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    //! [`BuildContext`] is a (mostly) static information about a build task.

    use crate::core::compiler::unit_graph::UnitGraph;
    use crate::core::compiler::{BuildConfig, CompileKind, Unit};
    use crate::core::profiles::Profiles;
    use crate::core::PackageSet;
    use crate::core::Workspace;
    use crate::util::context::GlobalContext;
    use crate::util::errors::CargoResult;
    use crate::util::interning::InternedString;
    use crate::util::Rustc;
    use std::collections::{HashMap, HashSet};

    mod target_info;
    pub use self::target_info::{
        FileFlavor, FileType, RustDocFingerprint, RustcTargetData, TargetInfo,
    };

    /// The build context, containing complete information needed for a build task
    /// before it gets started.
    ///
    /// It is intended that this is mostly static information. Stuff that mutates
    /// during the build can be found in the parent [`BuildRunner`]. (I say mostly,
    /// because this has internal caching, but nothing that should be observable
    /// or require &mut.)
    ///
    /// As a result, almost every field on `BuildContext` is public, including
    ///
    /// * a resolved [`UnitGraph`] of your dependencies,
    /// * a [`Profiles`] containing compiler flags presets,
    /// * a [`RustcTargetData`] containing host and target platform information,
    /// * and a [`PackageSet`] for further package downloads,
    ///
    /// just to name a few. Learn more on each own documentation.
    ///
    /// # How to use
    ///
    /// To prepare a build task, you may not want to use [`BuildContext::new`] directly,
    /// since it is often too lower-level.
    /// Instead, [`ops::create_bcx`] is usually what you are looking for.
    ///
    /// After a `BuildContext` is built, the next stage of building is handled in [`BuildRunner`].
    ///
    /// [`BuildRunner`]: crate::core::compiler::BuildRunner
    /// [`ops::create_bcx`]: crate::ops::create_bcx
    pub struct BuildContext<'a, 'gctx> {
        /// The workspace the build is for.
        pub ws: &'a Workspace<'gctx>,

        /// The cargo context.
        pub gctx: &'gctx GlobalContext,

        /// This contains a collection of compiler flags presets.
        pub profiles: Profiles,

        /// Configuration information for a rustc build.
        pub build_config: &'a BuildConfig,

        /// Extra compiler args for either `rustc` or `rustdoc`.
        pub extra_compiler_args: HashMap<Unit, Vec<String>>,

        /// Package downloader.
        ///
        /// This holds ownership of the `Package` objects.
        pub packages: PackageSet<'gctx>,

        /// Information about rustc and the target platform.
        pub target_data: RustcTargetData<'gctx>,

        /// The root units of `unit_graph` (units requested on the command-line).
        pub roots: Vec<Unit>,

        /// The dependency graph of units to compile.
        pub unit_graph: UnitGraph,

        /// Reverse-dependencies of documented units, used by the `rustdoc --scrape-examples` flag.
        pub scrape_units: Vec<Unit>,

        /// The list of all kinds that are involved in this build
        pub all_kinds: HashSet<CompileKind>,
    }

    impl<'a, 'gctx> BuildContext<'a, 'gctx> {
        pub fn new(
            ws: &'a Workspace<'gctx>,
            packages: PackageSet<'gctx>,
            build_config: &'a BuildConfig,
            profiles: Profiles,
            extra_compiler_args: HashMap<Unit, Vec<String>>,
            target_data: RustcTargetData<'gctx>,
            roots: Vec<Unit>,
            unit_graph: UnitGraph,
            scrape_units: Vec<Unit>,
        ) -> CargoResult<BuildContext<'a, 'gctx>> {
            let all_kinds = unit_graph
                .keys()
                .map(|u| u.kind)
                .chain(build_config.requested_kinds.iter().copied())
                .chain(std::iter::once(CompileKind::Host))
                .collect();

            Ok(BuildContext {
                ws,
                gctx: ws.gctx(),
                packages,
                build_config,
                profiles,
                extra_compiler_args,
                target_data,
                roots,
                unit_graph,
                scrape_units,
                all_kinds,
            })
        }

        /// Information of the `rustc` this build task will use.
        pub fn rustc(&self) -> &Rustc {
            &self.target_data.rustc
        }

        /// Gets the host architecture triple.
        ///
        /// For example, x86_64-unknown-linux-gnu, would be
        /// - machine: x86_64,
        /// - hardware-platform: unknown,
        /// - operating system: linux-gnu.
        pub fn host_triple(&self) -> InternedString {
            self.target_data.rustc.host
        }

        /// Gets the number of jobs specified for this build.
        pub fn jobs(&self) -> u32 {
            self.build_config.jobs
        }

        /// Extra compiler args for either `rustc` or `rustdoc`.
        ///
        /// As of now, these flags come from the trailing args of either
        /// `cargo rustc` or `cargo rustdoc`.
        pub fn extra_args_for(&self, unit: &Unit) -> Option<&Vec<String>> {
            self.extra_compiler_args.get(unit)
        }
    }