zlayer_toolchain/

source_build.rs

//! Build runtime toolchains **from source** into a self-contained, absolute
//! cache keg — "our apt-get" for the macOS sandbox, which has no package
//! manager.
//!
//! # Why source-build instead of a Homebrew bottle
//!
//! Relocating a Homebrew *bottle* (rewriting its baked `@@HOMEBREW_PREFIX@@`
//! install-name placeholders) is a dead end: the rewrite is length-preserving
//! and silently skips placeholders shorter than the cache prefix, so the keg's
//! binary keeps `@@HOMEBREW_PREFIX@@/...` `LC_LOAD_DYLIB` paths. Under a darwin
//! Seatbelt container those paths don't exist and macOS strips `DYLD_*` from
//! the signed binary, so dyld aborts (`Symbol not found … Abort trap: 6`).
//!
//! Building from source at an absolute keg prefix sidesteps both failure modes:
//! every `LC_LOAD_DYLIB` is an absolute path to a macOS system library
//! (`/usr/lib/...`) or an absolute sibling-keg path — never `@@HOMEBREW@@` — and
//! the compiled `sysconfdir`/`prefix` live inside the keg, so the tool reads its
//! own config instead of `/etc/*` (which EPERMs under the deny-default profile).
//!
//! # A fully generic, data-driven build
//!
//! There is **no per-formula recipe table**. Everything the build needs is
//! derived from the Homebrew formula JSON we already parse plus the extracted
//! source tree:
//!
//! - **Dependencies come from the formula's data.** Anything in
//!   `uses_from_macos` is provided by macOS itself (the Seatbelt profile already
//!   grants `/usr/lib` + `/usr/include` via the Command Line Tools) so it is
//!   skipped. Every *other* `dependency` / `build_dependency` is resolved
//!   **recursively** as a sibling keg via [`crate::ensure_macos_keg`] and wired
//!   onto the build with *absolute* keg paths — build tools land on `PATH`,
//!   libraries contribute `-I<keg>/include` / `-L<keg>/lib` /
//!   `-Wl,-rpath,<keg>/lib` / `PKG_CONFIG_PATH=<keg>/lib/pkgconfig`. So git's
//!   `gettext`/`pcre2` and jq's `oniguruma` become resolved kegs automatically —
//!   no `NO_GETTEXT`, no `--with-oniguruma=builtin`, no hardcoded skip lists.
//! - **The build system is autodetected** from the extracted tree (a generated
//!   `configure`, a `CMake` self-host `bootstrap`, a `CMakeLists.txt`, a bare
//!   `Makefile`, or an autotools project shipped as `configure.ac`).
//! - **Irreducible env is derived from the install layout, not the name.** A keg
//!   that installed `<keg>/libexec/git-core` gets `GIT_EXEC_PATH` pointed there —
//!   true for any git-exec-helper tool, asserted by layout, never by `== "git"`.
//!
//! If a formula's generic build fails (a custom `install do` / patches the
//! generic build can't reproduce), [`ensure_from_source`] falls through to
//! [`crate::brew_emulate`], which runs the formula's *real* Homebrew recipe at
//! the keg prefix — so genuinely-custom formulae still work with **zero**
//! hardcoding.

use std::collections::HashMap;
use std::path::{Path, PathBuf};

use tracing::{info, warn};

use crate::error::{Result, ToolchainError};
use crate::formula::{self, Formula};
use crate::manifest::{KegManifest, KegSource};

/// Resolved source-build coordinates for a tool.
#[derive(Debug, Clone)]
pub struct SourceSpec {
    /// Stable version string (e.g. `2.55.0`).
    pub version: String,
    /// URL of the source tarball.
    pub tarball_url: String,
    /// The source tarball's sha256 (bare hex, `sha256:` prefix stripped). Empty
    /// when the formula publishes no `urls.stable.checksum`.
    pub sha256: String,
    /// Runtime dependency formula names.
    pub dependencies: Vec<String>,
    /// Build-only dependency formula names.
    pub build_dependencies: Vec<String>,
    /// Dependency names macOS itself provides (need no keg).
    pub macos_provided: Vec<String>,
}

/// Which build system a recipe drives, autodetected from the extracted tree.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum BuildSystem {
    /// `./configure --prefix=<keg> && make && make install` (a generated
    /// `configure`, or `configure.ac`/`autogen.sh` regenerated first).
    Autotools,
    /// `cmake -DCMAKE_INSTALL_PREFIX=<keg> … && cmake --build && cmake --install`
    /// using a `cmake` resolved as a build-dependency keg.
    CMake,
    /// A self-hosting `CMake` (`bootstrap` + `CMakeLists.txt`, i.e. cmake itself):
    /// `./bootstrap --prefix=<keg> --parallel=N && make && make install`.
    CMakeBootstrap,
    /// A bare hand-written `Makefile`: `make prefix=<keg> … install`.
    MakePrefix,
}

/// Host architecture token used in cache keys (`arm64` / `x86_64`).
fn arch_token() -> &'static str {
    match std::env::consts::ARCH {
        "aarch64" => "arm64",
        other => other,
    }
}

/// Fetch the formula and extract its source-build coordinates.
///
/// # Errors
///
/// Returns [`ToolchainError::RegistryError`] if the formula cannot be fetched
/// or carries no stable version / source URL.
pub async fn resolve_source_spec(formula: &str) -> Result<SourceSpec> {
    let info: Formula = formula::fetch_formula(formula).await?;

    let version = info
        .stable_version()
        .ok_or_else(|| ToolchainError::RegistryError {
            message: format!("formula {formula} has no stable version"),
        })?
        .to_string();

    let tarball_url = info
        .stable_url()
        .ok_or_else(|| ToolchainError::RegistryError {
            message: format!("formula {formula} has no stable source URL"),
        })?
        .to_string();

    Ok(SourceSpec {
        version,
        tarball_url,
        sha256: info.stable_checksum().unwrap_or_default(),
        dependencies: info.dependencies.clone(),
        build_dependencies: info.build_dependencies.clone(),
        macos_provided: info.macos_provided(),
    })
}

/// Build `formula` from source into a self-contained keg under `cache_dir`,
/// writing a [`KegManifest`] and returning the keg path.
///
/// Idempotent: a `<keg>/.ready` marker (written LAST, after the manifest)
/// short-circuits a populated keg. A cold build removes any partial keg, builds
/// into a scratch dir, installs into the keg prefix, writes the manifest, then
/// stamps `.ready`.
///
/// # Errors
///
/// Propagates formula-resolution, download, extraction, dependency, and build
/// failures.
pub async fn ensure_from_source(
    formula: &str,
    cache_dir: &Path,
    lockfile: Option<&crate::ToolchainLockfile>,
) -> Result<PathBuf> {
    let mut spec = resolve_source_spec(formula).await?;

    // A lock hit pins the exact version + source URL + digest (consume-only).
    // The dependency graph still comes from the resolved formula.
    if let Some(locked) = lockfile.and_then(|l| {
        use crate::ToolchainLockfileExt;
        l.lookup(formula, "macos", arch_token())
    }) {
        spec.version = locked.version.clone();
        spec.tarball_url = locked.url.clone();
        spec.sha256 = locked.sha256.clone();
    }

    let keg = cache_dir.join(format!("{formula}-{}-{}", spec.version, arch_token()));
    let ready_marker = keg.join(".ready");

    if tokio::fs::try_exists(&ready_marker).await.unwrap_or(false) {
        return Ok(keg);
    }

    // Try the generic build first. If it can't build this formula — no build
    // system detected (a custom `install do` with no
    // `configure`/`CMakeLists.txt`/`Makefile`, e.g. a `cargo install` / `go
    // build` formula), a required dependency keg won't build, or the build
    // errors in a way the generic flags don't cover — fall back to running the
    // formula's REAL Homebrew recipe at the keg prefix (`brew_emulate`).
    match try_generic_source_build(formula, &spec, &keg, cache_dir, lockfile).await {
        Ok(()) => Ok(keg),
        Err(e) => {
            warn!(
                formula,
                error = %e,
                "generic source build failed; falling back to brew-emulate at the keg prefix"
            );
            // Drop the partial generic keg so the brew-emulate install starts
            // from a clean prefix (it reuses the same `<keg>` cache key).
            let _ = tokio::fs::remove_dir_all(&keg).await;
            crate::brew_emulate::ensure_via_brew(formula, &spec, cache_dir).await
        }
    }
}

/// Attempt the generic (autotools/CMake/Makefile) source build into `keg`.
///
/// On success the keg is fully populated: manifest written and `.ready` stamped.
/// On any failure (detection or build) the caller falls back to
/// [`crate::brew_emulate`]. Kept as a separate fallible step so the fallback
/// decision is a single `match` at the call site.
async fn try_generic_source_build(
    formula: &str,
    spec: &SourceSpec,
    keg: &Path,
    cache_dir: &Path,
    lockfile: Option<&crate::ToolchainLockfile>,
) -> Result<()> {
    // Fresh build. Remove any partial keg so a crashed prior attempt can't leave
    // a half-installed prefix that confuses the installer.
    let _ = tokio::fs::remove_dir_all(keg).await;
    tokio::fs::create_dir_all(keg).await?;

    let scratch = keg.join(".build");
    tokio::fs::create_dir_all(&scratch).await?;

    // 1. Resolve dependencies as sibling kegs and assemble the build env. macOS-
    //    provided deps (`uses_from_macos`) are skipped; everything else is built
    //    recursively as a keg with absolute paths.
    let (build_env, resolved_build_deps) =
        resolve_dependencies(formula, spec, cache_dir, lockfile).await?;

    // 2. Download + extract the source tarball into `<scratch>/src`.
    let src_dir = download_and_extract(formula, spec, &scratch).await?;

    // 3. Autodetect the build system and run it into the keg prefix.
    let system = detect_build_system(&src_dir).await?;
    info!(formula, ?system, "detected build system");
    run_build(formula, &src_dir, keg, system, &build_env).await?;

    // 4. Write the manifest, clean scratch, then stamp `.ready` LAST.
    let manifest = build_manifest(formula, spec, keg, resolved_build_deps).await;
    manifest.write_to_keg(keg).await?;

    if let Err(e) = tokio::fs::remove_dir_all(&scratch).await {
        warn!(error = %e, "failed to clean source scratch dir (non-fatal)");
    }
    tokio::fs::write(keg.join(".ready"), b"").await?;

    Ok(())
}

/// Build the [`KegManifest`] for a freshly-installed source keg, deriving any
/// irreducible runtime env from the **installed layout** (never the formula
/// name): a keg that produced `<keg>/libexec/git-core` gets `GIT_EXEC_PATH`
/// pointed there, so git discovers its exec-helpers out of the keg.
async fn build_manifest(
    formula: &str,
    spec: &SourceSpec,
    keg: &Path,
    build_deps: Vec<String>,
) -> KegManifest {
    let mut path_dirs = Vec::new();
    let bin = keg.join("bin");
    if tokio::fs::try_exists(&bin).await.unwrap_or(false) {
        path_dirs.push(bin.display().to_string());
    }

    let mut env: HashMap<String, String> = HashMap::new();
    // Layout-derived, not name-derived: any tool that installs git's exec-helper
    // dir needs `GIT_EXEC_PATH` to find them out of the keg rather than the host.
    let git_exec = keg.join("libexec/git-core");
    if tokio::fs::try_exists(&git_exec).await.unwrap_or(false) {
        env.insert("GIT_EXEC_PATH".to_string(), git_exec.display().to_string());
    }

    KegManifest {
        tool: formula.to_string(),
        version: spec.version.clone(),
        arch: arch_token().to_string(),
        platform: "macos".to_string(),
        path_dirs,
        env,
        source: KegSource::SourceBuild {
            url: spec.tarball_url.clone(),
            sha256: spec.sha256.clone(),
        },
        build_deps,
        provisioned_at: chrono::Utc::now().to_rfc3339(),
    }
}

/// Environment accumulated for a source build: `PATH` plus linker/include/
/// pkg-config flags pointing at resolved dependency kegs.
#[derive(Debug, Default, Clone)]
struct BuildEnv {
    path_prefix: Vec<String>,
    cppflags: Vec<String>,
    ldflags: Vec<String>,
    pkg_config_path: Vec<String>,
}

/// Resolve a formula's build + runtime dependencies into sibling kegs and build
/// the [`BuildEnv`], **purely from the formula's data**:
///
/// - Deps macOS itself provides (`uses_from_macos`) are skipped — the Command
///   Line Tools already expose them under `/usr/lib` + `/usr/include`, which the
///   Seatbelt profile grants.
/// - Every other build dependency is **required** (its absence fails the build,
///   routing the formula to brew-emulate) and its `bin` dirs go on `PATH`.
/// - Every other runtime dependency is best-effort (a missing optional library
///   should not abort) and is wired via `-I`/`-L`/`-rpath`/`PKG_CONFIG_PATH`.
///
/// Resolution is **recursive**: [`crate::ensure_macos_keg`] re-enters the whole
/// provisioning pipeline for each dep (prebuilt-lang fetch or another source
/// build), so an arbitrarily deep dependency graph is materialized as kegs.
async fn resolve_dependencies(
    formula: &str,
    spec: &SourceSpec,
    cache_dir: &Path,
    lockfile: Option<&crate::ToolchainLockfile>,
) -> Result<(BuildEnv, Vec<String>)> {
    let mut env = BuildEnv::default();
    let mut resolved_build_deps = Vec::new();

    // A dependency provided by macOS itself needs no keg.
    let is_macos_provided = |dep: &str| spec.macos_provided.iter().any(|d| d == dep);

    // Build dependencies — required; their bin dirs go on PATH.
    for dep in &spec.build_dependencies {
        if is_macos_provided(dep) {
            continue;
        }
        let keg = Box::pin(crate::ensure_macos_keg(dep, cache_dir, lockfile)).await?;
        let manifest = KegManifest::load_or_synthesize(&keg).await?;
        env.path_prefix.extend(manifest.path_dirs.clone());
        add_dep_link_flags(&mut env, &keg);
        resolved_build_deps.push(dep.clone());
        info!(formula, dep, keg = %keg.display(), "resolved build dependency keg");
    }

    // Runtime dependencies — best effort; wire link/include/pkg-config flags so
    // the binary's load commands reference the absolute dependency-keg path.
    for dep in &spec.dependencies {
        if is_macos_provided(dep) {
            continue;
        }
        match Box::pin(crate::ensure_macos_keg(dep, cache_dir, lockfile)).await {
            Ok(keg) => {
                if let Ok(manifest) = KegManifest::load_or_synthesize(&keg).await {
                    env.path_prefix.extend(manifest.path_dirs.clone());
                }
                add_dep_link_flags(&mut env, &keg);
                info!(formula, dep, keg = %keg.display(), "resolved runtime dependency keg");
            }
            Err(e) => warn!(
                formula, dep, error = %e,
                "runtime dependency keg unavailable; continuing without it"
            ),
        }
    }

    Ok((env, resolved_build_deps))
}

/// Add `-I`/`-L`/`-rpath`/pkg-config entries for a dependency keg so the build
/// links against its absolute path (never `@@HOMEBREW@@`).
fn add_dep_link_flags(env: &mut BuildEnv, keg: &Path) {
    let include = keg.join("include");
    let lib = keg.join("lib");
    if include.is_dir() {
        env.cppflags.push(format!("-I{}", include.display()));
    }
    if lib.is_dir() {
        env.ldflags.push(format!("-L{}", lib.display()));
        env.ldflags.push(format!("-Wl,-rpath,{}", lib.display()));
        let pc = lib.join("pkgconfig");
        if pc.is_dir() {
            env.pkg_config_path.push(pc.display().to_string());
        }
    }
}

/// Download the source tarball and extract it (stripping the top-level dir) into
/// `<scratch>/src`. macOS `tar` (libarchive) auto-detects the compression, so a
/// single `tar xf` handles `.tar.xz` / `.tar.gz` / `.tgz` / `.tar.bz2`.
async fn download_and_extract(formula: &str, spec: &SourceSpec, scratch: &Path) -> Result<PathBuf> {
    let tar_name = spec
        .tarball_url
        .rsplit('/')
        .next()
        .filter(|s| !s.is_empty())
        .unwrap_or("source.tar");
    let tar_path = scratch.join(tar_name);
    info!(url = %spec.tarball_url, "downloading {formula} source tarball");
    // Stream + verify against the formula's `urls.stable.checksum` when present;
    // otherwise the digest is computed (trust-on-first-download) and recorded in
    // the manifest. A mismatch deletes the partial and aborts the build.
    let expected = (!spec.sha256.is_empty()).then_some(spec.sha256.as_str());
    crate::package_index::download_verified(&spec.tarball_url, &tar_path, expected).await?;

    let src_dir = scratch.join("src");
    let _ = tokio::fs::remove_dir_all(&src_dir).await;
    tokio::fs::create_dir_all(&src_dir).await?;
    let untar = tokio::process::Command::new("tar")
        .arg("xf")
        .arg(&tar_path)
        .args(["--strip-components", "1", "-C"])
        .arg(&src_dir)
        .output()
        .await?;
    if !untar.status.success() {
        return Err(ToolchainError::RegistryError {
            message: format!(
                "failed to extract {formula} source: {}",
                String::from_utf8_lossy(&untar.stderr)
            ),
        });
    }
    Ok(src_dir)
}

/// Detect the build system of an extracted source tree, preferring the path that
/// needs the least extra tooling and is canonical for the project shape:
///
/// 1. `bootstrap` (+ `CMakeLists.txt`) → a self-hosting `CMake` (cmake itself).
/// 2. a generated `configure` → autotools (ready to run).
/// 3. a hand-written top-level `Makefile`/`GNUmakefile` → make-prefix (git).
/// 4. `CMakeLists.txt` → `CMake` (built with a `cmake` keg).
/// 5. `configure.ac`/`configure.in`/`autogen.sh`/`bootstrap.sh` → autotools
///    (regenerate `configure` first).
///
/// # Errors
///
/// Returns [`ToolchainError::RegistryError`] if no recognised build system is
/// present.
async fn detect_build_system(src_dir: &Path) -> Result<BuildSystem> {
    let exists = |rel: &str| {
        let p = src_dir.join(rel);
        async move { tokio::fs::try_exists(&p).await.unwrap_or(false) }
    };

    let has_bootstrap = exists("bootstrap").await || exists("bootstrap.sh").await;
    let has_cmakelists = exists("CMakeLists.txt").await;

    if has_bootstrap && has_cmakelists {
        // Self-hosting CMake (e.g. cmake's own source): its `bootstrap` builds a
        // minimal cmake then generates the real build — can't use a cmake keg to
        // build cmake. The bootstrap wrapper bakes `--prefix` into the build.
        Ok(BuildSystem::CMakeBootstrap)
    } else if exists("configure").await {
        Ok(BuildSystem::Autotools)
    } else if exists("Makefile").await || exists("GNUmakefile").await {
        // A ready top-level Makefile (not Makefile.in) is a hand-written build
        // (git, simple C tools): `make prefix=<keg> install`.
        Ok(BuildSystem::MakePrefix)
    } else if has_cmakelists {
        Ok(BuildSystem::CMake)
    } else if exists("configure.ac").await
        || exists("configure.in").await
        || exists("autogen.sh").await
        || has_bootstrap
    {
        // Autotools project shipped without a generated `configure`. Generate it
        // (needs autoconf/automake/libtool on PATH from build-dep kegs).
        Ok(BuildSystem::Autotools)
    } else {
        Err(ToolchainError::RegistryError {
            message: format!(
                "could not detect a build system \
                 (configure/CMakeLists.txt/Makefile/bootstrap) in {}",
                src_dir.display()
            ),
        })
    }
}

/// Run the detected build system into the keg prefix using the host CLT plus the
/// resolved dependency kegs (no per-formula flags — every quirk is data-driven).
#[allow(clippy::too_many_lines)]
async fn run_build(
    formula: &str,
    src_dir: &Path,
    keg: &Path,
    system: BuildSystem,
    build_env: &BuildEnv,
) -> Result<()> {
    let jobs = std::thread::available_parallelism()
        .map_or(4, std::num::NonZero::get)
        .to_string();
    let keg_str = keg.display().to_string();

    match system {
        BuildSystem::MakePrefix => {
            // Hand-written Makefile: one `make -jN prefix=<keg> install`. The
            // Makefile bakes its own install/sysconfdir from `prefix=`.
            let mut cmd = tokio::process::Command::new("make");
            cmd.current_dir(src_dir)
                .arg(format!("-j{jobs}"))
                .arg(format!("prefix={keg_str}"))
                .arg("install");
            run_cmd(formula, "make install", &mut cmd, build_env).await?;
        }
        BuildSystem::CMakeBootstrap => {
            // Self-hosting CMake: bootstrap (bakes the install prefix), then make.
            run_cmd(
                formula,
                "bootstrap",
                tokio::process::Command::new("./bootstrap")
                    .current_dir(src_dir)
                    .arg(format!("--prefix={keg_str}"))
                    .arg(format!("--parallel={jobs}")),
                build_env,
            )
            .await?;
            run_cmd(
                formula,
                "make",
                tokio::process::Command::new("make")
                    .current_dir(src_dir)
                    .arg(format!("-j{jobs}")),
                build_env,
            )
            .await?;
            run_cmd(
                formula,
                "make install",
                tokio::process::Command::new("make")
                    .current_dir(src_dir)
                    .arg("install"),
                build_env,
            )
            .await?;
        }
        BuildSystem::Autotools => {
            // Generate `configure` if the tarball shipped only configure.ac.
            if !src_dir.join("configure").is_file() {
                let autogen = src_dir.join("autogen.sh");
                if autogen.is_file() {
                    run_cmd(
                        formula,
                        "autogen.sh",
                        tokio::process::Command::new("sh")
                            .current_dir(src_dir)
                            .arg("autogen.sh"),
                        build_env,
                    )
                    .await?;
                } else {
                    run_cmd(
                        formula,
                        "autoreconf",
                        tokio::process::Command::new("autoreconf")
                            .current_dir(src_dir)
                            .arg("-fi"),
                        build_env,
                    )
                    .await?;
                }
            }

            let mut configure = tokio::process::Command::new("./configure");
            configure
                .current_dir(src_dir)
                .arg(format!("--prefix={keg_str}"));
            run_cmd(formula, "configure", &mut configure, build_env).await?;

            let mut make = tokio::process::Command::new("make");
            make.current_dir(src_dir).arg(format!("-j{jobs}"));
            run_cmd(formula, "make", &mut make, build_env).await?;

            run_cmd(
                formula,
                "make install",
                tokio::process::Command::new("make")
                    .current_dir(src_dir)
                    .arg("install"),
                build_env,
            )
            .await?;
        }
        BuildSystem::CMake => {
            let build_dir = src_dir.join("_zl_build");
            let mut configure = tokio::process::Command::new("cmake");
            configure
                .current_dir(src_dir)
                .arg("-S")
                .arg(".")
                .arg("-B")
                .arg(&build_dir)
                .arg(format!("-DCMAKE_INSTALL_PREFIX={keg_str}"))
                .arg("-DCMAKE_BUILD_TYPE=Release");
            run_cmd(formula, "cmake configure", &mut configure, build_env).await?;

            run_cmd(
                formula,
                "cmake build",
                tokio::process::Command::new("cmake")
                    .current_dir(src_dir)
                    .arg("--build")
                    .arg(&build_dir)
                    .arg("-j")
                    .arg(&jobs),
                build_env,
            )
            .await?;

            run_cmd(
                formula,
                "cmake install",
                tokio::process::Command::new("cmake")
                    .current_dir(src_dir)
                    .arg("--install")
                    .arg(&build_dir),
                build_env,
            )
            .await?;
        }
    }
    Ok(())
}

/// Apply the [`BuildEnv`] to a command and run it, returning a build error with
/// the tail of stderr on failure. The host environment is inherited; `PATH`,
/// `CPPFLAGS`, `LDFLAGS` and `PKG_CONFIG_PATH` are prepended/augmented.
async fn run_cmd(
    formula: &str,
    step: &str,
    cmd: &mut tokio::process::Command,
    env: &BuildEnv,
) -> Result<()> {
    // PATH: dependency keg bins first, then the host CLT/system paths.
    let host_path = std::env::var("PATH").unwrap_or_default();
    let system_path = "/usr/bin:/bin:/usr/sbin:/sbin";
    let mut path_parts: Vec<String> = env.path_prefix.clone();
    if !host_path.is_empty() {
        path_parts.push(host_path);
    }
    path_parts.push(system_path.to_string());
    cmd.env("PATH", path_parts.join(":"));

    if !env.cppflags.is_empty() {
        cmd.env("CPPFLAGS", env.cppflags.join(" "));
    }
    if !env.ldflags.is_empty() {
        cmd.env("LDFLAGS", env.ldflags.join(" "));
    }
    if !env.pkg_config_path.is_empty() {
        cmd.env("PKG_CONFIG_PATH", env.pkg_config_path.join(":"));
    }

    info!(formula, step, "running source build step");
    let out = cmd.output().await?;
    if !out.status.success() {
        let tail = String::from_utf8_lossy(&out.stderr)
            .lines()
            .rev()
            .take(25)
            .collect::<Vec<_>>()
            .into_iter()
            .rev()
            .collect::<Vec<_>>()
            .join("\n");
        return Err(ToolchainError::RegistryError {
            message: format!("{formula} `{step}` failed:\n{tail}"),
        });
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[tokio::test]
    async fn detect_autotools_from_configure() {
        let tmp = tempfile::tempdir().unwrap();
        tokio::fs::write(tmp.path().join("configure"), b"#!/bin/sh\n")
            .await
            .unwrap();
        assert_eq!(
            detect_build_system(tmp.path()).await.unwrap(),
            BuildSystem::Autotools
        );
    }

    #[tokio::test]
    async fn detect_cmake_from_cmakelists() {
        let tmp = tempfile::tempdir().unwrap();
        tokio::fs::write(tmp.path().join("CMakeLists.txt"), b"project(x)\n")
            .await
            .unwrap();
        assert_eq!(
            detect_build_system(tmp.path()).await.unwrap(),
            BuildSystem::CMake
        );
    }

    #[tokio::test]
    async fn detect_make_from_bare_makefile() {
        let tmp = tempfile::tempdir().unwrap();
        tokio::fs::write(tmp.path().join("Makefile"), b"all:\n\ttrue\n")
            .await
            .unwrap();
        assert_eq!(
            detect_build_system(tmp.path()).await.unwrap(),
            BuildSystem::MakePrefix
        );
    }

    /// A self-hosting `CMake` (cmake itself ships `bootstrap` + `CMakeLists.txt`)
    /// must bootstrap, NOT try to build with a cmake we don't yet have.
    #[tokio::test]
    async fn detect_cmake_bootstrap_for_self_host() {
        let tmp = tempfile::tempdir().unwrap();
        tokio::fs::write(tmp.path().join("bootstrap"), b"#!/bin/sh\n")
            .await
            .unwrap();
        tokio::fs::write(tmp.path().join("CMakeLists.txt"), b"project(cmake)\n")
            .await
            .unwrap();
        assert_eq!(
            detect_build_system(tmp.path()).await.unwrap(),
            BuildSystem::CMakeBootstrap
        );
    }

    /// A generated `configure` wins over a sibling `Makefile.in`; and a tree with
    /// only `configure.ac` is still autotools (regenerated first).
    #[tokio::test]
    async fn detect_autotools_from_configure_ac_only() {
        let tmp = tempfile::tempdir().unwrap();
        tokio::fs::write(tmp.path().join("configure.ac"), b"AC_INIT([x],[1])\n")
            .await
            .unwrap();
        assert_eq!(
            detect_build_system(tmp.path()).await.unwrap(),
            BuildSystem::Autotools
        );
    }

    /// A hand-written `Makefile` that also ships `configure.ac` (git's shape:
    /// no generated `configure`) takes the ready Makefile path, not the
    /// regenerate-with-autotools path.
    #[tokio::test]
    async fn detect_prefers_ready_makefile_over_configure_ac() {
        let tmp = tempfile::tempdir().unwrap();
        tokio::fs::write(tmp.path().join("Makefile"), b"all:\n\ttrue\n")
            .await
            .unwrap();
        tokio::fs::write(tmp.path().join("configure.ac"), b"AC_INIT([git],[1])\n")
            .await
            .unwrap();
        assert_eq!(
            detect_build_system(tmp.path()).await.unwrap(),
            BuildSystem::MakePrefix
        );
    }

    #[tokio::test]
    async fn detect_fails_on_unknown_tree() {
        let tmp = tempfile::tempdir().unwrap();
        tokio::fs::write(tmp.path().join("README"), b"hi\n")
            .await
            .unwrap();
        assert!(detect_build_system(tmp.path()).await.is_err());
    }

    #[test]
    fn dep_link_flags_use_absolute_keg_paths() {
        let tmp = tempfile::tempdir().unwrap();
        let keg = tmp.path();
        std::fs::create_dir_all(keg.join("include")).unwrap();
        std::fs::create_dir_all(keg.join("lib/pkgconfig")).unwrap();
        let mut env = BuildEnv::default();
        add_dep_link_flags(&mut env, keg);
        assert!(env.cppflags.iter().any(|f| f.contains("/include")));
        assert!(env.ldflags.iter().any(|f| f.starts_with("-L")));
        assert!(env
            .ldflags
            .iter()
            .any(|f| f.contains("-Wl,-rpath,") && !f.contains("@@HOMEBREW")));
        assert!(env.pkg_config_path.iter().any(|p| p.contains("pkgconfig")));
    }

    /// `resolve_dependencies` skips `uses_from_macos` deps without touching the
    /// network: a spec whose every dep is macOS-provided resolves to an empty
    /// build env and no resolved build deps.
    #[tokio::test]
    async fn macos_provided_deps_are_skipped_offline() {
        let tmp = tempfile::tempdir().unwrap();
        let spec = SourceSpec {
            version: "1.0".to_string(),
            tarball_url: "https://example/x.tar.gz".to_string(),
            sha256: String::new(),
            dependencies: vec!["curl".to_string(), "zlib".to_string()],
            build_dependencies: vec!["expat".to_string()],
            macos_provided: vec!["curl".to_string(), "zlib".to_string(), "expat".to_string()],
        };
        let (env, build_deps) = resolve_dependencies("demo", &spec, tmp.path(), None)
            .await
            .expect("all-macos-provided deps resolve offline");
        assert!(build_deps.is_empty(), "no keg deps to resolve");
        assert!(env.path_prefix.is_empty());
        assert!(env.cppflags.is_empty());
        assert!(env.ldflags.is_empty());
        assert!(env.pkg_config_path.is_empty());
    }

    /// The manifest's env is derived from the installed LAYOUT, not the formula
    /// name: a keg with `libexec/git-core` gets `GIT_EXEC_PATH`; one without
    /// gets none — for the same formula name either way.
    #[tokio::test]
    async fn manifest_env_is_layout_derived_not_name_derived() {
        let spec = SourceSpec {
            version: "2.55.0".to_string(),
            tarball_url: "https://example/git.tar.xz".to_string(),
            sha256: String::new(),
            dependencies: vec![],
            build_dependencies: vec![],
            macos_provided: vec![],
        };

        // Keg WITH the git-core exec dir → GIT_EXEC_PATH present.
        let with_dir = tempfile::tempdir().unwrap();
        tokio::fs::create_dir_all(with_dir.path().join("libexec/git-core"))
            .await
            .unwrap();
        let m = build_manifest("git", &spec, with_dir.path(), vec![]).await;
        assert_eq!(
            m.env.get("GIT_EXEC_PATH"),
            Some(
                &with_dir
                    .path()
                    .join("libexec/git-core")
                    .display()
                    .to_string()
            )
        );

        // Same formula NAME, no git-core dir → no GIT_EXEC_PATH (layout-driven).
        let without_dir = tempfile::tempdir().unwrap();
        let m2 = build_manifest("git", &spec, without_dir.path(), vec![]).await;
        assert!(!m2.env.contains_key("GIT_EXEC_PATH"));
    }
}