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Enable code coverage in Xcode for swift-built targets #1623

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Merged
aaronsky merged 2 commits into from
Dec 5, 2025
Merged

Enable code coverage in Xcode for swift-built targets #1623

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df4b841
Enable code coverage in Xcode
aaronsky Dec 3, 2025
3fff8bb
rename feature, make it scarier
aaronsky Dec 3, 2025
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12 changes: 12 additions & 0 deletions swift/internal/feature_names.bzl
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,18 @@ SWIFT_FEATURE_DEBUG_PREFIX_MAP = "swift.debug_prefix_map"
# of remote builds.
SWIFT_FEATURE_COVERAGE_PREFIX_MAP = "swift.coverage_prefix_map"

# A private feature that is used to embed absolute source paths in coverage builds.
#
# If enabled, coverage builds will use a `-coverage-prefix-map` that remaps
# the current working directory to a canonical location, which permits
# coverage representation in non-sandboxed builds with tools that expect
# absolute paths such as Xcode.
#
# This feature should only be used with non-sandboxed builds inside tools such as
# Xcode, and enabling it effectively breaks Bazel's ability to rely on the
# remote cache those builds. It should not be enabled by users of the toolchain.
SWIFT_FEATURE__COVERAGE_PREFIX_MAP_ABSOLUTE_SOURCES_NON_HERMETIC = "swift._coverage_prefix_map_absolute_sources_non_hermetic"

# If enabled, C and Objective-C libraries that are direct or transitive
# dependencies of a Swift library will emit explicit precompiled modules that
# are compatible with Swift's ClangImporter and propagate them up the build
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12 changes: 12 additions & 0 deletions swift/toolchains/config/compile_config.bzl
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Expand Up @@ -90,6 +90,7 @@ load(
"SWIFT_FEATURE_USE_GLOBAL_MODULE_CACHE",
"SWIFT_FEATURE_USE_PCH_OUTPUT_DIR",
"SWIFT_FEATURE_VFSOVERLAY",
"SWIFT_FEATURE__COVERAGE_PREFIX_MAP_ABSOLUTE_SOURCES_NON_HERMETIC",
"SWIFT_FEATURE__NUM_THREADS_0_IN_SWIFTCOPTS",
"SWIFT_FEATURE__SUPPORTS_UPCOMING_FEATURES",
"SWIFT_FEATURE__SUPPORTS_V6",
Expand Down Expand Up @@ -558,6 +559,17 @@ def compile_action_configs(
features = [
[SWIFT_FEATURE_COVERAGE_PREFIX_MAP, SWIFT_FEATURE_COVERAGE],
],
not_features = [SWIFT_FEATURE__COVERAGE_PREFIX_MAP_ABSOLUTE_SOURCES_NON_HERMETIC],
),
ActionConfigInfo(
actions = all_compile_action_names(),
configurators = [
add_arg("-Xwrapped-swift=-coverage-prefix-pwd-is-canonical"),
],
features = [
[SWIFT_FEATURE__COVERAGE_PREFIX_MAP_ABSOLUTE_SOURCES_NON_HERMETIC, SWIFT_FEATURE_COVERAGE],
],
not_features = [SWIFT_FEATURE_COVERAGE_PREFIX_MAP, SWIFT_FEATURE_FILE_PREFIX_MAP],
),

# Ensure that .swiftsourceinfo files are tracked and not deleted by the worker
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18 changes: 15 additions & 3 deletions tools/worker/swift_runner.cc
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Expand Up @@ -288,11 +288,12 @@ bool SwiftRunner::ProcessArgument(

// Helper function for adding path remapping flags that depend on information
// only known at execution time.
auto add_prefix_map_flags = [&](const std::string &flag) {
auto add_prefix_map_flags = [&](const std::string &flag,
const std::string &new_path = ".") {
// Get the actual current working directory (the execution root), which
// we didn't know at analysis time.
consumer(flag);
consumer(std::filesystem::current_path().string() + "=.");
consumer(std::filesystem::current_path().string() + "=" + new_path);

#if __APPLE__
std::string developer_dir = "__BAZEL_XCODE_DEVELOPER_DIR__";
Expand All @@ -316,7 +317,18 @@ bool SwiftRunner::ProcessArgument(
} else if (new_arg == "-coverage-prefix-pwd-is-dot") {
// Replace the $PWD with . to make the paths relative to the workspace
// without breaking hermiticity.
add_prefix_map_flags("-file-prefix-map");
add_prefix_map_flags("-coverage-prefix-map");
changed = true;
} else if (new_arg == "-coverage-prefix-pwd-is-canonical") {
// Replace the $PWD with . to make the paths relative to the workspace
// without breaking hermiticity.
auto cwd = std::filesystem::current_path();
// The bazel execroot is a normal directory, but inside of it there are
// symlinks to our source tree. This fetches the true path of a known
// directory in order to get the actual source root of the project. This
// should only work with sandboxing disabled.
auto target_path = std::filesystem::canonical(cwd / "BUILD.bazel").parent_path();
add_prefix_map_flags("-coverage-prefix-map", target_path.string());
changed = true;
} else if (new_arg == "-file-prefix-pwd-is-dot") {
// Replace the $PWD with . to make the paths relative to the workspace
Expand Down