Added cargo_build_info rule

Author: UebelAndre

cargo/defs.bzl

@@ -8,6 +8,10 @@ load(
     _cargo_bootstrap_repository = "cargo_bootstrap_repository",
     _cargo_env = "cargo_env",
 )
+load(
+    "//cargo/private:cargo_build_info.bzl",
+    _cargo_build_info = "cargo_build_info",
+)
 load(
     "//cargo/private:cargo_build_script_wrapper.bzl",
     _cargo_build_script = "cargo_build_script",
@@ -23,6 +27,7 @@ load(
 load("//cargo/private:cargo_toml_env_vars.bzl", _cargo_toml_env_vars = "cargo_toml_env_vars")
 
 cargo_bootstrap_repository = _cargo_bootstrap_repository
+cargo_build_info = _cargo_build_info
 cargo_env = _cargo_env
 
 cargo_build_script = _cargo_build_script

cargo/private/BUILD.bazel

@@ -2,6 +2,13 @@ load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
 load("@bazel_skylib//rules:copy_file.bzl", "copy_file")
 load("//rust:defs.bzl", "rust_binary")
 
+rust_binary(
+    name = "cargo_build_info_runner",
+    srcs = ["cargo_build_info_runner.rs"],
+    edition = "2021",
+    visibility = ["//visibility:public"],
+)
+
 rust_binary(
     name = "copy_file",
     srcs = ["copy_file.rs"],

cargo/private/cargo_build_info.bzl

@@ -0,0 +1,152 @@
+"""Generic rule for packaging files as a `BuildInfo` provider with optional `CcInfo` propagation.
+
+Serves as a build-script replacement for `-sys` crates that need files placed in `OUT_DIR`
+and/or linking against a C/C++ library.
+"""
+
+load("@rules_cc//cc:defs.bzl", "CcInfo")
+load("@rules_cc//cc/common:cc_common.bzl", "cc_common")
+load("//rust:rust_common.bzl", "BuildInfo")
+
+# buildifier: disable=bzl-visibility
+load("//rust/private:utils.bzl", "get_lib_name_default")
+
+def _get_user_link_flags(cc_info):
+    linker_flags = []
+    for linker_input in cc_info.linking_context.linker_inputs.to_list():
+        linker_flags.extend(linker_input.user_link_flags)
+    return linker_flags
+
+def _cargo_build_info_impl(ctx):
+    out_dir = ctx.actions.declare_directory(ctx.label.name + ".out_dir")
+    env_out = ctx.actions.declare_file(ctx.label.name + ".env")
+    dep_env_out = ctx.actions.declare_file(ctx.label.name + ".depenv")
+    flags_out = ctx.actions.declare_file(ctx.label.name + ".flags")
+    link_flags = ctx.actions.declare_file(ctx.label.name + ".linkflags")
+    link_search_paths = ctx.actions.declare_file(ctx.label.name + ".linksearchpaths")
+
+    compile_data = []
+    cc_link_flags = []
+    cc_link_search_paths = []
+
+    if ctx.attr.cc_lib:
+        cc_info = ctx.attr.cc_lib[CcInfo]
+        for linker_input in cc_info.linking_context.linker_inputs.to_list():
+            for lib in linker_input.libraries:
+                if lib.static_library:
+                    cc_link_flags.append("-lstatic={}".format(get_lib_name_default(lib.static_library)))
+                    cc_link_search_paths.append(lib.static_library.dirname)
+                    compile_data.append(lib.static_library)
+                elif lib.pic_static_library:
+                    cc_link_flags.append("-lstatic={}".format(get_lib_name_default(lib.pic_static_library)))
+                    cc_link_search_paths.append(lib.pic_static_library.dirname)
+                    compile_data.append(lib.pic_static_library)
+
+    dep_env_lines = []
+    if ctx.attr.dep_env:
+        if ctx.attr.links:
+            prefix = "DEP_{}_".format(ctx.attr.links.replace("-", "_").upper())
+        else:
+            prefix = ""
+        dep_env_lines = ["{}{}={}".format(prefix, k, v) for k, v in ctx.attr.dep_env.items()]
+
+    # Collect files and their destinations, validating single-file labels.
+    input_files = []
+    file_args = []
+    for label, dests_json in ctx.attr.out_dir_files.items():
+        src_files = label.files.to_list()
+        if len(src_files) != 1:
+            fail("Expected exactly one file for {}, got {}".format(label, len(src_files)))
+        src_file = src_files[0]
+        input_files.append(src_file)
+        for dest in json.decode(dests_json):
+            file_args.append("{}={}".format(dest, src_file.path))
+
+    args = ctx.actions.args()
+    args.add(out_dir.path, format = "--out_dir=%s")
+    args.add(env_out, format = "--env_out=%s")
+    args.add(flags_out, format = "--flags_out=%s")
+    args.add(link_flags, format = "--link_flags=%s")
+    args.add(link_search_paths, format = "--link_search_paths=%s")
+    args.add(dep_env_out, format = "--dep_env_out=%s")
+
+    args.add_all(file_args, format_each = "--file=%s")
+    args.add_all(ctx.attr.rustc_flags, format_each = "--rustc_flag=%s")
+    args.add_all(
+        [
+            "{}={}".format(k, v)
+            for k, v in ctx.attr.rustc_env.items()
+        ],
+        format_each = "--rustc_env=%s",
+    )
+    args.add_all(dep_env_lines, format_each = "--dep_env=%s")
+    args.add_all(cc_link_flags, format_each = "--link_flag=%s")
+    args.add_all(
+        depset(cc_link_search_paths).to_list(),
+        format_each = "--link_search_path=%s",
+    )
+
+    ctx.actions.run(
+        mnemonic = "CargoBuildInfo",
+        executable = ctx.executable._runner,
+        arguments = [args],
+        inputs = input_files + compile_data,
+        outputs = [out_dir, env_out, dep_env_out, flags_out, link_flags, link_search_paths],
+    )
+
+    providers = [
+        DefaultInfo(files = depset([out_dir])),
+        BuildInfo(
+            out_dir = out_dir,
+            rustc_env = env_out,
+            dep_env = dep_env_out,
+            flags = flags_out,
+            linker_flags = link_flags,
+            link_search_paths = link_search_paths,
+            compile_data = depset(compile_data),
+        ),
+    ]
+
+    if ctx.attr.cc_lib:
+        providers.append(CcInfo(
+            linking_context = cc_common.create_linking_context(
+                linker_inputs = depset([cc_common.create_linker_input(
+                    owner = ctx.label,
+                    user_link_flags = _get_user_link_flags(ctx.attr.cc_lib[CcInfo]),
+                )]),
+            ),
+        ))
+
+    return providers
+
+cargo_build_info = rule(
+    doc = "Packages files into an `OUT_DIR` and returns a `BuildInfo` provider, serving as a drop-in replacement for `cargo_build_script`.",
+    implementation = _cargo_build_info_impl,
+    attrs = {
+        "cc_lib": attr.label(
+            doc = "Optional `cc_library` whose `CcInfo` linking context is propagated. Static libraries are added to link flags and search paths.",
+            providers = [CcInfo],
+        ),
+        "dep_env": attr.string_dict(
+            doc = "Environment variables exported to dependent build scripts. Keys are auto-prefixed with `DEP_{LINKS}_` when `links` is set.",
+        ),
+        "links": attr.string(
+            doc = "The Cargo `links` field value. Used to prefix `dep_env` keys with `DEP_{LINKS}_`.",
+        ),
+        "out_dir_files": attr.label_keyed_string_dict(
+            doc = "Map of source file labels to JSON-encoded lists of destination paths within `OUT_DIR`. Use the `cargo_build_info` macro for an ergonomic `{dest: label}` interface.",
+            allow_files = True,
+        ),
+        "rustc_env": attr.string_dict(
+            doc = "Extra environment variables to set for rustc.",
+        ),
+        "rustc_flags": attr.string_list(
+            doc = "Extra flags to pass to rustc.",
+        ),
+        "_runner": attr.label(
+            executable = True,
+            cfg = "exec",
+            default = Label("//cargo/private:cargo_build_info_runner"),
+        ),
+    },
+)

cargo/private/cargo_build_info_runner.rs

@@ -0,0 +1,144 @@
+//! Process wrapper for `CargoBuildInfo` actions.
+//!
+//! Copies source files into an OUT_DIR and writes metadata files
+//! (env, dep_env, flags, link_flags, link_search_paths) consumed by `BuildInfo`.
+
+use std::fs;
+use std::path::Path;
+
+struct Args {
+    /// Directory path for the `OUT_DIR` output tree.
+    out_dir: String,
+    /// Files to copy into `out_dir` as `(dest_relative_path, src_path)` pairs.
+    files: Vec<(String, String)>,
+    /// Output path for the `BuildInfo.rustc_env` file (one `K=V` per line).
+    env_out: String,
+    /// Output path for the `BuildInfo.flags` file (one rustc flag per line).
+    flags_out: String,
+    /// Output path for the `BuildInfo.linker_flags` file (one linker flag per line).
+    link_flags_out: String,
+    /// Output path for the `BuildInfo.link_search_paths` file (one `-Lnative=` path per line).
+    link_search_paths_out: String,
+    /// Output path for the `BuildInfo.dep_env` file (one `K=V` per line, already prefixed).
+    dep_env_out: String,
+    /// Extra flags to pass to rustc, written to `flags_out`.
+    rustc_flags: Vec<String>,
+    /// Extra environment variables for rustc as `K=V`, written to `env_out`.
+    rustc_envs: Vec<String>,
+    /// Dependency environment variables as `K=V`, written to `dep_env_out`.
+    dep_envs: Vec<String>,
+    /// Linker flags derived from `CcInfo` (e.g. `-lstatic=crypto`), written to `link_flags_out`.
+    link_flags: Vec<String>,
+    /// Library search paths derived from `CcInfo`, formatted as `-Lnative=` and written to `link_search_paths_out`.
+    link_search_paths: Vec<String>,
+}
+
+impl Args {
+    /// Parse command line arguments.
+    fn parse() -> Self {
+        let mut out_dir: Option<String> = None;
+        let mut files = Vec::new();
+        let mut env_out: Option<String> = None;
+        let mut flags_out: Option<String> = None;
+        let mut link_flags_out: Option<String> = None;
+        let mut link_search_paths_out: Option<String> = None;
+        let mut dep_env_out: Option<String> = None;
+        let mut rustc_flags = Vec::new();
+        let mut rustc_envs = Vec::new();
+        let mut dep_envs = Vec::new();
+        let mut link_flags = Vec::new();
+        let mut link_search_paths = Vec::new();
+
+        for mut arg in std::env::args().skip(1) {
+            if arg.starts_with("--out_dir=") {
+                out_dir = Some(arg.split_off("--out_dir=".len()));
+            } else if arg.starts_with("--file=") {
+                let val = arg.split_off("--file=".len());
+                let (dest, src) = val
+                    .split_once('=')
+                    .unwrap_or_else(|| panic!("--file value must be dest=src, got: {val}"));
+                files.push((dest.to_owned(), src.to_owned()));
+            } else if arg.starts_with("--env_out=") {
+                env_out = Some(arg.split_off("--env_out=".len()));
+            } else if arg.starts_with("--flags_out=") {
+                flags_out = Some(arg.split_off("--flags_out=".len()));
+            } else if arg.starts_with("--link_flags=") {
+                link_flags_out = Some(arg.split_off("--link_flags=".len()));
+            } else if arg.starts_with("--link_search_paths=") {
+                link_search_paths_out = Some(arg.split_off("--link_search_paths=".len()));
+            } else if arg.starts_with("--dep_env_out=") {
+                dep_env_out = Some(arg.split_off("--dep_env_out=".len()));
+            } else if arg.starts_with("--rustc_flag=") {
+                rustc_flags.push(arg.split_off("--rustc_flag=".len()));
+            } else if arg.starts_with("--rustc_env=") {
+                rustc_envs.push(arg.split_off("--rustc_env=".len()));
+            } else if arg.starts_with("--dep_env=") {
+                dep_envs.push(arg.split_off("--dep_env=".len()));
+            } else if arg.starts_with("--link_flag=") {
+                link_flags.push(arg.split_off("--link_flag=".len()));
+            } else if arg.starts_with("--link_search_path=") {
+                link_search_paths.push(arg.split_off("--link_search_path=".len()));
+            } else {
+                panic!("cargo_build_info_runner: unknown argument: {arg}");
+            }
+        }
+
+        Args {
+            out_dir: out_dir.expect("--out_dir is required"),
+            files,
+            env_out: env_out.expect("--env_out is required"),
+            flags_out: flags_out.expect("--flags_out is required"),
+            link_flags_out: link_flags_out.expect("--link_flags is required"),
+            link_search_paths_out: link_search_paths_out.expect("--link_search_paths is required"),
+            dep_env_out: dep_env_out.expect("--dep_env_out is required"),
+            rustc_flags,
+            rustc_envs,
+            dep_envs,
+            link_flags,
+            link_search_paths,
+        }
+    }
+}
+
+fn write_lines(path: &str, lines: &[String]) {
+    let content = if lines.is_empty() {
+        String::new()
+    } else {
+        lines.join("\n")
+    };
+    fs::write(path, content).unwrap_or_else(|e| panic!("Failed to write {path}: {e}"));
+}
+
+fn main() {
+    let args = Args::parse();
+
+    fs::create_dir_all(&args.out_dir)
+        .unwrap_or_else(|e| panic!("Failed to create out_dir {:?}: {e}", args.out_dir));
+
+    if args.files.is_empty() {
+        fs::write(Path::new(&args.out_dir).join(".empty"), "")
+            .unwrap_or_else(|e| panic!("Failed to write .empty sentinel: {e}"));
+    }
+
+    for (dest_name, src_path) in &args.files {
+        let dest = Path::new(&args.out_dir).join(dest_name);
+        if let Some(parent) = dest.parent() {
+            fs::create_dir_all(parent)
+                .unwrap_or_else(|e| panic!("Failed to create parent dir {:?}: {e}", parent));
+        }
+        fs::copy(src_path, &dest)
+            .unwrap_or_else(|e| panic!("Failed to copy {:?} -> {:?}: {e}", src_path, dest));
+    }
+
+    write_lines(&args.flags_out, &args.rustc_flags);
+    write_lines(&args.env_out, &args.rustc_envs);
+    write_lines(&args.dep_env_out, &args.dep_envs);
+    write_lines(&args.link_flags_out, &args.link_flags);
+
+    let search_paths: Vec<String> = args
+        .link_search_paths
+        .iter()
+        .map(|p| format!("-Lnative=${{pwd}}/{p}"))
+        .collect();
+    write_lines(&args.link_search_paths_out, &search_paths);
+}

cargo/private/cargo_build_info_wrapper.bzl

@@ -0,0 +1,62 @@
+"""cargo_build_info wrapper that only exists until the min supported version
+of Bazel includes https://github.com/bazelbuild/bazel/issues/7989
+"""
+
+load(":cargo_build_info.bzl", _cargo_build_info = "cargo_build_info")
+
+def cargo_build_info(
+        name,
+        out_dir_files = {},
+        cc_lib = None,
+        rustc_flags = None,
+        rustc_env = None,
+        dep_env = None,
+        links = "",
+        **kwargs):
+    """Packages files into an `OUT_DIR` and returns a `BuildInfo` provider.
+
+    This is a generic build-script replacement for `-sys` crates. It places
+    arbitrary files into an `OUT_DIR` directory, optionally propagates `CcInfo`
+    from a `cc_library`, and returns `BuildInfo` so the crate's `lib.rs` can
+    use `include!(concat!(env!("OUT_DIR"), "/..."))` unchanged.
+
+    Use with `override_target_build_script` in crate annotations:
+
+    ```python
+    crate.annotation(
+        crate = "my-native-sys",
+        override_target_build_script = "//path:my_sys_bs",
+    )
+    ```
+
+    Args:
+        name: Unique name for this target.
+        out_dir_files: Dict mapping destination filenames (within `OUT_DIR`) to
+            source file labels. A single label can appear as multiple destinations.
+            Example: `{"bindings.rs": ":my_bindgen", "config.h": ":my_header"}`
+        cc_lib: Optional `cc_library` label for `CcInfo` propagation (link flags,
+            search paths). The library's static archives are added as link dependencies.
+        rustc_flags: Extra flags to pass to rustc.
+        rustc_env: Extra environment variables for rustc.
+        dep_env: Environment variables exported to dependent build scripts.
+            Auto-prefixed with `DEP_{LINKS}_` when `links` is set.
+        links: Cargo `links` field value, used to prefix `dep_env` keys.
+        **kwargs: Common attributes forwarded to the underlying rule
+            (`visibility`, `tags`, `target_compatible_with`, `exec_compatible_with`).
+    """
+    inverted = {}
+    for dest, label in out_dir_files.items():
+        if label not in inverted:
+            inverted[label] = []
+        inverted[label].append(dest)
+
+    _cargo_build_info(
+        name = name,
+        out_dir_files = {label: json.encode(dests) for label, dests in inverted.items()},
+        cc_lib = cc_lib,
+        rustc_flags = rustc_flags or [],
+        rustc_env = rustc_env or {},
+        dep_env = dep_env or {},
+        links = links,
+        **kwargs
+    )