Support filegroups

filegroup is a module that contains a list of files, and can be used
to export files across package boundaries.  filegroups (and genrules)
can be referenced from srcs properties of other modules using the
syntax ":module".

Test: m -j
Change-Id: I3d6fc4819c0b4225b474e0ad42f0d947f55a5961

Android.bp

@@ -159,6 +159,7 @@ bootstrap_go_package {
         "soong-android",
     ],
     srcs: [
+        "genrule/filegroup.go",
         "genrule/genrule.go",
     ],
     pluginFor: ["soong_build"],

README.md

@@ -8,7 +8,9 @@ declarative descriptions of modules to build.
 
 By design, Android.bp files are very simple.  There are no conditionals or
 control flow statements - any complexity is handled in build logic written in
-Go.
+Go.  The syntax and semantics of Android.bp files are intentionally similar
+to [Bazel BUILD files](https://www.bazel.io/versions/master/docs/be/overview.html)
+when possible.
 
 ### Modules
 

android/module.go

@@ -711,6 +711,38 @@ func findStringInSlice(str string, slice []string) int {
 	return -1
 }
 
+func SrcIsModule(s string) string {
+	if len(s) > 1 && s[0] == ':' {
+		return s[1:]
+	}
+	return ""
+}
+
+type sourceDependencyTag struct {
+	blueprint.BaseDependencyTag
+}
+
+var SourceDepTag sourceDependencyTag
+
+// Returns a list of modules that must be depended on to satisfy filegroup or generated sources
+// modules listed in srcFiles using ":module" syntax
+func ExtractSourcesDeps(ctx BottomUpMutatorContext, srcFiles []string) {
+	var deps []string
+	for _, s := range srcFiles {
+		if m := SrcIsModule(s); m != "" {
+			deps = append(deps, m)
+		}
+	}
+
+	ctx.AddDependency(ctx.Module(), SourceDepTag, deps...)
+}
+
+type SourceFileProducer interface {
+	Srcs() Paths
+}
+
+// Returns a list of paths expanded from globs and modules referenced using ":module" syntax.
+// ExpandSourceDeps must have already been called during the dependency resolution phase.
 func (ctx *androidModuleContext) ExpandSources(srcFiles, excludes []string) Paths {
 	prefix := PathForModuleSrc(ctx).String()
 	for i, e := range excludes {
@@ -724,7 +756,14 @@ func (ctx *androidModuleContext) ExpandSources(srcFiles, excludes []string) Path
 
 	globbedSrcFiles := make(Paths, 0, len(srcFiles))
 	for _, s := range srcFiles {
-		if pathtools.IsGlob(s) {
+		if m := SrcIsModule(s); m != "" {
+			module := ctx.GetDirectDepWithTag(m, SourceDepTag)
+			if srcProducer, ok := module.(SourceFileProducer); ok {
+				globbedSrcFiles = append(globbedSrcFiles, srcProducer.Srcs()...)
+			} else {
+				ctx.ModuleErrorf("srcs dependency %q is not a source file producing module", m)
+			}
+		} else if pathtools.IsGlob(s) {
 			globbedSrcFiles = append(globbedSrcFiles, ctx.Glob(filepath.Join(prefix, s), excludes)...)
 		} else {
 			globbedSrcFiles = append(globbedSrcFiles, PathForModuleSrc(ctx, s))

cc/cc.go

@@ -833,7 +833,7 @@ func (c *Module) depsToPaths(ctx android.ModuleContext) PathDeps {
 		cc, _ := m.(*Module)
 		if cc == nil {
 			switch tag {
-			case android.DefaultsDepTag:
+			case android.DefaultsDepTag, android.SourceDepTag:
 			case genSourceDepTag:
 				if genRule, ok := m.(genrule.SourceFileGenerator); ok {
 					depPaths.GeneratedSources = append(depPaths.GeneratedSources,

cc/compiler.go

@@ -29,6 +29,8 @@ import (
 
 type BaseCompilerProperties struct {
 	// list of source files used to compile the C/C++ module.  May be .c, .cpp, or .S files.
+	// srcs may reference the outputs of other modules that produce source files like genrule
+	// or filegroup using the syntax ":module".
 	Srcs []string `android:"arch_variant"`
 
 	// list of source files that should not be used to build the C/C++ module.
@@ -133,6 +135,8 @@ func (compiler *baseCompiler) compilerDeps(ctx DepsContext, deps Deps) Deps {
 	deps.GeneratedSources = append(deps.GeneratedSources, compiler.Properties.Generated_sources...)
 	deps.GeneratedHeaders = append(deps.GeneratedHeaders, compiler.Properties.Generated_headers...)
 
+	android.ExtractSourcesDeps(ctx, compiler.Properties.Srcs)
+
 	if compiler.hasSrcExt(".proto") {
 		deps = protoDeps(ctx, deps, &compiler.Proto)
 	}

genrule/filegroup.go

@@ -0,0 +1,61 @@
+// Copyright 2016 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 genrule
+
+import (
+	"github.com/google/blueprint"
+
+	"android/soong/android"
+)
+
+func init() {
+	android.RegisterModuleType("filegroup", fileGroupFactory)
+}
+
+type fileGroupProperties struct {
+	// srcs lists files that will be included in this filegroup
+	Srcs []string
+
+	Exclude_srcs []string
+}
+
+type fileGroup struct {
+	android.ModuleBase
+	properties fileGroupProperties
+	srcs       android.Paths
+}
+
+var _ android.SourceFileProducer = (*fileGroup)(nil)
+
+// filegroup modules contain a list of files, and can be used to export files across package
+// boundaries.  filegroups (and genrules) can be referenced from srcs properties of other modules
+// using the syntax ":module".
+func fileGroupFactory() (blueprint.Module, []interface{}) {
+	module := &fileGroup{}
+
+	return android.InitAndroidModule(module, &module.properties)
+}
+
+func (fg *fileGroup) DepsMutator(ctx android.BottomUpMutatorContext) {
+	android.ExtractSourcesDeps(ctx, fg.properties.Srcs)
+}
+
+func (fg *fileGroup) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+	fg.srcs = ctx.ExpandSources(fg.properties.Srcs, fg.properties.Exclude_srcs)
+}
+
+func (fg *fileGroup) Srcs() android.Paths {
+	return fg.srcs
+}

genrule/genrule.go

@@ -96,6 +96,10 @@ func (g *generator) GeneratedSourceFiles() android.Paths {
 	return g.outputFiles
 }
 
+func (g *generator) Srcs() android.Paths {
+	return g.outputFiles
+}
+
 func (g *generator) GeneratedHeaderDirs() android.Paths {
 	return g.exportedIncludeDirs
 }