Add override_android_app module type.

This is a new implementation of overriding module types that makes use
of local variants. With this, product owners can use PRODUCT_PACKAGES to
decide which override module to include in their products.

Bug: 122957760
Bug: 123640028
Test: app_test.go
Change-Id: Ie65e97f615d006b6e9475193b6017ea9d97e8e97
diff --git a/java/app.go b/java/app.go
index 8f5d010..b31f232 100644
--- a/java/app.go
+++ b/java/app.go
@@ -33,16 +33,13 @@
 	android.RegisterModuleType("android_test", AndroidTestFactory)
 	android.RegisterModuleType("android_test_helper_app", AndroidTestHelperAppFactory)
 	android.RegisterModuleType("android_app_certificate", AndroidAppCertificateFactory)
+	android.RegisterModuleType("override_android_app", OverrideAndroidAppModuleFactory)
 }
 
 // AndroidManifest.xml merging
 // package splits
 
 type appProperties struct {
-	// The name of a certificate in the default certificate directory, blank to use the default product certificate,
-	// or an android_app_certificate module name in the form ":module".
-	Certificate *string
-
 	// Names of extra android_app_certificate modules to sign the apk with in the form ":module".
 	Additional_certificates []string
 
@@ -79,14 +76,24 @@
 	Use_embedded_dex *bool
 }
 
+// android_app properties that can be overridden by override_android_app
+type overridableAppProperties struct {
+	// The name of a certificate in the default certificate directory, blank to use the default product certificate,
+	// or an android_app_certificate module name in the form ":module".
+	Certificate *string
+}
+
 type AndroidApp struct {
 	Library
 	aapt
+	android.OverridableModuleBase
 
 	certificate Certificate
 
 	appProperties appProperties
 
+	overridableAppProperties overridableAppProperties
+
 	installJniLibs []jniLib
 
 	bundleFile android.Path
@@ -320,7 +327,7 @@
 
 func (a *AndroidApp) generateAndroidBuildActions(ctx android.ModuleContext) {
 	// Check if the install APK name needs to be overridden.
-	a.installApkName = ctx.DeviceConfig().OverridePackageNameFor(ctx.ModuleName())
+	a.installApkName = ctx.DeviceConfig().OverridePackageNameFor(a.Name())
 
 	// Process all building blocks, from AAPT to certificates.
 	a.aaptBuildActions(ctx)
@@ -339,6 +346,7 @@
 	certificates := a.certificateBuildActions(certificateDeps, ctx)
 
 	// Build a final signed app package.
+	// TODO(jungjw): Consider changing this to installApkName.
 	packageFile := android.PathForModuleOut(ctx, ctx.ModuleName()+".apk")
 	CreateAppPackage(ctx, packageFile, a.exportPackage, jniJarFile, dexJarFile, certificates)
 	a.outputFile = packageFile
@@ -413,7 +421,7 @@
 	if overridden {
 		return ":" + certificate
 	}
-	return String(a.appProperties.Certificate)
+	return String(a.overridableAppProperties.Certificate)
 }
 
 // android_app compiles sources and Android resources into an Android application package `.apk` file.
@@ -432,7 +440,8 @@
 		&module.Module.dexpreoptProperties,
 		&module.Module.protoProperties,
 		&module.aaptProperties,
-		&module.appProperties)
+		&module.appProperties,
+		&module.overridableAppProperties)
 
 	module.Prefer32(func(ctx android.BaseModuleContext, base *android.ModuleBase, class android.OsClass) bool {
 		return class == android.Device && ctx.Config().DevicePrefer32BitApps()
@@ -440,6 +449,7 @@
 
 	android.InitAndroidMultiTargetsArchModule(module, android.DeviceSupported, android.MultilibCommon)
 	android.InitDefaultableModule(module)
+	android.InitOverridableModule(module, &module.appProperties.Overrides)
 
 	return module
 }
@@ -503,6 +513,7 @@
 		&module.aaptProperties,
 		&module.appProperties,
 		&module.appTestProperties,
+		&module.overridableAppProperties,
 		&module.testProperties)
 
 	android.InitAndroidMultiTargetsArchModule(module, android.DeviceSupported, android.MultilibCommon)
@@ -541,7 +552,8 @@
 		&module.Module.protoProperties,
 		&module.aaptProperties,
 		&module.appProperties,
-		&module.appTestHelperAppProperties)
+		&module.appTestHelperAppProperties,
+		&module.overridableAppProperties)
 
 	android.InitAndroidMultiTargetsArchModule(module, android.DeviceSupported, android.MultilibCommon)
 	android.InitDefaultableModule(module)
@@ -575,3 +587,24 @@
 		android.PathForModuleSrc(ctx, cert+".pk8"),
 	}
 }
+
+type OverrideAndroidApp struct {
+	android.ModuleBase
+	android.OverrideModuleBase
+}
+
+func (i *OverrideAndroidApp) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+	// All the overrides happen in the base module.
+	// TODO(jungjw): Check the base module type.
+}
+
+// override_android_app is used to create an android_app module based on another android_app by overriding
+// some of its properties.
+func OverrideAndroidAppModuleFactory() android.Module {
+	m := &OverrideAndroidApp{}
+	m.AddProperties(&overridableAppProperties{})
+
+	android.InitAndroidModule(m)
+	android.InitOverrideModule(m)
+	return m
+}
diff --git a/java/app_test.go b/java/app_test.go
index 1bad123..cf57c80 100644
--- a/java/app_test.go
+++ b/java/app_test.go
@@ -827,3 +827,75 @@
 		t.Errorf("target package renaming flag, %q is missing in aapt2 link flags, %q", e, aapt2Flags)
 	}
 }
+
+func TestOverrideAndroidApp(t *testing.T) {
+	ctx := testJava(t, `
+		android_app {
+			name: "foo",
+			srcs: ["a.java"],
+			overrides: ["baz"],
+		}
+
+		override_android_app {
+			name: "bar",
+			base: "foo",
+			certificate: ":new_certificate",
+		}
+
+		android_app_certificate {
+			name: "new_certificate",
+			certificate: "cert/new_cert",
+		}
+		`)
+
+	expectedVariants := []struct {
+		variantName string
+		apkName     string
+		apkPath     string
+		signFlag    string
+		overrides   []string
+	}{
+		{
+			variantName: "android_common",
+			apkPath:     "/target/product/test_device/system/app/foo/foo.apk",
+			signFlag:    "build/target/product/security/testkey.x509.pem build/target/product/security/testkey.pk8",
+			overrides:   []string{"baz"},
+		},
+		{
+			variantName: "bar_android_common",
+			apkPath:     "/target/product/test_device/system/app/bar/bar.apk",
+			signFlag:    "cert/new_cert.x509.pem cert/new_cert.pk8",
+			overrides:   []string{"baz", "foo"},
+		},
+	}
+	for _, expected := range expectedVariants {
+		variant := ctx.ModuleForTests("foo", expected.variantName)
+
+		// Check the final apk name
+		outputs := variant.AllOutputs()
+		expectedApkPath := buildDir + expected.apkPath
+		found := false
+		for _, o := range outputs {
+			if o == expectedApkPath {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Errorf("Can't find %q in output files.\nAll outputs:%v", expectedApkPath, outputs)
+		}
+
+		// Check the certificate paths
+		signapk := variant.Output("foo.apk")
+		signFlag := signapk.Args["certificates"]
+		if expected.signFlag != signFlag {
+			t.Errorf("Incorrect signing flags, expected: %q, got: %q", expected.signFlag, signFlag)
+		}
+
+		mod := variant.Module().(*AndroidApp)
+		if !reflect.DeepEqual(expected.overrides, mod.appProperties.Overrides) {
+			t.Errorf("Incorrect overrides property value, expected: %q, got: %q",
+				expected.overrides, mod.appProperties.Overrides)
+		}
+	}
+}
diff --git a/java/java.go b/java/java.go
index e0da006..3eae932 100644
--- a/java/java.go
+++ b/java/java.go
@@ -2068,6 +2068,7 @@
 		&androidLibraryProperties{},
 		&appProperties{},
 		&appTestProperties{},
+		&overridableAppProperties{},
 		&ImportProperties{},
 		&AARImportProperties{},
 		&sdkLibraryProperties{},
diff --git a/java/java_test.go b/java/java_test.go
index 35dd696..ec6d27a 100644
--- a/java/java_test.go
+++ b/java/java_test.go
@@ -86,10 +86,12 @@
 	ctx.RegisterModuleType("droiddoc_host", android.ModuleFactoryAdaptor(DroiddocHostFactory))
 	ctx.RegisterModuleType("droiddoc_template", android.ModuleFactoryAdaptor(ExportedDroiddocDirFactory))
 	ctx.RegisterModuleType("java_sdk_library", android.ModuleFactoryAdaptor(SdkLibraryFactory))
+	ctx.RegisterModuleType("override_android_app", android.ModuleFactoryAdaptor(OverrideAndroidAppModuleFactory))
 	ctx.RegisterModuleType("prebuilt_apis", android.ModuleFactoryAdaptor(PrebuiltApisFactory))
 	ctx.PreArchMutators(android.RegisterPrebuiltsPreArchMutators)
 	ctx.PreArchMutators(android.RegisterPrebuiltsPostDepsMutators)
 	ctx.PreArchMutators(android.RegisterDefaultsPreArchMutators)
+	ctx.PreArchMutators(android.RegisterOverridePreArchMutators)
 	ctx.PreArchMutators(func(ctx android.RegisterMutatorsContext) {
 		ctx.TopDown("prebuilt_apis", PrebuiltApisMutator).Parallel()
 		ctx.TopDown("java_sdk_library", SdkLibraryMutator).Parallel()