#
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::UserIntent;
    43use crate::core::compiler::unit_dependencies::build_unit_dependencies;
    44use crate::core::compiler::unit_graph::{self, UnitDep, UnitGraph};
    45use crate::core::compiler::{BuildConfig, BuildContext, BuildRunner, Compilation};
    46use crate::core::compiler::{CompileKind, CompileTarget, RustcTargetData, Unit};
    47use crate::core::compiler::{CrateType, TargetInfo, apply_env_config, standard_lib};
    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::{SpecsAndResolvedFeatures, 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
    63pub(super) mod 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        specs_and_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    let mut units = Vec::new();
    367    let mut unit_graph = HashMap::new();
    368    let mut scrape_units = Vec::new();
    369
    370    for SpecsAndResolvedFeatures {
    371        specs,
    372        resolved_features,
    373    } in &specs_and_features
    374    {
    375        // Passing `build_config.requested_kinds` instead of
    376        // `explicit_host_kinds` here so that `generate_root_units` can do
    377        // its own special handling of `CompileKind::Host`. It will
    378        // internally replace the host kind by the `explicit_host_kind`
    379        // before setting as a unit.
    380        let spec_names = specs.iter().map(|spec| spec.name()).collect::<Vec<_>>();
    381        let packages = to_builds
    382            .iter()
    383            .filter(|package| spec_names.contains(&package.name().as_str()))
    384            .cloned()
    385            .collect::<Vec<_>>();
    386        let generator = UnitGenerator {
    387            ws,
    388            packages: &packages,
    389            spec,
    390            target_data: &target_data,
    391            filter,
    392            requested_kinds: &build_config.requested_kinds,
    393            explicit_host_kind,
    394            intent: build_config.intent,
    395            resolve: &resolve,
    396            workspace_resolve: &workspace_resolve,
    397            resolved_features: &resolved_features,
    398            package_set: &pkg_set,
    399            profiles: &profiles,
    400            interner,
    401            has_dev_units,
    402        };
    403        let mut targeted_root_units = generator.generate_root_units()?;
    404
    405        if let Some(args) = target_rustc_crate_types {
    406            override_rustc_crate_types(&mut targeted_root_units, args, interner)?;
    407        }
    408
    409        let should_scrape =
    410            build_config.intent.is_doc() && gctx.cli_unstable().rustdoc_scrape_examples;
    411        let targeted_scrape_units = if should_scrape {
    412            generator.generate_scrape_units(&targeted_root_units)?
    413        } else {
    414            Vec::new()
    415        };
    416
    417        let std_roots = if let Some(crates) = gctx.cli_unstable().build_std.as_ref() {
    418            let (std_resolve, std_features) = std_resolve_features.as_ref().unwrap();
    419            standard_lib::generate_std_roots(
    420                &crates,
    421                &targeted_root_units,
    422                std_resolve,
    423                std_features,
    424                &explicit_host_kinds,
    425                &pkg_set,
    426                interner,
    427                &profiles,
    428                &target_data,
    429            )?
    430        } else {
    431            Default::default()
    432        };
    433
    434        unit_graph.extend(build_unit_dependencies(
    435            ws,
    436            &pkg_set,
    437            &resolve,
    438            &resolved_features,
    439            std_resolve_features.as_ref(),
    440            &targeted_root_units,
    441            &targeted_scrape_units,
    442            &std_roots,
    443            build_config.intent,
    444            &target_data,
    445            &profiles,
    446            interner,
    447        )?);
    448        units.extend(targeted_root_units);
    449        scrape_units.extend(targeted_scrape_units);
    450    }
    451
    452    // TODO: In theory, Cargo should also dedupe the roots, but I'm uncertain
    453    // what heuristics to use in that case.
    454    if build_config.intent.wants_deps_docs() {
    455        remove_duplicate_doc(build_config, &units, &mut unit_graph);
    456    }
    457
    458    let host_kind_requested = build_config
    459        .requested_kinds
    460        .iter()
    461        .any(CompileKind::is_host);
    462    // Rebuild the unit graph, replacing the explicit host targets with
    463    // CompileKind::Host, removing `artifact_target_for_features` and merging any dependencies
    464    // shared with build and artifact dependencies.
    465    (units, scrape_units, unit_graph) = rebuild_unit_graph_shared(
    466        interner,
    467        unit_graph,
    468        &units,
    469        &scrape_units,
    470        host_kind_requested.then_some(explicit_host_kind),
    471        build_config.compile_time_deps_only,
    472    );
    473
    474    let mut extra_compiler_args = HashMap::new();
    475    if let Some(args) = extra_args {
    476        if units.len() != 1 {
    477            anyhow::bail!(
    478                "extra arguments to `{}` can only be passed to one \
    479                 target, consider filtering\nthe package by passing, \
    480                 e.g., `--lib` or `--bin NAME` to specify a single target",
    481                extra_args_name
    482            );
    483        }
    484        extra_compiler_args.insert(units[0].clone(), args);
    485    }
    486
    487    for unit in units
    488        .iter()
    489        .filter(|unit| unit.mode.is_doc() || unit.mode.is_doc_test())
    490        .filter(|unit| rustdoc_document_private_items || unit.target.is_bin())
    491    {
    492        // Add `--document-private-items` rustdoc flag if requested or if
    493        // the target is a binary. Binary crates get their private items
    494        // documented by default.
    495        let mut args = vec!["--document-private-items".into()];
    496        if unit.target.is_bin() {
    497            // This warning only makes sense if it's possible to document private items
    498            // sometimes and ignore them at other times. But cargo consistently passes
    499            // `--document-private-items`, so the warning isn't useful.
    500            args.push("-Arustdoc::private-intra-doc-links".into());
    501        }
    502        extra_compiler_args
    503            .entry(unit.clone())
    504            .or_default()
    505            .extend(args);
    506    }
    507
    508    if honor_rust_version.unwrap_or(true) {
    509        let rustc_version = target_data.rustc.version.clone().into();
    510
    511        let mut incompatible = Vec::new();
    512        let mut local_incompatible = false;
    513        for unit in unit_graph.keys() {
    514            let Some(pkg_msrv) = unit.pkg.rust_version() else {
    515                continue;
    516            };
    517
    518            if pkg_msrv.is_compatible_with(&rustc_version) {
    519                continue;
    520            }
    521
    522            local_incompatible |= unit.is_local();
    523            incompatible.push((unit, pkg_msrv));
    524        }
    525        if !incompatible.is_empty() {
    526            use std::fmt::Write as _;
    527
    528            let plural = if incompatible.len() == 1 { "" } else { "s" };
    529            let mut message = format!(
    530                "rustc {rustc_version} is not supported by the following package{plural}:\n"
    531            );
    532            incompatible.sort_by_key(|(unit, _)| (unit.pkg.name(), unit.pkg.version()));
    533            for (unit, msrv) in incompatible {
    534                let name = &unit.pkg.name();
    535                let version = &unit.pkg.version();
    536                writeln!(&mut message, "  {name}@{version} requires rustc {msrv}").unwrap();
    537            }
    538            if ws.is_ephemeral() {
    539                if ws.ignore_lock() {
    540                    writeln!(
    541                        &mut message,
    542                        "Try re-running `cargo install` with `--locked`"
    543                    )
    544                    .unwrap();
    545                }
    546            } else if !local_incompatible {
    547                writeln!(
    548                    &mut message,
    549                    "Either upgrade rustc or select compatible dependency versions with
    550`cargo update <name>@<current-ver> --precise <compatible-ver>`
    551where `<compatible-ver>` is the latest version supporting rustc {rustc_version}",
    552                )
    553                .unwrap();
    554            }
    555            return Err(anyhow::Error::msg(message));
    556        }
    557    }
    558
    559    let bcx = BuildContext::new(
    560        ws,
    561        pkg_set,
    562        build_config,
    563        profiles,
    564        extra_compiler_args,
    565        target_data,
    566        units,
    567        unit_graph,
    568        scrape_units,
    569    )?;
    570
    571    Ok(bcx)
    572}
    573
    574/// This is used to rebuild the unit graph, sharing host dependencies if possible,
    575/// and applying other unit adjustments based on the whole graph.
    576///
    577/// This will translate any unit's `CompileKind::Target(host)` to
    578/// `CompileKind::Host` if `to_host` is not `None` and the kind is equal to `to_host`.
    579/// This also handles generating the unit `dep_hash`, and merging shared units if possible.
    580///
    581/// This is necessary because if normal dependencies used `CompileKind::Host`,
    582/// there would be no way to distinguish those units from build-dependency
    583/// units or artifact dependency units.
    584/// This can cause a problem if a shared normal/build/artifact dependency needs
    585/// to link to another dependency whose features differ based on whether or
    586/// not it is a normal, build or artifact dependency. If all units used
    587/// `CompileKind::Host`, then they would end up being identical, causing a
    588/// collision in the `UnitGraph`, and Cargo would end up randomly choosing one
    589/// value or the other.
    590///
    591/// The solution is to keep normal, build and artifact dependencies separate when
    592/// building the unit graph, and then run this second pass which will try to
    593/// combine shared dependencies safely. By adding a hash of the dependencies
    594/// to the `Unit`, this allows the `CompileKind` to be changed back to `Host`
    595/// and `artifact_target_for_features` to be removed without fear of an unwanted
    596/// collision for build or artifact dependencies.
    597///
    598/// This is also responsible for adjusting the `strip` profile option to
    599/// opportunistically strip if debug is 0 for all dependencies. This helps
    600/// remove debuginfo added by the standard library.
    601///
    602/// This is also responsible for adjusting the `debug` setting for host
    603/// dependencies, turning off debug if the user has not explicitly enabled it,
    604/// and the unit is not shared with a target unit.
    605///
    606/// This is also responsible for adjusting whether each unit should be compiled
    607/// or not regarding `--compile-time-deps` flag.
    608fn rebuild_unit_graph_shared(
    609    interner: &UnitInterner,
    610    unit_graph: UnitGraph,
    611    roots: &[Unit],
    612    scrape_units: &[Unit],
    613    to_host: Option<CompileKind>,
    614    compile_time_deps_only: bool,
    615) -> (Vec<Unit>, Vec<Unit>, UnitGraph) {
    616    let mut result = UnitGraph::new();
    617    // Map of the old unit to the new unit, used to avoid recursing into units
    618    // that have already been computed to improve performance.
    619    let mut memo = HashMap::new();
    620    let new_roots = roots
    621        .iter()
    622        .map(|root| {
    623            traverse_and_share(
    624                interner,
    625                &mut memo,
    626                &mut result,
    627                &unit_graph,
    628                root,
    629                true,
    630                false,
    631                to_host,
    632                compile_time_deps_only,
    633            )
    634        })
    635        .collect();
    636    // If no unit in the unit graph ended up having scrape units attached as dependencies,
    637    // then they won't have been discovered in traverse_and_share and hence won't be in
    638    // memo. So we filter out missing scrape units.
    639    let new_scrape_units = scrape_units
    640        .iter()
    641        .map(|unit| memo.get(unit).unwrap().clone())
    642        .collect();
    643    (new_roots, new_scrape_units, result)
    644}
    645
    646/// Recursive function for rebuilding the graph.
    647///
    648/// This walks `unit_graph`, starting at the given `unit`. It inserts the new
    649/// units into `new_graph`, and returns a new updated version of the given
    650/// unit (`dep_hash` is filled in, and `kind` switched if necessary).
    651fn traverse_and_share(
    652    interner: &UnitInterner,
    653    memo: &mut HashMap<Unit, Unit>,
    654    new_graph: &mut UnitGraph,
    655    unit_graph: &UnitGraph,
    656    unit: &Unit,
    657    unit_is_root: bool,
    658    unit_is_for_host: bool,
    659    to_host: Option<CompileKind>,
    660    compile_time_deps_only: bool,
    661) -> Unit {
    662    if let Some(new_unit) = memo.get(unit) {
    663        // Already computed, no need to recompute.
    664        return new_unit.clone();
    665    }
    666    let mut dep_hash = StableHasher::new();
    667    let skip_non_compile_time_deps = compile_time_deps_only
    668        && (!unit.target.is_compile_time_dependency() ||
    669            // Root unit is not a dependency unless other units are dependant
    670            // to it.
    671            unit_is_root);
    672    let new_deps: Vec<_> = unit_graph[unit]
    673        .iter()
    674        .map(|dep| {
    675            let new_dep_unit = traverse_and_share(
    676                interner,
    677                memo,
    678                new_graph,
    679                unit_graph,
    680                &dep.unit,
    681                false,
    682                dep.unit_for.is_for_host(),
    683                to_host,
    684                // If we should compile the current unit, we should also compile
    685                // its dependencies. And if not, we should compile compile time
    686                // dependencies only.
    687                skip_non_compile_time_deps,
    688            );
    689            new_dep_unit.hash(&mut dep_hash);
    690            UnitDep {
    691                unit: new_dep_unit,
    692                ..dep.clone()
    693            }
    694        })
    695        .collect();
    696    // Here, we have recursively traversed this unit's dependencies, and hashed them: we can
    697    // finalize the dep hash.
    698    let new_dep_hash = Hasher::finish(&dep_hash);
    699
    700    // This is the key part of the sharing process: if the unit is a runtime dependency, whose
    701    // target is the same as the host, we canonicalize the compile kind to `CompileKind::Host`.
    702    // A possible host dependency counterpart to this unit would have that kind, and if such a unit
    703    // exists in the current `unit_graph`, they will unify in the new unit graph map `new_graph`.
    704    // The resulting unit graph will be optimized with less units, thanks to sharing these host
    705    // dependencies.
    706    let canonical_kind = match to_host {
    707        Some(to_host) if to_host == unit.kind => CompileKind::Host,
    708        _ => unit.kind,
    709    };
    710
    711    let mut profile = unit.profile.clone();
    712    if profile.strip.is_deferred() {
    713        // If strip was not manually set, and all dependencies of this unit together
    714        // with this unit have debuginfo turned off, we enable debuginfo stripping.
    715        // This will remove pre-existing debug symbols coming from the standard library.
    716        if !profile.debuginfo.is_turned_on()
    717            && new_deps
    718                .iter()
    719                .all(|dep| !dep.unit.profile.debuginfo.is_turned_on())
    720        {
    721            profile.strip = profile.strip.strip_debuginfo();
    722        }
    723    }
    724
    725    // If this is a build dependency, and it's not shared with runtime dependencies, we can weaken
    726    // its debuginfo level to optimize build times. We do nothing if it's an artifact dependency,
    727    // as it and its debuginfo may end up embedded in the main program.
    728    if unit_is_for_host
    729        && to_host.is_some()
    730        && profile.debuginfo.is_deferred()
    731        && !unit.artifact.is_true()
    732    {
    733        // We create a "probe" test to see if a unit with the same explicit debuginfo level exists
    734        // in the graph. This is the level we'd expect if it was set manually or the default value
    735        // set by a profile for a runtime dependency: its canonical value.
    736        let canonical_debuginfo = profile.debuginfo.finalize();
    737        let mut canonical_profile = profile.clone();
    738        canonical_profile.debuginfo = canonical_debuginfo;
    739        let unit_probe = interner.intern(
    740            &unit.pkg,
    741            &unit.target,
    742            canonical_profile,
    743            to_host.unwrap(),
    744            unit.mode,
    745            unit.features.clone(),
    746            unit.rustflags.clone(),
    747            unit.rustdocflags.clone(),
    748            unit.links_overrides.clone(),
    749            unit.is_std,
    750            unit.dep_hash,
    751            unit.artifact,
    752            unit.artifact_target_for_features,
    753            unit.skip_non_compile_time_dep,
    754        );
    755
    756        // We can now turn the deferred value into its actual final value.
    757        profile.debuginfo = if unit_graph.contains_key(&unit_probe) {
    758            // The unit is present in both build time and runtime subgraphs: we canonicalize its
    759            // level to the other unit's, thus ensuring reuse between the two to optimize build times.
    760            canonical_debuginfo
    761        } else {
    762            // The unit is only present in the build time subgraph, we can weaken its debuginfo
    763            // level to optimize build times.
    764            canonical_debuginfo.weaken()
    765        }
    766    }
    767
    768    let new_unit = interner.intern(
    769        &unit.pkg,
    770        &unit.target,
    771        profile,
    772        canonical_kind,
    773        unit.mode,
    774        unit.features.clone(),
    775        unit.rustflags.clone(),
    776        unit.rustdocflags.clone(),
    777        unit.links_overrides.clone(),
    778        unit.is_std,
    779        new_dep_hash,
    780        unit.artifact,
    781        // Since `dep_hash` is now filled in, there's no need to specify the artifact target
    782        // for target-dependent feature resolution
    783        None,
    784        skip_non_compile_time_deps,
    785    );
    786    if !unit_is_root || !compile_time_deps_only {
    787        assert!(memo.insert(unit.clone(), new_unit.clone()).is_none());
    788    }
    789    new_graph.entry(new_unit.clone()).or_insert(new_deps);
    790    new_unit
    791}
    792
    793/// Removes duplicate `CompileMode::Doc` units that would cause problems with
    794/// filename collisions.
    795///
    796/// Rustdoc only separates units by crate name in the file directory
    797/// structure. If any two units with the same crate name exist, this would
    798/// cause a filename collision, causing different rustdoc invocations to stomp
    799/// on one another's files.
    800///
    801/// Unfortunately this does not remove all duplicates, as some of them are
    802/// either user error, or difficult to remove. Cases that I can think of:
    803///
    804/// - Same target name in different packages. See the `collision_doc` test.
    805/// - Different sources. See `collision_doc_sources` test.
    806///
    807/// Ideally this would not be necessary.
    808fn remove_duplicate_doc(
    809    build_config: &BuildConfig,
    810    root_units: &[Unit],
    811    unit_graph: &mut UnitGraph,
    812) {
    813    // First, create a mapping of crate_name -> Unit so we can see where the
    814    // duplicates are.
    815    let mut all_docs: HashMap<String, Vec<Unit>> = HashMap::new();
    816    for unit in unit_graph.keys() {
    817        if unit.mode.is_doc() {
    818            all_docs
    819                .entry(unit.target.crate_name())
    820                .or_default()
    821                .push(unit.clone());
    822        }
    823    }
    824    // Keep track of units to remove so that they can be efficiently removed
    825    // from the unit_deps.
    826    let mut removed_units: HashSet<Unit> = HashSet::new();
    827    let mut remove = |units: Vec<Unit>, reason: &str, cb: &dyn Fn(&Unit) -> bool| -> Vec<Unit> {
    828        let (to_remove, remaining_units): (Vec<Unit>, Vec<Unit>) = units
    829            .into_iter()
    830            .partition(|unit| cb(unit) && !root_units.contains(unit));
    831        for unit in to_remove {
    832            tracing::debug!(
    833                "removing duplicate doc due to {} for package {} target `{}`",
    834                reason,
    835                unit.pkg,
    836                unit.target.name()
    837            );
    838            unit_graph.remove(&unit);
    839            removed_units.insert(unit);
    840        }
    841        remaining_units
    842    };
    843    // Iterate over the duplicates and try to remove them from unit_graph.
    844    for (_crate_name, mut units) in all_docs {
    845        if units.len() == 1 {
    846            continue;
    847        }
    848        // Prefer target over host if --target was not specified.
    849        if build_config
    850            .requested_kinds
    851            .iter()
    852            .all(CompileKind::is_host)
    853        {
    854            // Note these duplicates may not be real duplicates, since they
    855            // might get merged in rebuild_unit_graph_shared. Either way, it
    856            // shouldn't hurt to remove them early (although the report in the
    857            // log might be confusing).
    858            units = remove(units, "host/target merger", &|unit| unit.kind.is_host());
    859            if units.len() == 1 {
    860                continue;
    861            }
    862        }
    863        // Prefer newer versions over older.
    864        let mut source_map: HashMap<(InternedString, SourceId, CompileKind), Vec<Unit>> =
    865            HashMap::new();
    866        for unit in units {
    867            let pkg_id = unit.pkg.package_id();
    868            // Note, this does not detect duplicates from different sources.
    869            source_map
    870                .entry((pkg_id.name(), pkg_id.source_id(), unit.kind))
    871                .or_default()
    872                .push(unit);
    873        }
    874        let mut remaining_units = Vec::new();
    875        for (_key, mut units) in source_map {
    876            if units.len() > 1 {
    877                units.sort_by(|a, b| a.pkg.version().partial_cmp(b.pkg.version()).unwrap());
    878                // Remove any entries with version < newest.
    879                let newest_version = units.last().unwrap().pkg.version().clone();
    880                let keep_units = remove(units, "older version", &|unit| {
    881                    unit.pkg.version() < &newest_version
    882                });
    883                remaining_units.extend(keep_units);
    884            } else {
    885                remaining_units.extend(units);
    886            }
    887        }
    888        if remaining_units.len() == 1 {
    889            continue;
    890        }
    891        // Are there other heuristics to remove duplicates that would make
    892        // sense? Maybe prefer path sources over all others?
    893    }
    894    // Also remove units from the unit_deps so there aren't any dangling edges.
    895    for unit_deps in unit_graph.values_mut() {
    896        unit_deps.retain(|unit_dep| !removed_units.contains(&unit_dep.unit));
    897    }
    898    // Remove any orphan units that were detached from the graph.
    899    let mut visited = HashSet::new();
    900    fn visit(unit: &Unit, graph: &UnitGraph, visited: &mut HashSet<Unit>) {
    901        if !visited.insert(unit.clone()) {
    902            return;
    903        }
    904        for dep in &graph[unit] {
    905            visit(&dep.unit, graph, visited);
    906        }
    907    }
    908    for unit in root_units {
    909        visit(unit, unit_graph, &mut visited);
    910    }
    911    unit_graph.retain(|unit, _| visited.contains(unit));
    912}
    913
    914/// Override crate types for given units.
    915///
    916/// This is primarily used by `cargo rustc --crate-type`.
    917fn override_rustc_crate_types(
    918    units: &mut [Unit],
    919    args: &[String],
    920    interner: &UnitInterner,
    921) -> CargoResult<()> {
    922    if units.len() != 1 {
    923        anyhow::bail!(
    924            "crate types to rustc can only be passed to one \
    925            target, consider filtering\nthe package by passing, \
    926            e.g., `--lib` or `--example` to specify a single target"
    927        );
    928    }
    929
    930    let unit = &units[0];
    931    let override_unit = |f: fn(Vec<CrateType>) -> TargetKind| {
    932        let crate_types = args.iter().map(|s| s.into()).collect();
    933        let mut target = unit.target.clone();
    934        target.set_kind(f(crate_types));
    935        interner.intern(
    936            &unit.pkg,
    937            &target,
    938            unit.profile.clone(),
    939            unit.kind,
    940            unit.mode,
    941            unit.features.clone(),
    942            unit.rustflags.clone(),
    943            unit.rustdocflags.clone(),
    944            unit.links_overrides.clone(),
    945            unit.is_std,
    946            unit.dep_hash,
    947            unit.artifact,
    948            unit.artifact_target_for_features,
    949            unit.skip_non_compile_time_dep,
    950        )
    951    };
    952    units[0] = match unit.target.kind() {
    953        TargetKind::Lib(_) => override_unit(TargetKind::Lib),
    954        TargetKind::ExampleLib(_) => override_unit(TargetKind::ExampleLib),
    955        _ => {
    956            anyhow::bail!(
    957                "crate types can only be specified for libraries and example libraries.\n\
    958                Binaries, tests, and benchmarks are always the `bin` crate type"
    959            );
    960        }
    961    };
    962
    963    Ok(())
    964}
    965
    966/// Gets all of the features enabled for a package, plus its dependencies'
    967/// features.
    968///
    969/// Dependencies are added as `dep_name/feat_name` because `required-features`
    970/// wants to support that syntax.
    971pub fn resolve_all_features(
    972    resolve_with_overrides: &Resolve,
    973    resolved_features: &features::ResolvedFeatures,
    974    package_set: &PackageSet<'_>,
    975    package_id: PackageId,
    976) -> HashSet<String> {
    977    let mut features: HashSet<String> = resolved_features
    978        .activated_features(package_id, FeaturesFor::NormalOrDev)
    979        .iter()
    980        .map(|s| s.to_string())
    981        .collect();
    982
    983    // Include features enabled for use by dependencies so targets can also use them with the
    984    // required-features field when deciding whether to be built or skipped.
    985    for (dep_id, deps) in resolve_with_overrides.deps(package_id) {
    986        let is_proc_macro = package_set
    987            .get_one(dep_id)
    988            .expect("packages downloaded")
    989            .proc_macro();
    990        for dep in deps {
    991            let features_for = FeaturesFor::from_for_host(is_proc_macro || dep.is_build());
    992            for feature in resolved_features
    993                .activated_features_unverified(dep_id, features_for)
    994                .unwrap_or_default()
    995            {
    996                features.insert(format!("{}/{}", dep.name_in_toml(), feature));
    997            }
    998        }
    999    }
    1000
    1001    features
    1002}