units,
    451        host_kind_requested.then_some(explicit_host_kind),
    452        build_config.compile_time_deps_only,
    453    );
    454
    455    let mut extra_compiler_args = HashMap::new();
    456    if let Some(args) = extra_args {
    457        if units.len() != 1 {
    458            anyhow::bail!(
    459                "extra arguments to `{}` can only be passed to one \
    460                 target, consider filtering\nthe package by passing, \
    461                 e.g., `--lib` or `--bin NAME` to specify a single target",
    462                extra_args_name
    463            );
    464        }
    465        extra_compiler_args.insert(units[0].clone(), args);
    466    }
    467
    468    for unit in units
    469        .iter()
    470        .filter(|unit| unit.mode.is_doc() || unit.mode.is_doc_test())
    471        .filter(|unit| rustdoc_document_private_items || unit.target.is_bin())
    472    {
    473        // Add `--document-private-items` rustdoc flag if requested or if
    474        // the target is a binary. Binary crates get their private items
    475        // documented by default.
    476        let mut args = vec!["--document-private-items".into()];
    477        if unit.target.is_bin() {
    478            // This warning only makes sense if it's possible to document private items
    479            // sometimes and ignore them at other times. But cargo consistently passes
    480            // `--document-private-items`, so the warning isn't useful.
    481            args.push("-Arustdoc::private-intra-doc-links".into());
    482        }
    483        extra_compiler_args
    484            .entry(unit.clone())
    485            .or_default()
    486            .extend(args);
    487    }
    488
    489    if honor_rust_version.unwrap_or(true) {
    490        let rustc_version = target_data.rustc.version.clone().into();
    491
    492        let mut incompatible = Vec::new();
    493        let mut local_incompatible = false;
    494        for unit in unit_graph.keys() {
    495            let Some(pkg_msrv) = unit.pkg.rust_version() else {
    496                continue;
    497            };
    498
    499            if pkg_msrv.is_compatible_with(&rustc_version) {
    500                continue;
    501            }
    502
    503            local_incompatible |= unit.is_local();
    504            incompatible.push((unit, pkg_msrv));
    505        }
    506        if !incompatible.is_empty() {
    507            use std::fmt::Write as _;
    508
    509            let plural = if incompatible.len() == 1 { "" } else { "s" };
    510            let mut message = format!(
    511                "rustc {rustc_version} is not supported by the following package{plural}:\n"
    512            );
    513            incompatible.sort_by_key(|(unit, _)| (unit.pkg.name(), unit.pkg.version()));
    514            for (unit, msrv) in incompatible {
    515                let name = &unit.pkg.name();
    516                let version = &unit.pkg.version();
    517                writeln!(&mut message, "  {name}@{version} requires rustc {msrv}").unwrap();
    518            }
    519            if ws.is_ephemeral() {
    520                if ws.ignore_lock() {
    521                    writeln!(
    522                        &mut message,
    523                        "Try re-running `cargo install` with `--locked`"
    524                    )
    525                    .unwrap();
    526                }
    527            } else if !local_incompatible {
    528                writeln!(
    529                    &mut message,
    530                    "Either upgrade rustc or select compatible dependency versions with
    531`cargo update <name>@<current-ver> --precise <compatible-ver>`
    532where `<compatible-ver>` is the latest version supporting rustc {rustc_version}",
    533                )
    534                .unwrap();
    535            }
    536            return Err(anyhow::Error::msg(message));
    537        }
    538    }
    539
    540    let bcx = BuildContext::new(
    541        ws,
    542        pkg_set,
    543        build_config,
    544        profiles,
    545        extra_compiler_args,
    546        target_data,
    547        units,
    548        unit_graph,
    549        scrape_units,
    550    )?;
    551
    552    Ok(bcx)
    553}
    554
    555/// This is used to rebuild the unit graph, sharing host dependencies if possible,
    556/// and applying other unit adjustments based on the whole graph.
    557///
    558/// This will translate any unit's `CompileKind::Target(host)` to
    559/// `CompileKind::Host` if `to_host` is not `None` and the kind is equal to `to_host`.
    560/// This also handles generating the unit `dep_hash`, and merging shared units if possible.
    561///
    562/// This is necessary because if normal dependencies used `CompileKind::Host`,
    563/// there would be no way to distinguish those units from build-dependency
    564/// units or artifact dependency units.
    565/// This can cause a problem if a shared normal/build/artifact dependency needs
    566/// to link to another dependency whose features differ based on whether or
    567/// not it is a normal, build or artifact dependency. If all units used
    568/// `CompileKind::Host`, then they would end up being identical, causing a
    569/// collision in the `UnitGraph`, and Cargo would end up randomly choosing one
    570/// value or the other.
    571///
    572/// The solution is to keep normal, build and artifact dependencies separate when
    573/// building the unit graph, and then run this second pass which will try to
    574/// combine shared dependencies safely. By adding a hash of the dependencies
    575/// to the `Unit`, this allows the `CompileKind` to be changed back to `Host`
    576/// and `artifact_target_for_features` to be removed without fear of an unwanted
    577/// collision for build or artifact dependencies.
    578///
    579/// This is also responsible for adjusting the `strip` profile option to
    580/// opportunistically strip if debug is 0 for all dependencies. This helps
    581/// remove debuginfo added by the standard library.
    582///
    583/// This is also responsible for adjusting the `debug` setting for host
    584/// dependencies, turning off debug if the user has not explicitly enabled it,
    585/// and the unit is not shared with a target unit.
    586///
    587/// This is also responsible for adjusting whether each unit should be compiled
    588/// or not regarding `--compile-time-deps` flag.
    589fn rebuild_unit_graph_shared(
    590    interner: &UnitInterner,
    591    unit_graph: UnitGraph,
    592    roots: &[Unit],
    593    scrape_units: &[Unit],
    594    to_host: Option<CompileKind>,
    595    compile_time_deps_only: bool,
    596) -> (Vec<Unit>, Vec<Unit>, UnitGraph) {
    597    let mut result = UnitGraph::new();
    598    // Map of the old unit to the new unit, used to avoid recursing into units
    599    // that have already been computed to improve performance.
    600    let mut memo = HashMap::new();
    601    let new_roots = roots
    602        .iter()
    603        .map(|root| {
    604            traverse_and_share(
    605                interner,
    606                &mut memo,
    607                &mut result,
    608                &unit_graph,
    609                root,
    610                true,
    611                false,
    612                to_host,
    613                compile_time_deps_only,
    614            )
    615        })
    616        .collect();
    617    // If no unit in the unit graph ended up having scrape units attached as dependencies,
    618    // then they won't have been discovered in traverse_and_share and hence won't be in
    619    // memo. So we filter out missing scrape units.
    620    let new_scrape_units = scrape_units
    621        .iter()
    622        .map(|unit| memo.get(unit).unwrap().clone())
    623        .collect();
    624    (new_roots, new_scrape_units, result)
    625}
    626
    627/// Recursive function for rebuilding the graph.
    628///
    629/// This walks `unit_graph`, starting at the given `unit`. It inserts the new
    630/// units into `new_graph`, and returns a new updated version of the given
    631/// unit (`dep_hash` is filled in, and `kind` switched if necessary).
    632fn traverse_and_share(
    633    interner: &UnitInterner,
    634    memo: &mut HashMap<Unit, Unit>,
    635    new_graph: &mut UnitGraph,
    636    unit_graph: &UnitGraph,
    637    unit: &Unit,
    638    unit_is_root: bool,
    639    unit_is_for_host: bool,
    640    to_host: Option<CompileKind>,
    641    compile_time_deps_only: bool,
    642) -> Unit {
    643    if let Some(new_unit) = memo.get(unit) {
    644        // Already computed, no need to recompute.
    645        return new_unit.clone();
    646    }
    647    let mut dep_hash = StableHasher::new();
    648    let skip_non_compile_time_deps = compile_time_deps_only
    649        && (!unit.target.is_compile_time_dependency() ||
    650            // Root unit is not a dependency unless other units are dependant
    651            // to it.
    652            unit_is_root);
    653    let new_deps: Vec<_> = unit_graph[unit]
    654        .iter()
    655        .map(|dep| {
    656            let new_dep_unit = traverse_and_share(
    657                interner,
    658                memo,
    659                new_graph,
    660                unit_graph,
    661                &dep.unit,
    662                false,
    663                dep.unit_for.is_for_host(),
    664                to_host,
    665                // If we should compile the current unit, we should also compile
    666                // its dependencies. And if not, we should compile compile time
    667                // dependencies only.
    668                skip_non_compile_time_deps,
    669            );
    670            new_dep_unit.hash(&mut dep_hash);
    671            UnitDep {
    672                unit: new_dep_unit,
    673                ..dep.clone()
    674            }
    675        })
    676        .collect();
    677    // Here, we have recursively traversed this unit's dependencies, and hashed them: we can
    678    // finalize the dep hash.
    679    let new_dep_hash = Hasher::finish(&dep_hash);
    680
    681    // This is the key part of the sharing process: if the unit is a runtime dependency, whose
    682    // target is the same as the host, we canonicalize the compile kind to `CompileKind::Host`.
    683    // A possible host dependency counterpart to this unit would have that kind, and if such a unit
    684    // exists in the current `unit_graph`, they will unify in the new unit graph map `new_graph`.
    685    // The resulting unit graph will be optimized with less units, thanks to sharing these host
    686    // dependencies.
    687    let canonical_kind = match to_host {
    688        Some(to_host) if to_host == unit.kind => CompileKind::Host,
    689        _ => unit.kind,
    690    };
    691
    692    let mut profile = unit.profile.clone();
    693    if profile.strip.is_deferred() {
    694        // If strip was not manually set, and all dependencies of this unit together
    695        // with this unit have debuginfo turned off, we enable debuginfo stripping.
    696        // This will remove pre-existing debug symbols coming from the standard library.
    697        if !profile.debuginfo.is_turned_on()
    698            && new_deps
    699                .iter()
    700                .all(|dep| !dep.unit.profile.debuginfo.is_turned_on())
    701        {
    702            profile.strip = profile.strip.strip_debuginfo();
    703        }
    704    }
    705
    706    // If this is a build dependency, and it's not shared with runtime dependencies, we can weaken
    707    // its debuginfo level to optimize build times. We do nothing if it's an artifact dependency,
    708    // as it and its debuginfo may end up embedded in the main program.
    709    if unit_is_for_host
    710        && to_host.is_some()
    711        && profile.debuginfo.is_deferred()
    712        && !unit.artifact.is_true()
    713    {
    714        // We create a "probe" test to see if a unit with the same explicit debuginfo level exists
    715        // in the graph. This is the level we'd expect if it was set manually or the default value
    716        // set by a profile for a runtime dependency: its canonical value.
    717        let canonical_debuginfo = profile.debuginfo.finalize();
    718        let mut canonical_profile = profile.clone();
    719        canonical_profile.debuginfo = canonical_debuginfo;
    720        let unit_probe = interner.intern(
    721            &unit.pkg,
    722            &unit.target,
    723            canonical_profile,
    724            to_host.unwrap(),
    725            unit.mode,
    726            unit.features.clone(),
    727            unit.rustflags.clone(),
    728            unit.rustdocflags.clone(),
    729            unit.links_overrides.clone(),
    730            unit.is_std,
    731            unit.dep_hash,
    732            unit.artifact,
    733            unit.artifact_target_for_features,
    734            unit.skip_non_compile_time_dep,
    735        );
    736
    737        // We can now turn the deferred value into its actual final value.
    738        profile.debuginfo = if unit_graph.contains_key(&unit_probe) {
    739            // The unit is present in both build time and runtime subgraphs: we canonicalize its
    740            // level to the other unit's, thus ensuring reuse between the two to optimize build times.
    741            canonical_debuginfo
    742        } else {
    743            // The unit is only present in the build time subgraph, we can weaken its debuginfo
    744            // level to optimize build times.
    745            canonical_debuginfo.weaken()
    746        }
    747    }
    748
    749    let new_unit = interner.intern(
    750        &unit.pkg,
    751        &unit.target,
    752        profile,
    753        canonical_kind,
    754        unit.mode,
    755        unit.features.clone(),
    756        unit.rustflags.clone(),
    757        unit.rustdocflags.clone(),
    758        unit.links_overrides.clone(),
    759        unit.is_std,
    760        new_dep_hash,
    761        unit.artifact,
    762        // Since `dep_hash` is now filled in, there's no need to specify the artifact target
    763        // for target-dependent feature resolution
    764        None,
    765        skip_non_compile_time_deps,
    766    );
    767    if !unit_is_root || !compile_time_deps_only {
    768        assert!(memo.insert(unit.clone(), new_unit.clone()).is_none());
    769    }
    770    new_graph.entry(new_unit.clone()).or_insert(new_deps);
    771    new_unit
    772}
    773
    774/// Removes duplicate `CompileMode::Doc` units that would cause problems with
    775/// filename collisions.
    776///
    777/// Rustdoc only separates units by crate name in the file directory
    778/// structure. If any two units with the same crate name exist, this would
    779/// cause a filename collision, causing different rustdoc invocations to stomp
    780/// on one another's files.
    781///
    782/// Unfortunately this does not remove all duplicates, as some of them are
    783/// either user error, or difficult to remove. Cases that I can think of:
    784///
    785/// - Same target name in different packages. See the `collision_doc` test.
    786/// - Different sources. See `collision_doc_sources` test.
    787///
    788/// Ideally this would not be necessary.
    789fn remove_duplicate_doc(
    790    build_config: &BuildConfig,
    791    root_units: &[Unit],
    792    unit_graph: &mut UnitGraph,
    793) {
    794    // First, create a mapping of crate_name -> Unit so we can see where the
    795    // duplicates are.
    796    let mut all_docs: HashMap<String, Vec<Unit>> = HashMap::new();
    797    for unit in unit_graph.keys() {
    798        if unit.mode.is_doc() {
    799            all_docs
    800                .entry(unit.target.crate_name())
    801                .or_default()
    802                .push(unit.clone());
    803        }
    804    }
    805    // Keep track of units to remove so that they can be efficiently removed
    806    // from the unit_deps.
    807    let mut removed_units: HashSet<Unit> = HashSet::new();
    808    let mut remove = |units: Vec<Unit>, reason: &str, cb: &dyn Fn(&Unit) -> bool| -> Vec<Unit> {
    809        let (to_remove, remaining_units): (Vec<Unit>, Vec<Unit>) = units
    810            .into_iter()
    811            .partition(|unit| cb(unit) && !root_units.contains(unit));
    812        for unit in to_remove {
    813            tracing::debug!(
    814                "removing duplicate doc due to {} for package {} target `{}`",
    815                reason,
    816                unit.pkg,
    817                unit.target.name()
    818            );
    819            unit_graph.remove(&unit);
    820            removed_units.insert(unit);
    821        }
    822        remaining_units
    823    };
    824    // Iterate over the duplicates and try to remove them from unit_graph.
    825    for (_crate_name, mut units) in all_docs {
    826        if units.len() == 1 {
    827            continue;
    828        }
    829        // Prefer target over host if --target was not specified.
    830        if build_config
    831            .requested_kinds
    832            .iter()
    833            .all(CompileKind::is_host)
    834        {
    835            // Note these duplicates may not be real duplicates, since they
    836            // might get merged in rebuild_unit_graph_shared. Either way, it
    837            // shouldn't hurt to remove them early (although the report in the
    838            // log might be confusing).
    839            units = remove(units, "host/target merger", &|unit| unit.kind.is_host());
    840            if units.len() == 1 {
    841                continue;
    842            }
    843        }
    844        // Prefer newer versions over older.
    845        let mut source_map: HashMap<(InternedString, SourceId, CompileKind), Vec<Unit>> =
    846            HashMap::new();
    847        for unit in units {
    848            let pkg_id = unit.pkg.package_id();
    849            // Note, this does not detect duplicates from different sources.
    850            source_map
    851                .entry((pkg_id.name(), pkg_id.source_id(), unit.kind))
    852                .or_default()
    853                .push(unit);
    854        }
    855        let mut remaining_units = Vec::new();
    856        for (_key, mut units) in source_map {
    857            if units.len() > 1 {
    858                units.sort_by(|a, b| a.pkg.version().partial_cmp(b.pkg.version()).unwrap());
    859                // Remove any entries with version < newest.
    860                let newest_version = units.last().unwrap().pkg.version().clone();
    861                let keep_units = remove(units, "older version", &|unit| {
    862                    unit.pkg.version() < &newest_version
    863                });
    864                remaining_units.extend(keep_units);
    865            } else {
    866                remaining_units.extend(units);
    867            }
    868        }
    869        if remaining_units.len() == 1 {
    870            continue;
    871        }
    872        // Are there other heuristics to remove duplicates that would make
    873        // sense? Maybe prefer path sources over all others?
    874    }
    875    // Also remove units from the unit_deps so there aren't any dangling edges.
    876    for unit_deps in unit_graph.values_mut() {
    877        unit_deps.retain(|unit_dep| !removed_units.contains(&unit_dep.unit));
    878    }
    879    // Remove any orphan units that were detached from the graph.
    880    let mut visited = HashSet::new();
    881    fn visit(unit: &Unit, graph: &UnitGraph, visited: &mut HashSet<Unit>) {
    882        if !visited.insert(unit.clone()) {
    883            return;
    884        }
    885        for dep in &graph[unit] {
    886            visit(&dep.unit, graph, visited);
    887        }
    888    }
    889    for unit in root_units {
    890        visit(unit, unit_graph, &mut visited);
    891    }
    892    unit_graph.retain(|unit, _| visited.contains(unit));
    893}
    894
    895/// Override crate types for given units.
    896///
    897/// This is primarily used by `cargo rustc --crate-type`.
    898fn override_rustc_crate_types(
    899    units: &mut [Unit],
    900    args: &[String],
    901    interner: &UnitInterner,
    902) -> CargoResult<()> {
    903    if units.len() != 1 {
    904        anyhow::bail!(
    905            "crate types to rustc can only be passed to one \
    906            target, consider filtering\nthe package by passing, \
    907            e.g., `--lib` or `--example` to specify a single target"
    908        );
    909    }
    910
    911    let unit = &units[0];
    912    let override_unit = |f: fn(Vec<CrateType>) -> TargetKind| {
    913        let crate_types = args.iter().map(|s| s.into()).collect();
    914        let mut target = unit.target.clone();
    915        target.set_kind(f(crate_types));
    916        interner.intern(
    917            &unit.pkg,
    918            &target,
    919            unit.profile.clone(),
    920            unit.kind,
    921            unit.mode,
    922            unit.features.clone(),
    923            unit.rustflags.clone(),
    924            unit.rustdocflags.clone(),
    925            unit.links_overrides.clone(),
    926            unit.is_std,
    927            unit.dep_hash,
    928            unit.artifact,
    929            unit.artifact_target_for_features,
    930            unit.skip_non_compile_time_dep,
    931        )
    932    };
    933    units[0] = match unit.target.kind() {
    934        TargetKind::Lib(_) => override_unit(TargetKind::Lib),
    935        TargetKind::ExampleLib(_) => override_unit(TargetKind::ExampleLib),
    936        _ => {
    937            anyhow::bail!(
    938                "crate types can only be specified for libraries and example libraries.\n\
    939                Binaries, tests, and benchmarks are always the `bin` crate type"
    940            );
    941        }
    942    };
    943
    944    Ok(())
    945}
    946
    947/// Gets all of the features enabled for a package, plus its dependencies'
    948/// features.
    949///
    950/// Dependencies are added as `dep_name/feat_name` because `required-features`
    951/// wants to support that syntax.
    952pub fn resolve_all_features(
    953    resolve_with_overrides: &Resolve,
    954    resolved_features: &features::ResolvedFeatures,
    955    package_set: &PackageSet<'_>,
    956    package_id: PackageId,
    957) -> HashSet<String> {
    958    let mut features: HashSet<String> = resolved_features
    959        .activated_features(package_id, FeaturesFor::NormalOrDev)
    960        .iter()
    961        .map(|s| s.to_string())
    962        .collect();
    963
    964    // Include features enabled for use by dependencies so targets can also use them with the
    965    // required-features field when deciding whether to be built or skipped.
    966    for (dep_id, deps) in resolve_with_overrides.deps(package_id) {
    967        let is_proc_macro = package_set
    968            .get_one(dep_id)
    969            .expect("packages downloaded")
    970            .proc_macro();
    971        for dep in deps {
    972            let features_for = FeaturesFor::from_for_host(is_proc_macro || dep.is_build());
    973            for feature in resolved_features
    974                .activated_features_unverified(dep_id, features_for)
    975                .unwrap_or_default()
    976            {
    977                features.insert(format!("{}/{}", dep.name_in_toml(), feature));
    978            }
    979        }
    980    }
    981
    982    features
    983}