Added support for split_coverage_post_processing

.bazelci/presubmit.yml

@@ -42,6 +42,10 @@ coverage_validation_post_shell_commands: &coverage_validation_post_shell_command
       ; 1>&2 cat bazel-out/_coverage/_coverage_report.dat \
       ; exit 1 \
       ; }
+split_coverage_postprocessing_shell_commands: &split_coverage_postprocessing_shell_commands
+  - echo "coverage --experimental_fetch_all_coverage_outputs" >> user.bazelrc
+  - echo "coverage --experimental_split_coverage_postprocessing" >> user.bazelrc
+  - echo "build --//rust/settings:experimental_use_coverage_metadata_files" >> user.bazelrc
 tasks:
   ubuntu2004:
     build_targets: *default_linux_targets
@@ -69,6 +73,18 @@ tasks:
   windows:
     build_targets: *default_windows_targets
     test_targets: *default_windows_targets
+  ubuntu2004_split_coverage_postprocessing:
+    name: Split Coverage Postprocessing
+    platform: ubuntu2004
+    shell_commands: *split_coverage_postprocessing_shell_commands
+    coverage_targets: *default_linux_targets
+    post_shell_commands: *coverage_validation_post_shell_commands
+  macos_split_coverage_postprocessing:
+    name: Split Coverage Postprocessing
+    platform: macos
+    shell_commands: *split_coverage_postprocessing_shell_commands
+    coverage_targets: *default_macos_targets
+    post_shell_commands: *coverage_validation_post_shell_commands
   ubuntu2004_opt:
     name: Opt Mode
     platform: ubuntu2004

rust/private/rust.bzl

@@ -480,13 +480,17 @@ def _rust_test_impl(ctx):
         if not toolchain.llvm_profdata:
             fail("toolchain.llvm_profdata is required if toolchain.llvm_cov is set.")
 
-        llvm_cov_path = toolchain.llvm_cov.short_path
-        if llvm_cov_path.startswith("../"):
-            llvm_cov_path = llvm_cov_path[len("../"):]
+        if toolchain._experimental_use_coverage_metadata_files:
+            llvm_cov_path = toolchain.llvm_cov.path
+            llvm_profdata_path = toolchain.llvm_profdata.path
+        else:
+            llvm_cov_path = toolchain.llvm_cov.path
+            if llvm_cov_path.startswith("../"):
+                llvm_cov_path = llvm_cov_path[len("../"):]
 
-        llvm_profdata_path = toolchain.llvm_profdata.short_path
-        if llvm_profdata_path.startswith("../"):
-            llvm_profdata_path = llvm_profdata_path[len("../"):]
+            llvm_profdata_path = toolchain.llvm_profdata.short_path
+            if llvm_profdata_path.startswith("../"):
+                llvm_profdata_path = llvm_profdata_path[len("../"):]
 
         env["RUST_LLVM_COV"] = llvm_cov_path
         env["RUST_LLVM_PROFDATA"] = llvm_profdata_path
@@ -742,7 +746,7 @@ _common_attrs = {
 
 _coverage_attrs = {
     "_collect_cc_coverage": attr.label(
-        default = Label("//util:collect_coverage"),
+        default = Label("//util/collect_coverage"),
         executable = True,
         cfg = "exec",
     ),

rust/private/rustc.bzl

@@ -997,6 +997,7 @@ def construct_arguments(
         rustc_flags.add("proc_macro")
 
     if toolchain.llvm_cov and ctx.configuration.coverage_enabled:
+        # https://doc.rust-lang.org/rustc/instrument-coverage.html
         rustc_flags.add("--codegen=instrument-coverage")
 
     # Make bin crate data deps available to tests.
@@ -1364,8 +1365,10 @@ def rustc_compile_action(
     if toolchain.llvm_cov and ctx.configuration.coverage_enabled and crate_info.is_test:
         coverage_runfiles = [toolchain.llvm_cov, toolchain.llvm_profdata]
 
+    experimental_use_coverage_metadata_files = toolchain._experimental_use_coverage_metadata_files
+
     runfiles = ctx.runfiles(
-        files = getattr(ctx.files, "data", []) + coverage_runfiles,
+        files = getattr(ctx.files, "data", []) + ([] if experimental_use_coverage_metadata_files else coverage_runfiles),
         collect_data = True,
     )
     if getattr(ctx.attr, "crate", None):
@@ -1376,18 +1379,29 @@ def rustc_compile_action(
     # https://github.com/bazelbuild/rules_rust/issues/771
     out_binary = getattr(attr, "out_binary", False)
 
+    executable = crate_info.output if crate_info.type == "bin" or crate_info.is_test or out_binary else None
+
+    instrumented_files_kwargs = {
+        "dependency_attributes": ["deps", "crate"],
+        "extensions": ["rs"],
+        "source_attributes": ["srcs"],
+    }
+
+    if experimental_use_coverage_metadata_files:
+        instrumented_files_kwargs.update({
+            "metadata_files": coverage_runfiles + [executable] if executable else [],
+        })
+
     providers = [
         DefaultInfo(
             # nb. This field is required for cc_library to depend on our output.
             files = depset(outputs),
             runfiles = runfiles,
-            executable = crate_info.output if crate_info.type == "bin" or crate_info.is_test or out_binary else None,
+            executable = executable,
         ),
         coverage_common.instrumented_files_info(
             ctx,
-            dependency_attributes = ["deps", "crate"],
-            extensions = ["rs"],
-            source_attributes = ["srcs"],
+            **instrumented_files_kwargs
         ),
     ]
 

rust/repositories.bzl

@@ -67,11 +67,11 @@ def rules_rust_dependencies():
     maybe(
         http_archive,
         name = "bazel_skylib",
+        sha256 = "66ffd9315665bfaafc96b52278f57c7e2dd09f5ede279ea6d39b2be471e7e3aa",
         urls = [
-            "https://github.com/bazelbuild/bazel-skylib/releases/download/1.2.0/bazel-skylib-1.2.0.tar.gz",
-            "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.2.0/bazel-skylib-1.2.0.tar.gz",
+            "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.4.2/bazel-skylib-1.4.2.tar.gz",
+            "https://github.com/bazelbuild/bazel-skylib/releases/download/1.4.2/bazel-skylib-1.4.2.tar.gz",
         ],
-        sha256 = "af87959afe497dc8dfd4c6cb66e1279cb98ccc84284619ebfec27d9c09a903de",
     )
 
     # Make the iOS simulator constraint available, which is referenced in abi_to_constraints()

rust/settings/BUILD.bazel

@@ -52,6 +52,13 @@ bool_flag(
     build_setting_default = False,
 )
 
+# A flag to have coverage tooling added as `coverage_common.instrumented_files_info.metadata_files` instead of
+# reporting tools like `llvm-cov` and `llvm-profdata` as runfiles to each test.
+bool_flag(
+    name = "experimental_use_coverage_metadata_files",
+    build_setting_default = False,
+)
+
 bzl_library(
     name = "bzl_lib",
     srcs = glob(["**/*.bzl"]),

rust/toolchain.bzl

@@ -640,6 +640,7 @@ def _rust_toolchain_impl(ctx):
         _pipelined_compilation = pipelined_compilation,
         _experimental_use_cc_common_link = experimental_use_cc_common_link,
         _experimental_use_global_allocator = experimental_use_global_allocator,
+        _experimental_use_coverage_metadata_files = ctx.attr._experimental_use_coverage_metadata_files[BuildSettingInfo].value,
         _no_std = no_std,
     )
     return [
@@ -784,6 +785,9 @@ rust_toolchain = rule(
         "_cc_toolchain": attr.label(
             default = Label("@bazel_tools//tools/cpp:current_cc_toolchain"),
         ),
+        "_experimental_use_coverage_metadata_files": attr.label(
+            default = Label("//rust/settings:experimental_use_coverage_metadata_files"),
+        ),
         "_experimental_use_global_allocator": attr.label(
             default = Label("//rust/settings:experimental_use_global_allocator"),
             doc = (

util/BUILD.bazel

@@ -4,8 +4,8 @@ sh_binary(
     tags = ["manual"],
 )
 
-filegroup(
+alias(
     name = "collect_coverage",
-    srcs = ["collect_coverage.sh"],
+    actual = "//util/collect_coverage",
     visibility = ["//visibility:public"],
 )

util/collect_coverage/BUILD.bazel

@@ -0,0 +1,8 @@
+load("//rust:defs.bzl", "rust_binary")
+
+rust_binary(
+    name = "collect_coverage",
+    srcs = ["collect_coverage.rs"],
+    edition = "2018",
+    visibility = ["//visibility:public"],
+)