Overridden APEX doesn't contribute to the file contexts

This change fixes the problem that when an apex module is overridden by
another override_apex, the <apex_name>-file_contexts are duplicated when
creating the system-level file-contexts.

Fixing this by not emitting the file_context info for the overridden
apex.

In doing so, OverridableModule interface was extended to have
GetOverriddenBy() method which can be used to test whether a module is
an overridden one or not.

Bug: 144338929
Test: m (apex_test amended)
Test: add "override_apex {name:"com.googlge.android.tzdata",
Change-Id: I5e9401c32899bb9987c90cba4185f571dc1a87f0
base:"com.android.tzdata"}" and the build is successful

android/override_module.go

@@ -82,13 +82,16 @@ func InitOverrideModule(m OverrideModule) {
 
 // Interface for overridable module types, e.g. android_app, apex
 type OverridableModule interface {
+	Module
+	moduleBase() *OverridableModuleBase
+
 	setOverridableProperties(prop []interface{})
 
 	addOverride(o OverrideModule)
 	getOverrides() []OverrideModule
 
 	override(ctx BaseModuleContext, o OverrideModule)
-	getOverriddenBy() string
+	GetOverriddenBy() string
 
 	setOverridesProperty(overridesProperties *[]string)
 
@@ -97,6 +100,10 @@ type OverridableModule interface {
 	OverridablePropertiesDepsMutator(ctx BottomUpMutatorContext)
 }
 
+type overridableModuleProperties struct {
+	OverriddenBy string `blueprint:"mutated"`
+}
+
 // Base module struct for overridable module types
 type OverridableModuleBase struct {
 	// List of OverrideModules that override this base module
@@ -114,12 +121,17 @@ type OverridableModuleBase struct {
 	// override information is propagated and aggregated correctly.
 	overridesProperty *[]string
 
-	overriddenBy string
+	properties overridableModuleProperties
 }
 
 func InitOverridableModule(m OverridableModule, overridesProperty *[]string) {
 	m.setOverridableProperties(m.(Module).GetProperties())
 	m.setOverridesProperty(overridesProperty)
+	m.AddProperties(&m.moduleBase().properties)
+}
+
+func (o *OverridableModuleBase) moduleBase() *OverridableModuleBase {
+	return o
 }
 
 func (b *OverridableModuleBase) setOverridableProperties(prop []interface{}) {
@@ -162,11 +174,15 @@ func (b *OverridableModuleBase) override(ctx BaseModuleContext, o OverrideModule
 			}
 		}
 	}
-	b.overriddenBy = o.Name()
+	b.properties.OverriddenBy = o.Name()
 }
 
-func (b *OverridableModuleBase) getOverriddenBy() string {
+// GetOverriddenBy returns the name of the override module that has overridden this module.
-	return b.overriddenBy
+// For example, if an override module foo has its 'base' property set to bar, then another local variant
+// of bar is created and its properties are overriden by foo. This method returns bar when called from
+// the new local variant. It returns "" when called from the original variant of bar.
+func (b *OverridableModuleBase) GetOverriddenBy() string {
+	return b.properties.OverriddenBy
 }
 
 func (b *OverridableModuleBase) OverridablePropertiesDepsMutator(ctx BottomUpMutatorContext) {
@@ -247,7 +263,7 @@ func overridableModuleDepsMutator(ctx BottomUpMutatorContext) {
 
 func replaceDepsOnOverridingModuleMutator(ctx BottomUpMutatorContext) {
 	if b, ok := ctx.Module().(OverridableModule); ok {
-		if o := b.getOverriddenBy(); o != "" {
+		if o := b.GetOverriddenBy(); o != "" {
 			// Redirect dependencies on the overriding module to this overridden module. Overriding
 			// modules are basically pseudo modules, and all build actions are associated to overridden
 			// modules. Therefore, dependencies on overriding modules need to be forwarded there as well.

apex/apex_test.go

@@ -2977,6 +2977,15 @@ func TestOverrideApex(t *testing.T) {
 		}
 	`)
 
+	originalVariant := ctx.ModuleForTests("myapex", "android_common_myapex_image").Module().(android.OverridableModule)
+	overriddenVariant := ctx.ModuleForTests("myapex", "android_common_override_myapex_myapex_image").Module().(android.OverridableModule)
+	if originalVariant.GetOverriddenBy() != "" {
+		t.Errorf("GetOverriddenBy should be empty, but was %q", originalVariant.GetOverriddenBy())
+	}
+	if overriddenVariant.GetOverriddenBy() != "override_myapex" {
+		t.Errorf("GetOverriddenBy should be \"override_myapex\", but was %q", overriddenVariant.GetOverriddenBy())
+	}
+
 	module := ctx.ModuleForTests("myapex", "android_common_override_myapex_myapex_image")
 	apexRule := module.Rule("apexRule")
 	copyCmds := apexRule.Args["copy_commands"]

apex/builder.go

@@ -476,7 +476,7 @@ func (a *apexBundle) buildFlattenedApex(ctx android.ModuleContext) {
 	apexName := proptools.StringDefault(a.properties.Apex_name, ctx.ModuleName())
 	a.outputFile = android.PathForModuleInstall(&factx, "apex", apexName)
 
-	if a.installable() {
+	if a.installable() && a.GetOverriddenBy() == "" {
 		installPath := android.PathForModuleInstall(ctx, "apex", apexName)
 		devicePath := android.InstallPathToOnDevicePath(ctx, installPath)
 		addFlattenedFileContextsInfos(ctx, apexName+":"+devicePath+":"+a.fileContexts.String())