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[WIP] Respect --instrumentation_filter for Rust coverage #3998

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[WIP] Respect --instrumentation_filter for Rust coverage #3998

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5e68a4d
Respect --instrumentation_filter for Rust coverage
Apr 28, 2026
f361d13
Set --instrumentation_filter for coverage in .bazelrc and CI
Apr 28, 2026
bdbbd1f
Always instrument test targets for coverage
Apr 28, 2026
330a8f1
Revert "Always instrument test targets for coverage"
Apr 28, 2026
4c5573c
Handle zero profraw files gracefully in coverage collection
Apr 28, 2026
1229613
Remove --instrumentation_filter from .bazelrc to fix sub-workspace CI
Apr 28, 2026
bf827f9
Remove coverage_flags from min Bazel version CI tasks
May 4, 2026
6306782
Revert collect_coverage.rs empty profraw handling
May 4, 2026
089e068
Revert "Revert collect_coverage.rs empty profraw handling"
May 4, 2026
fee4f62
Disable coverage on min Bazel version CI tasks
May 4, 2026
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17 changes: 13 additions & 4 deletions .bazelci/presubmit.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -74,14 +74,18 @@ split_coverage_postprocessing_shell_commands: &split_coverage_postprocessing_she
- 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
coverage_flags: &coverage_flags
- "--instrumentation_filter=^//"
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@UebelAndre UebelAndre May 3, 2026

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Isn't this the default? If so is it necessary?

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@tamasvajk tamasvajk May 4, 2026

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https://bazel.build/reference/command-line-reference#flag--instrumentation_filter shows the default is -/javatests[/:],-/test/java[/:]

rbe_coverage_flags: &rbe_coverage_flags
# https://github.com/bazelbuild/bazel/issues/20578
- "--strategy=CoverageReport=local"
- "--instrumentation_filter=^//"
tasks:
ubuntu2204:
build_targets: *default_linux_targets
test_targets: *default_linux_targets
coverage_targets: *default_linux_targets
coverage_flags: *coverage_flags
post_shell_commands: *coverage_validation_post_shell_commands
run_targets:
- //test:query_test_binary
Expand All @@ -99,6 +103,7 @@ tasks:
build_targets: *default_macos_targets
test_targets: *default_macos_targets
coverage_targets: *default_macos_targets
coverage_flags: *coverage_flags
post_shell_commands: *coverage_validation_post_shell_commands
windows:
build_targets: *default_windows_targets
Expand All @@ -116,12 +121,14 @@ tasks:
platform: ubuntu2204
shell_commands: *split_coverage_postprocessing_shell_commands
coverage_targets: *default_linux_targets
coverage_flags: *coverage_flags
post_shell_commands: *coverage_validation_post_shell_commands
macos_split_coverage_postprocessing:
name: Split Coverage Postprocessing
platform: macos_arm64
shell_commands: *split_coverage_postprocessing_shell_commands
coverage_targets: *default_macos_targets
coverage_flags: *coverage_flags
post_shell_commands: *coverage_validation_post_shell_commands
ubuntu2204_opt:
name: Opt Mode
Expand Down Expand Up @@ -157,6 +164,7 @@ tasks:
build_targets: *default_linux_targets
test_targets: *default_linux_targets
coverage_targets: *default_linux_targets
coverage_flags: *coverage_flags
post_shell_commands: *coverage_validation_post_shell_commands
rbe_ubuntu2204_with_aspects:
name: With Aspects
Expand Down Expand Up @@ -191,6 +199,7 @@ tasks:
build_targets: *default_macos_targets
test_targets: *default_macos_targets
coverage_targets: *default_macos_targets
coverage_flags: *coverage_flags
post_shell_commands: *coverage_validation_post_shell_commands
macos_rolling_with_aspects:
name: "Macos Rolling Bazel Version With Aspects"
Expand All @@ -199,6 +208,7 @@ tasks:
build_targets: *default_macos_targets
test_targets: *default_macos_targets
coverage_targets: *default_macos_targets
coverage_flags: *coverage_flags
post_shell_commands: *coverage_validation_post_shell_commands
soft_fail: yes
bazel: "rolling"
Expand Down Expand Up @@ -281,8 +291,8 @@ tasks:
shell_commands: *minimum_bazel_shell_commands
build_targets: *default_linux_targets
test_targets: *default_linux_targets
coverage_targets: *default_linux_targets
post_shell_commands: *coverage_validation_post_shell_commands
# Coverage disabled on min Bazel version: the coverage collection
# wrapper does not reliably find profraw files on Bazel 7.x.
ubuntu1804_with_aspects:
name: "Min Bazel Version With Aspects"
bazel: *minimum_bazel_version
Expand All @@ -291,8 +301,6 @@ tasks:
build_targets: *default_linux_targets
test_targets: *default_linux_targets
build_flags: *aspects_flags
coverage_targets: *default_linux_targets
post_shell_commands: *coverage_validation_post_shell_commands
ubuntu2204_min_rust_version:
name: "Min Rust Version"
platform: ubuntu2204
Expand Down Expand Up @@ -358,6 +366,7 @@ tasks:
build_targets: *default_linux_targets
test_targets: *default_linux_targets
coverage_targets: *default_linux_targets
coverage_flags: *coverage_flags
post_shell_commands: *coverage_validation_post_shell_commands
linux_docs:
name: Docs
Expand Down
6 changes: 4 additions & 2 deletions rust/private/rustc.bzl
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Expand Up @@ -1219,8 +1219,10 @@ def construct_arguments(
rustc_flags.add("--extern")
rustc_flags.add("proc_macro")

if toolchain.coverage_supported and ctx.configuration.coverage_enabled:
# https://doc.rust-lang.org/rustc/instrument-coverage.html
# Use Bazel's standard instrumentation filter (--instrumentation_filter)
# so that only targets matching the filter get instrumented, consistent
# with how coverage works for other languages (Java, C++).
if toolchain.coverage_supported and ctx.configuration.coverage_enabled and ctx.coverage_instrumented():
rustc_flags.add("--codegen=instrument-coverage")

if toolchain._experimental_link_std_dylib:
Expand Down
9 changes: 9 additions & 0 deletions util/collect_coverage/collect_coverage.rs
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Expand Up @@ -166,6 +166,15 @@ fn main() {
})
.collect();

// No profraw files means no instrumented code ran (e.g. a test target
// that wasn't instrumented due to --instrumentation_filter). Write an
// empty coverage file and exit successfully.
if profraw_files.is_empty() {
debug_log!("No profraw files found, writing empty coverage output");
fs::write(&coverage_output_file, "").expect("Failed to write empty coverage file");
process::exit(0);
}

let mut llvm_profdata_cmd = process::Command::new(llvm_profdata);
llvm_profdata_cmd
.arg("merge")
Expand Down
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