Create java_api_contribution and java_api_library module

Context
- Droidstubs module is currently responsible not only for java api stubs
  generation, but also for checking api equality and compatibility.
- Generating stubs with incomplete api text file that does not list
  entire api surface is done through metalava implicitly adding unlisted
  methods from java source files to the stubs in droidstubs module.
- These factors make java stubs generation harder to debug, thus
  introduce `java_api_contribution` and `java_api_library` modules to make java
  api stubs and jar generation more explicit in Android.bp level and
  eventually easier to debug.

Implementation
- `java_api_contribution` module is included in api domains' directory and
  lists api text file directory to be added to the api surface
- `java_api_library` collects all api text file that forms the api surface
  and creates stubs invoking metalava. Generated java stub files are
  converted into `.srcjar`, and eventually `.jar` file which is the complete
  api surface.

Test: m
Change-Id: I86f097cc8592334a5eaa900cec12764c5fcc09e7

java/java.go

@@ -25,6 +25,7 @@ import (
 
 	"android/soong/bazel"
 	"android/soong/bazel/cquery"
+	"android/soong/remoteexec"
 
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
@@ -59,6 +60,8 @@ func registerJavaBuildComponents(ctx android.RegistrationContext) {
 	ctx.RegisterModuleType("java_device_for_host", DeviceForHostFactory)
 	ctx.RegisterModuleType("java_host_for_device", HostForDeviceFactory)
 	ctx.RegisterModuleType("dex_import", DexImportFactory)
+	ctx.RegisterModuleType("java_api_library", ApiLibraryFactory)
+	ctx.RegisterModuleType("java_api_contribution", ApiContributionFactory)
 
 	// This mutator registers dependencies on dex2oat for modules that should be
 	// dexpreopted. This is done late when the final variants have been
@@ -1501,6 +1504,182 @@ func BinaryHostFactory() android.Module {
 	return module
 }
 
+type JavaApiContribution struct {
+	android.ModuleBase
+	android.DefaultableModuleBase
+
+	properties struct {
+		// name of the API surface
+		Api_surface *string
+
+		// relative path to the API signature text file
+		Api_file *string `android:"path"`
+	}
+}
+
+func ApiContributionFactory() android.Module {
+	module := &JavaApiContribution{}
+	android.InitAndroidModule(module)
+	android.InitDefaultableModule(module)
+	module.AddProperties(&module.properties)
+	return module
+}
+
+type JavaApiImportInfo struct {
+	ApiFile android.Path
+}
+
+var JavaApiImportProvider = blueprint.NewProvider(JavaApiImportInfo{})
+
+func (ap *JavaApiContribution) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+	apiFile := android.PathForModuleSrc(ctx, String(ap.properties.Api_file))
+	ctx.SetProvider(JavaApiImportProvider, JavaApiImportInfo{
+		ApiFile: apiFile,
+	})
+}
+
+type ApiLibrary struct {
+	android.ModuleBase
+	android.DefaultableModuleBase
+
+	properties JavaApiLibraryProperties
+
+	stubsSrcJar android.WritablePath
+	stubsJar    android.WritablePath
+}
+
+type JavaApiLibraryProperties struct {
+	// name of the API surface
+	Api_surface *string
+
+	// list of API provider modules that consists this API surface
+	Api_providers []string
+
+	// List of flags to be passed to the javac compiler to generate jar file
+	Javacflags []string
+}
+
+func ApiLibraryFactory() android.Module {
+	module := &ApiLibrary{}
+	android.InitAndroidArchModule(module, android.DeviceSupported, android.MultilibCommon)
+	android.InitDefaultableModule(module)
+	module.AddProperties(&module.properties)
+	return module
+}
+
+func (al *ApiLibrary) ApiSurface() *string {
+	return al.properties.Api_surface
+}
+
+func (al *ApiLibrary) StubsJar() android.Path {
+	return al.stubsJar
+}
+
+func metalavaStubCmd(ctx android.ModuleContext, rule *android.RuleBuilder,
+	srcs android.Paths, homeDir android.WritablePath) *android.RuleBuilderCommand {
+	rule.Command().Text("rm -rf").Flag(homeDir.String())
+	rule.Command().Text("mkdir -p").Flag(homeDir.String())
+
+	cmd := rule.Command()
+	cmd.FlagWithArg("ANDROID_PREFS_ROOT=", homeDir.String())
+
+	if metalavaUseRbe(ctx) {
+		rule.Remoteable(android.RemoteRuleSupports{RBE: true})
+		execStrategy := ctx.Config().GetenvWithDefault("RBE_METALAVA_EXEC_STRATEGY", remoteexec.LocalExecStrategy)
+		labels := map[string]string{"type": "tool", "name": "metalava"}
+
+		pool := ctx.Config().GetenvWithDefault("RBE_METALAVA_POOL", "java16")
+		rule.Rewrapper(&remoteexec.REParams{
+			Labels:          labels,
+			ExecStrategy:    execStrategy,
+			ToolchainInputs: []string{config.JavaCmd(ctx).String()},
+			Platform:        map[string]string{remoteexec.PoolKey: pool},
+		})
+	}
+
+	cmd.BuiltTool("metalava").ImplicitTool(ctx.Config().HostJavaToolPath(ctx, "metalava.jar")).
+		Flag(config.JavacVmFlags).
+		Flag("-J--add-opens=java.base/java.util=ALL-UNNAMED").
+		FlagWithArg("-encoding ", "UTF-8").
+		FlagWithInputList("--source-files ", srcs, " ")
+
+	cmd.Flag("--no-banner").
+		Flag("--color").
+		Flag("--quiet").
+		Flag("--format=v2").
+		FlagWithArg("--repeat-errors-max ", "10").
+		FlagWithArg("--hide ", "UnresolvedImport").
+		FlagWithArg("--hide ", "InvalidNullabilityOverride").
+		FlagWithArg("--hide ", "ChangedDefault")
+
+	return cmd
+}
+
+func (al *ApiLibrary) stubsFlags(ctx android.ModuleContext, cmd *android.RuleBuilderCommand, stubsDir android.OptionalPath) {
+	if stubsDir.Valid() {
+		cmd.FlagWithArg("--stubs ", stubsDir.String())
+	}
+}
+
+var javaApiProviderTag = dependencyTag{name: "java-api-provider"}
+
+func (al *ApiLibrary) DepsMutator(ctx android.BottomUpMutatorContext) {
+	apiProviders := al.properties.Api_providers
+	for _, apiProviderName := range apiProviders {
+		ctx.AddDependency(ctx.Module(), javaApiProviderTag, apiProviderName)
+	}
+}
+
+func (al *ApiLibrary) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+
+	rule := android.NewRuleBuilder(pctx, ctx)
+
+	rule.Sbox(android.PathForModuleOut(ctx, "metalava"),
+		android.PathForModuleOut(ctx, "metalava.sbox.textproto")).
+		SandboxInputs()
+
+	var stubsDir android.OptionalPath
+	stubsDir = android.OptionalPathForPath(android.PathForModuleOut(ctx, "metalava", "stubsDir"))
+	rule.Command().Text("rm -rf").Text(stubsDir.String())
+	rule.Command().Text("mkdir -p").Text(stubsDir.String())
+
+	homeDir := android.PathForModuleOut(ctx, "metalava", "home")
+
+	apiProviders := al.properties.Api_providers
+	srcFiles := make([]android.Path, len(apiProviders))
+	for i, apiProviderName := range apiProviders {
+		apiProvider := ctx.GetDirectDepWithTag(apiProviderName, javaApiProviderTag)
+		if apiProvider == nil {
+			panic(fmt.Errorf("Java API provider module %s not found, called from %s", apiProviderName, al.Name()))
+		}
+		provider := ctx.OtherModuleProvider(apiProvider, JavaApiImportProvider).(JavaApiImportInfo)
+		srcFiles[i] = android.PathForModuleSrc(ctx, provider.ApiFile.String())
+	}
+
+	cmd := metalavaStubCmd(ctx, rule, srcFiles, homeDir)
+
+	al.stubsFlags(ctx, cmd, stubsDir)
+
+	al.stubsSrcJar = android.PathForModuleOut(ctx, "metalava", ctx.ModuleName()+"-"+"stubs.srcjar")
+	rule.Command().
+		BuiltTool("soong_zip").
+		Flag("-write_if_changed").
+		Flag("-jar").
+		FlagWithOutput("-o ", al.stubsSrcJar).
+		FlagWithArg("-C ", stubsDir.String()).
+		FlagWithArg("-D ", stubsDir.String())
+
+	rule.Build("metalava", "metalava merged")
+
+	al.stubsJar = android.PathForModuleOut(ctx, ctx.ModuleName(), "android.jar")
+
+	var flags javaBuilderFlags
+	flags.javacFlags = strings.Join(al.properties.Javacflags, " ")
+
+	TransformJavaToClasses(ctx, al.stubsJar, 0, android.Paths{},
+		android.Paths{al.stubsSrcJar}, flags, android.Paths{})
+}
+
 //
 // Java prebuilts
 //