src/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
  18 use crate::core::compiler::Unit;
  19 use crate::core::compiler::{BuildContext, CompileMode, Kind};
  20 use crate::core::dependency::Kind as DepKind;
  21 use crate::core::package::Downloads;
  22 use crate::core::profiles::{Profile, UnitFor};
  23 use crate::core::resolver::Resolve;
  24 use crate::core::{InternedString, Package, PackageId, Target};
  25 use crate::CargoResult;
  26 use log::trace;
  27 use std::collections::{HashMap, HashSet};
  28
  29 /// The dependency graph of Units.
  30 pub type UnitGraph<'a> = HashMap<Unit<'a>, Vec<UnitDep<'a>>>;
  31
  32 /// A unit dependency.
  33 #[derive(Debug, Clone, Hash, Eq, PartialEq, PartialOrd, Ord)]
  34 pub struct UnitDep<'a> {
  35     /// The dependency unit.
  36     pub unit: Unit<'a>,
  37     /// The purpose of this dependency (a dependency for a test, or a build
  38     /// script, etc.).
  39     pub unit_for: UnitFor,
  40     /// The name the parent uses to refer to this dependency.
  41     pub extern_crate_name: InternedString,
  42     /// Whether or not this is a public dependency.
  43     pub public: bool,
  44 }
  45
  46 /// Collection of stuff used while creating the `UnitGraph`.
  47 struct State<'a, 'cfg> {
  48     bcx: &'a BuildContext<'a, 'cfg>,
  49     waiting_on_download: HashSet<PackageId>,
  50     downloads: Downloads<'a, 'cfg>,
  51     unit_dependencies: UnitGraph<'a>,
  52     package_cache: HashMap<PackageId, &'a Package>,
  53     usr_resolve: &'a Resolve,
  54     std_resolve: Option<&'a Resolve>,
  55     /// This flag is `true` while generating the dependencies for the standard
  56     /// library.
  57     is_std: bool,
  58 }
  59
  60 pub fn build_unit_dependencies<'a, 'cfg>(
  61     bcx: &'a BuildContext<'a, 'cfg>,
  62     resolve: &'a Resolve,
  63     std_resolve: Option<&'a Resolve>,
  64     roots: &[Unit<'a>],
  65     std_roots: &[Unit<'a>],
  66 ) -> CargoResult<UnitGraph<'a>> {
  67     let mut state = State {
  68         bcx,
  69         downloads: bcx.packages.enable_download()?,
  70         waiting_on_download: HashSet::new(),
  71         unit_dependencies: HashMap::new(),
  72         package_cache: HashMap::new(),
  73         usr_resolve: resolve,
  74         std_resolve,
  75         is_std: false,
  76     };
  77
  78     let std_unit_deps = calc_deps_of_std(&mut state, std_roots)?;
  79
  80     deps_of_roots(roots, &mut state)?;
  81     super::links::validate_links(state.resolve(), &state.unit_dependencies)?;
  82     // Hopefully there aren't any links conflicts with the standard library?
  83
  84     if let Some(std_unit_deps) = std_unit_deps {
  85         attach_std_deps(&mut state, std_roots, std_unit_deps);
  86     }
  87
  88     connect_run_custom_build_deps(&mut state.unit_dependencies);
  89
  90     // Dependencies are used in tons of places throughout the backend, many of
  91     // which affect the determinism of the build itself. As a result be sure
  92     // that dependency lists are always sorted to ensure we've always got a
  93     // deterministic output.
  94     for list in state.unit_dependencies.values_mut() {
  95         list.sort();
  96     }
  97     trace!("ALL UNIT DEPENDENCIES {:#?}", state.unit_dependencies);
  98
  99     Ok(state.unit_dependencies)
 100 }
 101
 102 /// Compute all the dependencies for the standard library.
 103 fn calc_deps_of_std<'a, 'cfg>(
 104     mut state: &mut State<'a, 'cfg>,
 105     std_roots: &[Unit<'a>],
 106 ) -> CargoResult<Option<UnitGraph<'a>>> {
 107     if std_roots.is_empty() {
 108         return Ok(None);
 109     }
 110     // Compute dependencies for the standard library.
 111     state.is_std = true;
 112     deps_of_roots(std_roots, &mut state)?;
 113     state.is_std = false;
 114     Ok(Some(std::mem::replace(
 115         &mut state.unit_dependencies,
 116         HashMap::new(),
 117     )))
 118 }
 119
 120 /// Add the standard library units to the `unit_dependencies`.
 121 fn attach_std_deps<'a, 'cfg>(
 122     state: &mut State<'a, 'cfg>,
 123     std_roots: &[Unit<'a>],
 124     std_unit_deps: UnitGraph<'a>,
 125 ) {
 126     // Attach the standard library as a dependency of every target unit.
 127     for (unit, deps) in state.unit_dependencies.iter_mut() {
 128         if unit.kind == Kind::Target && !unit.mode.is_run_custom_build() {
 129             deps.extend(std_roots.iter().map(|unit| UnitDep {
 130                 unit: *unit,
 131                 unit_for: UnitFor::new_normal(),
 132                 extern_crate_name: unit.pkg.name(),
 133                 // TODO: Does this `public` make sense?
 134                 public: true,
 135             }));
 136         }
 137     }
 138     // And also include the dependencies of the standard library itself.
 139     for (unit, deps) in std_unit_deps.into_iter() {
 140         if let Some(other_unit) = state.unit_dependencies.insert(unit, deps) {
 141             panic!("std unit collision with existing unit: {:?}", other_unit);
 142         }
 143     }
 144 }
 145
 146 /// Compute all the dependencies of the given root units.
 147 /// The result is stored in state.unit_dependencies.
 148 fn deps_of_roots<'a, 'cfg>(roots: &[Unit<'a>], mut state: &mut State<'a, 'cfg>) -> CargoResult<()> {
 149     // Loop because we are downloading while building the dependency graph.
 150     // The partially-built unit graph is discarded through each pass of the
 151     // loop because it is incomplete because not all required Packages have
 152     // been downloaded.
 153     loop {
 154         for unit in roots.iter() {
 155             state.get(unit.pkg.package_id())?;
 156
 157             // Dependencies of tests/benches should not have `panic` set.
 158             // We check the global test mode to see if we are running in `cargo
 159             // test` in which case we ensure all dependencies have `panic`
 160             // cleared, and avoid building the lib thrice (once with `panic`, once
 161             // without, once for `--test`). In particular, the lib included for
 162             // Doc tests and examples are `Build` mode here.
 163             let unit_for = if unit.mode.is_any_test() || state.bcx.build_config.test() {
 164                 UnitFor::new_test()
 165             } else if unit.target.is_custom_build() {
 166                 // This normally doesn't happen, except `clean` aggressively
 167                 // generates all units.
 168                 UnitFor::new_build()
 169             } else if unit.target.for_host() {
 170                 // Proc macro / plugin should never have panic set.
 171                 UnitFor::new_compiler()
 172             } else {
 173                 UnitFor::new_normal()
 174             };
 175             deps_of(unit, &mut state, unit_for)?;
 176         }
 177
 178         if !state.waiting_on_download.is_empty() {
 179             state.finish_some_downloads()?;
 180             state.unit_dependencies.clear();
 181         } else {
 182             break;
 183         }
 184     }
 185     Ok(())
 186 }
 187
 188 /// Compute the dependencies of a single unit.
 189 fn deps_of<'a, 'cfg>(
 190     unit: &Unit<'a>,
 191     state: &mut State<'a, 'cfg>,
 192     unit_for: UnitFor,
 193 ) -> CargoResult<()> {
 194     // Currently the `unit_dependencies` map does not include `unit_for`. This should
 195     // be safe for now. `TestDependency` only exists to clear the `panic`
 196     // flag, and you'll never ask for a `unit` with `panic` set as a
 197     // `TestDependency`. `CustomBuild` should also be fine since if the
 198     // requested unit's settings are the same as `Any`, `CustomBuild` can't
 199     // affect anything else in the hierarchy.
 200     if !state.unit_dependencies.contains_key(unit) {
 201         let unit_deps = compute_deps(unit, state, unit_for)?;
 202         state.unit_dependencies.insert(*unit, unit_deps.clone());
 203         for unit_dep in unit_deps {
 204             deps_of(&unit_dep.unit, state, unit_dep.unit_for)?;
 205         }
 206     }
 207     Ok(())
 208 }
 209
 210 /// For a package, returns all targets that are registered as dependencies
 211 /// for that package.
 212 /// This returns a `Vec` of `(Unit, UnitFor)` pairs. The `UnitFor`
 213 /// is the profile type that should be used for dependencies of the unit.
 214 fn compute_deps<'a, 'cfg>(
 215     unit: &Unit<'a>,
 216     state: &mut State<'a, 'cfg>,
 217     unit_for: UnitFor,
 218 ) -> CargoResult<Vec<UnitDep<'a>>> {
 219     if unit.mode.is_run_custom_build() {
 220         return compute_deps_custom_build(unit, state);
 221     } else if unit.mode.is_doc() {
 222         // Note: this does not include doc test.
 223         return compute_deps_doc(unit, state);
 224     }
 225
 226     let bcx = state.bcx;
 227     let id = unit.pkg.package_id();
 228     let deps = state.resolve().deps(id).filter(|&(_id, deps)| {
 229         assert!(!deps.is_empty());
 230         deps.iter().any(|dep| {
 231             // If this target is a build command, then we only want build
 232             // dependencies, otherwise we want everything *other than* build
 233             // dependencies.
 234             if unit.target.is_custom_build() != dep.is_build() {
 235                 return false;
 236             }
 237
 238             // If this dependency is **not** a transitive dependency, then it
 239             // only applies to test/example targets.
 240             if !dep.is_transitive()
 241                 && !unit.target.is_test()
 242                 && !unit.target.is_example()
 243                 && !unit.mode.is_any_test()
 244             {
 245                 return false;
 246             }
 247
 248             // If this dependency is only available for certain platforms,
 249             // make sure we're only enabling it for that platform.
 250             if !bcx.dep_platform_activated(dep, unit.kind) {
 251                 return false;
 252             }
 253
 254             // If we've gotten past all that, then this dependency is
 255             // actually used!
 256             true
 257         })
 258     });
 259
 260     let mut ret = Vec::new();
 261     for (id, _) in deps {
 262         let pkg = match state.get(id)? {
 263             Some(pkg) => pkg,
 264             None => continue,
 265         };
 266         let lib = match pkg.targets().iter().find(|t| t.is_lib()) {
 267             Some(t) => t,
 268             None => continue,
 269         };
 270         let mode = check_or_build_mode(unit.mode, lib);
 271         let dep_unit_for = unit_for.with_for_host(lib.for_host());
 272
 273         if bcx.config.cli_unstable().dual_proc_macros
 274             && lib.proc_macro()
 275             && unit.kind == Kind::Target
 276         {
 277             let unit_dep = new_unit_dep(state, unit, pkg, lib, dep_unit_for, Kind::Target, mode)?;
 278             ret.push(unit_dep);
 279             let unit_dep = new_unit_dep(state, unit, pkg, lib, dep_unit_for, Kind::Host, mode)?;
 280             ret.push(unit_dep);
 281         } else {
 282             let unit_dep = new_unit_dep(
 283                 state,
 284                 unit,
 285                 pkg,
 286                 lib,
 287                 dep_unit_for,
 288                 unit.kind.for_target(lib),
 289                 mode,
 290             )?;
 291             ret.push(unit_dep);
 292         }
 293     }
 294
 295     // If this target is a build script, then what we've collected so far is
 296     // all we need. If this isn't a build script, then it depends on the
 297     // build script if there is one.
 298     if unit.target.is_custom_build() {
 299         return Ok(ret);
 300     }
 301     ret.extend(dep_build_script(unit, state)?);
 302
 303     // If this target is a binary, test, example, etc, then it depends on
 304     // the library of the same package. The call to `resolve.deps` above
 305     // didn't include `pkg` in the return values, so we need to special case
 306     // it here and see if we need to push `(pkg, pkg_lib_target)`.
 307     if unit.target.is_lib() && unit.mode != CompileMode::Doctest {
 308         return Ok(ret);
 309     }
 310     ret.extend(maybe_lib(unit, state, unit_for)?);
 311
 312     // If any integration tests/benches are being run, make sure that
 313     // binaries are built as well.
 314     if !unit.mode.is_check()
 315         && unit.mode.is_any_test()
 316         && (unit.target.is_test() || unit.target.is_bench())
 317     {
 318         ret.extend(
 319             unit.pkg
 320                 .targets()
 321                 .iter()
 322                 .filter(|t| {
 323                     let no_required_features = Vec::new();
 324
 325                     t.is_bin() &&
 326                         // Skip binaries with required features that have not been selected.
 327                         t.required_features().unwrap_or(&no_required_features).iter().all(|f| {
 328                             unit.features.contains(&f.as_str())
 329                         })
 330                 })
 331                 .map(|t| {
 332                     new_unit_dep(
 333                         state,
 334                         unit,
 335                         unit.pkg,
 336                         t,
 337                         UnitFor::new_normal(),
 338                         unit.kind.for_target(t),
 339                         CompileMode::Build,
 340                     )
 341                 })
 342                 .collect::<CargoResult<Vec<UnitDep<'a>>>>()?,
 343         );
 344     }
 345
 346     Ok(ret)
 347 }
 348
 349 /// Returns the dependencies needed to run a build script.
 350 ///
 351 /// The `unit` provided must represent an execution of a build script, and
 352 /// the returned set of units must all be run before `unit` is run.
 353 fn compute_deps_custom_build<'a, 'cfg>(
 354     unit: &Unit<'a>,
 355     state: &mut State<'a, 'cfg>,
 356 ) -> CargoResult<Vec<UnitDep<'a>>> {
 357     if let Some(links) = unit.pkg.manifest().links() {
 358         if state.bcx.script_override(links, unit.kind).is_some() {
 359             // Overridden build scripts don't have any dependencies.
 360             return Ok(Vec::new());
 361         }
 362     }
 363     // When not overridden, then the dependencies to run a build script are:
 364     //
 365     // 1. Compiling the build script itself.
 366     // 2. For each immediate dependency of our package which has a `links`
 367     //    key, the execution of that build script.
 368     //
 369     // We don't have a great way of handling (2) here right now so this is
 370     // deferred until after the graph of all unit dependencies has been
 371     // constructed.
 372     let unit_dep = new_unit_dep(
 373         state,
 374         unit,
 375         unit.pkg,
 376         unit.target,
 377         // All dependencies of this unit should use profiles for custom
 378         // builds.
 379         UnitFor::new_build(),
 380         // Build scripts always compiled for the host.
 381         Kind::Host,
 382         CompileMode::Build,
 383     )?;
 384     Ok(vec![unit_dep])
 385 }
 386
 387 /// Returns the dependencies necessary to document a package.
 388 fn compute_deps_doc<'a, 'cfg>(
 389     unit: &Unit<'a>,
 390     state: &mut State<'a, 'cfg>,
 391 ) -> CargoResult<Vec<UnitDep<'a>>> {
 392     let bcx = state.bcx;
 393     let deps = state
 394         .resolve()
 395         .deps(unit.pkg.package_id())
 396         .filter(|&(_id, deps)| {
 397             deps.iter().any(|dep| match dep.kind() {
 398                 DepKind::Normal => bcx.dep_platform_activated(dep, unit.kind),
 399                 _ => false,
 400             })
 401         });
 402
 403     // To document a library, we depend on dependencies actually being
 404     // built. If we're documenting *all* libraries, then we also depend on
 405     // the documentation of the library being built.
 406     let mut ret = Vec::new();
 407     for (id, _deps) in deps {
 408         let dep = match state.get(id)? {
 409             Some(dep) => dep,
 410             None => continue,
 411         };
 412         let lib = match dep.targets().iter().find(|t| t.is_lib()) {
 413             Some(lib) => lib,
 414             None => continue,
 415         };
 416         // Rustdoc only needs rmeta files for regular dependencies.
 417         // However, for plugins/proc macros, deps should be built like normal.
 418         let mode = check_or_build_mode(unit.mode, lib);
 419         let dep_unit_for = UnitFor::new_normal().with_for_host(lib.for_host());
 420         let lib_unit_dep = new_unit_dep(
 421             state,
 422             unit,
 423             dep,
 424             lib,
 425             dep_unit_for,
 426             unit.kind.for_target(lib),
 427             mode,
 428         )?;
 429         ret.push(lib_unit_dep);
 430         if let CompileMode::Doc { deps: true } = unit.mode {
 431             // Document this lib as well.
 432             let doc_unit_dep = new_unit_dep(
 433                 state,
 434                 unit,
 435                 dep,
 436                 lib,
 437                 dep_unit_for,
 438                 unit.kind.for_target(lib),
 439                 unit.mode,
 440             )?;
 441             ret.push(doc_unit_dep);
 442         }
 443     }
 444
 445     // Be sure to build/run the build script for documented libraries.
 446     ret.extend(dep_build_script(unit, state)?);
 447
 448     // If we document a binary/example, we need the library available.
 449     if unit.target.is_bin() || unit.target.is_example() {
 450         ret.extend(maybe_lib(unit, state, UnitFor::new_normal())?);
 451     }
 452     Ok(ret)
 453 }
 454
 455 fn maybe_lib<'a>(
 456     unit: &Unit<'a>,
 457     state: &mut State<'a, '_>,
 458     unit_for: UnitFor,
 459 ) -> CargoResult<Option<UnitDep<'a>>> {
 460     unit.pkg
 461         .targets()
 462         .iter()
 463         .find(|t| t.linkable())
 464         .map(|t| {
 465             let mode = check_or_build_mode(unit.mode, t);
 466             new_unit_dep(
 467                 state,
 468                 unit,
 469                 unit.pkg,
 470                 t,
 471                 unit_for,
 472                 unit.kind.for_target(t),
 473                 mode,
 474             )
 475         })
 476         .transpose()
 477 }
 478
 479 /// If a build script is scheduled to be run for the package specified by
 480 /// `unit`, this function will return the unit to run that build script.
 481 ///
 482 /// Overriding a build script simply means that the running of the build
 483 /// script itself doesn't have any dependencies, so even in that case a unit
 484 /// of work is still returned. `None` is only returned if the package has no
 485 /// build script.
 486 fn dep_build_script<'a>(
 487     unit: &Unit<'a>,
 488     state: &State<'a, '_>,
 489 ) -> CargoResult<Option<UnitDep<'a>>> {
 490     unit.pkg
 491         .targets()
 492         .iter()
 493         .find(|t| t.is_custom_build())
 494         .map(|t| {
 495             // The profile stored in the Unit is the profile for the thing
 496             // the custom build script is running for.
 497             let profile = state
 498                 .bcx
 499                 .profiles
 500                 .get_profile_run_custom_build(&unit.profile);
 501             new_unit_dep_with_profile(
 502                 state,
 503                 unit,
 504                 unit.pkg,
 505                 t,
 506                 UnitFor::new_build(),
 507                 unit.kind,
 508                 CompileMode::RunCustomBuild,
 509                 profile,
 510             )
 511         })
 512         .transpose()
 513 }
 514
 515 /// Choose the correct mode for dependencies.
 516 fn check_or_build_mode(mode: CompileMode, target: &Target) -> CompileMode {
 517     match mode {
 518         CompileMode::Check { .. } | CompileMode::Doc { .. } => {
 519             if target.for_host() {
 520                 // Plugin and proc macro targets should be compiled like
 521                 // normal.
 522                 CompileMode::Build
 523             } else {
 524                 // Regular dependencies should not be checked with --test.
 525                 // Regular dependencies of doc targets should emit rmeta only.
 526                 CompileMode::Check { test: false }
 527             }
 528         }
 529         _ => CompileMode::Build,
 530     }
 531 }
 532
 533 /// Create a new Unit for a dependency from `parent` to `pkg` and `target`.
 534 fn new_unit_dep<'a>(
 535     state: &State<'a, '_>,
 536     parent: &Unit<'a>,
 537     pkg: &'a Package,
 538     target: &'a Target,
 539     unit_for: UnitFor,
 540     kind: Kind,
 541     mode: CompileMode,
 542 ) -> CargoResult<UnitDep<'a>> {
 543     let profile = state.bcx.profiles.get_profile(
 544         pkg.package_id(),
 545         state.bcx.ws.is_member(pkg),
 546         unit_for,
 547         mode,
 548         state.bcx.build_config.release,
 549     );
 550     new_unit_dep_with_profile(state, parent, pkg, target, unit_for, kind, mode, profile)
 551 }
 552
 553 fn new_unit_dep_with_profile<'a>(
 554     state: &State<'a, '_>,
 555     parent: &Unit<'a>,
 556     pkg: &'a Package,
 557     target: &'a Target,
 558     unit_for: UnitFor,
 559     kind: Kind,
 560     mode: CompileMode,
 561     profile: Profile,
 562 ) -> CargoResult<UnitDep<'a>> {
 563     // TODO: consider making extern_crate_name return InternedString?
 564     let extern_crate_name = InternedString::new(&state.resolve().extern_crate_name(
 565         parent.pkg.package_id(),
 566         pkg.package_id(),
 567         target,
 568     )?);
 569     let public = state
 570         .resolve()
 571         .is_public_dep(parent.pkg.package_id(), pkg.package_id());
 572     let features = state.resolve().features_sorted(pkg.package_id());
 573     let unit = state
 574         .bcx
 575         .units
 576         .intern(pkg, target, profile, kind, mode, features, state.is_std);
 577     Ok(UnitDep {
 578         unit,
 579         unit_for,
 580         extern_crate_name,
 581         public,
 582     })
 583 }
 584
 585 /// Fill in missing dependencies for units of the `RunCustomBuild`
 586 ///
 587 /// As mentioned above in `compute_deps_custom_build` each build script
 588 /// execution has two dependencies. The first is compiling the build script
 589 /// itself (already added) and the second is that all crates the package of the
 590 /// build script depends on with `links` keys, their build script execution. (a
 591 /// bit confusing eh?)
 592 ///
 593 /// Here we take the entire `deps` map and add more dependencies from execution
 594 /// of one build script to execution of another build script.
 595 fn connect_run_custom_build_deps(unit_dependencies: &mut UnitGraph<'_>) {
 596     let mut new_deps = Vec::new();
 597
 598     {
 599         // First up build a reverse dependency map. This is a mapping of all
 600         // `RunCustomBuild` known steps to the unit which depends on them. For
 601         // example a library might depend on a build script, so this map will
 602         // have the build script as the key and the library would be in the
 603         // value's set.
 604         let mut reverse_deps_map = HashMap::new();
 605         for (unit, deps) in unit_dependencies.iter() {
 606             for dep in deps {
 607                 if dep.unit.mode == CompileMode::RunCustomBuild {
 608                     reverse_deps_map
 609                         .entry(dep.unit)
 610                         .or_insert_with(HashSet::new)
 611                         .insert(unit);
 612                 }
 613             }
 614         }
 615
 616         // Next, we take a look at all build scripts executions listed in the
 617         // dependency map. Our job here is to take everything that depends on
 618         // this build script (from our reverse map above) and look at the other
 619         // package dependencies of these parents.
 620         //
 621         // If we depend on a linkable target and the build script mentions
 622         // `links`, then we depend on that package's build script! Here we use
 623         // `dep_build_script` to manufacture an appropriate build script unit to
 624         // depend on.
 625         for unit in unit_dependencies
 626             .keys()
 627             .filter(|k| k.mode == CompileMode::RunCustomBuild)
 628         {
 629             // This is the lib that runs this custom build.
 630             let reverse_deps = match reverse_deps_map.get(unit) {
 631                 Some(set) => set,
 632                 None => continue,
 633             };
 634
 635             let to_add = reverse_deps
 636                 .iter()
 637                 // Get all deps for lib.
 638                 .flat_map(|reverse_dep| unit_dependencies[reverse_dep].iter())
 639                 // Only deps with `links`.
 640                 .filter(|other| {
 641                     other.unit.pkg != unit.pkg
 642                         && other.unit.target.linkable()
 643                         && other.unit.pkg.manifest().links().is_some()
 644                 })
 645                 // Get the RunCustomBuild for other lib.
 646                 .filter_map(|other| {
 647                     unit_dependencies[&other.unit]
 648                         .iter()
 649                         .find(|other_dep| other_dep.unit.mode == CompileMode::RunCustomBuild)
 650                         .cloned()
 651                 })
 652                 .collect::<HashSet<_>>();
 653
 654             if !to_add.is_empty() {
 655                 // (RunCustomBuild, set(other RunCustomBuild))
 656                 new_deps.push((*unit, to_add));
 657             }
 658         }
 659     }
 660
 661     // And finally, add in all the missing dependencies!
 662     for (unit, new_deps) in new_deps {
 663         unit_dependencies.get_mut(&unit).unwrap().extend(new_deps);
 664     }
 665 }
 666
 667 impl<'a, 'cfg> State<'a, 'cfg> {
 668     fn resolve(&self) -> &'a Resolve {
 669         if self.is_std {
 670             self.std_resolve.unwrap()
 671         } else {
 672             self.usr_resolve
 673         }
 674     }
 675
 676     fn get(&mut self, id: PackageId) -> CargoResult<Option<&'a Package>> {
 677         if let Some(pkg) = self.package_cache.get(&id) {
 678             return Ok(Some(pkg));
 679         }
 680         if !self.waiting_on_download.insert(id) {
 681             return Ok(None);
 682         }
 683         if let Some(pkg) = self.downloads.start(id)? {
 684             self.package_cache.insert(id, pkg);
 685             self.waiting_on_download.remove(&id);
 686             return Ok(Some(pkg));
 687         }
 688         Ok(None)
 689     }
 690
 691     /// Completes at least one downloading, maybe waiting for more to complete.
 692     ///
 693     /// This function will block the current thread waiting for at least one
 694     /// crate to finish downloading. The function may continue to download more
 695     /// crates if it looks like there's a long enough queue of crates to keep
 696     /// downloading. When only a handful of packages remain this function
 697     /// returns, and it's hoped that by returning we'll be able to push more
 698     /// packages to download into the queue.
 699     fn finish_some_downloads(&mut self) -> CargoResult<()> {
 700         assert!(self.downloads.remaining() > 0);
 701         loop {
 702             let pkg = self.downloads.wait()?;
 703             self.waiting_on_download.remove(&pkg.package_id());
 704             self.package_cache.insert(pkg.package_id(), pkg);
 705
 706             // Arbitrarily choose that 5 or more packages concurrently download
 707             // is a good enough number to "fill the network pipe". If we have
 708             // less than this let's recompute the whole unit dependency graph
 709             // again and try to find some more packages to download.
 710             if self.downloads.remaining() < 5 {
 711                 break;
 712             }
 713         }
 714         Ok(())
 715     }
 716 }