tool.rs

use std::env;
use std::fs;
use std::path::PathBuf;
use std::process::Command;

use crate::core::build_steps::compile;
use crate::core::build_steps::toolstate::ToolState;
use crate::core::builder::{Builder, Cargo as CargoCommand, RunConfig, ShouldRun, Step};
use crate::core::config::TargetSelection;
use crate::utils::channel::GitInfo;
use crate::utils::exec::BootstrapCommand;
use crate::utils::helpers::{add_dylib_path, exe, t};
use crate::Compiler;
use crate::Mode;
use crate::{gha, Kind};

#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
pub enum SourceType {
    InTree,
    Submodule,
}

#[derive(Debug, Clone, Hash, PartialEq, Eq)]
struct ToolBuild {
    compiler: Compiler,
    target: TargetSelection,
    tool: &'static str,
    path: &'static str,
    mode: Mode,
    is_optional_tool: bool,
    source_type: SourceType,
    extra_features: Vec<String>,
    /// Nightly-only features that are allowed (comma-separated list).
    allow_features: &'static str,
}

impl Builder<'_> {
    #[track_caller]
    fn msg_tool(
        &self,
        mode: Mode,
        tool: &str,
        build_stage: u32,
        host: &TargetSelection,
        target: &TargetSelection,
    ) -> Option<gha::Group> {
        match mode {
            // depends on compiler stage, different to host compiler
            Mode::ToolRustc => self.msg_sysroot_tool(
                Kind::Build,
                build_stage,
                format_args!("tool {tool}"),
                *host,
                *target,
            ),
            // doesn't depend on compiler, same as host compiler
            _ => self.msg(Kind::Build, build_stage, format_args!("tool {tool}"), *host, *target),
        }
    }
}

impl Step for ToolBuild {
    type Output = Option<PathBuf>;

    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
        run.never()
    }

    /// Builds a tool in `src/tools`
    ///
    /// This will build the specified tool with the specified `host` compiler in
    /// `stage` into the normal cargo output directory.
    fn run(self, builder: &Builder<'_>) -> Option<PathBuf> {
        let compiler = self.compiler;
        let target = self.target;
        let mut tool = self.tool;
        let path = self.path;
        let is_optional_tool = self.is_optional_tool;

        match self.mode {
            Mode::ToolRustc => {
                builder.ensure(compile::Std::new(compiler, compiler.host));
                builder.ensure(compile::Rustc::new(compiler, target));
            }
            Mode::ToolStd => builder.ensure(compile::Std::new(compiler, target)),
            Mode::ToolBootstrap => {} // uses downloaded stage0 compiler libs
            _ => panic!("unexpected Mode for tool build"),
        }

        let mut cargo = prepare_tool_cargo(
            builder,
            compiler,
            self.mode,
            target,
            "build",
            path,
            self.source_type,
            &self.extra_features,
        );
        if !self.allow_features.is_empty() {
            cargo.allow_features(self.allow_features);
        }
        let _guard = builder.msg_tool(
            self.mode,
            self.tool,
            self.compiler.stage,
            &self.compiler.host,
            &self.target,
        );

        let mut cargo = Command::from(cargo);
        // we check this in `is_optional_tool` in a second
        let is_expected = builder.run_cmd(BootstrapCommand::from(&mut cargo).allow_failure());

        builder.save_toolstate(
            tool,
            if is_expected { ToolState::TestFail } else { ToolState::BuildFail },
        );

        if !is_expected {
            if !is_optional_tool {
                crate::exit!(1);
            } else {
                None
            }
        } else {
            // HACK(#82501): on Windows, the tools directory gets added to PATH when running tests, and
            // compiletest confuses HTML tidy with the in-tree tidy. Name the in-tree tidy something
            // different so the problem doesn't come up.
            if tool == "tidy" {
                tool = "rust-tidy";
            }
            let cargo_out = builder.cargo_out(compiler, self.mode, target).join(exe(tool, target));
            let bin = builder.tools_dir(compiler).join(exe(tool, target));
            builder.copy(&cargo_out, &bin);
            Some(bin)
        }
    }
}

pub fn prepare_tool_cargo(
    builder: &Builder<'_>,
    compiler: Compiler,
    mode: Mode,
    target: TargetSelection,
    command: &'static str,
    path: &str,
    source_type: SourceType,
    extra_features: &[String],
) -> CargoCommand {
    let mut cargo = builder.cargo(compiler, mode, source_type, target, command);
    let dir = builder.src.join(path);
    cargo.arg("--manifest-path").arg(dir.join("Cargo.toml"));

    let mut features = extra_features.to_vec();
    if builder.build.config.cargo_native_static {
        if path.ends_with("cargo")
            || path.ends_with("rls")
            || path.ends_with("clippy")
            || path.ends_with("miri")
            || path.ends_with("rustfmt")
        {
            cargo.env("LIBZ_SYS_STATIC", "1");
        }
        if path.ends_with("cargo") {
            features.push("all-static".to_string());
        }
    }

    // clippy tests need to know about the stage sysroot. Set them consistently while building to
    // avoid rebuilding when running tests.
    cargo.env("SYSROOT", builder.sysroot(compiler));

    // if tools are using lzma we want to force the build script to build its
    // own copy
    cargo.env("LZMA_API_STATIC", "1");

    // CFG_RELEASE is needed by rustfmt (and possibly other tools) which
    // import rustc-ap-rustc_attr which requires this to be set for the
    // `#[cfg(version(...))]` attribute.
    cargo.env("CFG_RELEASE", builder.rust_release());
    cargo.env("CFG_RELEASE_CHANNEL", &builder.config.channel);
    cargo.env("CFG_VERSION", builder.rust_version());
    cargo.env("CFG_RELEASE_NUM", &builder.version);
    cargo.env("DOC_RUST_LANG_ORG_CHANNEL", builder.doc_rust_lang_org_channel());
    if let Some(ref ver_date) = builder.rust_info().commit_date() {
        cargo.env("CFG_VER_DATE", ver_date);
    }
    if let Some(ref ver_hash) = builder.rust_info().sha() {
        cargo.env("CFG_VER_HASH", ver_hash);
    }

    let info = GitInfo::new(builder.config.omit_git_hash, &dir);
    if let Some(sha) = info.sha() {
        cargo.env("CFG_COMMIT_HASH", sha);
    }
    if let Some(sha_short) = info.sha_short() {
        cargo.env("CFG_SHORT_COMMIT_HASH", sha_short);
    }
    if let Some(date) = info.commit_date() {
        cargo.env("CFG_COMMIT_DATE", date);
    }
    if !features.is_empty() {
        cargo.arg("--features").arg(&features.join(", "));
    }

    // Enable internal lints for clippy and rustdoc
    // NOTE: this doesn't enable lints for any other tools unless they explicitly add `#![warn(rustc::internal)]`
    // See https://github.com/rust-lang/rust/pull/80573#issuecomment-754010776
    //
    // NOTE: We unconditionally set this here to avoid recompiling tools between `x check $tool`
    // and `x test $tool` executions.
    // See https://github.com/rust-lang/rust/issues/116538
    cargo.rustflag("-Zunstable-options");

    cargo
}

macro_rules! bootstrap_tool {
    ($(
        $name:ident, $path:expr, $tool_name:expr
        $(,is_external_tool = $external:expr)*
        $(,is_unstable_tool = $unstable:expr)*
        $(,allow_features = $allow_features:expr)?
        ;
    )+) => {
        #[derive(Copy, PartialEq, Eq, Clone)]
        pub enum Tool {
            $(
                $name,
            )+
        }

        impl<'a> Builder<'a> {
            pub fn tool_exe(&self, tool: Tool) -> PathBuf {
                match tool {
                    $(Tool::$name =>
                        self.ensure($name {
                            compiler: self.compiler(0, self.config.build),
                            target: self.config.build,
                        }),
                    )+
                }
            }
        }

        $(
            #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
        pub struct $name {
            pub compiler: Compiler,
            pub target: TargetSelection,
        }

        impl Step for $name {
            type Output = PathBuf;

            fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
                run.path($path)
            }

            fn make_run(run: RunConfig<'_>) {
                run.builder.ensure($name {
                    // snapshot compiler
                    compiler: run.builder.compiler(0, run.builder.config.build),
                    target: run.target,
                });
            }

            fn run(self, builder: &Builder<'_>) -> PathBuf {
                builder.ensure(ToolBuild {
                    compiler: self.compiler,
                    target: self.target,
                    tool: $tool_name,
                    mode: if false $(|| $unstable)* {
                        // use in-tree libraries for unstable features
                        Mode::ToolStd
                    } else {
                        Mode::ToolBootstrap
                    },
                    path: $path,
                    is_optional_tool: false,
                    source_type: if false $(|| $external)* {
                        SourceType::Submodule
                    } else {
                        SourceType::InTree
                    },
                    extra_features: vec![],
                    allow_features: concat!($($allow_features)*),
                }).expect("expected to build -- essential tool")
            }
        }
        )+
    }
}

bootstrap_tool!(
    Rustbook, "src/tools/rustbook", "rustbook";
    UnstableBookGen, "src/tools/unstable-book-gen", "unstable-book-gen";
    Tidy, "src/tools/tidy", "tidy";
    Linkchecker, "src/tools/linkchecker", "linkchecker";
    CargoTest, "src/tools/cargotest", "cargotest";
    Compiletest, "src/tools/compiletest", "compiletest", is_unstable_tool = true, allow_features = "test";
    BuildManifest, "src/tools/build-manifest", "build-manifest";
    RemoteTestClient, "src/tools/remote-test-client", "remote-test-client";
    RustInstaller, "src/tools/rust-installer", "rust-installer";
    RustdocTheme, "src/tools/rustdoc-themes", "rustdoc-themes";
    ExpandYamlAnchors, "src/tools/expand-yaml-anchors", "expand-yaml-anchors";
    LintDocs, "src/tools/lint-docs", "lint-docs";
    JsonDocCk, "src/tools/jsondocck", "jsondocck";
    JsonDocLint, "src/tools/jsondoclint", "jsondoclint";
    HtmlChecker, "src/tools/html-checker", "html-checker";
    BumpStage0, "src/tools/bump-stage0", "bump-stage0";
    ReplaceVersionPlaceholder, "src/tools/replace-version-placeholder", "replace-version-placeholder";
    CollectLicenseMetadata, "src/tools/collect-license-metadata", "collect-license-metadata";
    GenerateCopyright, "src/tools/generate-copyright", "generate-copyright";
    SuggestTests, "src/tools/suggest-tests", "suggest-tests";
    GenerateWindowsSys, "src/tools/generate-windows-sys", "generate-windows-sys";
    RustdocGUITest, "src/tools/rustdoc-gui-test", "rustdoc-gui-test", is_unstable_tool = true, allow_features = "test";
    OptimizedDist, "src/tools/opt-dist", "opt-dist";
    CoverageDump, "src/tools/coverage-dump", "coverage-dump";
);

#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, Ord, PartialOrd)]
pub struct ErrorIndex {
    pub compiler: Compiler,
}

impl ErrorIndex {
    pub fn command(builder: &Builder<'_>) -> Command {
        // Error-index-generator links with the rustdoc library, so we need to add `rustc_lib_paths`
        // for rustc_private and libLLVM.so, and `sysroot_lib` for libstd, etc.
        let host = builder.config.build;
        let compiler = builder.compiler_for(builder.top_stage, host, host);
        let mut cmd = Command::new(builder.ensure(ErrorIndex { compiler }));
        let mut dylib_paths = builder.rustc_lib_paths(compiler);
        dylib_paths.push(PathBuf::from(&builder.sysroot_libdir(compiler, compiler.host)));
        add_dylib_path(dylib_paths, &mut cmd);
        cmd
    }
}

impl Step for ErrorIndex {
    type Output = PathBuf;

    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
        run.path("src/tools/error_index_generator")
    }

    fn make_run(run: RunConfig<'_>) {
        // Compile the error-index in the same stage as rustdoc to avoid
        // recompiling rustdoc twice if we can.
        //
        // NOTE: This `make_run` isn't used in normal situations, only if you
        // manually build the tool with `x.py build
        // src/tools/error-index-generator` which almost nobody does.
        // Normally, `x.py test` or `x.py doc` will use the
        // `ErrorIndex::command` function instead.
        let compiler =
            run.builder.compiler(run.builder.top_stage.saturating_sub(1), run.builder.config.build);
        run.builder.ensure(ErrorIndex { compiler });
    }

    fn run(self, builder: &Builder<'_>) -> PathBuf {
        builder
            .ensure(ToolBuild {
                compiler: self.compiler,
                target: self.compiler.host,
                tool: "error_index_generator",
                mode: Mode::ToolRustc,
                path: "src/tools/error_index_generator",
                is_optional_tool: false,
                source_type: SourceType::InTree,
                extra_features: Vec::new(),
                allow_features: "",
            })
            .expect("expected to build -- essential tool")
    }
}

#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
pub struct RemoteTestServer {
    pub compiler: Compiler,
    pub target: TargetSelection,
}

impl Step for RemoteTestServer {
    type Output = PathBuf;

    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
        run.path("src/tools/remote-test-server")
    }

    fn make_run(run: RunConfig<'_>) {
        run.builder.ensure(RemoteTestServer {
            compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
            target: run.target,
        });
    }

    fn run(self, builder: &Builder<'_>) -> PathBuf {
        builder
            .ensure(ToolBuild {
                compiler: self.compiler,
                target: self.target,
                tool: "remote-test-server",
                mode: Mode::ToolStd,
                path: "src/tools/remote-test-server",
                is_optional_tool: false,
                source_type: SourceType::InTree,
                extra_features: Vec::new(),
                allow_features: "",
            })
            .expect("expected to build -- essential tool")
    }
}

#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, Ord, PartialOrd)]
pub struct Rustdoc {
    /// This should only ever be 0 or 2.
    /// We sometimes want to reference the "bootstrap" rustdoc, which is why this option is here.
    pub compiler: Compiler,
}

impl Step for Rustdoc {
    type Output = PathBuf;
    const DEFAULT: bool = true;
    const ONLY_HOSTS: bool = true;

    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
        run.path("src/tools/rustdoc").path("src/librustdoc")
    }

    fn make_run(run: RunConfig<'_>) {
        run.builder.ensure(Rustdoc {
            // NOTE: this is somewhat unique in that we actually want a *target*
            // compiler here, because rustdoc *is* a compiler. We won't be using
            // this as the compiler to build with, but rather this is "what
            // compiler are we producing"?
            compiler: run.builder.compiler(run.builder.top_stage, run.target),
        });
    }

    fn run(self, builder: &Builder<'_>) -> PathBuf {
        let target_compiler = self.compiler;
        if target_compiler.stage == 0 {
            if !target_compiler.is_snapshot(builder) {
                panic!("rustdoc in stage 0 must be snapshot rustdoc");
            }
            return builder.initial_rustc.with_file_name(exe("rustdoc", target_compiler.host));
        }
        let target = target_compiler.host;
        // Similar to `compile::Assemble`, build with the previous stage's compiler. Otherwise
        // we'd have stageN/bin/rustc and stageN/bin/rustdoc be effectively different stage
        // compilers, which isn't what we want. Rustdoc should be linked in the same way as the
        // rustc compiler it's paired with, so it must be built with the previous stage compiler.
        let build_compiler = builder.compiler(target_compiler.stage - 1, builder.config.build);

        // When using `download-rustc` and a stage0 build_compiler, copying rustc doesn't actually
        // build stage0 libstd (because the libstd in sysroot has the wrong ABI). Explicitly build
        // it.
        builder.ensure(compile::Std::new(build_compiler, target_compiler.host));
        builder.ensure(compile::Rustc::new(build_compiler, target_compiler.host));
        // NOTE: this implies that `download-rustc` is pretty useless when compiling with the stage0
        // compiler, since you do just as much work.
        if !builder.config.dry_run() && builder.download_rustc() && build_compiler.stage == 0 {
            println!(
                "WARNING: `download-rustc` does nothing when building stage1 tools; consider using `--stage 2` instead"
            );
        }

        // The presence of `target_compiler` ensures that the necessary libraries (codegen backends,
        // compiler libraries, ...) are built. Rustdoc does not require the presence of any
        // libraries within sysroot_libdir (i.e., rustlib), though doctests may want it (since
        // they'll be linked to those libraries). As such, don't explicitly `ensure` any additional
        // libraries here. The intuition here is that If we've built a compiler, we should be able
        // to build rustdoc.
        //
        let mut features = Vec::new();
        if builder.config.jemalloc {
            features.push("jemalloc".to_string());
        }

        let mut cargo = prepare_tool_cargo(
            builder,
            build_compiler,
            Mode::ToolRustc,
            target,
            "build",
            "src/tools/rustdoc",
            SourceType::InTree,
            features.as_slice(),
        );

        if builder.config.rustc_parallel {
            cargo.rustflag("--cfg=parallel_compiler");
        }

        let _guard = builder.msg_tool(
            Mode::ToolRustc,
            "rustdoc",
            build_compiler.stage,
            &self.compiler.host,
            &target,
        );
        builder.run(&mut cargo.into());

        // Cargo adds a number of paths to the dylib search path on windows, which results in
        // the wrong rustdoc being executed. To avoid the conflicting rustdocs, we name the "tool"
        // rustdoc a different name.
        let tool_rustdoc = builder
            .cargo_out(build_compiler, Mode::ToolRustc, target)
            .join(exe("rustdoc_tool_binary", target_compiler.host));

        // don't create a stage0-sysroot/bin directory.
        if target_compiler.stage > 0 {
            let sysroot = builder.sysroot(target_compiler);
            let bindir = sysroot.join("bin");
            t!(fs::create_dir_all(&bindir));
            let bin_rustdoc = bindir.join(exe("rustdoc", target_compiler.host));
            let _ = fs::remove_file(&bin_rustdoc);
            builder.copy(&tool_rustdoc, &bin_rustdoc);
            bin_rustdoc
        } else {
            tool_rustdoc
        }
    }
}

#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
pub struct Cargo {
    pub compiler: Compiler,
    pub target: TargetSelection,
}

impl Step for Cargo {
    type Output = PathBuf;
    const DEFAULT: bool = true;
    const ONLY_HOSTS: bool = true;

    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
        let builder = run.builder;
        run.path("src/tools/cargo").default_condition(
            builder.config.extended
                && builder.config.tools.as_ref().map_or(
                    true,
                    // If `tools` is set, search list for this tool.
                    |tools| tools.iter().any(|tool| tool == "cargo"),
                ),
        )
    }

    fn make_run(run: RunConfig<'_>) {
        run.builder.ensure(Cargo {
            compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
            target: run.target,
        });
    }

    fn run(self, builder: &Builder<'_>) -> PathBuf {
        let cargo_bin_path = builder
            .ensure(ToolBuild {
                compiler: self.compiler,
                target: self.target,
                tool: "cargo",
                mode: Mode::ToolRustc,
                path: "src/tools/cargo",
                is_optional_tool: false,
                source_type: SourceType::Submodule,
                extra_features: Vec::new(),
                allow_features: "",
            })
            .expect("expected to build -- essential tool");
        cargo_bin_path
    }
}

#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
pub struct LldWrapper {
    pub compiler: Compiler,
    pub target: TargetSelection,
}

impl Step for LldWrapper {
    type Output = PathBuf;

    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
        run.never()
    }

    fn run(self, builder: &Builder<'_>) -> PathBuf {
        let src_exe = builder
            .ensure(ToolBuild {
                compiler: self.compiler,
                target: self.target,
                tool: "lld-wrapper",
                mode: Mode::ToolStd,
                path: "src/tools/lld-wrapper",
                is_optional_tool: false,
                source_type: SourceType::InTree,
                extra_features: Vec::new(),
                allow_features: "",
            })
            .expect("expected to build -- essential tool");

        src_exe
    }
}

#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
pub struct RustAnalyzer {
    pub compiler: Compiler,
    pub target: TargetSelection,
}

impl RustAnalyzer {
    pub const ALLOW_FEATURES: &'static str = "rustc_private,proc_macro_internals,proc_macro_diagnostic,proc_macro_span,proc_macro_span_shrink";
}

impl Step for RustAnalyzer {
    type Output = Option<PathBuf>;
    const DEFAULT: bool = true;
    const ONLY_HOSTS: bool = true;

    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
        let builder = run.builder;
        run.path("src/tools/rust-analyzer").default_condition(
            builder.config.extended
                && builder
                    .config
                    .tools
                    .as_ref()
                    .map_or(true, |tools| tools.iter().any(|tool| tool == "rust-analyzer")),
        )
    }

    fn make_run(run: RunConfig<'_>) {
        run.builder.ensure(RustAnalyzer {
            compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
            target: run.target,
        });
    }

    fn run(self, builder: &Builder<'_>) -> Option<PathBuf> {
        builder.ensure(ToolBuild {
            compiler: self.compiler,
            target: self.target,
            tool: "rust-analyzer",
            mode: Mode::ToolRustc,
            path: "src/tools/rust-analyzer",
            extra_features: vec!["rust-analyzer/in-rust-tree".to_owned()],
            is_optional_tool: false,
            source_type: SourceType::InTree,
            allow_features: RustAnalyzer::ALLOW_FEATURES,
        })
    }
}

#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
pub struct RustAnalyzerProcMacroSrv {
    pub compiler: Compiler,
    pub target: TargetSelection,
}

impl Step for RustAnalyzerProcMacroSrv {
    type Output = Option<PathBuf>;
    const DEFAULT: bool = true;
    const ONLY_HOSTS: bool = true;

    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
        let builder = run.builder;
        // Allow building `rust-analyzer-proc-macro-srv` both as part of the `rust-analyzer` and as a stand-alone tool.
        run.path("src/tools/rust-analyzer")
            .path("src/tools/rust-analyzer/crates/proc-macro-srv-cli")
            .default_condition(builder.config.tools.as_ref().map_or(true, |tools| {
                tools
                    .iter()
                    .any(|tool| tool == "rust-analyzer" || tool == "rust-analyzer-proc-macro-srv")
            }))
    }

    fn make_run(run: RunConfig<'_>) {
        run.builder.ensure(RustAnalyzerProcMacroSrv {
            compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
            target: run.target,
        });
    }

    fn run(self, builder: &Builder<'_>) -> Option<PathBuf> {
        let path = builder.ensure(ToolBuild {
            compiler: self.compiler,
            target: self.target,
            tool: "rust-analyzer-proc-macro-srv",
            mode: Mode::ToolStd,
            path: "src/tools/rust-analyzer/crates/proc-macro-srv-cli",
            extra_features: vec!["sysroot-abi".to_owned(), "in-rust-tree".to_owned()],
            is_optional_tool: false,
            source_type: SourceType::InTree,
            allow_features: RustAnalyzer::ALLOW_FEATURES,
        })?;

        // Copy `rust-analyzer-proc-macro-srv` to `<sysroot>/libexec/`
        // so that r-a can use it.
        let libexec_path = builder.sysroot(self.compiler).join("libexec");
        t!(fs::create_dir_all(&libexec_path));
        builder.copy(&path, &libexec_path.join("rust-analyzer-proc-macro-srv"));

        Some(path)
    }
}

macro_rules! tool_extended {
    (($sel:ident, $builder:ident),
       $($name:ident,
       $path:expr,
       $tool_name:expr,
       stable = $stable:expr
       $(,tool_std = $tool_std:literal)?
       $(,allow_features = $allow_features:expr)?
       $(,add_bins_to_sysroot = $add_bins_to_sysroot:expr)?
       ;)+) => {
        $(
            #[derive(Debug, Clone, Hash, PartialEq, Eq)]
        pub struct $name {
            pub compiler: Compiler,
            pub target: TargetSelection,
            pub extra_features: Vec<String>,
        }

        impl Step for $name {
            type Output = Option<PathBuf>;
            const DEFAULT: bool = true; // Overwritten below
            const ONLY_HOSTS: bool = true;

            fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
                let builder = run.builder;
                run.path($path).default_condition(
                    builder.config.extended
                        && builder.config.tools.as_ref().map_or(
                            // By default, on nightly/dev enable all tools, else only
                            // build stable tools.
                            $stable || builder.build.unstable_features(),
                            // If `tools` is set, search list for this tool.
                            |tools| {
                                tools.iter().any(|tool| match tool.as_ref() {
                                    "clippy" => $tool_name == "clippy-driver",
                                    x => $tool_name == x,
                            })
                        }),
                )
            }

            fn make_run(run: RunConfig<'_>) {
                run.builder.ensure($name {
                    compiler: run.builder.compiler(run.builder.top_stage, run.builder.config.build),
                    target: run.target,
                    extra_features: Vec::new(),
                });
            }

            #[allow(unused_mut)]
            fn run(mut $sel, $builder: &Builder<'_>) -> Option<PathBuf> {
                let tool = $builder.ensure(ToolBuild {
                    compiler: $sel.compiler,
                    target: $sel.target,
                    tool: $tool_name,
                    mode: if false $(|| $tool_std)? { Mode::ToolStd } else { Mode::ToolRustc },
                    path: $path,
                    extra_features: $sel.extra_features,
                    is_optional_tool: true,
                    source_type: SourceType::InTree,
                    allow_features: concat!($($allow_features)*),
                })?;

                if (false $(|| !$add_bins_to_sysroot.is_empty())?) && $sel.compiler.stage > 0 {
                    let bindir = $builder.sysroot($sel.compiler).join("bin");
                    t!(fs::create_dir_all(&bindir));

                    #[allow(unused_variables)]
                    let tools_out = $builder
                        .cargo_out($sel.compiler, Mode::ToolRustc, $sel.target);

                    $(for add_bin in $add_bins_to_sysroot {
                        let bin_source = tools_out.join(exe(add_bin, $sel.target));
                        let bin_destination = bindir.join(exe(add_bin, $sel.compiler.host));
                        $builder.copy(&bin_source, &bin_destination);
                    })?

                    let tool = bindir.join(exe($tool_name, $sel.compiler.host));
                    Some(tool)
                } else {
                    Some(tool)
                }
            }
        }
        )+
    }
}

// NOTE: tools need to be also added to `Builder::get_step_descriptions` in `builder.rs`
// to make `./x.py build <tool>` work.
// NOTE: Most submodule updates for tools are handled by bootstrap.py, since they're needed just to
// invoke Cargo to build bootstrap. See the comment there for more details.
tool_extended!((self, builder),
    Cargofmt, "src/tools/rustfmt", "cargo-fmt", stable=true;
    CargoClippy, "src/tools/clippy", "cargo-clippy", stable=true;
    Clippy, "src/tools/clippy", "clippy-driver", stable=true, add_bins_to_sysroot = ["clippy-driver", "cargo-clippy"];
    Miri, "src/tools/miri", "miri", stable=false, add_bins_to_sysroot = ["miri"];
    CargoMiri, "src/tools/miri/cargo-miri", "cargo-miri", stable=true, add_bins_to_sysroot = ["cargo-miri"];
    // FIXME: tool_std is not quite right, we shouldn't allow nightly features.
    // But `builder.cargo` doesn't know how to handle ToolBootstrap in stages other than 0,
    // and this is close enough for now.
    Rls, "src/tools/rls", "rls", stable=true, tool_std=true;
    RustDemangler, "src/tools/rust-demangler", "rust-demangler", stable=false, tool_std=true;
    Rustfmt, "src/tools/rustfmt", "rustfmt", stable=true, add_bins_to_sysroot = ["rustfmt", "cargo-fmt"];
);

impl<'a> Builder<'a> {
    /// Gets a `Command` which is ready to run `tool` in `stage` built for
    /// `host`.
    pub fn tool_cmd(&self, tool: Tool) -> Command {
        let mut cmd = Command::new(self.tool_exe(tool));
        let compiler = self.compiler(0, self.config.build);
        let host = &compiler.host;
        // Prepares the `cmd` provided to be able to run the `compiler` provided.
        //
        // Notably this munges the dynamic library lookup path to point to the
        // right location to run `compiler`.
        let mut lib_paths: Vec<PathBuf> = vec![
            self.build.rustc_snapshot_libdir(),
            self.cargo_out(compiler, Mode::ToolBootstrap, *host).join("deps"),
        ];

        // On MSVC a tool may invoke a C compiler (e.g., compiletest in run-make
        // mode) and that C compiler may need some extra PATH modification. Do
        // so here.
        if compiler.host.is_msvc() {
            let curpaths = env::var_os("PATH").unwrap_or_default();
            let curpaths = env::split_paths(&curpaths).collect::<Vec<_>>();
            for &(ref k, ref v) in self.cc.borrow()[&compiler.host].env() {
                if k != "PATH" {
                    continue;
                }
                for path in env::split_paths(v) {
                    if !curpaths.contains(&path) {
                        lib_paths.push(path);
                    }
                }
            }
        }

        add_dylib_path(lib_paths, &mut cmd);

        // Provide a RUSTC for this command to use.
        cmd.env("RUSTC", &self.initial_rustc);

        cmd
    }
}