Generate java_api_contribution module from droidstubs module

Context
- droidstubs module are either generated from the java_sdk_library
  module or defined in the bp files.
- Since droidstubs module contains API text file property,
  java_api_contribution module can by dynamically created from
  droidstubs.

Implementation
- Add `api_surface` property in droidstubs module. This property is
  either inherited from the java_sdk_library or written in the module
  definition in the bp file.
- Add defaultable hook in droidstubs module to generate the child
  java_api_contribution module.

Test: m
Change-Id: Ica43d65614723c623cd0c155266f9844e69e5d5e

java/droidstubs.go

@@ -148,6 +148,10 @@ type DroidstubsProperties struct {
 	// path or filegroup to file defining extension an SDK name <-> numerical ID mapping and
 	// what APIs exist in which SDKs; passed to metalava via --sdk-extensions-info
 	Extensions_info_file *string `android:"path"`
+
+	// API surface of this module. If set, the module contributes to an API surface.
+	// For the full list of available API surfaces, refer to soong/android/sdk_version.go
+	Api_surface *string
 }
 
 // Used by xsd_config
@@ -178,6 +182,10 @@ func DroidstubsFactory() android.Module {
 		&module.Javadoc.properties)
 
 	InitDroiddocModule(module, android.HostAndDeviceSupported)
+
+	module.SetDefaultableHook(func(ctx android.DefaultableHookContext) {
+		module.createApiContribution(ctx)
+	})
 	return module
 }
 
@@ -862,6 +870,23 @@ func (d *Droidstubs) ConvertWithApiBp2build(ctx android.TopDownMutatorContext) {
 	}, attrs)
 }
 
+func (d *Droidstubs) createApiContribution(ctx android.DefaultableHookContext) {
+	api_file := d.properties.Check_api.Current.Api_file
+	api_surface := d.properties.Api_surface
+
+	props := struct {
+		Name        *string
+		Api_surface *string
+		Api_file    *string
+	}{}
+
+	props.Name = proptools.StringPtr(d.Name() + ".api.contribution")
+	props.Api_surface = api_surface
+	props.Api_file = api_file
+
+	ctx.CreateModule(ApiContributionFactory, &props)
+}
+
 // TODO (b/262014796): Export the API contributions of CorePlatformApi
 // A map to populate the api surface of a droidstub from a substring appearing in its name
 // This map assumes that droidstubs (either checked-in or created by java_sdk_library)

java/droidstubs_test.go

@@ -346,3 +346,27 @@ func TestApiSurfaceFromDroidStubsName(t *testing.T) {
 		android.AssertStringEquals(t, tc.desc, tc.expectedApiSurface, bazelApiSurfaceName(tc.name))
 	}
 }
+
+func TestDroidStubsApiContributionGeneration(t *testing.T) {
+	ctx, _ := testJavaWithFS(t, `
+		droidstubs {
+			name: "foo",
+			srcs: ["A/a.java"],
+			api_surface: "public",
+			check_api: {
+				current: {
+					api_file: "A/current.txt",
+					removed_api_file: "A/removed.txt",
+				}
+			}
+		}
+		`,
+		map[string][]byte{
+			"A/a.java":      nil,
+			"A/current.txt": nil,
+			"A/removed.txt": nil,
+		},
+	)
+
+	ctx.ModuleForTests("foo.api.contribution", "")
+}

java/java.go

@@ -1594,7 +1594,11 @@ type JavaApiImportInfo struct {
 var JavaApiImportProvider = blueprint.NewProvider(JavaApiImportInfo{})
 
 func (ap *JavaApiContribution) GenerateAndroidBuildActions(ctx android.ModuleContext) {
-	apiFile := android.PathForModuleSrc(ctx, String(ap.properties.Api_file))
+	var apiFile android.Path = nil
+	if apiFileString := ap.properties.Api_file; apiFileString != nil {
+		apiFile = android.PathForModuleSrc(ctx, String(apiFileString))
+	}
+
 	ctx.SetProvider(JavaApiImportProvider, JavaApiImportInfo{
 		ApiFile: apiFile,
 	})
@@ -1725,7 +1729,11 @@ func (al *ApiLibrary) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 		switch tag {
 		case javaApiContributionTag:
 			provider := ctx.OtherModuleProvider(dep, JavaApiImportProvider).(JavaApiImportInfo)
-			srcFiles = append(srcFiles, android.PathForSource(ctx, provider.ApiFile.String()))
+			providerApiFile := provider.ApiFile
+			if providerApiFile == nil {
+				ctx.ModuleErrorf("Error: %s has an empty api file.", dep.Name())
+			}
+			srcFiles = append(srcFiles, android.PathForSource(ctx, providerApiFile.String()))
 		case libTag:
 			provider := ctx.OtherModuleProvider(dep, JavaInfoProvider).(JavaInfo)
 			classPaths = append(classPaths, provider.HeaderJars...)

java/java_test.go

@@ -1840,6 +1840,20 @@ func TestDeviceBinaryWrapperGeneration(t *testing.T) {
 		}`)
 }
 
+func TestJavaApiContributionEmptyApiFile(t *testing.T) {
+	testJavaError(t,
+		"Error: foo has an empty api file.",
+		`java_api_contribution {
+			name: "foo",
+		}
+		java_api_library {
+			name: "bar",
+			api_surface: "public",
+			api_contributions: ["foo"],
+		}
+	`)
+}
+
 func TestJavaApiLibraryAndProviderLink(t *testing.T) {
 	provider_bp_a := `
 	java_api_contribution {

java/sdk_library.go

@@ -1599,6 +1599,7 @@ func (module *SdkLibrary) createStubsSourcesAndApi(mctx android.DefaultableHookC
 		Srcs                             []string
 		Installable                      *bool
 		Sdk_version                      *string
+		Api_surface                      *string
 		System_modules                   *string
 		Libs                             []string
 		Output_javadoc_comments          *bool
@@ -1638,6 +1639,7 @@ func (module *SdkLibrary) createStubsSourcesAndApi(mctx android.DefaultableHookC
 	props.Srcs = append(props.Srcs, module.properties.Srcs...)
 	props.Srcs = append(props.Srcs, module.sdkLibraryProperties.Api_srcs...)
 	props.Sdk_version = module.deviceProperties.Sdk_version
+	props.Api_surface = &apiScope.name
 	props.System_modules = module.deviceProperties.System_modules
 	props.Installable = proptools.BoolPtr(false)
 	// A droiddoc module has only one Libs property and doesn't distinguish between