Update rust_bindgen_library to only link cc_lib into the direct consumer

Author: UebelAndre

bindgen/private/bindgen.bzl

@@ -20,6 +20,7 @@ load(
 )
 load("@rules_cc//cc:defs.bzl", "CcInfo")
 load("//rust:defs.bzl", "rust_library")
+load("//rust:rust_common.bzl", "BuildInfo")
 
 # buildifier: disable=bzl-visibility
 load("//rust/private:rustc.bzl", "get_linker_and_args")
@@ -64,27 +65,100 @@ def rust_bindgen_library(
     if "tags" in kwargs:
         kwargs.pop("tags")
 
+    sub_tags = tags + ([] if "manual" in tags else ["manual"])
+
     deps = kwargs.get("deps") or []
     if "deps" in kwargs:
         kwargs.pop("deps")
 
+    bindgen_kwargs = {}
+    if "leak_symbols" in kwargs:
+        bindgen_kwargs.update({"leak_symbols": kwargs.pop("leak_symbols")})
+
     rust_bindgen(
         name = name + "__bindgen",
         header = header,
         cc_lib = cc_lib,
         bindgen_flags = bindgen_flags or [],
         clang_flags = clang_flags or [],
-        tags = ["manual"],
+        tags = sub_tags,
+        **bindgen_kwargs
     )
 
+    for custom_tag in ["__bindgen", "no-clippy", "no-rustfmt"]:
+        tags = tags + ([] if custom_tag in tags else [custom_tag])
+
     rust_library(
         name = name,
         srcs = [name + "__bindgen.rs"],
-        tags = tags + ["__bindgen", "noclippy"],
-        deps = deps + [cc_lib],
+        deps = deps + [name + "__bindgen"],
+        tags = tags,
         **kwargs
     )
 
+def _generate_cc_link_build_info(ctx, cc_lib):
+    """Produce the eqivilant cargo_build_script providers for use in linking the library.
+
+    Args:
+        ctx (ctx): The rule's context object
+        cc_lib (Target): The `rust_bindgen.cc_lib` target.
+
+    Returns:
+        The `BuildInfo` provider.
+    """
+    compile_data = []
+    linker_flags = []
+    linker_search_paths = []
+
+    for linker_input in cc_lib[CcInfo].linking_context.linker_inputs.to_list():
+        for lib in linker_input.libraries:
+            if lib.static_library:
+                linker_flags.append("-lstatic={}".format(lib.static_library.owner.name))
+                linker_search_paths.append(lib.static_library.dirname)
+                compile_data.append(lib.static_library)
+            elif lib.pic_static_library:
+                linker_flags.append("-lstatic={}".format(lib.pic_static_library.owner.name))
+                linker_search_paths.append(lib.pic_static_library.dirname)
+                compile_data.append(lib.pic_static_library)
+
+        linker_flags.extend(linker_input.user_link_flags)
+
+    if not compile_data:
+        fail("No static libraries found in {}".format(
+            cc_lib.label,
+        ))
+
+    empty_file = ctx.actions.declare_file("{}.empty".format(ctx.label.name))
+    ctx.actions.write(
+        output = empty_file,
+        content = "",
+    )
+
+    link_flags = ctx.actions.declare_file("{}.link_flags".format(ctx.label.name))
+    ctx.actions.write(
+        output = link_flags,
+        content = "\n".join(linker_flags),
+    )
+
+    link_search_paths = ctx.actions.declare_file("{}.link_search_paths".format(ctx.label.name))
+    ctx.actions.write(
+        output = link_search_paths,
+        content = "\n".join([
+            "-Lnative=${{pwd}}/{}".format(path)
+            for path in depset(linker_search_paths).to_list()
+        ]),
+    )
+
+    return BuildInfo(
+        out_dir = None,
+        rustc_env = empty_file,
+        dep_env = empty_file,
+        flags = empty_file,
+        link_flags = link_flags,
+        link_search_paths = link_search_paths,
+        compile_data = depset(compile_data),
+    )
+
 def _rust_bindgen_impl(ctx):
     # nb. We can't grab the cc_library`s direct headers, so a header must be provided.
     cc_lib = ctx.attr.cc_lib
@@ -200,6 +274,19 @@ def _rust_bindgen_impl(ctx):
         tools = tools,
     )
 
+    if ctx.attr.leak_symbols:
+        providers = [cc_common.merge_cc_infos(
+            direct_cc_infos = [cc_lib[CcInfo]],
+        )]
+    else:
+        providers = [_generate_cc_link_build_info(ctx, cc_lib)]
+
+    return providers + [
+        OutputGroupInfo(
+            bindgen_bindings = depset([output]),
+        ),
+    ]
+
 rust_bindgen = rule(
     doc = "Generates a rust source file from a cc_library and a header.",
     implementation = _rust_bindgen_impl,
@@ -220,6 +307,13 @@ rust_bindgen = rule(
             allow_single_file = True,
             mandatory = True,
         ),
+        "leak_symbols": attr.bool(
+            doc = (
+                "If True, `cc_lib` will be exposed and linked into all downstream consumers of the target vs. the " +
+                "`rust_library` directly consuming it."
+            ),
+            default = False,
+        ),
         "_cc_toolchain": attr.label(
             default = Label("@bazel_tools//tools/cpp:current_cc_toolchain"),
         ),

cargo/private/cargo_build_script.bzl

@@ -301,6 +301,7 @@ def _cargo_build_script_impl(ctx):
             flags = flags_out,
             link_flags = link_flags,
             link_search_paths = link_search_paths,
+            compile_data = depset([]),
         ),
         OutputGroupInfo(
             streams = depset([streams.stdout, streams.stderr]),
@@ -449,6 +450,7 @@ def _cargo_dep_env_implementation(ctx):
             link_search_paths = empty_file,
             out_dir = out_dir,
             rustc_env = empty_file,
+            compile_data = depset([]),
         ))
     return [
         DefaultInfo(files = depset(ctx.files.src)),
@@ -465,8 +467,9 @@ def _cargo_dep_env_implementation(ctx):
             flags = empty_file,
             link_flags = empty_file,
             link_search_paths = empty_file,
-            out_dir = empty_dir,
+            out_dir = None,
             rustc_env = empty_file,
+            compile_data = depset([]),
         ),
         # Information here is used directly by dependencies, and it is an error to have more than
         # one dependency which sets this. This is the main way to specify information from build

examples/bindgen/BUILD.bazel

@@ -1,19 +1,15 @@
-load("@rules_cc//cc:defs.bzl", "cc_library")
 load("@rules_rust//bindgen:bindgen.bzl", "rust_bindgen_library")
 load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_test")
 
-cc_library(
-    name = "simple",
-    srcs = ["simple.h"],
-)
-
 rust_bindgen_library(
     name = "simple_bindgen",
     bindgen_flags = [
+        "--allowlist-function=simple_.*",
         "--allowlist-var=SIMPLE_.*",
     ],
-    cc_lib = ":simple",
-    header = "simple.h",
+    cc_lib = "//bindgen/simple",
+    header = "//bindgen/simple:simple.h",
+    leak_symbols = False,
 )
 
 rust_binary(
@@ -26,3 +22,25 @@ rust_test(
     name = "simple_test",
     crate = ":simple_example",
 )
+
+rust_bindgen_library(
+    name = "simple_leaked_bindgen",
+    bindgen_flags = [
+        "--allowlist-function=simple_.*",
+        "--allowlist-var=SIMPLE_.*",
+    ],
+    cc_lib = "//bindgen/simple",
+    header = "//bindgen/simple:simple.h",
+    leak_symbols = True,
+)
+
+rust_binary(
+    name = "simple_leaked_example",
+    srcs = ["main_leaked.rs"],
+    deps = [":simple_leaked_bindgen"],
+)
+
+rust_test(
+    name = "simple_leaked_test",
+    crate = ":simple_leaked_example",
+)

examples/bindgen/main.rs

@@ -1,11 +1,22 @@
+use simple_bindgen;
+
+fn simple_function() -> i64 {
+    unsafe { return simple_bindgen::simple_function() }
+}
+
 fn main() {
-    println!("The value is {}!", simple_bindgen::SIMPLE_VALUE);
+    println!(
+        "The values are {} and {}!",
+        simple_bindgen::SIMPLE_VALUE,
+        simple_function()
+    );
 }
 
 #[cfg(test)]
 mod test {
     #[test]
     fn do_the_test() {
         assert_eq!(42, simple_bindgen::SIMPLE_VALUE);
+        assert_eq!(1337, super::simple_function());
     }
 }

examples/bindgen/main_leaked.rs

@@ -0,0 +1,22 @@
+use simple_leaked_bindgen;
+
+fn simple_function() -> i64 {
+    unsafe { return simple_leaked_bindgen::simple_function() }
+}
+
+fn main() {
+    println!(
+        "The values are {} and {}!",
+        simple_leaked_bindgen::SIMPLE_VALUE,
+        simple_function()
+    );
+}
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn do_the_test() {
+        assert_eq!(42, simple_leaked_bindgen::SIMPLE_VALUE);
+        assert_eq!(1337, super::simple_function());
+    }
+}

examples/bindgen/simple.h

@@ -0,0 +1,15 @@
+load("@rules_cc//cc:defs.bzl", "cc_library")
+
+exports_files(
+    [
+        "simple.h",
+    ],
+    visibility = ["//bindgen:__pkg__"],
+)
+
+cc_library(
+    name = "simple",
+    srcs = ["simple.cc"],
+    hdrs = ["simple.h"],
+    visibility = ["//bindgen:__pkg__"],
+)

examples/bindgen/simple/BUILD.bazel

@@ -0,0 +1,3 @@
+#include "simple.h"
+
+EXTERN_C const int64_t simple_function() { return 1337; }

examples/bindgen/simple/simple.cc

@@ -0,0 +1,16 @@
+#ifndef __SIMPLE_H_INCLUDE__
+#define __SIMPLE_H_INCLUDE__
+
+#ifdef __cplusplus
+#define EXTERN_C extern "C"
+#else
+#define EXTERN_C
+#endif
+
+#include <stdint.h>
+
+EXTERN_C const int64_t SIMPLE_VALUE = 42;
+
+EXTERN_C const int64_t simple_function();
+
+#endif

examples/bindgen/simple/simple.h

@@ -72,11 +72,12 @@ CrateGroupInfo = provider(
 BuildInfo = provider(
     doc = "A provider containing `rustc` build settings for a given Crate.",
     fields = {
+        "compile_data": "Depset[File]: Compile data provided by the build script that was not copied into `out_dir`.",
         "dep_env": "File: extra build script environment varibles to be set to direct dependencies.",
         "flags": "File: file containing additional flags to pass to rustc",
         "link_flags": "File: file containing flags to pass to the linker",
         "link_search_paths": "File: file containing search paths to pass to the linker",
-        "out_dir": "File: directory containing the result of a build script",
+        "out_dir": "Optional[File]: directory containing the result of a build script",
         "rustc_env": "File: file containing additional environment variables to set for rustc.",
     },
 )