feat: add simple compile_commands.json generation

cpp/extension.bzl

@@ -1,9 +1,11 @@
-load("//cpp:repositories.bzl", "download_llvm")
+load("//cpp:repositories.bzl", "download_llvm", "setup_tools")
 
 def _init_toolchain(ctx):
     for mod in ctx.modules:
         for llvm in mod.tags.llvm:
             download_llvm(ctx, llvm.name, llvm.version)
+        for tools in mod.tags.tools:
+            setup_tools(ctx, tools.name)
 
 _llvm = tag_class(
     attrs = {
@@ -12,7 +14,13 @@ _llvm = tag_class(
     },
 )
 
+_tools = tag_class(
+    attrs = {
+        "name": attr.string(),
+    }
+)
+
 cpp = module_extension(
     implementation = _init_toolchain,
-    tag_classes = {"llvm": _llvm},
+    tag_classes = {"llvm": _llvm, "tools": _tools},
 )

cpp/private/refresh_compile_commands.py

@@ -0,0 +1,55 @@
+import subprocess
+import re
+import os
+import json
+
+
+def get_bazel_root():
+    info = subprocess.run(["bazel info"], shell=True, capture_output=True, text=True).stderr
+    return re.search(r"The pertinent workspace directory is: \'(.*)\'", info).group(1)
+
+def parse_actions(actions):
+    actions = actions.split("\n\n")
+
+    mappings = []
+
+    for action in actions:
+        if action == "":
+            continue
+        #print(action)
+        #print(re.search(r"Inputs: \[(.*)\]", action))
+        sources = []
+        for src in re.search(r"Inputs: \[(.*)\]", action).group(1).split(","):
+            if src.endswith('.cpp') or src.endswith('.c'):
+                sources.append(src.strip())
+        prefix = "Command Line: (exec "
+        command_line = action[action.find(prefix) + len(prefix):]
+        command_line = command_line[:command_line.find(")\n")]
+        command_line = command_line.replace("\\\n", "")
+
+        for src in sources:
+            command_line = command_line.replace(src, "")
+
+        command_line = command_line.split()
+
+        for src in sources:
+            mappings.append({"file": src, "arguments": command_line})
+
+    return mappings
+
+
+def save_compile_commands(mappings):
+    compile_commands = []
+
+    for m in mappings:
+        compile_commands.append({"directory": os.getcwd(), "file": m['file'], "arguments": m['arguments']})
+
+    with open('compile_commands.json', 'w', encoding='utf-8') as f:
+        json.dump(compile_commands, f, indent=2)
+
+
+base_path = get_bazel_root()
+os.chdir(base_path)
+actions = subprocess.run(["bazel aquery 'mnemonic(\"CppCompile\", (inputs(\".*cpp\", //...)))'"], shell=True, capture_output=True, text=True).stdout
+mappings = parse_actions(actions)
+save_compile_commands(mappings)

cpp/private/tools.BUILD

@@ -0,0 +1,5 @@
+load("//:tools_rules.bzl", "refresh_compile_commands")
+
+refresh_compile_commands(
+    name = "refresh_compile_commands"
+)

cpp/private/tools_rules.bzl

@@ -0,0 +1,9 @@
+def refresh_compile_commands(name):
+    native.py_binary(
+        name = name,
+        main = "refresh_compile_commands.py",
+        srcs = [
+            "refresh_compile_commands.py",
+        ],
+        imports = [''],
+    )

cpp/repositories.bzl

@@ -37,3 +37,22 @@ def download_llvm(mctx, repo_name, version):
         sha256 = clang_repo[version]["sha256"],
         build_file = "//cpp/private:llvm.BUILD",
     )
+
+def _tools_impl(rctx):
+    rctx.symlink(Label("//cpp/private:refresh_compile_commands.py"), "refresh_compile_commands.py")
+    # rctx.symlink("//cpp/private:tools.BUILD", "BUILD.bazel")
+    rctx.symlink(Label("//cpp/private:tools_rules.bzl"), "tools_rules.bzl")
+    build = rctx.read(Label("//cpp/private:tools.BUILD"))
+    rctx.file("WORKSPACE", executable=False)
+    rctx.file("BUILD", content=build)
+
+_tools = repository_rule(
+    implementation=_tools_impl,
+    configure=True,
+    # local=True,
+)
+
+def setup_tools(mctx, repo_name):
+    _tools(
+        name = repo_name,
+    )

integration_tests/.gitignore

@@ -0,0 +1,2 @@
+*.lock
+compile_commands.json

integration_tests/toolchains/BUILD.bazel

@@ -13,5 +13,8 @@ cc_library(
 cc_binary(
     name = "test",
     srcs = ["src/main.cpp"],
-    deps = [":foo"],
+    deps = [
+        ":foo",
+        "//lib2",
+    ],
 )

integration_tests/toolchains/MODULE.bazel

@@ -14,4 +14,7 @@ cpp.llvm(
     name = "llvm-17",
     version = "17.0.6",
 )
-use_repo(cpp, "llvm-17")
+cpp.tools(
+    name = "cpp_tools",
+)
+use_repo(cpp, "cpp_tools", "llvm-17")

integration_tests/toolchains/lib2/BUILD.bazel

@@ -0,0 +1,5 @@
+cc_library(
+    name = "lib2",
+    srcs = ["foo.cpp"],
+    visibility = ["//visibility:public"],
+)

integration_tests/toolchains/test_linux.sh

@@ -4,6 +4,8 @@ set -eu
 
 bazel build //...
 bazel run //:test
+bazel run @cpp_tools//:refresh_compile_commands
+test -f "compile_commands.json"
 
 bazel run --crosstool_top=@llvm-17//:toolchain //:test
 bazel run --crosstool_top=@llvm-17//:toolchain -c dbg //:test