Convert android.TransitionMutator to TransitionInfo

Use the ApexInfo instead of a string as the TransitionInfo for apex
variations.  This removes the need for apexInfoMutator, which is the
last remaining top down mutator.

This has a variety of ramifications.  One is that it is no longer
possible to add a dependency onto the apex variation of a module,
as that would require constructing a matching ApexInfo.  Instead,
anything that wants to add a dependency on the apex variation has
to depend on the apex instead, and get to the module by walking
its transistive dependencies.

Another ramification is that modules in apexes can no longer
determine which apexes they are in (unless they set
UniqueApexVariations so that each variation is in exactly one
apex).  This prevents some of the existing container violation
checks from working after this CL, tracked in b/394955484.

It also requires using unique variation names for the prebuilt
and source dependencies of apexes, so the apex variations
for dependencies of prebuilts now have a prebuilt_ prefix.

Bug: 372543712
Bug: 394955484
Test: go test ./...
Change-Id: I3d08aca1ac956ab0e343ec3f235a736cd93be0e1

1 files changed, 46 insertions, 75 deletions

diff --git a/apex/prebuilt.go b/apex/prebuilt.go
index 85b64e743..e7d92c3a4 100644
--- a/apex/prebuilt.go
+++ b/apex/prebuilt.go
@@ -310,89 +310,34 @@ func (p *prebuiltCommon) IncomingDepIsInSameApex(tag blueprint.DependencyTag) bo
 	return true
 }
 
-// apexInfoMutator marks any modules for which this apex exports a file as requiring an apex
-// specific variant and checks that they are supported.
-//
-// The apexMutator will ensure that the ApexInfo objects passed to BuildForApex(ApexInfo) are
-// associated with the apex specific variant using the ApexInfoProvider for later retrieval.
-//
-// Unlike the source apex module type the prebuilt_apex module type cannot share compatible variants
-// across prebuilt_apex modules. That is because there is no way to determine whether two
-// prebuilt_apex modules that export files for the same module are compatible. e.g. they could have
-// been built from different source at different times or they could have been built with different
-// build options that affect the libraries.
-//
-// While it may be possible to provide sufficient information to determine whether two prebuilt_apex
-// modules were compatible it would be a lot of work and would not provide much benefit for a couple
-// of reasons:
-//   - The number of prebuilt_apex modules that will be exporting files for the same module will be
-//     low as the prebuilt_apex only exports files for the direct dependencies that require it and
-//     very few modules are direct dependencies of multiple prebuilt_apex modules, e.g. there are a
-//     few com.android.art* apex files that contain the same contents and could export files for the
-//     same modules but only one of them needs to do so. Contrast that with source apex modules which
-//     need apex specific variants for every module that contributes code to the apex, whether direct
-//     or indirect.
-//   - The build cost of a prebuilt_apex variant is generally low as at worst it will involve some
-//     extra copying of files. Contrast that with source apex modules that has to build each variant
-//     from source.
-func (p *prebuiltCommon) apexInfoMutator(mctx android.TopDownMutatorContext) {
-	// Collect the list of dependencies.
-	var dependencies []android.ApexModule
-	mctx.WalkDeps(func(child, parent android.Module) bool {
-		// If the child is not in the same apex as the parent then exit immediately and do not visit
-		// any of the child's dependencies.
-		if !android.IsDepInSameApex(mctx, parent, child) {
-			return false
-		}
-
-		tag := mctx.OtherModuleDependencyTag(child)
-		depName := mctx.OtherModuleName(child)
+func (p *prebuiltCommon) checkExportedDependenciesArePrebuilts(ctx android.ModuleContext) {
+	ctx.VisitDirectDeps(func(dep android.Module) {
+		tag := ctx.OtherModuleDependencyTag(dep)
+		depName := ctx.OtherModuleName(dep)
 		if exportedTag, ok := tag.(exportedDependencyTag); ok {
 			propertyName := exportedTag.name
 
 			// It is an error if the other module is not a prebuilt.
-			if !android.IsModulePrebuilt(child) {
-				mctx.PropertyErrorf(propertyName, "%q is not a prebuilt module", depName)
-				return false
+			if !android.IsModulePrebuilt(dep) {
+				ctx.PropertyErrorf(propertyName, "%q is not a prebuilt module", depName)
 			}
 
 			// It is an error if the other module is not an ApexModule.
-			if _, ok := child.(android.ApexModule); !ok {
-				mctx.PropertyErrorf(propertyName, "%q is not usable within an apex", depName)
-				return false
+			if _, ok := dep.(android.ApexModule); !ok {
+				ctx.PropertyErrorf(propertyName, "%q is not usable within an apex", depName)
 			}
 		}
 
-		// Ignore any modules that do not implement ApexModule as they cannot have an APEX specific
-		// variant.
-		if _, ok := child.(android.ApexModule); !ok {
-			return false
-		}
-
-		// Strip off the prebuilt_ prefix if present before storing content to ensure consistent
-		// behavior whether there is a corresponding source module present or not.
-		depName = android.RemoveOptionalPrebuiltPrefix(depName)
-
-		// Add the module to the list of dependencies that need to have an APEX variant.
-		dependencies = append(dependencies, child.(android.ApexModule))
-
-		return true
 	})
+}
 
-	android.SetProvider(mctx, android.ApexBundleInfoProvider, android.ApexBundleInfo{})
-
-	// Create an ApexInfo for the prebuilt_apex.
-	apexVariationName := p.ApexVariationName()
-	apexInfo := android.ApexInfo{
-		ApexVariationName: apexVariationName,
-		InApexVariants:    []string{apexVariationName},
+// generateApexInfo returns an android.ApexInfo configuration suitable for dependencies of this apex.
+func (p *prebuiltCommon) generateApexInfo(ctx generateApexInfoContext) android.ApexInfo {
+	return android.ApexInfo{
+		ApexVariationName: "prebuilt_" + p.ApexVariationName(),
+		BaseApexName:      p.ApexVariationName(),
 		ForPrebuiltApex:   true,
 	}
-
-	// Mark the dependencies of this module as requiring a variant for this module.
-	for _, am := range dependencies {
-		am.BuildForApex(apexInfo)
-	}
 }
 
 type Prebuilt struct {
@@ -596,10 +541,22 @@ func (p *Prebuilt) ComponentDepsMutator(ctx android.BottomUpMutatorContext) {
 	p.prebuiltApexContentsDeps(ctx)
 }
 
-var _ ApexInfoMutator = (*Prebuilt)(nil)
+var _ ApexTransitionMutator = (*Prebuilt)(nil)
+
+func (p *Prebuilt) ApexTransitionMutatorSplit(ctx android.BaseModuleContext) []android.ApexInfo {
+	return []android.ApexInfo{p.generateApexInfo(ctx)}
+}
+
+func (p *Prebuilt) ApexTransitionMutatorOutgoing(ctx android.OutgoingTransitionContext, sourceInfo android.ApexInfo) android.ApexInfo {
+	return sourceInfo
+}
+
+func (p *Prebuilt) ApexTransitionMutatorIncoming(ctx android.IncomingTransitionContext, outgoingInfo android.ApexInfo) android.ApexInfo {
+	return p.generateApexInfo(ctx)
+}
 
-func (p *Prebuilt) ApexInfoMutator(mctx android.TopDownMutatorContext) {
-	p.apexInfoMutator(mctx)
+func (p *Prebuilt) ApexTransitionMutatorMutate(ctx android.BottomUpMutatorContext, info android.ApexInfo) {
+	android.SetProvider(ctx, android.ApexBundleInfoProvider, android.ApexBundleInfo{})
 }
 
 // creates the build rules to deapex the prebuilt, and returns a deapexerInfo
@@ -665,6 +622,8 @@ func (p *Prebuilt) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 		validateApexClasspathFragments(ctx)
 	}
 
+	p.checkExportedDependenciesArePrebuilts(ctx)
+
 	p.apexKeysPath = writeApexKeys(ctx, p)
 	// TODO(jungjw): Check the key validity.
 	p.inputApex = android.PathForModuleSrc(ctx, p.properties.prebuiltApexSelector(ctx, ctx.Module()))
@@ -825,10 +784,22 @@ func (a *ApexSet) ComponentDepsMutator(ctx android.BottomUpMutatorContext) {
 	a.prebuiltApexContentsDeps(ctx)
 }
 
-var _ ApexInfoMutator = (*ApexSet)(nil)
+var _ ApexTransitionMutator = (*ApexSet)(nil)
+
+func (a *ApexSet) ApexTransitionMutatorSplit(ctx android.BaseModuleContext) []android.ApexInfo {
+	return []android.ApexInfo{a.generateApexInfo(ctx)}
+}
+
+func (a *ApexSet) ApexTransitionMutatorOutgoing(ctx android.OutgoingTransitionContext, sourceInfo android.ApexInfo) android.ApexInfo {
+	return sourceInfo
+}
+
+func (a *ApexSet) ApexTransitionMutatorIncoming(ctx android.IncomingTransitionContext, outgoingInfo android.ApexInfo) android.ApexInfo {
+	return a.generateApexInfo(ctx)
+}
 
-func (a *ApexSet) ApexInfoMutator(mctx android.TopDownMutatorContext) {
-	a.apexInfoMutator(mctx)
+func (a *ApexSet) ApexTransitionMutatorMutate(ctx android.BottomUpMutatorContext, info android.ApexInfo) {
+	android.SetProvider(ctx, android.ApexBundleInfoProvider, android.ApexBundleInfo{})
 }
 
 func (a *ApexSet) GenerateAndroidBuildActions(ctx android.ModuleContext) {