Convert coverageMutator to a TransitionMutator

Convert coverageMutator to a TransitionMutator as a step towards
variants-on-demand.

Bug: 319288033
Test: coverage_test.go
Test: treehugger coverage builds
Change-Id: Ic50c0040dea8b42c36b5d784221daa00b7b0d379

apex/apex.go

@@ -1418,7 +1418,7 @@ func (a *apexBundle) TaggedOutputs() map[string]android.Paths {
 var _ cc.Coverage = (*apexBundle)(nil)
 
 // Implements cc.Coverage
-func (a *apexBundle) IsNativeCoverageNeeded(ctx android.BaseModuleContext) bool {
+func (a *apexBundle) IsNativeCoverageNeeded(ctx android.IncomingTransitionContext) bool {
 	return ctx.DeviceConfig().NativeCoverageEnabled()
 }
 

cc/cc.go

@@ -68,7 +68,7 @@ func RegisterCCBuildComponents(ctx android.RegistrationContext) {
 
 		ctx.TopDown("fuzz_deps", fuzzMutatorDeps)
 
-		ctx.BottomUp("coverage", coverageMutator).Parallel()
+		ctx.Transition("coverage", &coverageTransitionMutator{})
 
 		ctx.TopDown("afdo_deps", afdoDepsMutator)
 		ctx.BottomUp("afdo", afdoMutator).Parallel()

cc/coverage.go

@@ -223,7 +223,7 @@ func SetCoverageProperties(ctx android.BaseModuleContext, properties CoveragePro
 
 type UseCoverage interface {
 	android.Module
-	IsNativeCoverageNeeded(ctx android.BaseModuleContext) bool
+	IsNativeCoverageNeeded(ctx android.IncomingTransitionContext) bool
 }
 
 // Coverage is an interface for non-CC modules to implement to be mutated for coverage
@@ -235,43 +235,86 @@ type Coverage interface {
 	EnableCoverageIfNeeded()
 }
 
-func coverageMutator(mctx android.BottomUpMutatorContext) {
-	if c, ok := mctx.Module().(*Module); ok && c.coverage != nil {
-		needCoverageVariant := c.coverage.Properties.NeedCoverageVariant
-		needCoverageBuild := c.coverage.Properties.NeedCoverageBuild
-		if needCoverageVariant {
-			m := mctx.CreateVariations("", "cov")
+type coverageTransitionMutator struct{}
 
-			// Setup the non-coverage version and set HideFromMake and
-			// PreventInstall to true.
-			m[0].(*Module).coverage.Properties.CoverageEnabled = false
-			m[0].(*Module).coverage.Properties.IsCoverageVariant = false
-			m[0].(*Module).Properties.HideFromMake = true
-			m[0].(*Module).Properties.PreventInstall = true
+var _ android.TransitionMutator = (*coverageTransitionMutator)(nil)
 
-			// The coverage-enabled version inherits HideFromMake,
-			// PreventInstall from the original module.
-			m[1].(*Module).coverage.Properties.CoverageEnabled = needCoverageBuild
-			m[1].(*Module).coverage.Properties.IsCoverageVariant = true
+func (c coverageTransitionMutator) Split(ctx android.BaseModuleContext) []string {
+	if c, ok := ctx.Module().(*Module); ok && c.coverage != nil {
+		if c.coverage.Properties.NeedCoverageVariant {
+			return []string{"", "cov"}
 		}
-	} else if cov, ok := mctx.Module().(Coverage); ok && cov.IsNativeCoverageNeeded(mctx) {
+	} else if cov, ok := ctx.Module().(Coverage); ok && cov.IsNativeCoverageNeeded(ctx) {
 		// APEX and Rust modules fall here
 
 		// Note: variant "" is also created because an APEX can be depended on by another
 		// module which are split into "" and "cov" variants. e.g. when cc_test refers
 		// to an APEX via 'data' property.
-		m := mctx.CreateVariations("", "cov")
-		m[0].(Coverage).MarkAsCoverageVariant(false)
-		m[0].(Coverage).SetPreventInstall()
-		m[0].(Coverage).HideFromMake()
-
-		m[1].(Coverage).MarkAsCoverageVariant(true)
-		m[1].(Coverage).EnableCoverageIfNeeded()
-	} else if cov, ok := mctx.Module().(UseCoverage); ok && cov.IsNativeCoverageNeeded(mctx) {
+		return []string{"", "cov"}
+	} else if cov, ok := ctx.Module().(UseCoverage); ok && cov.IsNativeCoverageNeeded(ctx) {
+		// Module itself doesn't have to have "cov" variant, but it should use "cov" variants of
+		// deps.
+		return []string{"cov"}
+	}
+
+	return []string{""}
+}
+
+func (c coverageTransitionMutator) OutgoingTransition(ctx android.OutgoingTransitionContext, sourceVariation string) string {
+	return sourceVariation
+}
+
+func (c coverageTransitionMutator) IncomingTransition(ctx android.IncomingTransitionContext, incomingVariation string) string {
+	if c, ok := ctx.Module().(*Module); ok && c.coverage != nil {
+		if !c.coverage.Properties.NeedCoverageVariant {
+			return ""
+		}
+	} else if cov, ok := ctx.Module().(Coverage); ok {
+		if !cov.IsNativeCoverageNeeded(ctx) {
+			return ""
+		}
+	} else if cov, ok := ctx.Module().(UseCoverage); ok && cov.IsNativeCoverageNeeded(ctx) {
+		// Module only has a "cov" variation, so all incoming variations should use "cov".
+		return "cov"
+	} else {
+		return ""
+	}
+
+	return incomingVariation
+}
+
+func (c coverageTransitionMutator) Mutate(ctx android.BottomUpMutatorContext, variation string) {
+	if c, ok := ctx.Module().(*Module); ok && c.coverage != nil {
+		if variation == "" && c.coverage.Properties.NeedCoverageVariant {
+			// Setup the non-coverage version and set HideFromMake and
+			// PreventInstall to true.
+			c.coverage.Properties.CoverageEnabled = false
+			c.coverage.Properties.IsCoverageVariant = false
+			c.Properties.HideFromMake = true
+			c.Properties.PreventInstall = true
+		} else if variation == "cov" {
+			// The coverage-enabled version inherits HideFromMake,
+			// PreventInstall from the original module.
+			c.coverage.Properties.CoverageEnabled = c.coverage.Properties.NeedCoverageBuild
+			c.coverage.Properties.IsCoverageVariant = true
+		}
+	} else if cov, ok := ctx.Module().(Coverage); ok && cov.IsNativeCoverageNeeded(ctx) {
+		// APEX and Rust modules fall here
+
+		// Note: variant "" is also created because an APEX can be depended on by another
+		// module which are split into "" and "cov" variants. e.g. when cc_test refers
+		// to an APEX via 'data' property.
+		if variation == "" {
+			cov.MarkAsCoverageVariant(false)
+			cov.SetPreventInstall()
+			cov.HideFromMake()
+		} else if variation == "cov" {
+			cov.MarkAsCoverageVariant(true)
+			cov.EnableCoverageIfNeeded()
+		}
+	} else if cov, ok := ctx.Module().(UseCoverage); ok && cov.IsNativeCoverageNeeded(ctx) {
 		// 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

@@ -512,6 +512,6 @@ func sha1sum(values []string) string {
 
 var _ cc.UseCoverage = (*filesystem)(nil)
 
-func (*filesystem) IsNativeCoverageNeeded(ctx android.BaseModuleContext) bool {
+func (*filesystem) IsNativeCoverageNeeded(ctx android.IncomingTransitionContext) bool {
 	return ctx.Device() && ctx.DeviceConfig().NativeCoverageEnabled()
 }

java/app.go

@@ -1108,7 +1108,7 @@ func (a *AndroidApp) Privileged() bool {
 	return Bool(a.appProperties.Privileged)
 }
 
-func (a *AndroidApp) IsNativeCoverageNeeded(ctx android.BaseModuleContext) bool {
+func (a *AndroidApp) IsNativeCoverageNeeded(ctx android.IncomingTransitionContext) bool {
 	return ctx.Device() && ctx.DeviceConfig().NativeCoverageEnabled()
 }
 

java/java.go

@@ -1084,7 +1084,7 @@ func (j *JavaTestImport) InstallInTestcases() bool {
 	return true
 }
 
-func (j *TestHost) IsNativeCoverageNeeded(ctx android.BaseModuleContext) bool {
+func (j *TestHost) IsNativeCoverageNeeded(ctx android.IncomingTransitionContext) bool {
 	return ctx.DeviceConfig().NativeCoverageEnabled()
 }
 

rust/rust.go

@@ -535,7 +535,7 @@ func (mod *Module) isCoverageVariant() bool {
 
 var _ cc.Coverage = (*Module)(nil)
 
-func (mod *Module) IsNativeCoverageNeeded(ctx android.BaseModuleContext) bool {
+func (mod *Module) IsNativeCoverageNeeded(ctx android.IncomingTransitionContext) bool {
 	return mod.coverage != nil && mod.coverage.Properties.NeedCoverageVariant
 }