#
cargo/core/compiler/
unit_dependencies.rs

    1//! Constructs the dependency graph for compilation.
    2//!
    3//! Rust code is typically organized as a set of Cargo packages. The
    4//! dependencies between the packages themselves are stored in the
    5//! [`Resolve`] struct. However, we can't use that information as is for
    6//! compilation! A package typically contains several targets, or crates,
    7//! and these targets has inter-dependencies. For example, you need to
    8//! compile the `lib` target before the `bin` one, and you need to compile
    9//! `build.rs` before either of those.
    10//!
    11//! So, we need to lower the `Resolve`, which specifies dependencies between
    12//! *packages*, to a graph of dependencies between their *targets*, and this
    13//! is exactly what this module is doing! Well, almost exactly: another
    14//! complication is that we might want to compile the same target several times
    15//! (for example, with and without tests), so we actually build a dependency
    16//! graph of [`Unit`]s, which capture these properties.
    17
    18use std::collections::{HashMap, HashSet};
    19
    20use tracing::trace;
    21
    22use crate::core::compiler::artifact::match_artifacts_kind_with_targets;
    23use crate::core::compiler::unit_graph::{UnitDep, UnitGraph};
    24use crate::core::compiler::UserIntent;
    25use crate::core::compiler::{
    26    CompileKind, CompileMode, CrateType, RustcTargetData, Unit, UnitInterner,
    27};
    28use crate::core::dependency::{Artifact, ArtifactKind, ArtifactTarget, DepKind};
    29use crate::core::profiles::{Profile, Profiles, UnitFor};
    30use crate::core::resolver::features::{FeaturesFor, ResolvedFeatures};
    31use crate::core::resolver::Resolve;
    32use crate::core::{Dependency, Package, PackageId, PackageSet, Target, TargetKind, Workspace};
    33use crate::ops::resolve_all_features;
    34use crate::util::interning::InternedString;
    35use crate::util::GlobalContext;
    36use crate::CargoResult;
    37
    38const IS_NO_ARTIFACT_DEP: Option<&'static Artifact> = None;
    39
    40/// Collection of stuff used while creating the [`UnitGraph`].
    41struct State<'a, 'gctx> {
    42    ws: &'a Workspace<'gctx>,
    43    gctx: &'gctx GlobalContext,
    44    /// Stores the result of building the [`UnitGraph`].
    45    unit_dependencies: UnitGraph,
    46    package_set: &'a PackageSet<'gctx>,
    47    usr_resolve: &'a Resolve,
    48    usr_features: &'a ResolvedFeatures,
    49    /// Like `usr_resolve` but for building standard library (`-Zbuild-std`).
    50    std_resolve: Option<&'a Resolve>,
    51    /// Like `usr_features` but for building standard library (`-Zbuild-std`).
    52    std_features: Option<&'a ResolvedFeatures>,
    53    /// `true` while generating the dependencies for the standard library.
    54    is_std: bool,
    55    /// The high-level operation requested by the user.
    56    /// Used for preventing from building lib thrice.
    57    intent: UserIntent,
    58    target_data: &'a RustcTargetData<'gctx>,
    59    profiles: &'a Profiles,
    60    interner: &'a UnitInterner,
    61    // Units for `-Zrustdoc-scrape-examples`.
    62    scrape_units: &'a [Unit],
    63
    64    /// A set of edges in `unit_dependencies` where (a, b) means that the
    65    /// dependency from a to b was added purely because it was a dev-dependency.
    66    /// This is used during `connect_run_custom_build_deps`.
    67    dev_dependency_edges: HashSet<(Unit, Unit)>,
    68}
    69
    70/// A boolean-like to indicate if a `Unit` is an artifact or not.
    71#[derive(Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
    72pub enum IsArtifact {
    73    Yes,
    74    No,
    75}
    76
    77impl IsArtifact {
    78    pub fn is_true(&self) -> bool {
    79        matches!(self, IsArtifact::Yes)
    80    }
    81}
    82
    83/// Then entry point for building a dependency graph of compilation units.
    84///
    85/// You can find some information for arguments from doc of [`State`].
    86#[tracing::instrument(skip_all)]
    87pub fn build_unit_dependencies<'a, 'gctx>(
    88    ws: &'a Workspace<'gctx>,
    89    package_set: &'a PackageSet<'gctx>,
    90    resolve: &'a Resolve,
    91    features: &'a ResolvedFeatures,
    92    std_resolve: Option<&'a (Resolve, ResolvedFeatures)>,
    93    roots: &[Unit],
    94    scrape_units: &[Unit],
    95    std_roots: &HashMap<CompileKind, Vec<Unit>>,
    96    intent: UserIntent,
    97    target_data: &'a RustcTargetData<'gctx>,
    98    profiles: &'a Profiles,
    99    interner: &'a UnitInterner,
    100) -> CargoResult<UnitGraph> {
    101    if roots.is_empty() {
    102        // If -Zbuild-std, don't attach units if there is nothing to build.
    103        // Otherwise, other parts of the code may be confused by seeing units
    104        // in the dep graph without a root.
    105        return Ok(HashMap::new());
    106    }
    107    let (std_resolve, std_features) = match std_resolve {
    108        Some((r, f)) => (Some(r), Some(f)),
    109        None => (None, None),
    110    };
    111    let mut state = State {
    112        ws,
    113        gctx: ws.gctx(),
    114        unit_dependencies: HashMap::new(),
    115        package_set,
    116        usr_resolve: resolve,
    117        usr_features: features,
    118        std_resolve,
    119        std_features,
    120        is_std: false,
    121        intent,
    122        target_data,
    123        profiles,
    124        interner,
    125        scrape_units,
    126        dev_dependency_edges: HashSet::new(),
    127    };
    128
    129    let std_unit_deps = calc_deps_of_std(&mut state, std_roots)?;
    130
    131    deps_of_roots(roots, &mut state)?;
    132    super::links::validate_links(state.resolve(), &state.unit_dependencies)?;
    133    // Hopefully there aren't any links conflicts with the standard library?
    134
    135    if let Some(std_unit_deps) = std_unit_deps {
    136        attach_std_deps(&mut state, std_roots, std_unit_deps);
    137    }
    138
    139    connect_run_custom_build_deps(&mut state);
    140
    141    // Dependencies are used in tons of places throughout the backend, many of
    142    // which affect the determinism of the build itself. As a result be sure
    143    // that dependency lists are always sorted to ensure we've always got a
    144    // deterministic output.
    145    for list in state.unit_dependencies.values_mut() {
    146        list.sort();
    147    }
    148    trace!("ALL UNIT DEPENDENCIES {:#?}", state.unit_dependencies);
    149
    150    Ok(state.unit_dependencies)
    151}
    152
    153/// Compute all the dependencies for the standard library.
    154fn calc_deps_of_std(
    155    state: &mut State<'_, '_>,
    156    std_roots: &HashMap<CompileKind, Vec<Unit>>,
    157) -> CargoResult<Option<UnitGraph>> {
    158    if std_roots.is_empty() {
    159        return Ok(None);
    160    }
    161    // Compute dependencies for the standard library.
    162    state.is_std = true;
    163    for roots in std_roots.values() {
    164        deps_of_roots(roots, state)?;
    165    }
    166    state.is_std = false;
    167    Ok(Some(std::mem::take(&mut state.unit_dependencies)))
    168}
    169
    170/// Add the standard library units to the `unit_dependencies`.
    171fn attach_std_deps(
    172    state: &mut State<'_, '_>,
    173    std_roots: &HashMap<CompileKind, Vec<Unit>>,
    174    std_unit_deps: UnitGraph,
    175) {
    176    // Attach the standard library as a dependency of every target unit.
    177    let mut found = false;
    178    for (unit, deps) in state.unit_dependencies.iter_mut() {
    179        if !unit.kind.is_host() && !unit.mode.is_run_custom_build() {
    180            deps.extend(std_roots[&unit.kind].iter().map(|unit| UnitDep {
    181                unit: unit.clone(),
    182                unit_for: UnitFor::new_normal(unit.kind),
    183                extern_crate_name: unit.pkg.name(),
    184                dep_name: None,
    185                // TODO: Does this `public` make sense?
    186                public: true,
    187                noprelude: true,
    188            }));
    189            found = true;
    190        }
    191    }
    192    // And also include the dependencies of the standard library itself. Don't
    193    // include these if no units actually needed the standard library.
    194    if found {
    195        for (unit, deps) in std_unit_deps.into_iter() {
    196            if let Some(other_unit) = state.unit_dependencies.insert(unit, deps) {
    197                panic!("std unit collision with existing unit: {:?}", other_unit);
    198            }
    199        }
    200    }
    201}
    202
    203/// Compute all the dependencies of the given root units.
    204/// The result is stored in `state.unit_dependencies`.
    205fn deps_of_roots(roots: &[Unit], state: &mut State<'_, '_>) -> CargoResult<()> {
    206    for unit in roots.iter() {
    207        // Dependencies of tests/benches should not have `panic` set.
    208        // We check the user intent to see if we are running in `cargo test` in
    209        // which case we ensure all dependencies have `panic` cleared, and
    210        // avoid building the lib thrice (once with `panic`, once without, once
    211        // for `--test`). In particular, the lib included for Doc tests and
    212        // examples are `Build` mode here.
    213        let root_compile_kind = unit.kind;
    214        let unit_for = if unit.mode.is_any_test() || state.intent.is_rustc_test() {
    215            if unit.target.proc_macro() {
    216                // Special-case for proc-macros, which are forced to for-host
    217                // since they need to link with the proc_macro crate.
    218                UnitFor::new_host_test(state.gctx, root_compile_kind)
    219            } else {
    220                UnitFor::new_test(state.gctx, root_compile_kind)
    221            }
    222        } else if unit.target.is_custom_build() {
    223            // This normally doesn't happen, except `clean` aggressively
    224            // generates all units.
    225            UnitFor::new_host(false, root_compile_kind)
    226        } else if unit.target.proc_macro() {
    227            UnitFor::new_host(true, root_compile_kind)
    228        } else if unit.target.for_host() {
    229            // Plugin should never have panic set.
    230            UnitFor::new_compiler(root_compile_kind)
    231        } else {
    232            UnitFor::new_normal(root_compile_kind)
    233        };
    234        deps_of(unit, state, unit_for)?;
    235    }
    236
    237    Ok(())
    238}
    239
    240/// Compute the dependencies of a single unit, recursively computing all
    241/// transitive dependencies.
    242///
    243/// The result is stored in `state.unit_dependencies`.
    244fn deps_of(unit: &Unit, state: &mut State<'_, '_>, unit_for: UnitFor) -> CargoResult<()> {
    245    // Currently the `unit_dependencies` map does not include `unit_for`. This should
    246    // be safe for now. `TestDependency` only exists to clear the `panic`
    247    // flag, and you'll never ask for a `unit` with `panic` set as a
    248    // `TestDependency`. `CustomBuild` should also be fine since if the
    249    // requested unit's settings are the same as `Any`, `CustomBuild` can't
    250    // affect anything else in the hierarchy.
    251    if !state.unit_dependencies.contains_key(unit) {
    252        let unit_deps = compute_deps(unit, state, unit_for)?;
    253        state
    254            .unit_dependencies
    255            .insert(unit.clone(), unit_deps.clone());
    256        for unit_dep in unit_deps {
    257            deps_of(&unit_dep.unit, state, unit_dep.unit_for)?;
    258        }
    259    }
    260    Ok(())
    261}
    262
    263/// Returns the direct unit dependencies for the given `Unit`.
    264fn compute_deps(
    265    unit: &Unit,
    266    state: &mut State<'_, '_>,
    267    unit_for: UnitFor,
    268) -> CargoResult<Vec<UnitDep>> {
    269    if unit.mode.is_run_custom_build() {
    270        return compute_deps_custom_build(unit, unit_for, state);
    271    } else if unit.mode.is_doc() {
    272        // Note: this does not include doc test.
    273        return compute_deps_doc(unit, state, unit_for);
    274    }
    275
    276    let mut ret = Vec::new();
    277    let mut dev_deps = Vec::new();
    278    for (dep_pkg_id, deps) in state.deps(unit, unit_for) {
    279        let Some(dep_lib) = calc_artifact_deps(unit, unit_for, dep_pkg_id, &deps, state, &mut ret)?
    280        else {
    281            continue;
    282        };
    283        let dep_pkg = state.get(dep_pkg_id);
    284        let mode = check_or_build_mode(unit.mode, dep_lib);
    285        let dep_unit_for = unit_for.with_dependency(unit, dep_lib, unit_for.root_compile_kind());
    286
    287        let start = ret.len();
    288        if state.gctx.cli_unstable().dual_proc_macros
    289            && dep_lib.proc_macro()
    290            && !unit.kind.is_host()
    291        {
    292            let unit_dep = new_unit_dep(
    293                state,
    294                unit,
    295                dep_pkg,
    296                dep_lib,
    297                dep_unit_for,
    298                unit.kind,
    299                mode,
    300                IS_NO_ARTIFACT_DEP,
    301            )?;
    302            ret.push(unit_dep);
    303            let unit_dep = new_unit_dep(
    304                state,
    305                unit,
    306                dep_pkg,
    307                dep_lib,
    308                dep_unit_for,
    309                CompileKind::Host,
    310                mode,
    311                IS_NO_ARTIFACT_DEP,
    312            )?;
    313            ret.push(unit_dep);
    314        } else {
    315            let unit_dep = new_unit_dep(
    316                state,
    317                unit,
    318                dep_pkg,
    319                dep_lib,
    320                dep_unit_for,
    321                unit.kind.for_target(dep_lib),
    322                mode,
    323                IS_NO_ARTIFACT_DEP,
    324            )?;
    325            ret.push(unit_dep);
    326        }
    327
    328        // If the unit added was a dev-dependency unit, then record that in the
    329        // dev-dependencies array. We'll add this to
    330        // `state.dev_dependency_edges` at the end and process it later in
    331        // `connect_run_custom_build_deps`.
    332        if deps.iter().all(|d| !d.is_transitive()) {
    333            for dep in ret[start..].iter() {
    334                dev_deps.push((unit.clone(), dep.unit.clone()));
    335            }
    336        }
    337    }
    338    state.dev_dependency_edges.extend(dev_deps);
    339
    340    // If this target is a build script, then what we've collected so far is
    341    // all we need. If this isn't a build script, then it depends on the
    342    // build script if there is one.
    343    if unit.target.is_custom_build() {
    344        return Ok(ret);
    345    }
    346    ret.extend(dep_build_script(unit, unit_for, state)?);
    347
    348    // If this target is a binary, test, example, etc, then it depends on
    349    // the library of the same package. The call to `resolve.deps` above
    350    // didn't include `pkg` in the return values, so we need to special case
    351    // it here and see if we need to push `(pkg, pkg_lib_target)`.
    352    if unit.target.is_lib() && unit.mode != CompileMode::Doctest {
    353        return Ok(ret);
    354    }
    355    ret.extend(maybe_lib(unit, state, unit_for)?);
    356
    357    // If any integration tests/benches are being run, make sure that
    358    // binaries are built as well.
    359    if !unit.mode.is_check()
    360        && unit.mode.is_any_test()
    361        && (unit.target.is_test() || unit.target.is_bench())
    362    {
    363        let id = unit.pkg.package_id();
    364        ret.extend(
    365            unit.pkg
    366                .targets()
    367                .iter()
    368                .filter(|t| {
    369                    // Skip binaries with required features that have not been selected.
    370                    match t.required_features() {
    371                        Some(rf) if t.is_bin() => {
    372                            let features = resolve_all_features(
    373                                state.resolve(),
    374                                state.features(),
    375                                state.package_set,
    376                                id,
    377                            );
    378                            rf.iter().all(|f| features.contains(f))
    379                        }
    380                        None if t.is_bin() => true,
    381                        _ => false,
    382                    }
    383                })
    384                .map(|t| {
    385                    new_unit_dep(
    386                        state,
    387                        unit,
    388                        &unit.pkg,
    389                        t,
    390                        UnitFor::new_normal(unit_for.root_compile_kind()),
    391                        unit.kind.for_target(t),
    392                        CompileMode::Build,
    393                        IS_NO_ARTIFACT_DEP,
    394                    )
    395                })
    396                .collect::<CargoResult<Vec<UnitDep>>>()?,
    397        );
    398    }
    399
    400    Ok(ret)
    401}
    402
    403/// Find artifacts for all `deps` of `unit` and add units that build these artifacts
    404/// to `ret`.
    405fn calc_artifact_deps<'a>(
    406    unit: &Unit,
    407    unit_for: UnitFor,
    408    dep_id: PackageId,
    409    deps: &[&Dependency],
    410    state: &State<'a, '_>,
    411    ret: &mut Vec<UnitDep>,
    412) -> CargoResult<Option<&'a Target>> {
    413    let mut has_artifact_lib = false;
    414    let mut maybe_non_artifact_lib = false;
    415    let artifact_pkg = state.get(dep_id);
    416    for dep in deps {
    417        let Some(artifact) = dep.artifact() else {
    418            maybe_non_artifact_lib = true;
    419            continue;
    420        };
    421        has_artifact_lib |= artifact.is_lib();
    422        // Custom build scripts (build/compile) never get artifact dependencies,
    423        // but the run-build-script step does (where it is handled).
    424        if !unit.target.is_custom_build() {
    425            debug_assert!(
    426                !unit.mode.is_run_custom_build(),
    427                "BUG: This should be handled in a separate branch"
    428            );
    429            ret.extend(artifact_targets_to_unit_deps(
    430                unit,
    431                unit_for.with_artifact_features(artifact),
    432                state,
    433                artifact
    434                    .target()
    435                    .and_then(|t| match t {
    436                        ArtifactTarget::BuildDependencyAssumeTarget => None,
    437                        ArtifactTarget::Force(kind) => Some(CompileKind::Target(kind)),
    438                    })
    439                    .unwrap_or(unit.kind),
    440                artifact_pkg,
    441                dep,
    442            )?);
    443        }
    444    }
    445    if has_artifact_lib || maybe_non_artifact_lib {
    446        Ok(artifact_pkg.targets().iter().find(|t| t.is_lib()))
    447    } else {
    448        Ok(None)
    449    }
    450}
    451
    452/// Returns the dependencies needed to run a build script.
    453///
    454/// The `unit` provided must represent an execution of a build script, and
    455/// the returned set of units must all be run before `unit` is run.
    456fn compute_deps_custom_build(
    457    unit: &Unit,
    458    unit_for: UnitFor,
    459    state: &State<'_, '_>,
    460) -> CargoResult<Vec<UnitDep>> {
    461    if let Some(links) = unit.pkg.manifest().links() {
    462        if unit.links_overrides.get(links).is_some() {
    463            // Overridden build scripts don't have any dependencies.
    464            return Ok(Vec::new());
    465        }
    466    }
    467    // All dependencies of this unit should use profiles for custom builds.
    468    // If this is a build script of a proc macro, make sure it uses host
    469    // features.
    470    let script_unit_for = unit_for.for_custom_build();
    471    // When not overridden, then the dependencies to run a build script are:
    472    //
    473    // 1. Compiling the build script itself.
    474    // 2. For each immediate dependency of our package which has a `links`
    475    //    key, the execution of that build script.
    476    //
    477    // We don't have a great way of handling (2) here right now so this is
    478    // deferred until after the graph of all unit dependencies has been
    479    // constructed.
    480    let compile_script_unit = new_unit_dep(
    481        state,
    482        unit,
    483        &unit.pkg,
    484        &unit.target,
    485        script_unit_for,
    486        // Build scripts always compiled for the host.
    487        CompileKind::Host,
    488        CompileMode::Build,
    489        IS_NO_ARTIFACT_DEP,
    490    )?;
    491
    492    let mut result = vec![compile_script_unit];
    493
    494    // Include any artifact dependencies.
    495    //
    496    // This is essentially the same as `calc_artifact_deps`, but there are some
    497    // subtle differences that require this to be implemented differently.
    498    //
    499    // Produce units that build all required artifact kinds (like binaries,
    500    // static libraries, etc) with the correct compile target.
    501    //
    502    // Computing the compile target for artifact units is more involved as it has to handle
    503    // various target configurations specific to artifacts, like `target = "target"` and
    504    // `target = "<triple>"`, which makes knowing the root units compile target
    505    // `root_unit_compile_target` necessary.
    506    let root_unit_compile_target = unit_for.root_compile_kind();
    507    let unit_for = UnitFor::new_host(/*host_features*/ true, root_unit_compile_target);
    508    for (dep_pkg_id, deps) in state.deps(unit, script_unit_for) {
    509        for dep in deps {
    510            if dep.kind() != DepKind::Build || dep.artifact().is_none() {
    511                continue;
    512            }
    513            let artifact_pkg = state.get(dep_pkg_id);
    514            let artifact = dep.artifact().expect("artifact dep");
    515            let resolved_artifact_compile_kind = artifact
    516                .target()
    517                .map(|target| target.to_resolved_compile_kind(root_unit_compile_target));
    518
    519            result.extend(artifact_targets_to_unit_deps(
    520                unit,
    521                unit_for.with_artifact_features_from_resolved_compile_kind(
    522                    resolved_artifact_compile_kind,
    523                ),
    524                state,
    525                resolved_artifact_compile_kind.unwrap_or(CompileKind::Host),
    526                artifact_pkg,
    527                dep,
    528            )?);
    529        }
    530    }
    531
    532    Ok(result)
    533}
    534
    535/// Given a `parent` unit containing a dependency `dep` whose package is `artifact_pkg`,
    536/// find all targets in `artifact_pkg` which refer to the `dep`s artifact declaration
    537/// and turn them into units.
    538/// Due to the nature of artifact dependencies, a single dependency in a manifest can
    539/// cause one or more targets to be build, for instance with
    540/// `artifact = ["bin:a", "bin:b", "staticlib"]`, which is very different from normal
    541/// dependencies which cause only a single unit to be created.
    542///
    543/// `compile_kind` is the computed kind for the future artifact unit
    544/// dependency, only the caller can pick the correct one.
    545fn artifact_targets_to_unit_deps(
    546    parent: &Unit,
    547    parent_unit_for: UnitFor,
    548    state: &State<'_, '_>,
    549    compile_kind: CompileKind,
    550    artifact_pkg: &Package,
    551    dep: &Dependency,
    552) -> CargoResult<Vec<UnitDep>> {
    553    let ret =
    554        match_artifacts_kind_with_targets(dep, artifact_pkg.targets(), parent.pkg.name().as_str())?
    555            .into_iter()
    556            .flat_map(|(artifact_kind, target)| {
    557                // We split target libraries into individual units, even though rustc is able
    558                // to produce multiple kinds in a single invocation for the sole reason that
    559                // each artifact kind has its own output directory, something we can't easily
    560                // teach rustc for now.
    561                match target.kind() {
    562                    TargetKind::Lib(kinds) => Box::new(
    563                        kinds
    564                            .iter()
    565                            .filter(move |tk| match (tk, artifact_kind) {
    566                                (CrateType::Cdylib, ArtifactKind::Cdylib) => true,
    567                                (CrateType::Staticlib, ArtifactKind::Staticlib) => true,
    568                                _ => false,
    569                            })
    570                            .map(|target_kind| {
    571                                new_unit_dep(
    572                                    state,
    573                                    parent,
    574                                    artifact_pkg,
    575                                    target
    576                                        .clone()
    577                                        .set_kind(TargetKind::Lib(vec![target_kind.clone()])),
    578                                    parent_unit_for,
    579                                    compile_kind,
    580                                    CompileMode::Build,
    581                                    dep.artifact(),
    582                                )
    583                            }),
    584                    ) as Box<dyn Iterator<Item = _>>,
    585                    _ => Box::new(std::iter::once(new_unit_dep(
    586                        state,
    587                        parent,
    588                        artifact_pkg,
    589                        target,
    590                        parent_unit_for,
    591                        compile_kind,
    592                        CompileMode::Build,
    593                        dep.artifact(),
    594                    ))),
    595                }
    596            })
    597            .collect::<Result<Vec<_>, _>>()?;
    598    Ok(ret)
    599}
    600
    601/// Returns the dependencies necessary to document a package.
    602fn compute_deps_doc(
    603    unit: &Unit,
    604    state: &mut State<'_, '_>,
    605    unit_for: UnitFor,
    606) -> CargoResult<Vec<UnitDep>> {
    607    // To document a library, we depend on dependencies actually being
    608    // built. If we're documenting *all* libraries, then we also depend on
    609    // the documentation of the library being built.
    610    let mut ret = Vec::new();
    611    for (id, deps) in state.deps(unit, unit_for) {
    612        let Some(dep_lib) = calc_artifact_deps(unit, unit_for, id, &deps, state, &mut ret)? else {
    613            continue;
    614        };
    615        let dep_pkg = state.get(id);
    616        // Rustdoc only needs rmeta files for regular dependencies.
    617        // However, for plugins/proc macros, deps should be built like normal.
    618        let mode = check_or_build_mode(unit.mode, dep_lib);
    619        let dep_unit_for = unit_for.with_dependency(unit, dep_lib, unit_for.root_compile_kind());
    620        let lib_unit_dep = new_unit_dep(
    621            state,
    622            unit,
    623            dep_pkg,
    624            dep_lib,
    625            dep_unit_for,
    626            unit.kind.for_target(dep_lib),
    627            mode,
    628            IS_NO_ARTIFACT_DEP,
    629        )?;
    630        ret.push(lib_unit_dep);
    631        if dep_lib.documented() && state.intent.wants_deps_docs() {
    632            // Document this lib as well.
    633            let doc_unit_dep = new_unit_dep(
    634                state,
    635                unit,
    636                dep_pkg,
    637                dep_lib,
    638                dep_unit_for,
    639                unit.kind.for_target(dep_lib),
    640                unit.mode,
    641                IS_NO_ARTIFACT_DEP,
    642            )?;
    643            ret.push(doc_unit_dep);
    644        }
    645    }
    646
    647    // Be sure to build/run the build script for documented libraries.
    648    ret.extend(dep_build_script(unit, unit_for, state)?);
    649
    650    // If we document a binary/example, we need the library available.
    651    if unit.target.is_bin() || unit.target.is_example() {
    652        // build the lib
    653        ret.extend(maybe_lib(unit, state, unit_for)?);
    654        // and also the lib docs for intra-doc links
    655        if let Some(lib) = unit
    656            .pkg
    657            .targets()
    658            .iter()
    659            .find(|t| t.is_linkable() && t.documented())
    660        {
    661            let dep_unit_for = unit_for.with_dependency(unit, lib, unit_for.root_compile_kind());
    662            let lib_doc_unit = new_unit_dep(
    663                state,
    664                unit,
    665                &unit.pkg,
    666                lib,
    667                dep_unit_for,
    668                unit.kind.for_target(lib),
    669                unit.mode,
    670                IS_NO_ARTIFACT_DEP,
    671            )?;
    672            ret.push(lib_doc_unit);
    673        }
    674    }
    675
    676    // Add all units being scraped for examples as a dependency of top-level Doc units.
    677    if state.ws.unit_needs_doc_scrape(unit) {
    678        for scrape_unit in state.scrape_units.iter() {
    679            let scrape_unit_for = UnitFor::new_normal(scrape_unit.kind);
    680            deps_of(scrape_unit, state, scrape_unit_for)?;
    681            ret.push(new_unit_dep(
    682                state,
    683                scrape_unit,
    684                &scrape_unit.pkg,
    685                &scrape_unit.target,
    686                scrape_unit_for,
    687                scrape_unit.kind,
    688                scrape_unit.mode,
    689                IS_NO_ARTIFACT_DEP,
    690            )?);
    691        }
    692    }
    693
    694    Ok(ret)
    695}
    696
    697fn maybe_lib(
    698    unit: &Unit,
    699    state: &mut State<'_, '_>,
    700    unit_for: UnitFor,
    701) -> CargoResult<Option<UnitDep>> {
    702    unit.pkg
    703        .targets()
    704        .iter()
    705        .find(|t| t.is_linkable())
    706        .map(|t| {
    707            let mode = check_or_build_mode(unit.mode, t);
    708            let dep_unit_for = unit_for.with_dependency(unit, t, unit_for.root_compile_kind());
    709            new_unit_dep(
    710                state,
    711                unit,
    712                &unit.pkg,
    713                t,
    714                dep_unit_for,
    715                unit.kind.for_target(t),
    716                mode,
    717                IS_NO_ARTIFACT_DEP,
    718            )
    719        })
    720        .transpose()
    721}
    722
    723/// If a build script is scheduled to be run for the package specified by
    724/// `unit`, this function will return the unit to run that build script.
    725///
    726/// Overriding a build script simply means that the running of the build
    727/// script itself doesn't have any dependencies, so even in that case a unit
    728/// of work is still returned. `None` is only returned if the package has no
    729/// build script.
    730fn dep_build_script(
    731    unit: &Unit,
    732    unit_for: UnitFor,
    733    state: &State<'_, '_>,
    734) -> CargoResult<Option<UnitDep>> {
    735    unit.pkg
    736        .targets()
    737        .iter()
    738        .find(|t| t.is_custom_build())
    739        .map(|t| {
    740            // The profile stored in the Unit is the profile for the thing
    741            // the custom build script is running for.
    742            let profile = state.profiles.get_profile_run_custom_build(&unit.profile);
    743            // UnitFor::for_custom_build is used because we want the `host` flag set
    744            // for all of our build dependencies (so they all get
    745            // build-override profiles), including compiling the build.rs
    746            // script itself.
    747            //
    748            // If `is_for_host_features` here is `false`, that means we are a
    749            // build.rs script for a normal dependency and we want to set the
    750            // CARGO_FEATURE_* environment variables to the features as a
    751            // normal dep.
    752            //
    753            // If `is_for_host_features` here is `true`, that means that this
    754            // package is being used as a build dependency or proc-macro, and
    755            // so we only want to set CARGO_FEATURE_* variables for the host
    756            // side of the graph.
    757            //
    758            // Keep in mind that the RunCustomBuild unit and the Compile
    759            // build.rs unit use the same features. This is because some
    760            // people use `cfg!` and `#[cfg]` expressions to check for enabled
    761            // features instead of just checking `CARGO_FEATURE_*` at runtime.
    762            // In the case with the new feature resolver (decoupled host
    763            // deps), and a shared dependency has different features enabled
    764            // for normal vs. build, then the build.rs script will get
    765            // compiled twice. I believe it is not feasible to only build it
    766            // once because it would break a large number of scripts (they
    767            // would think they have the wrong set of features enabled).
    768            let script_unit_for = unit_for.for_custom_build();
    769            new_unit_dep_with_profile(
    770                state,
    771                unit,
    772                &unit.pkg,
    773                t,
    774                script_unit_for,
    775                unit.kind,
    776                CompileMode::RunCustomBuild,
    777                profile,
    778                IS_NO_ARTIFACT_DEP,
    779            )
    780        })
    781        .transpose()
    782}
    783
    784/// Choose the correct mode for dependencies.
    785fn check_or_build_mode(mode: CompileMode, target: &Target) -> CompileMode {
    786    match mode {
    787        CompileMode::Check { .. } | CompileMode::Doc { .. } | CompileMode::Docscrape => {
    788            if target.for_host() {
    789                // Plugin and proc macro targets should be compiled like
    790                // normal.
    791                CompileMode::Build
    792            } else {
    793                // Regular dependencies should not be checked with --test.
    794                // Regular dependencies of doc targets should emit rmeta only.
    795                CompileMode::Check { test: false }
    796            }
    797        }
    798        _ => CompileMode::Build,
    799    }
    800}
    801
    802/// Create a new Unit for a dependency from `parent` to `pkg` and `target`.
    803fn new_unit_dep(
    804    state: &State<'_, '_>,
    805    parent: &Unit,
    806    pkg: &Package,
    807    target: &Target,
    808    unit_for: UnitFor,
    809    kind: CompileKind,
    810    mode: CompileMode,
    811    artifact: Option<&Artifact>,
    812) -> CargoResult<UnitDep> {
    813    let is_local = pkg.package_id().source_id().is_path() && !state.is_std;
    814    let profile = state.profiles.get_profile(
    815        pkg.package_id(),
    816        state.ws.is_member(pkg),
    817        is_local,
    818        unit_for,
    819        kind,
    820    );
    821    new_unit_dep_with_profile(
    822        state, parent, pkg, target, unit_for, kind, mode, profile, artifact,
    823    )
    824}
    825
    826fn new_unit_dep_with_profile(
    827    state: &State<'_, '_>,
    828    parent: &Unit,
    829    pkg: &Package,
    830    target: &Target,
    831    unit_for: UnitFor,
    832    kind: CompileKind,
    833    mode: CompileMode,
    834    profile: Profile,
    835    artifact: Option<&Artifact>,
    836) -> CargoResult<UnitDep> {
    837    let (extern_crate_name, dep_name) = state.resolve().extern_crate_name_and_dep_name(
    838        parent.pkg.package_id(),
    839        pkg.package_id(),
    840        target,
    841    )?;
    842    let public = state
    843        .resolve()
    844        .is_public_dep(parent.pkg.package_id(), pkg.package_id());
    845    let features_for = unit_for.map_to_features_for(artifact);
    846    let artifact_target = match features_for {
    847        FeaturesFor::ArtifactDep(target) => Some(target),
    848        _ => None,
    849    };
    850    let features = state.activated_features(pkg.package_id(), features_for);
    851    let unit = state.interner.intern(
    852        pkg,
    853        target,
    854        profile,
    855        kind,
    856        mode,
    857        features,
    858        state.target_data.info(kind).rustflags.clone(),
    859        state.target_data.info(kind).rustdocflags.clone(),
    860        state
    861            .target_data
    862            .target_config(kind)
    863            .links_overrides
    864            .clone(),
    865        state.is_std,
    866        /*dep_hash*/ 0,
    867        artifact.map_or(IsArtifact::No, |_| IsArtifact::Yes),
    868        artifact_target,
    869        false,
    870    );
    871    Ok(UnitDep {
    872        unit,
    873        unit_for,
    874        extern_crate_name,
    875        dep_name,
    876        public,
    877        noprelude: false,
    878    })
    879}
    880
    881/// Fill in missing dependencies for units of the `RunCustomBuild`
    882///
    883/// As mentioned above in `compute_deps_custom_build` each build script
    884/// execution has two dependencies. The first is compiling the build script
    885/// itself (already added) and the second is that all crates the package of the
    886/// build script depends on with `links` keys, their build script execution. (a
    887/// bit confusing eh?)
    888///
    889/// Here we take the entire `deps` map and add more dependencies from execution
    890/// of one build script to execution of another build script.
    891fn connect_run_custom_build_deps(state: &mut State<'_, '_>) {
    892    let mut new_deps = Vec::new();
    893
    894    {
    895        let state = &*state;
    896        // First up build a reverse dependency map. This is a mapping of all
    897        // `RunCustomBuild` known steps to the unit which depends on them. For
    898        // example a library might depend on a build script, so this map will
    899        // have the build script as the key and the library would be in the
    900        // value's set.
    901        let mut reverse_deps_map = HashMap::new();
    902        for (unit, deps) in state.unit_dependencies.iter() {
    903            for dep in deps {
    904                if dep.unit.mode == CompileMode::RunCustomBuild {
    905                    reverse_deps_map
    906                        .entry(dep.unit.clone())
    907                        .or_insert_with(HashSet::new)
    908                        .insert(unit);
    909                }
    910            }
    911        }
    912
    913        // Next, we take a look at all build scripts executions listed in the
    914        // dependency map. Our job here is to take everything that depends on
    915        // this build script (from our reverse map above) and look at the other
    916        // package dependencies of these parents.
    917        //
    918        // If we depend on a linkable target and the build script mentions
    919        // `links`, then we depend on that package's build script! Here we use
    920        // `dep_build_script` to manufacture an appropriate build script unit to
    921        // depend on.
    922        for unit in state
    923            .unit_dependencies
    924            .keys()
    925            .filter(|k| k.mode == CompileMode::RunCustomBuild)
    926        {
    927            // This list of dependencies all depend on `unit`, an execution of
    928            // the build script.
    929            let Some(reverse_deps) = reverse_deps_map.get(unit) else {
    930                continue;
    931            };
    932
    933            let to_add = reverse_deps
    934                .iter()
    935                // Get all sibling dependencies of `unit`
    936                .flat_map(|reverse_dep| {
    937                    state.unit_dependencies[reverse_dep]
    938                        .iter()
    939                        .map(move |a| (reverse_dep, a))
    940                })
    941                // Only deps with `links`.
    942                .filter(|(_parent, other)| {
    943                    other.unit.pkg != unit.pkg
    944                        && other.unit.target.is_linkable()
    945                        && other.unit.pkg.manifest().links().is_some()
    946                })
    947                // Avoid cycles when using the doc --scrape-examples feature:
    948                // Say a workspace has crates A and B where A has a build-dependency on B.
    949                // The Doc units for A and B will have a dependency on the Docscrape for both A and B.
    950                // So this would add a dependency from B-build to A-build, causing a cycle:
    951                //   B (build) -> A (build) -> B(build)
    952                // See the test scrape_examples_avoid_build_script_cycle for a concrete example.
    953                // To avoid this cycle, we filter out the B -> A (docscrape) dependency.
    954                .filter(|(_parent, other)| !other.unit.mode.is_doc_scrape())
    955                // Skip dependencies induced via dev-dependencies since
    956                // connections between `links` and build scripts only happens
    957                // via normal dependencies. Otherwise since dev-dependencies can
    958                // be cyclic we could have cyclic build-script executions.
    959                .filter_map(move |(parent, other)| {
    960                    if state
    961                        .dev_dependency_edges
    962                        .contains(&((*parent).clone(), other.unit.clone()))
    963                    {
    964                        None
    965                    } else {
    966                        Some(other)
    967                    }
    968                })
    969                // Get the RunCustomBuild for other lib.
    970                .filter_map(|other| {
    971                    state.unit_dependencies[&other.unit]
    972                        .iter()
    973                        .find(|other_dep| other_dep.unit.mode == CompileMode::RunCustomBuild)
    974                        .cloned()
    975                })
    976                .collect::<HashSet<_>>();
    977
    978            if !to_add.is_empty() {
    979                // (RunCustomBuild, set(other RunCustomBuild))
    980                new_deps.push((unit.clone(), to_add));
    981            }
    982        }
    983    }
    984
    985    // And finally, add in all the missing dependencies!
    986    for (unit, new_deps) in new_deps {
    987        state
    988            .unit_dependencies
    989            .get_mut(&unit)
    990            .unwrap()
    991            .extend(new_deps);
    992    }
    993}
    994
    995impl<'a, 'gctx> State<'a, 'gctx> {
    996    /// Gets `std_resolve` during building std, otherwise `usr_resolve`.
    997    fn resolve(&self) -> &'a Resolve {
    998        if self.is_std {
    999            self.std_resolve.unwrap()
    1000        } else {
    1001            self.usr_resolve
    1002        }
    1003    }
    1004
    1005    /// Gets `std_features` during building std, otherwise `usr_features`.
    1006    fn features(&self) -> &'a ResolvedFeatures {
    1007        if self.is_std {
    1008            self.std_features.unwrap()
    1009        } else {
    1010            self.usr_features
    1011        }
    1012    }
    1013
    1014    fn activated_features(
    1015        &self,
    1016        pkg_id: PackageId,
    1017        features_for: FeaturesFor,
    1018    ) -> Vec<InternedString> {
    1019        let features = self.features();
    1020        features.activated_features(pkg_id, features_for)
    1021    }
    1022
    1023    fn is_dep_activated(
    1024        &self,
    1025        pkg_id: PackageId,
    1026        features_for: FeaturesFor,
    1027        dep_name: InternedString,
    1028    ) -> bool {
    1029        self.features()
    1030            .is_dep_activated(pkg_id, features_for, dep_name)
    1031    }
    1032
    1033    fn get(&self, id: PackageId) -> &'a Package {
    1034        self.package_set
    1035            .get_one(id)
    1036            .unwrap_or_else(|_| panic!("expected {} to be downloaded", id))
    1037    }
    1038
    1039    /// Returns a filtered set of dependencies for the given unit.
    1040    fn deps(&self, unit: &Unit, unit_for: UnitFor) -> Vec<(PackageId, Vec<&Dependency>)> {
    1041        let pkg_id = unit.pkg.package_id();
    1042        let kind = unit.kind;
    1043        self.resolve()
    1044            .deps(pkg_id)
    1045            .filter_map(|(id, deps)| {
    1046                assert!(!deps.is_empty());
    1047                let deps: Vec<_> = deps
    1048                    .iter()
    1049                    .filter(|dep| {
    1050                        // If this target is a build command, then we only want build
    1051                        // dependencies, otherwise we want everything *other than* build
    1052                        // dependencies.
    1053                        if unit.target.is_custom_build() != dep.is_build() {
    1054                            return false;
    1055                        }
    1056
    1057                        // If this dependency is **not** a transitive dependency, then it
    1058                        // only applies to test/example targets.
    1059                        if !dep.is_transitive()
    1060                            && !unit.target.is_test()
    1061                            && !unit.target.is_example()
    1062                            && !unit.mode.is_any_test()
    1063                        {
    1064                            return false;
    1065                        }
    1066
    1067                        // If this dependency is only available for certain platforms,
    1068                        // make sure we're only enabling it for that platform.
    1069                        if !self.target_data.dep_platform_activated(dep, kind) {
    1070                            return false;
    1071                        }
    1072
    1073                        // If this is an optional dependency, and the new feature resolver
    1074                        // did not enable it, don't include it.
    1075                        if dep.is_optional() {
    1076                            // This `unit_for` is from parent dep and *SHOULD* contains its own
    1077                            // artifact dep information inside `artifact_target_for_features`.
    1078                            // So, no need to map any artifact info from an incorrect `dep.artifact()`.
    1079                            let features_for = unit_for.map_to_features_for(IS_NO_ARTIFACT_DEP);
    1080                            if !self.is_dep_activated(pkg_id, features_for, dep.name_in_toml()) {
    1081                                return false;
    1082                            }
    1083                        }
    1084
    1085                        // If we've gotten past all that, then this dependency is
    1086                        // actually used!
    1087                        true
    1088                    })
    1089                    .collect();
    1090                if deps.is_empty() {
    1091                    None
    1092                } else {
    1093                    Some((id, deps))
    1094                }
    1095            })
    1096            .collect()
    1097    }
    1098}