Implement aidl_library module type

We currently specifies aidl files directly to the srcs prop on a filegroup or other module types such as cc_library or java_library. We use aidl.include_dirs prop to specify paths to aidl headers. This include_dirs pattern isn't migratable to Bazel because Bazel requires explicit dependencies.

This CL introduces aidl_library to better map with Bazel's aidl_library rule and to enable aidl headers to be specified in a separate aidl_library or the hdrs prop. A follow-up CL will turn on inputs sandbox to enforce all aidl headers be explicitly specified in Android.bp

Test: go test
Bug: 278704136
Change-Id: I2c99af080525bf8a6c5724ed5ee2001842969098

aidl_library/aidl_library.go

@@ -0,0 +1,120 @@
+// Copyright 2023 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package aidl_library
+
+import (
+	"android/soong/android"
+
+	"github.com/google/blueprint"
+	"github.com/google/blueprint/proptools"
+)
+
+func init() {
+	registerAidlLibraryBuildComponents(android.InitRegistrationContext)
+}
+
+func registerAidlLibraryBuildComponents(ctx android.RegistrationContext) {
+	ctx.RegisterModuleType("aidl_library", AidlLibraryFactory)
+}
+
+type aidlLibraryProperties struct {
+	// srcs lists files that are included in this module for aidl compilation
+	Srcs []string `android:"path"`
+
+	// hdrs lists the headers that are imported by srcs but are not compiled by aidl to language binding code
+	// hdrs is provided to support Bazel migration. It is a no-op until
+	// we enable input sandbox in aidl compilation action
+	Hdrs []string `android:"path"`
+
+	// The prefix to strip from the paths of the .aidl files
+	// The remaining path is the package path of the aidl interface
+	Strip_import_prefix *string
+
+	// List of aidl files or aidl_library depended on by the module
+	Deps []string `android:"arch_variant"`
+}
+
+type AidlLibrary struct {
+	android.ModuleBase
+	properties aidlLibraryProperties
+}
+
+type AidlLibraryInfo struct {
+	// The direct aidl files of the module
+	Srcs android.Paths
+	// The include dirs to the direct aidl files and those provided from aidl_library deps
+	IncludeDirs android.DepSet
+}
+
+// AidlLibraryProvider provides the srcs and the transitive include dirs
+var AidlLibraryProvider = blueprint.NewProvider(AidlLibraryInfo{})
+
+func (lib *AidlLibrary) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+	includeDirsDepSetBuilder := android.NewDepSetBuilder(android.PREORDER)
+
+	if len(lib.properties.Srcs) == 0 && len(lib.properties.Hdrs) == 0 {
+		ctx.ModuleErrorf("at least srcs or hdrs prop must be non-empty")
+	}
+
+	srcs := android.PathsForModuleSrc(ctx, lib.properties.Srcs)
+	if lib.properties.Strip_import_prefix != nil {
+		srcs = android.PathsWithModuleSrcSubDir(
+			ctx,
+			srcs,
+			android.String(lib.properties.Strip_import_prefix))
+	}
+
+	includeDir := android.PathForModuleSrc(
+		ctx,
+		proptools.StringDefault(lib.properties.Strip_import_prefix, ""),
+	)
+
+	includeDirsDepSetBuilder.Direct(includeDir)
+
+	for _, dep := range ctx.GetDirectDepsWithTag(aidlLibraryTag) {
+		if ctx.OtherModuleHasProvider(dep, AidlLibraryProvider) {
+			info := ctx.OtherModuleProvider(dep, AidlLibraryProvider).(AidlLibraryInfo)
+			includeDirsDepSetBuilder.Transitive(&info.IncludeDirs)
+		}
+	}
+
+	// TODO(b/279960133) Propagate direct and transitive headers/srcs when aidl action sandboxes inputs
+	ctx.SetProvider(AidlLibraryProvider, AidlLibraryInfo{
+		Srcs:        srcs,
+		IncludeDirs: *includeDirsDepSetBuilder.Build(),
+	})
+}
+
+// aidl_library contains a list of .aidl files and the strip_import_prefix to
+// to strip from the paths of the .aidl files. The sub-path left-over after stripping
+// corresponds to the aidl package path the aidl interfaces are scoped in
+func AidlLibraryFactory() android.Module {
+	module := &AidlLibrary{}
+	module.AddProperties(&module.properties)
+	android.InitAndroidModule(module)
+	return module
+}
+
+type aidlDependencyTag struct {
+	blueprint.BaseDependencyTag
+}
+
+var aidlLibraryTag = aidlDependencyTag{}
+
+func (lib *AidlLibrary) DepsMutator(ctx android.BottomUpMutatorContext) {
+	for _, dep := range lib.properties.Deps {
+		ctx.AddDependency(lib, aidlLibraryTag, dep)
+	}
+}