Added phony module type for soong.

The "required" field within "phony" module in .bp file has to be
non-empty. And "phony" module doesn't contain any "src" files.
Bug: b/32981153
Test: make -j out/soong/build.ninja

Change-Id: Iaa2009467c44702572b97ca9cbd02c1d368c8d83

Android.bp

@@ -167,6 +167,19 @@ bootstrap_go_package {
     pluginFor: ["soong_build"],
 }
 
+bootstrap_go_package {
+    name: "soong-phony",
+    pkgPath: "android/soong/phony",
+    deps: [
+        "blueprint",
+        "soong-android",
+    ],
+    srcs: [
+        "phony/phony.go",
+    ],
+    pluginFor: ["soong_build"],
+}
+
 bootstrap_go_package {
     name: "soong-java",
     pkgPath: "android/soong/java",

android/androidmk.go

@@ -43,7 +43,7 @@ type AndroidMkData struct {
 	OutputFile OptionalPath
 	Disabled   bool
 
-	Custom func(w io.Writer, name, prefix string) error
+	Custom func(w io.Writer, name, prefix, moduleDir string) error
 
 	Extra []func(w io.Writer, outputFile Path) error
 }
@@ -185,7 +185,7 @@ func translateAndroidMkModule(ctx blueprint.SingletonContext, w io.Writer, mod b
 			prefix = "2ND_" + prefix
 		}
 
-		return data.Custom(w, name, prefix)
+		return data.Custom(w, name, prefix, filepath.Dir(ctx.BlueprintFile(mod)))
 	}
 
 	if data.Disabled {

android/module.go

@@ -89,6 +89,8 @@ type ModuleContext interface {
 
 	Proprietary() bool
 	InstallInData() bool
+
+	RequiredModuleNames() []string
 }
 
 type Module interface {
@@ -784,6 +786,10 @@ func (ctx *androidModuleContext) ExpandSourcesSubDir(srcFiles, excludes []string
 	return expandedSrcFiles
 }
 
+func (ctx *androidModuleContext) RequiredModuleNames() []string {
+	return ctx.module.base().commonProperties.Required
+}
+
 func (ctx *androidModuleContext) Glob(globPattern string, excludes []string) Paths {
 	ret, err := ctx.GlobWithDeps(globPattern, excludes)
 	if err != nil {

cc/androidmk.go

@@ -120,7 +120,7 @@ func (library *libraryDecorator) AndroidMk(ctx AndroidMkContext, ret *android.An
 }
 
 func (object *objectLinker) AndroidMk(ctx AndroidMkContext, ret *android.AndroidMkData) {
-	ret.Custom = func(w io.Writer, name, prefix string) error {
+	ret.Custom = func(w io.Writer, name, prefix, moduleDir string) error {
 		out := ret.OutputFile.Path()
 
 		fmt.Fprintln(w, "\n$("+prefix+"OUT_INTERMEDIATE_LIBRARIES)/"+name+objectExtension+":", out.String())

phony/phony.go

@@ -0,0 +1,63 @@
+// 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 phony
+
+import (
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/google/blueprint"
+
+	"android/soong/android"
+)
+
+func init() {
+	android.RegisterModuleType("phony", phonyFactory)
+}
+
+type phony struct {
+	android.ModuleBase
+	requiredModuleNames []string
+}
+
+func phonyFactory() (blueprint.Module, []interface{}) {
+	module := &phony{}
+
+	return android.InitAndroidModule(module)
+}
+
+func (p *phony) DepsMutator(ctx android.BottomUpMutatorContext) {
+}
+
+func (p *phony) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+	p.requiredModuleNames = ctx.RequiredModuleNames()
+	if len(p.requiredModuleNames) == 0 {
+		ctx.PropertyErrorf("required", "phony must not have empty required dependencies in order to be useful(and therefore permitted).")
+	}
+}
+
+func (p *phony) AndroidMk() (ret android.AndroidMkData, err error) {
+	ret.Custom = func(w io.Writer, name, prefix, moduleDir string) error {
+		fmt.Fprintln(w, "\ninclude $(CLEAR_VARS)")
+		fmt.Fprintln(w, "LOCAL_PATH :=", moduleDir)
+		fmt.Fprintln(w, "LOCAL_MODULE :=", name)
+		fmt.Fprintln(w, "LOCAL_REQUIRED_MODULES := "+strings.Join(p.requiredModuleNames, " "))
+		fmt.Fprintln(w, "include $(BUILD_PHONY_PACKAGE)")
+
+		return nil
+	}
+	return
+}