Make filesystem aware of coverage

filesystem should have coverage variants with coverage-enabled build.
Otherwise, it would fail to collect dependencies.

Bug: 273238141
Test: m nothing (soong tests)
Test: compare the artifacts
 $ SKIP_ABI_CHECKS=true SOONG_COLLECT_JAVA_DEPS=true EMMA_INSTRUMENT=true\
   EMMA_INSTRUMENT_FRAMEWORK=true CLANG_COVERAGE=true\
   NATIVE_COVERAGE_PATHS='*' m microdroid
 $ m microdroid
Change-Id: I792458ace00a63b4b5213898fd3209351a6e00be

cc/coverage.go

@@ -219,10 +219,14 @@ func SetCoverageProperties(ctx android.BaseModuleContext, properties CoveragePro
 	return properties
 }
 
-// Coverage is an interface for non-CC modules to implement to be mutated for coverage
-type Coverage interface {
+type UseCoverage interface {
 	android.Module
 	IsNativeCoverageNeeded(ctx android.BaseModuleContext) bool
+}
+
+// Coverage is an interface for non-CC modules to implement to be mutated for coverage
+type Coverage interface {
+	UseCoverage
 	SetPreventInstall()
 	HideFromMake()
 	MarkAsCoverageVariant(bool)
@@ -261,6 +265,11 @@ func coverageMutator(mctx android.BottomUpMutatorContext) {
 
 		m[1].(Coverage).MarkAsCoverageVariant(true)
 		m[1].(Coverage).EnableCoverageIfNeeded()
+	} else if cov, ok := mctx.Module().(UseCoverage); ok && cov.IsNativeCoverageNeeded(mctx) {
+		// Module itself doesn't have to have "cov" variant, but it should use "cov" variants of
+		// deps.
+		mctx.CreateVariations("cov")
+		mctx.AliasVariation("cov")
 	}
 }
 

filesystem/filesystem.go

@@ -22,6 +22,7 @@ import (
 	"strings"
 
 	"android/soong/android"
+	"android/soong/cc"
 
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
@@ -498,3 +499,11 @@ func sha1sum(values []string) string {
 	}
 	return fmt.Sprintf("%x", h.Sum(nil))
 }
+
+// Base cc.UseCoverage
+
+var _ cc.UseCoverage = (*filesystem)(nil)
+
+func (*filesystem) IsNativeCoverageNeeded(ctx android.BaseModuleContext) bool {
+	return ctx.Device() && ctx.DeviceConfig().NativeCoverageEnabled()
+}

filesystem/filesystem_test.go

@@ -20,6 +20,9 @@ import (
 
 	"android/soong/android"
 	"android/soong/cc"
+	"android/soong/etc"
+
+	"github.com/google/blueprint/proptools"
 )
 
 func TestMain(m *testing.M) {
@@ -28,6 +31,7 @@ func TestMain(m *testing.M) {
 
 var fixture = android.GroupFixturePreparers(
 	android.PrepareForIntegrationTestWithAndroid,
+	etc.PrepareForTestWithPrebuiltEtc,
 	cc.PrepareForIntegrationTestWithCc,
 	PrepareForTestWithFilesystemBuildComponents,
 )
@@ -225,3 +229,56 @@ func TestFileSystemShouldInstallCoreVariantIfTargetBuildAppsIsSet(t *testing.T)
 		inputs.Strings(),
 		"out/soong/.intermediates/libbar/android_arm64_armv8-a_shared/libbar.so")
 }
+
+func TestFileSystemWithCoverageVariants(t *testing.T) {
+	context := android.GroupFixturePreparers(
+		fixture,
+		android.FixtureModifyProductVariables(func(variables android.FixtureProductVariables) {
+			variables.GcovCoverage = proptools.BoolPtr(true)
+			variables.Native_coverage = proptools.BoolPtr(true)
+		}),
+	)
+
+	result := context.RunTestWithBp(t, `
+		prebuilt_etc {
+			name: "prebuilt",
+			src: ":myfilesystem",
+		}
+
+		android_system_image {
+			name: "myfilesystem",
+			deps: [
+				"libfoo",
+			],
+			linker_config_src: "linker.config.json",
+		}
+
+		cc_library {
+			name: "libfoo",
+			shared_libs: [
+				"libbar",
+			],
+			stl: "none",
+		}
+
+		cc_library {
+			name: "libbar",
+			stl: "none",
+		}
+	`)
+
+	filesystem := result.ModuleForTests("myfilesystem", "android_common_cov")
+	inputs := filesystem.Output("deps.zip").Implicits
+	android.AssertStringListContains(t, "filesystem should have libfoo(cov)",
+		inputs.Strings(),
+		"out/soong/.intermediates/libfoo/android_arm64_armv8-a_shared_cov/libfoo.so")
+	android.AssertStringListContains(t, "filesystem should have libbar(cov)",
+		inputs.Strings(),
+		"out/soong/.intermediates/libbar/android_arm64_armv8-a_shared_cov/libbar.so")
+
+	filesystemOutput := filesystem.Output("myfilesystem.img").Output
+	prebuiltInput := result.ModuleForTests("prebuilt", "android_arm64_armv8-a").Rule("Cp").Input
+	if filesystemOutput != prebuiltInput {
+		t.Error("prebuilt should use cov variant of filesystem")
+	}
+}