clang-tidy emit action per file to lint and merge stdout and error codes

Author: molar

example/src/cpp/main/BUILD

@@ -1,5 +1,5 @@
 load("@rules_cc//cc:defs.bzl", "cc_binary", "cc_library")
-
+load("//tools/lint:linters.bzl", "clang_tidy_test")
 cc_library(
     name = "hello-greet",
     srcs = ["hello-greet.cc"],
@@ -17,6 +17,11 @@ cc_binary(
     ],
 )
 
+clang_tidy_test(
+    name = "hello-world-clang-tidy-test",
+    srcs = ["hello-world"],
+)
+
 cc_library(
     name = "hello-greet-with-error",
     srcs = ["hello-greet-with-error.cc"],

lint/clang_tidy.bzl

@@ -309,29 +309,53 @@ def clang_tidy_action(ctx, compilation_context, executable, srcs, stdout, exit_c
 
     outputs = [stdout]
     env = _get_env(ctx, srcs)
-    env["CLANG_TIDY__STDOUT_STDERR_OUTPUT_FILE"] = stdout.path
 
     if exit_code:
-        env["CLANG_TIDY__EXIT_CODE_OUTPUT_FILE"] = exit_code.path
         outputs.append(exit_code)
 
     # pass compiler args via a params file. The command line may already be long due to
     # sources, which can't go the params file, so materialize it always.
-    clang_tidy_args = _get_args(ctx, compilation_context, srcs)
-    compiler_args = ctx.actions.args()
-    compiler_args.add_all(_get_compiler_args(ctx, compilation_context, srcs))
-    compiler_args.use_param_file("--config %s", use_always = True)
 
+    intermediate_outputs_stdout = []
+    intermediate_outputs_exit_code = []
+    # create an action for each file
+    for src in srcs:
+        out_intermediate_stdout = ctx.actions.declare_file(stdout.short_path+".{}.stdout".format(len(intermediate_outputs_stdout)))
+        env["CLANG_TIDY__STDOUT_STDERR_OUTPUT_FILE"] = out_intermediate_stdout.path
+        if exit_code:
+            out_intermediate_exit_code = ctx.actions.declare_file(exit_code.short_path+".{}.exit_code".format(len(intermediate_outputs_exit_code)))
+            env["CLANG_TIDY__EXIT_CODE_OUTPUT_FILE"] = out_intermediate_exit_code.path
+        clang_tidy_args = _get_args(ctx, compilation_context, [src])
+        compiler_args = ctx.actions.args()
+        compiler_args.add_all(_get_compiler_args(ctx, compilation_context, [src]))
+        compiler_args.use_param_file("--config %s", use_always = True)
+
+        ctx.actions.run_shell(
+            inputs = _gather_inputs(ctx, compilation_context, [src]),
+            outputs = [out_intermediate_stdout,]+([out_intermediate_exit_code] if exit_code else []),
+            tools = [executable._clang_tidy_wrapper, executable._clang_tidy, find_cpp_toolchain(ctx).all_files],
+            command = executable._clang_tidy_wrapper.path + " $@",
+            arguments = [executable._clang_tidy.path] + clang_tidy_args + ["--", compiler_args],
+            env = env,
+            mnemonic = _MNEMONIC,
+            progress_message = "Linting %{label} with clang-tidy",
+        )
+        intermediate_outputs_stdout.append(out_intermediate_stdout)
+        if exit_code:
+            intermediate_outputs_exit_code.append(out_intermediate_exit_code)
+
+    # emit
     ctx.actions.run_shell(
-        inputs = _gather_inputs(ctx, compilation_context, srcs),
-        outputs = outputs,
-        tools = [executable._clang_tidy_wrapper, executable._clang_tidy, find_cpp_toolchain(ctx).all_files],
-        command = executable._clang_tidy_wrapper.path + " $@",
-        arguments = [executable._clang_tidy.path] + clang_tidy_args + ["--", compiler_args],
-        env = env,
-        mnemonic = _MNEMONIC,
-        progress_message = "Linting %{label} with clang-tidy",
+        inputs = intermediate_outputs_stdout,
+        outputs = [stdout],
+        command = "cat {} > {}".format(" ".join([f.path for f in intermediate_outputs_stdout]),stdout.path)
     )
+    if exit_code:
+        ctx.actions.run_shell(
+            inputs = intermediate_outputs_exit_code,
+            outputs = [exit_code],
+            command = "cat {} | sort -nr | head -n 1 > {}".format(" ".join([f.path for f in intermediate_outputs_exit_code]),exit_code.path)
+        )
 
 def clang_tidy_fix(ctx, compilation_context, executable, srcs, patch, stdout, exit_code):
     """Create a Bazel Action that spawns clang-tidy with --fix.