android/bazel_handler.go - platform/build/soong - Git at Google

 // Copyright 2020 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 android

 import (
 	"bytes"
 	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"runtime"
 	"strings"
 	"sync"

 	"github.com/google/blueprint/bootstrap"

 	"android/soong/bazel"
 	"android/soong/shared"
 )

 type CqueryRequestType int

 const (
 	getAllFiles CqueryRequestType = iota
 )

 // Map key to describe bazel cquery requests.
 type cqueryKey struct {
 	label       string
 	requestType CqueryRequestType
 }

 type BazelContext interface {
 	// The below methods involve queuing cquery requests to be later invoked
 	// by bazel. If any of these methods return (_, false), then the request
 	// has been queued to be run later.

 	// Returns result files built by building the given bazel target label.
 	GetAllFiles(label string) ([]string, bool)

 	// TODO(cparsons): Other cquery-related methods should be added here.
 	// ** End cquery methods

 	// Issues commands to Bazel to receive results for all cquery requests
 	// queued in the BazelContext.
 	InvokeBazel() error

 	// Returns true if bazel is enabled for the given configuration.
 	BazelEnabled() bool

 	// Returns the bazel output base (the root directory for all bazel intermediate outputs).
 	OutputBase() string

 	// Returns build statements which should get registered to reflect Bazel's outputs.
 	BuildStatementsToRegister() []bazel.BuildStatement
 }

 // A context object which tracks queued requests that need to be made to Bazel,
 // and their results after the requests have been made.
 type bazelContext struct {
 	homeDir      string
 	bazelPath    string
 	outputBase   string
 	workspaceDir string
 	buildDir     string
 	metricsDir   string

 	requests     map[cqueryKey]bool // cquery requests that have not yet been issued to Bazel
 	requestMutex sync.Mutex         // requests can be written in parallel

 	results map[cqueryKey]string // Results of cquery requests after Bazel invocations

 	// Build statements which should get registered to reflect Bazel's outputs.
 	buildStatements []bazel.BuildStatement
 }

 var _ BazelContext = &bazelContext{}

 // A bazel context to use when Bazel is disabled.
 type noopBazelContext struct{}

 var _ BazelContext = noopBazelContext{}

 // A bazel context to use for tests.
 type MockBazelContext struct {
 	AllFiles map[string][]string
 }

 func (m MockBazelContext) GetAllFiles(label string) ([]string, bool) {
 	result, ok := m.AllFiles[label]
 	return result, ok
 }

 func (m MockBazelContext) InvokeBazel() error {
 	panic("unimplemented")
 }

 func (m MockBazelContext) BazelEnabled() bool {
 	return true
 }

 func (m MockBazelContext) OutputBase() string {
 	return "outputbase"
 }

 func (m MockBazelContext) BuildStatementsToRegister() []bazel.BuildStatement {
 	return []bazel.BuildStatement{}
 }

 var _ BazelContext = MockBazelContext{}

 func (bazelCtx *bazelContext) GetAllFiles(label string) ([]string, bool) {
 	result, ok := bazelCtx.cquery(label, getAllFiles)
 	if ok {
 		bazelOutput := strings.TrimSpace(result)
 		return strings.Split(bazelOutput, ", "), true
 	} else {
 		return nil, false
 	}
 }

 func (n noopBazelContext) GetAllFiles(label string) ([]string, bool) {
 	panic("unimplemented")
 }

 func (n noopBazelContext) InvokeBazel() error {
 	panic("unimplemented")
 }

 func (m noopBazelContext) OutputBase() string {
 	return ""
 }

 func (n noopBazelContext) BazelEnabled() bool {
 	return false
 }

 func (m noopBazelContext) BuildStatementsToRegister() []bazel.BuildStatement {
 	return []bazel.BuildStatement{}
 }

 func NewBazelContext(c *config) (BazelContext, error) {
 	// TODO(cparsons): Assess USE_BAZEL=1 instead once "mixed Soong/Bazel builds"
 	// are production ready.
 	if c.Getenv("USE_BAZEL_ANALYSIS") != "1" {
 		return noopBazelContext{}, nil
 	}

 	bazelCtx := bazelContext{buildDir: c.buildDir, requests: make(map[cqueryKey]bool)}
 	missingEnvVars := []string{}
 	if len(c.Getenv("BAZEL_HOME")) > 1 {
 		bazelCtx.homeDir = c.Getenv("BAZEL_HOME")
 	} else {
 		missingEnvVars = append(missingEnvVars, "BAZEL_HOME")
 	}
 	if len(c.Getenv("BAZEL_PATH")) > 1 {
 		bazelCtx.bazelPath = c.Getenv("BAZEL_PATH")
 	} else {
 		missingEnvVars = append(missingEnvVars, "BAZEL_PATH")
 	}
 	if len(c.Getenv("BAZEL_OUTPUT_BASE")) > 1 {
 		bazelCtx.outputBase = c.Getenv("BAZEL_OUTPUT_BASE")
 	} else {
 		missingEnvVars = append(missingEnvVars, "BAZEL_OUTPUT_BASE")
 	}
 	if len(c.Getenv("BAZEL_WORKSPACE")) > 1 {
 		bazelCtx.workspaceDir = c.Getenv("BAZEL_WORKSPACE")
 	} else {
 		missingEnvVars = append(missingEnvVars, "BAZEL_WORKSPACE")
 	}
 	if len(c.Getenv("BAZEL_METRICS_DIR")) > 1 {
 		bazelCtx.metricsDir = c.Getenv("BAZEL_METRICS_DIR")
 	} else {
 		missingEnvVars = append(missingEnvVars, "BAZEL_METRICS_DIR")
 	}
 	if len(missingEnvVars) > 0 {
 		return nil, errors.New(fmt.Sprintf("missing required env vars to use bazel: %s", missingEnvVars))
 	} else {
 		return &bazelCtx, nil
 	}
 }

 func (context *bazelContext) BazelMetricsDir() string {
 	return context.metricsDir
 }

 func (context *bazelContext) BazelEnabled() bool {
 	return true
 }

 // Adds a cquery request to the Bazel request queue, to be later invoked, or
 // returns the result of the given request if the request was already made.
 // If the given request was already made (and the results are available), then
 // returns (result, true). If the request is queued but no results are available,
 // then returns ("", false).
 func (context *bazelContext) cquery(label string, requestType CqueryRequestType) (string, bool) {
 	key := cqueryKey{label, requestType}
 	if result, ok := context.results[key]; ok {
 		return result, true
 	} else {
 		context.requestMutex.Lock()
 		defer context.requestMutex.Unlock()
 		context.requests[key] = true
 		return "", false
 	}
 }

 func pwdPrefix() string {
 	// Darwin doesn't have /proc
 	if runtime.GOOS != "darwin" {
 		return "PWD=/proc/self/cwd"
 	}
 	return ""
 }

 func (context *bazelContext) issueBazelCommand(runName bazel.RunName, command string, labels []string,
 	extraFlags ...string) (string, error) {

 	cmdFlags := []string{"--output_base=" + context.outputBase, command}
 	cmdFlags = append(cmdFlags, labels...)
 	cmdFlags = append(cmdFlags, "--package_path=%workspace%/"+context.intermediatesDir())
 	cmdFlags = append(cmdFlags, "--profile="+shared.BazelMetricsFilename(context, runName))
 	cmdFlags = append(cmdFlags, extraFlags...)

 	bazelCmd := exec.Command(context.bazelPath, cmdFlags...)
 	bazelCmd.Dir = context.workspaceDir
 	bazelCmd.Env = append(os.Environ(), "HOME="+context.homeDir, pwdPrefix())

 	stderr := &bytes.Buffer{}
 	bazelCmd.Stderr = stderr

 	if output, err := bazelCmd.Output(); err != nil {
 		return "", fmt.Errorf("bazel command failed. command: [%s], error [%s]", bazelCmd, stderr)
 	} else {
 		return string(output), nil
 	}
 }

 // Returns the string contents of a workspace file that should be output
 // adjacent to the main bzl file and build file.
 // This workspace file allows, via local_repository rule, sourcetree-level
 // BUILD targets to be referenced via @sourceroot.
 func (context *bazelContext) workspaceFileContents() []byte {
 	formatString := `
 # This file is generated by soong_build. Do not edit.
 local_repository(
     name = "sourceroot",
     path = "%s",
 )
 `
 	return []byte(fmt.Sprintf(formatString, context.workspaceDir))
 }

 func (context *bazelContext) mainBzlFileContents() []byte {
 	contents := `
 #####################################################
 # This file is generated by soong_build. Do not edit.
 #####################################################

 def _mixed_build_root_impl(ctx):
     return [DefaultInfo(files = depset(ctx.files.deps))]

 # Rule representing the root of the build, to depend on all Bazel targets that
 # are required for the build. Building this target will build the entire Bazel
 # build tree.
 mixed_build_root = rule(
     implementation = _mixed_build_root_impl,
     attrs = {"deps" : attr.label_list()},
 )

 def _phony_root_impl(ctx):
     return []

 # Rule to depend on other targets but build nothing.
 # This is useful as follows: building a target of this rule will generate
 # symlink forests for all dependencies of the target, without executing any
 # actions of the build.
 phony_root = rule(
     implementation = _phony_root_impl,
     attrs = {"deps" : attr.label_list()},
 )
 `
 	return []byte(contents)
 }

 // Returns a "canonicalized" corresponding to the given sourcetree-level label.
 // This abstraction is required because a sourcetree label such as //foo/bar:baz
 // must be referenced via the local repository prefix, such as
 // @sourceroot//foo/bar:baz.
 func canonicalizeLabel(label string) string {
 	if strings.HasPrefix(label, "//") {
 		return "@sourceroot" + label
 	} else {
 		return "@sourceroot//" + label
 	}
 }

 func (context *bazelContext) mainBuildFileContents() []byte {
 	formatString := `
 # This file is generated by soong_build. Do not edit.
 load(":main.bzl", "mixed_build_root", "phony_root")

 mixed_build_root(name = "buildroot",
     deps = [%s],
 )

 phony_root(name = "phonyroot",
     deps = [":buildroot"],
 )
 `
 	var buildRootDeps []string = nil
 	for val, _ := range context.requests {
 		buildRootDeps = append(buildRootDeps, fmt.Sprintf("\"%s\"", canonicalizeLabel(val.label)))
 	}
 	buildRootDepsString := strings.Join(buildRootDeps, ",\n            ")

 	return []byte(fmt.Sprintf(formatString, buildRootDepsString))
 }

 func (context *bazelContext) cqueryStarlarkFileContents() []byte {
 	formatString := `
 # This file is generated by soong_build. Do not edit.
 getAllFilesLabels = {
   %s
 }

 def format(target):
   if str(target.label) in getAllFilesLabels:
     return str(target.label) + ">>" + ', '.join([f.path for f in target.files.to_list()])
   else:
     # This target was not requested via cquery, and thus must be a dependency
     # of a requested target.
     return ""
 `
 	var buildRootDeps []string = nil
 	// TODO(cparsons): Sort by request type instead of assuming all requests
 	// are of GetAllFiles type.
 	for val, _ := range context.requests {
 		buildRootDeps = append(buildRootDeps, fmt.Sprintf("\"%s\" : True", canonicalizeLabel(val.label)))
 	}
 	buildRootDepsString := strings.Join(buildRootDeps, ",\n  ")

 	return []byte(fmt.Sprintf(formatString, buildRootDepsString))
 }

 // Returns a workspace-relative path containing build-related metadata required
 // for interfacing with Bazel. Example: out/soong/bazel.
 func (context *bazelContext) intermediatesDir() string {
 	return filepath.Join(context.buildDir, "bazel")
 }

 // Issues commands to Bazel to receive results for all cquery requests
 // queued in the BazelContext.
 func (context *bazelContext) InvokeBazel() error {
 	context.results = make(map[cqueryKey]string)

 	var cqueryOutput string
 	var err error

 	intermediatesDirPath := absolutePath(context.intermediatesDir())
 	if _, err := os.Stat(intermediatesDirPath); os.IsNotExist(err) {
 		err = os.Mkdir(intermediatesDirPath, 0777)
 	}

 	if err != nil {
 		return err
 	}
 	err = ioutil.WriteFile(
 		absolutePath(filepath.Join(context.intermediatesDir(), "main.bzl")),
 		context.mainBzlFileContents(), 0666)
 	if err != nil {
 		return err
 	}
 	err = ioutil.WriteFile(
 		absolutePath(filepath.Join(context.intermediatesDir(), "BUILD.bazel")),
 		context.mainBuildFileContents(), 0666)
 	if err != nil {
 		return err
 	}
 	cqueryFileRelpath := filepath.Join(context.intermediatesDir(), "buildroot.cquery")
 	err = ioutil.WriteFile(
 		absolutePath(cqueryFileRelpath),
 		context.cqueryStarlarkFileContents(), 0666)
 	if err != nil {
 		return err
 	}
 	workspaceFileRelpath := filepath.Join(context.intermediatesDir(), "WORKSPACE.bazel")
 	err = ioutil.WriteFile(
 		absolutePath(workspaceFileRelpath),
 		context.workspaceFileContents(), 0666)
 	if err != nil {
 		return err
 	}
 	buildrootLabel := "//:buildroot"
 	cqueryOutput, err = context.issueBazelCommand(bazel.CqueryBuildRootRunName, "cquery",
 		[]string{fmt.Sprintf("deps(%s)", buildrootLabel)},
 		"--output=starlark",
 		"--starlark:file="+cqueryFileRelpath)

 	if err != nil {
 		return err
 	}

 	cqueryResults := map[string]string{}
 	for _, outputLine := range strings.Split(cqueryOutput, "\n") {
 		if strings.Contains(outputLine, ">>") {
 			splitLine := strings.SplitN(outputLine, ">>", 2)
 			cqueryResults[splitLine[0]] = splitLine[1]
 		}
 	}

 	for val, _ := range context.requests {
 		if cqueryResult, ok := cqueryResults[canonicalizeLabel(val.label)]; ok {
 			context.results[val] = string(cqueryResult)
 		} else {
 			return fmt.Errorf("missing result for bazel target %s", val.label)
 		}
 	}

 	// Issue an aquery command to retrieve action information about the bazel build tree.
 	//
 	// TODO(cparsons): Use --target_pattern_file to avoid command line limits.
 	var aqueryOutput string
 	aqueryOutput, err = context.issueBazelCommand(bazel.AqueryBuildRootRunName, "aquery",
 		[]string{fmt.Sprintf("deps(%s)", buildrootLabel),
 			// Use jsonproto instead of proto; actual proto parsing would require a dependency on Bazel's
 			// proto sources, which would add a number of unnecessary dependencies.
 			"--output=jsonproto"})

 	if err != nil {
 		return err
 	}

 	context.buildStatements, err = bazel.AqueryBuildStatements([]byte(aqueryOutput))
 	if err != nil {
 		return err
 	}

 	// Issue a build command of the phony root to generate symlink forests for dependencies of the
 	// Bazel build. This is necessary because aquery invocations do not generate this symlink forest,
 	// but some of symlinks may be required to resolve source dependencies of the build.
 	_, err = context.issueBazelCommand(bazel.BazelBuildPhonyRootRunName, "build",
 		[]string{"//:phonyroot"})

 	if err != nil {
 		return err
 	}

 	fmt.Printf("Build statements %s", context.buildStatements)
 	// Clear requests.
 	context.requests = map[cqueryKey]bool{}
 	return nil
 }

 func (context *bazelContext) BuildStatementsToRegister() []bazel.BuildStatement {
 	return context.buildStatements
 }

 func (context *bazelContext) OutputBase() string {
 	return context.outputBase
 }

 // Singleton used for registering BUILD file ninja dependencies (needed
 // for correctness of builds which use Bazel.
 func BazelSingleton() Singleton {
 	return &bazelSingleton{}
 }

 type bazelSingleton struct{}

 func (c *bazelSingleton) GenerateBuildActions(ctx SingletonContext) {
 	// bazelSingleton is a no-op if mixed-soong-bazel-builds are disabled.
 	if !ctx.Config().BazelContext.BazelEnabled() {
 		return
 	}

 	// Add ninja file dependencies for files which all bazel invocations require.
 	bazelBuildList := absolutePath(filepath.Join(
 		filepath.Dir(bootstrap.ModuleListFile), "bazel.list"))
 	ctx.AddNinjaFileDeps(bazelBuildList)

 	data, err := ioutil.ReadFile(bazelBuildList)
 	if err != nil {
 		ctx.Errorf(err.Error())
 	}
 	files := strings.Split(strings.TrimSpace(string(data)), "\n")
 	for _, file := range files {
 		ctx.AddNinjaFileDeps(file)
 	}

 	// Register bazel-owned build statements (obtained from the aquery invocation).
 	for index, buildStatement := range ctx.Config().BazelContext.BuildStatementsToRegister() {
 		rule := NewRuleBuilder(pctx, ctx)
 		cmd := rule.Command()
 		cmd.Text(fmt.Sprintf("cd %s/execroot/__main__ && %s",
 			ctx.Config().BazelContext.OutputBase(), buildStatement.Command))

 		for _, outputPath := range buildStatement.OutputPaths {
 			cmd.ImplicitOutput(PathForBazelOut(ctx, outputPath))
 		}
 		for _, inputPath := range buildStatement.InputPaths {
 			cmd.Implicit(PathForBazelOut(ctx, inputPath))
 		}

 		// This is required to silence warnings pertaining to unexpected timestamps. Particularly,
 		// some Bazel builtins (such as files in the bazel_tools directory) have far-future
 		// timestamps. Without restat, Ninja would emit warnings that the input files of a
 		// build statement have later timestamps than the outputs.
 		rule.Restat()

 		rule.Build(fmt.Sprintf("bazel %d", index), buildStatement.Mnemonic)
 	}
 }
	// Copyright 2020 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 android

	import (
	"bytes"
	"errors"
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"
	"sync"

	"github.com/google/blueprint/bootstrap"

	"android/soong/bazel"
	"android/soong/shared"
	)

	type CqueryRequestType int

	const (
	getAllFiles CqueryRequestType = iota
	)

	// Map key to describe bazel cquery requests.
	type cqueryKey struct {
	label string
	requestType CqueryRequestType
	}

	type BazelContext interface {
	// The below methods involve queuing cquery requests to be later invoked
	// by bazel. If any of these methods return (_, false), then the request
	// has been queued to be run later.

	// Returns result files built by building the given bazel target label.
	GetAllFiles(label string) ([]string, bool)

	// TODO(cparsons): Other cquery-related methods should be added here.
	// ** End cquery methods

	// Issues commands to Bazel to receive results for all cquery requests
	// queued in the BazelContext.
	InvokeBazel() error

	// Returns true if bazel is enabled for the given configuration.
	BazelEnabled() bool

	// Returns the bazel output base (the root directory for all bazel intermediate outputs).
	OutputBase() string

	// Returns build statements which should get registered to reflect Bazel's outputs.
	BuildStatementsToRegister() []bazel.BuildStatement
	}

	// A context object which tracks queued requests that need to be made to Bazel,
	// and their results after the requests have been made.
	type bazelContext struct {
	homeDir string
	bazelPath string
	outputBase string
	workspaceDir string
	buildDir string
	metricsDir string

	requests map[cqueryKey]bool // cquery requests that have not yet been issued to Bazel
	requestMutex sync.Mutex // requests can be written in parallel

	results map[cqueryKey]string // Results of cquery requests after Bazel invocations

	// Build statements which should get registered to reflect Bazel's outputs.
	buildStatements []bazel.BuildStatement
	}

	var _ BazelContext = &bazelContext{}

	// A bazel context to use when Bazel is disabled.
	type noopBazelContext struct{}

	var _ BazelContext = noopBazelContext{}

	// A bazel context to use for tests.
	type MockBazelContext struct {
	AllFiles map[string][]string
	}

	func (m MockBazelContext) GetAllFiles(label string) ([]string, bool) {
	result, ok := m.AllFiles[label]
	return result, ok
	}

	func (m MockBazelContext) InvokeBazel() error {
	panic("unimplemented")
	}

	func (m MockBazelContext) BazelEnabled() bool {
	return true
	}

	func (m MockBazelContext) OutputBase() string {
	return "outputbase"
	}

	func (m MockBazelContext) BuildStatementsToRegister() []bazel.BuildStatement {
	return []bazel.BuildStatement{}
	}

	var _ BazelContext = MockBazelContext{}

	func (bazelCtx *bazelContext) GetAllFiles(label string) ([]string, bool) {
	result, ok := bazelCtx.cquery(label, getAllFiles)
	if ok {
	bazelOutput := strings.TrimSpace(result)
	return strings.Split(bazelOutput, ", "), true
	} else {
	return nil, false
	}
	}

	func (n noopBazelContext) GetAllFiles(label string) ([]string, bool) {
	panic("unimplemented")
	}

	func (n noopBazelContext) InvokeBazel() error {
	panic("unimplemented")
	}

	func (m noopBazelContext) OutputBase() string {
	return ""
	}

	func (n noopBazelContext) BazelEnabled() bool {
	return false
	}

	func (m noopBazelContext) BuildStatementsToRegister() []bazel.BuildStatement {
	return []bazel.BuildStatement{}
	}

	func NewBazelContext(c *config) (BazelContext, error) {
	// TODO(cparsons): Assess USE_BAZEL=1 instead once "mixed Soong/Bazel builds"
	// are production ready.
	if c.Getenv("USE_BAZEL_ANALYSIS") != "1" {
	return noopBazelContext{}, nil
	}

	bazelCtx := bazelContext{buildDir: c.buildDir, requests: make(map[cqueryKey]bool)}
	missingEnvVars := []string{}
	if len(c.Getenv("BAZEL_HOME")) > 1 {
	bazelCtx.homeDir = c.Getenv("BAZEL_HOME")
	} else {
	missingEnvVars = append(missingEnvVars, "BAZEL_HOME")
	}
	if len(c.Getenv("BAZEL_PATH")) > 1 {
	bazelCtx.bazelPath = c.Getenv("BAZEL_PATH")
	} else {
	missingEnvVars = append(missingEnvVars, "BAZEL_PATH")
	}
	if len(c.Getenv("BAZEL_OUTPUT_BASE")) > 1 {
	bazelCtx.outputBase = c.Getenv("BAZEL_OUTPUT_BASE")
	} else {
	missingEnvVars = append(missingEnvVars, "BAZEL_OUTPUT_BASE")
	}
	if len(c.Getenv("BAZEL_WORKSPACE")) > 1 {
	bazelCtx.workspaceDir = c.Getenv("BAZEL_WORKSPACE")
	} else {
	missingEnvVars = append(missingEnvVars, "BAZEL_WORKSPACE")
	}
	if len(c.Getenv("BAZEL_METRICS_DIR")) > 1 {
	bazelCtx.metricsDir = c.Getenv("BAZEL_METRICS_DIR")
	} else {
	missingEnvVars = append(missingEnvVars, "BAZEL_METRICS_DIR")
	}
	if len(missingEnvVars) > 0 {
	return nil, errors.New(fmt.Sprintf("missing required env vars to use bazel: %s", missingEnvVars))
	} else {
	return &bazelCtx, nil
	}
	}

	func (context *bazelContext) BazelMetricsDir() string {
	return context.metricsDir
	}

	func (context *bazelContext) BazelEnabled() bool {
	return true
	}

	// Adds a cquery request to the Bazel request queue, to be later invoked, or
	// returns the result of the given request if the request was already made.
	// If the given request was already made (and the results are available), then
	// returns (result, true). If the request is queued but no results are available,
	// then returns ("", false).
	func (context *bazelContext) cquery(label string, requestType CqueryRequestType) (string, bool) {
	key := cqueryKey{label, requestType}
	if result, ok := context.results[key]; ok {
	return result, true
	} else {
	context.requestMutex.Lock()
	defer context.requestMutex.Unlock()
	context.requests[key] = true
	return "", false
	}
	}

	func pwdPrefix() string {
	// Darwin doesn't have /proc
	if runtime.GOOS != "darwin" {
	return "PWD=/proc/self/cwd"
	}
	return ""
	}

	func (context *bazelContext) issueBazelCommand(runName bazel.RunName, command string, labels []string,
	extraFlags ...string) (string, error) {

	cmdFlags := []string{"--output_base=" + context.outputBase, command}
	cmdFlags = append(cmdFlags, labels...)
	cmdFlags = append(cmdFlags, "--package_path=%workspace%/"+context.intermediatesDir())
	cmdFlags = append(cmdFlags, "--profile="+shared.BazelMetricsFilename(context, runName))
	cmdFlags = append(cmdFlags, extraFlags...)

	bazelCmd := exec.Command(context.bazelPath, cmdFlags...)
	bazelCmd.Dir = context.workspaceDir
	bazelCmd.Env = append(os.Environ(), "HOME="+context.homeDir, pwdPrefix())

	stderr := &bytes.Buffer{}
	bazelCmd.Stderr = stderr

	if output, err := bazelCmd.Output(); err != nil {
	return "", fmt.Errorf("bazel command failed. command: [%s], error [%s]", bazelCmd, stderr)
	} else {
	return string(output), nil
	}
	}

	// Returns the string contents of a workspace file that should be output
	// adjacent to the main bzl file and build file.
	// This workspace file allows, via local_repository rule, sourcetree-level
	// BUILD targets to be referenced via @sourceroot.
	func (context *bazelContext) workspaceFileContents() []byte {
	formatString := `
	# This file is generated by soong_build. Do not edit.
	local_repository(
	name = "sourceroot",
	path = "%s",
	)
	`
	return []byte(fmt.Sprintf(formatString, context.workspaceDir))
	}

	func (context *bazelContext) mainBzlFileContents() []byte {
	contents := `
	#####################################################
	# This file is generated by soong_build. Do not edit.
	#####################################################

	def _mixed_build_root_impl(ctx):
	return [DefaultInfo(files = depset(ctx.files.deps))]

	# Rule representing the root of the build, to depend on all Bazel targets that
	# are required for the build. Building this target will build the entire Bazel
	# build tree.
	mixed_build_root = rule(
	implementation = _mixed_build_root_impl,
	attrs = {"deps" : attr.label_list()},
	)

	def _phony_root_impl(ctx):
	return []

	# Rule to depend on other targets but build nothing.
	# This is useful as follows: building a target of this rule will generate
	# symlink forests for all dependencies of the target, without executing any
	# actions of the build.
	phony_root = rule(
	implementation = _phony_root_impl,
	attrs = {"deps" : attr.label_list()},
	)
	`
	return []byte(contents)
	}

	// Returns a "canonicalized" corresponding to the given sourcetree-level label.
	// This abstraction is required because a sourcetree label such as //foo/bar:baz
	// must be referenced via the local repository prefix, such as
	// @sourceroot//foo/bar:baz.
	func canonicalizeLabel(label string) string {
	if strings.HasPrefix(label, "//") {
	return "@sourceroot" + label
	} else {
	return "@sourceroot//" + label
	}
	}

	func (context *bazelContext) mainBuildFileContents() []byte {
	formatString := `
	# This file is generated by soong_build. Do not edit.
	load(":main.bzl", "mixed_build_root", "phony_root")

	mixed_build_root(name = "buildroot",
	deps = [%s],
	)

	phony_root(name = "phonyroot",
	deps = [":buildroot"],
	)
	`
	var buildRootDeps []string = nil
	for val, _ := range context.requests {
	buildRootDeps = append(buildRootDeps, fmt.Sprintf("\"%s\"", canonicalizeLabel(val.label)))
	}
	buildRootDepsString := strings.Join(buildRootDeps, ",\n ")

	return []byte(fmt.Sprintf(formatString, buildRootDepsString))
	}

	func (context *bazelContext) cqueryStarlarkFileContents() []byte {
	formatString := `
	# This file is generated by soong_build. Do not edit.
	getAllFilesLabels = {
	%s
	}

	def format(target):
	if str(target.label) in getAllFilesLabels:
	return str(target.label) + ">>" + ', '.join([f.path for f in target.files.to_list()])
	else:
	# This target was not requested via cquery, and thus must be a dependency
	# of a requested target.
	return ""
	`
	var buildRootDeps []string = nil
	// TODO(cparsons): Sort by request type instead of assuming all requests
	// are of GetAllFiles type.
	for val, _ := range context.requests {
	buildRootDeps = append(buildRootDeps, fmt.Sprintf("\"%s\" : True", canonicalizeLabel(val.label)))
	}
	buildRootDepsString := strings.Join(buildRootDeps, ",\n ")

	return []byte(fmt.Sprintf(formatString, buildRootDepsString))
	}

	// Returns a workspace-relative path containing build-related metadata required
	// for interfacing with Bazel. Example: out/soong/bazel.
	func (context *bazelContext) intermediatesDir() string {
	return filepath.Join(context.buildDir, "bazel")
	}

	// Issues commands to Bazel to receive results for all cquery requests
	// queued in the BazelContext.
	func (context *bazelContext) InvokeBazel() error {
	context.results = make(map[cqueryKey]string)

	var cqueryOutput string
	var err error

	intermediatesDirPath := absolutePath(context.intermediatesDir())
	if _, err := os.Stat(intermediatesDirPath); os.IsNotExist(err) {
	err = os.Mkdir(intermediatesDirPath, 0777)
	}

	if err != nil {
	return err
	}
	err = ioutil.WriteFile(
	absolutePath(filepath.Join(context.intermediatesDir(), "main.bzl")),
	context.mainBzlFileContents(), 0666)
	if err != nil {
	return err
	}
	err = ioutil.WriteFile(
	absolutePath(filepath.Join(context.intermediatesDir(), "BUILD.bazel")),
	context.mainBuildFileContents(), 0666)
	if err != nil {
	return err
	}
	cqueryFileRelpath := filepath.Join(context.intermediatesDir(), "buildroot.cquery")
	err = ioutil.WriteFile(
	absolutePath(cqueryFileRelpath),
	context.cqueryStarlarkFileContents(), 0666)
	if err != nil {
	return err
	}
	workspaceFileRelpath := filepath.Join(context.intermediatesDir(), "WORKSPACE.bazel")
	err = ioutil.WriteFile(
	absolutePath(workspaceFileRelpath),
	context.workspaceFileContents(), 0666)
	if err != nil {
	return err
	}
	buildrootLabel := "//:buildroot"
	cqueryOutput, err = context.issueBazelCommand(bazel.CqueryBuildRootRunName, "cquery",
	[]string{fmt.Sprintf("deps(%s)", buildrootLabel)},
	"--output=starlark",
	"--starlark:file="+cqueryFileRelpath)

	if err != nil {
	return err
	}

	cqueryResults := map[string]string{}
	for _, outputLine := range strings.Split(cqueryOutput, "\n") {
	if strings.Contains(outputLine, ">>") {
	splitLine := strings.SplitN(outputLine, ">>", 2)
	cqueryResults[splitLine[0]] = splitLine[1]
	}
	}

	for val, _ := range context.requests {
	if cqueryResult, ok := cqueryResults[canonicalizeLabel(val.label)]; ok {
	context.results[val] = string(cqueryResult)
	} else {
	return fmt.Errorf("missing result for bazel target %s", val.label)
	}
	}

	// Issue an aquery command to retrieve action information about the bazel build tree.
	//
	// TODO(cparsons): Use --target_pattern_file to avoid command line limits.
	var aqueryOutput string
	aqueryOutput, err = context.issueBazelCommand(bazel.AqueryBuildRootRunName, "aquery",
	[]string{fmt.Sprintf("deps(%s)", buildrootLabel),
	// Use jsonproto instead of proto; actual proto parsing would require a dependency on Bazel's
	// proto sources, which would add a number of unnecessary dependencies.
	"--output=jsonproto"})

	if err != nil {
	return err
	}

	context.buildStatements, err = bazel.AqueryBuildStatements([]byte(aqueryOutput))
	if err != nil {
	return err
	}

	// Issue a build command of the phony root to generate symlink forests for dependencies of the
	// Bazel build. This is necessary because aquery invocations do not generate this symlink forest,
	// but some of symlinks may be required to resolve source dependencies of the build.
	_, err = context.issueBazelCommand(bazel.BazelBuildPhonyRootRunName, "build",
	[]string{"//:phonyroot"})

	if err != nil {
	return err
	}

	fmt.Printf("Build statements %s", context.buildStatements)
	// Clear requests.
	context.requests = map[cqueryKey]bool{}
	return nil
	}

	func (context *bazelContext) BuildStatementsToRegister() []bazel.BuildStatement {
	return context.buildStatements
	}

	func (context *bazelContext) OutputBase() string {
	return context.outputBase
	}

	// Singleton used for registering BUILD file ninja dependencies (needed
	// for correctness of builds which use Bazel.
	func BazelSingleton() Singleton {
	return &bazelSingleton{}
	}

	type bazelSingleton struct{}

	func (c *bazelSingleton) GenerateBuildActions(ctx SingletonContext) {
	// bazelSingleton is a no-op if mixed-soong-bazel-builds are disabled.
	if !ctx.Config().BazelContext.BazelEnabled() {
	return
	}

	// Add ninja file dependencies for files which all bazel invocations require.
	bazelBuildList := absolutePath(filepath.Join(
	filepath.Dir(bootstrap.ModuleListFile), "bazel.list"))
	ctx.AddNinjaFileDeps(bazelBuildList)

	data, err := ioutil.ReadFile(bazelBuildList)
	if err != nil {
	ctx.Errorf(err.Error())
	}
	files := strings.Split(strings.TrimSpace(string(data)), "\n")
	for _, file := range files {
	ctx.AddNinjaFileDeps(file)
	}

	// Register bazel-owned build statements (obtained from the aquery invocation).
	for index, buildStatement := range ctx.Config().BazelContext.BuildStatementsToRegister() {
	rule := NewRuleBuilder(pctx, ctx)
	cmd := rule.Command()
	cmd.Text(fmt.Sprintf("cd %s/execroot/__main__ && %s",
	ctx.Config().BazelContext.OutputBase(), buildStatement.Command))

	for _, outputPath := range buildStatement.OutputPaths {
	cmd.ImplicitOutput(PathForBazelOut(ctx, outputPath))
	}
	for _, inputPath := range buildStatement.InputPaths {
	cmd.Implicit(PathForBazelOut(ctx, inputPath))
	}

	// This is required to silence warnings pertaining to unexpected timestamps. Particularly,
	// some Bazel builtins (such as files in the bazel_tools directory) have far-future
	// timestamps. Without restat, Ninja would emit warnings that the input files of a
	// build statement have later timestamps than the outputs.
	rule.Restat()

	rule.Build(fmt.Sprintf("bazel %d", index), buildStatement.Mnemonic)
	}
	}