Support precompiled library binaries

.gitignore

@@ -1,2 +1,2 @@
-/Cargo.lock
-/target
+Cargo.lock
+target

Cargo.toml

@@ -1,5 +1,8 @@
-[package]
-name = "system-deps"
+[workspace]
+members = ["meta"]
+exclude = ["target"]
+
+[workspace.package]
 version = "7.0.5"
 authors = [
     "Guillaume Desmottes <[email protected]>",
@@ -18,17 +21,43 @@ keywords = [
 edition = "2018"
 rust-version = "1.78.0"
 documentation = "https://docs.rs/system-deps/"
+
+[workspace.dependencies]
+system-deps-meta = { path = "./meta" }
+
+[package]
+name = "system-deps"
+version.workspace = true
+authors.workspace = true
+license.workspace = true
+description.workspace = true
+keywords.workspace = true
+edition.workspace = true
+documentation.workspace = true
 readme = "README.md"
 
 [dependencies]
-pkg-config = "0.3.25"
+system-deps-meta = { workspace = true, optional = true }
+pkg-config = "0.3"
 toml = { version = "0.8", default-features = false, features = ["parse"] }
 version-compare = "0.2"
 heck = "0.5"
 # allow cfg-expr between 0.17 and 0.20 to keep MSRV lower
 cfg-expr = { version = ">= 0.17, < 0.21", features = ["targets"] }
 
+[build-dependencies]
+system-deps-meta = { workspace = true, optional = true }
+
 [dev-dependencies]
-lazy_static = "1"
+system-deps-meta = { workspace = true, features = ["test"] }
 itertools = "0.14"
 assert_matches = "1.5"
+tiny_http = "0.12"
+
+[features]
+default = []
+# FIXME: How can this be done when using resolver v2? Features are separated
+binary = ["system-deps-meta/binary"]
+gz = ["system-deps-meta/gz"]
+xz = ["system-deps-meta/xz"]
+zip = ["system-deps-meta/zip"]

build.rs

@@ -0,0 +1,35 @@
+pub fn main() {
+    #[cfg(feature = "binary")]
+    binary::build().unwrap_or_else(|e| panic!("{}", e));
+}
+
+#[cfg(feature = "binary")]
+mod binary {
+    use std::{fs, path::Path};
+
+    use system_deps_meta::{
+        binary::{merge, Paths},
+        error::{BinaryError, Error},
+        parse::read_metadata,
+        BUILD_MANIFEST, TARGET_DIR,
+    };
+
+    // Add pkg-config paths to the overrides
+    pub fn build() -> Result<(), Error> {
+        // Read metadata from the crate graph
+        let metadata = read_metadata(BUILD_MANIFEST, "system-deps", merge)?;
+
+        // Download the binaries and get their pkg_config paths
+        let paths: Paths = metadata.into_iter().collect();
+
+        // Write the binary paths to a file for later use
+        let dest = Path::new(TARGET_DIR).join("paths.toml");
+        fs::write(&dest, paths.to_string()?).map_err(BinaryError::InvalidDirectory)?;
+        println!(
+            "cargo:rustc-env=SYSTEM_DEPS_BINARY_PATHS={}",
+            dest.display()
+        );
+
+        Ok(())
+    }
+}

meta/Cargo.toml

@@ -0,0 +1,28 @@
+[package]
+name = "system-deps-meta"
+version.workspace = true
+authors.workspace = true
+license.workspace = true
+description.workspace = true
+keywords.workspace = true
+edition.workspace = true
+documentation.workspace = true
+
+[dependencies]
+cargo_metadata = "0.20"
+serde = "1.0"
+toml = "0.8"
+cfg-expr = { version = ">= 0.17, < 0.21", features = ["targets"] }
+sha256 = { version = "1.6", optional = true }
+attohttpc = { version = "0.29", optional = true }
+flate2 = { version = "1.1", optional = true }
+xz = { version = "0.1", optional = true }
+tar = { version = "0.4", optional = true }
+zip = { version = "2.4", optional = true }
+
+[features]
+binary = ["dep:sha256", "dep:attohttpc"]
+gz = ["dep:flate2", "dep:tar"]
+xz = ["dep:xz", "dep:tar"]
+zip = ["dep:zip"]
+test = []

meta/build.rs

@@ -0,0 +1,81 @@
+use std::{
+    env,
+    path::{Path, PathBuf},
+};
+
+/// Environment variable to override the top level `Cargo.toml`.
+const MANIFEST_VAR: &str = "SYSTEM_DEPS_BUILD_MANIFEST";
+
+/// Environment variable to override the directory where `system-deps`
+/// will store build products such as binary outputs.
+const TARGET_VAR: &str = "SYSTEM_DEPS_TARGET_DIR";
+
+/// Try to find the project root using locate-project
+fn find_with_cargo(dir: &Path) -> Option<PathBuf> {
+    let out = std::process::Command::new(env!("CARGO"))
+        .current_dir(dir)
+        .arg("locate-project")
+        .arg("--workspace")
+        .arg("--message-format=plain")
+        .output()
+        .ok()?
+        .stdout;
+    if out.is_empty() {
+        return None;
+    }
+    Some(PathBuf::from(std::str::from_utf8(&out).ok()?.trim()))
+}
+
+/// Get the manifest from the project directory. This is **not** the directory
+/// where `system-deps` is cloned, it should point to the top level `Cargo.toml`
+/// file. This is needed to obtain metadata from all of dependencies, including
+/// those downstream of the package being compiled.
+///
+/// If the target directory is not a subfolder of the project it will not be
+/// possible to detect it automatically. In this case, the user will be asked
+/// to specify the `SYSTEM_DEPS_MANIFEST` variable to point to it.
+///
+/// See https://github.com/rust-lang/cargo/issues/3946 for updates on first
+/// class support for finding the workspace root.
+fn manifest() -> PathBuf {
+    println!("cargo:rerun-if-env-changed={}", MANIFEST_VAR);
+    if let Ok(root) = env::var(MANIFEST_VAR) {
+        return PathBuf::from(&root);
+    }
+
+    // When build scripts are invoked, they have one argument pointing to the
+    // build path of the crate in the target directory. This is different than
+    // the `OUT_DIR` environment variable, that can point to a target directory
+    // where the checkout of the dependency is.
+    let mut dir = PathBuf::from(
+        std::env::args()
+            .next()
+            .expect("There should be cargo arguments for determining the root"),
+    );
+    dir.pop();
+
+    // Try to find the project with cargo
+    find_with_cargo(&dir).expect(
+        "Error determining the cargo root manifest.\n\
+         Please set `SYSTEM_DEPS_MANIFEST` to the path of your project's Cargo.toml",
+    )
+}
+
+/// Set compile time values for the manifest and target paths, and the compile target.
+/// This step needs to happen in a build script so that the paths are only calculated
+/// once and every invocation of `system-deps` references the same metadata.
+pub fn main() {
+    let manifest = manifest();
+    println!("cargo:rerun-if-changed={}", manifest.display());
+    println!("cargo:rustc-env={}={}", MANIFEST_VAR, manifest.display());
+
+    // TODO: Use an user cache dir, similar to .cargo?
+    let target_dir = env::var(TARGET_VAR).or(env::var("OUT_DIR")).unwrap();
+    println!("cargo:rerun-if-env-changed={}", TARGET_VAR);
+    println!("cargo:rustc-env={}={}", TARGET_VAR, target_dir);
+
+    println!(
+        "cargo:rustc-env=TARGET={}",
+        std::env::var("TARGET").unwrap()
+    );
+}