Use aquery to declare bazel actions in the ninja file.

This effectively moves execution of Bazel actions outside of soong_build
and alongside ninja execution of the actual ninja files, whether that be
by ninja or by Bazel itself.

This almost allows for mixed builds and Bazel-as-Ninja-executor to
coexist, but requires hacks explained in b/175307058.

Test: Treehugger
Test: lunch aosp_flame && USE_BAZEL_ANALYSIS=1 m libc
Test: lunch aosp_flame && USE_BAZEL=1 USE_BAZEL_ANALYSIS=1 m libc,
though this requires a hack of the main BUILD file. See b/175307058

Change-Id: Ia2f6b0f1057e8cea3809de66d8287f13d84b510c

android/bazel_handler.go

@@ -26,9 +26,10 @@ import (
 	"strings"
 	"sync"
 
+	"github.com/google/blueprint/bootstrap"
+
 	"android/soong/bazel"
 	"android/soong/shared"
-	"github.com/google/blueprint/bootstrap"
 )
 
 type CqueryRequestType int
@@ -60,6 +61,12 @@ type BazelContext interface {
 
 	// 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,
@@ -76,6 +83,9 @@ type bazelContext struct {
 	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{}
@@ -103,6 +113,14 @@ 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) {
@@ -123,10 +141,18 @@ 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.
@@ -241,14 +267,32 @@ local_repository(
 
 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)
 }
@@ -268,11 +312,15 @@ func canonicalizeLabel(label string) string {
 func (context *bazelContext) mainBuildFileContents() []byte {
 	formatString := `
 # This file is generated by soong_build. Do not edit.
-load(":main.bzl", "mixed_build_root")
+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 {
@@ -379,22 +427,46 @@ func (context *bazelContext) InvokeBazel() error {
 		}
 	}
 
-	// Issue a build command.
+	// Issue an aquery command to retrieve action information about the bazel build tree.
-	// TODO(cparsons): Invoking bazel execution during soong_build should be avoided;
+	//
-	// bazel actions should either be added to the Ninja file and executed later,
-	// or bazel should handle execution.
 	// TODO(cparsons): Use --target_pattern_file to avoid command line limits.
-	_, err = context.issueBazelCommand(bazel.BazelBuildPhonyRootRunName, "build", []string{buildroot_label})
+	var aqueryOutput string
+	aqueryOutput, err = context.issueBazelCommand(bazel.AqueryBuildRootRunName, "aquery",
+		[]string{fmt.Sprintf("deps(%s)", buildroot_label),
+			// 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 = bazel.AqueryBuildStatements([]byte(aqueryOutput))
+
+	// 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 {
@@ -404,7 +476,12 @@ func BazelSingleton() Singleton {
 type bazelSingleton struct{}
 
 func (c *bazelSingleton) GenerateBuildActions(ctx SingletonContext) {
-	if ctx.Config().BazelContext.BazelEnabled() {
+	// 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)
@@ -417,5 +494,27 @@ func (c *bazelSingleton) GenerateBuildActions(ctx SingletonContext) {
 	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 %s", index), buildStatement.Mnemonic)
 	}
 }

android/paths.go

@@ -1154,6 +1154,17 @@ func pathForModule(ctx ModuleContext) OutputPath {
 	return PathForOutput(ctx, ".intermediates", ctx.ModuleDir(), ctx.ModuleName(), ctx.ModuleSubDir())
 }
 
+type BazelOutPath struct {
+	OutputPath
+}
+
+var _ Path = BazelOutPath{}
+var _ objPathProvider = BazelOutPath{}
+
+func (p BazelOutPath) objPathWithExt(ctx ModuleContext, subdir, ext string) ModuleObjPath {
+	return PathForModuleObj(ctx, subdir, pathtools.ReplaceExtension(p.path, ext))
+}
+
 // PathForVndkRefAbiDump returns an OptionalPath representing the path of the
 // reference abi dump for the given module. This is not guaranteed to be valid.
 func PathForVndkRefAbiDump(ctx ModuleContext, version, fileName string,
@@ -1192,6 +1203,24 @@ func PathForVndkRefAbiDump(ctx ModuleContext, version, fileName string,
 		fileName+ext)
 }
 
+// PathForBazelOut returns a Path representing the paths... under an output directory dedicated to
+// bazel-owned outputs.
+func PathForBazelOut(ctx PathContext, paths ...string) BazelOutPath {
+	execRootPathComponents := append([]string{"execroot", "__main__"}, paths...)
+	execRootPath := filepath.Join(execRootPathComponents...)
+	validatedExecRootPath, err := validatePath(execRootPath)
+	if err != nil {
+		reportPathError(ctx, err)
+	}
+
+	outputPath := OutputPath{basePath{"", ctx.Config(), ""},
+		ctx.Config().BazelContext.OutputBase()}
+
+	return BazelOutPath{
+		OutputPath: outputPath.withRel(validatedExecRootPath),
+	}
+}
+
 // PathForModuleOut returns a Path representing the paths... under the module's
 // output directory.
 func PathForModuleOut(ctx ModuleContext, paths ...string) ModuleOutPath {

bazel/Android.bp

@@ -2,10 +2,14 @@ bootstrap_go_package {
     name: "soong-bazel",
     pkgPath: "android/soong/bazel",
     srcs: [
+        "aquery.go",
         "constants.go",
         "properties.go",
     ],
     pluginFor: [
         "soong_build",
     ],
+    deps: [
+        "blueprint",
+    ],
 }

bazel/aquery.go

@@ -0,0 +1,116 @@
+// 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 bazel
+
+import (
+	"encoding/json"
+	"strings"
+
+	"github.com/google/blueprint/proptools"
+)
+
+// artifact contains relevant portions of Bazel's aquery proto, Artifact.
+// Represents a single artifact, whether it's a source file or a derived output file.
+type artifact struct {
+	Id       string
+	ExecPath string
+}
+
+// KeyValuePair represents Bazel's aquery proto, KeyValuePair.
+type KeyValuePair struct {
+	Key   string
+	Value string
+}
+
+// depSetOfFiles contains relevant portions of Bazel's aquery proto, DepSetOfFiles.
+// Represents a data structure containing one or more files. Depsets in Bazel are an efficient
+// data structure for storing large numbers of file paths.
+type depSetOfFiles struct {
+	Id string
+	// TODO(cparsons): Handle non-flat depsets.
+	DirectArtifactIds []string
+}
+
+// action contains relevant portions of Bazel's aquery proto, Action.
+// Represents a single command line invocation in the Bazel build graph.
+type action struct {
+	Arguments            []string
+	EnvironmentVariables []KeyValuePair
+	InputDepSetIds       []string
+	Mnemonic             string
+	OutputIds            []string
+}
+
+// actionGraphContainer contains relevant portions of Bazel's aquery proto, ActionGraphContainer.
+// An aquery response from Bazel contains a single ActionGraphContainer proto.
+type actionGraphContainer struct {
+	Artifacts     []artifact
+	Actions       []action
+	DepSetOfFiles []depSetOfFiles
+}
+
+// BuildStatement contains information to register a build statement corresponding (one to one)
+// with a Bazel action from Bazel's action graph.
+type BuildStatement struct {
+	Command     string
+	OutputPaths []string
+	InputPaths  []string
+	Env         []KeyValuePair
+	Mnemonic    string
+}
+
+// AqueryBuildStatements returns an array of BuildStatements which should be registered (and output
+// to a ninja file) to correspond one-to-one with the given action graph json proto (from a bazel
+// aquery invocation).
+func AqueryBuildStatements(aqueryJsonProto []byte) []BuildStatement {
+	buildStatements := []BuildStatement{}
+
+	var aqueryResult actionGraphContainer
+	json.Unmarshal(aqueryJsonProto, &aqueryResult)
+
+	artifactIdToPath := map[string]string{}
+	for _, artifact := range aqueryResult.Artifacts {
+		artifactIdToPath[artifact.Id] = artifact.ExecPath
+	}
+	depsetIdToArtifactIds := map[string][]string{}
+	for _, depset := range aqueryResult.DepSetOfFiles {
+		depsetIdToArtifactIds[depset.Id] = depset.DirectArtifactIds
+	}
+
+	for _, actionEntry := range aqueryResult.Actions {
+		outputPaths := []string{}
+		for _, outputId := range actionEntry.OutputIds {
+			// TODO(cparsons): Validate the id is present.
+			outputPaths = append(outputPaths, artifactIdToPath[outputId])
+		}
+		inputPaths := []string{}
+		for _, inputDepSetId := range actionEntry.InputDepSetIds {
+			// TODO(cparsons): Validate the id is present.
+			for _, inputId := range depsetIdToArtifactIds[inputDepSetId] {
+				// TODO(cparsons): Validate the id is present.
+				inputPaths = append(inputPaths, artifactIdToPath[inputId])
+			}
+		}
+		buildStatement := BuildStatement{
+			Command:     strings.Join(proptools.ShellEscapeList(actionEntry.Arguments), " "),
+			OutputPaths: outputPaths,
+			InputPaths:  inputPaths,
+			Env:         actionEntry.EnvironmentVariables,
+			Mnemonic:    actionEntry.Mnemonic}
+		buildStatements = append(buildStatements, buildStatement)
+	}
+
+	return buildStatements
+}

genrule/genrule.go

@@ -206,7 +206,7 @@ func (c *Module) generateBazelBuildActions(ctx android.ModuleContext, label stri
 	if ok {
 		var bazelOutputFiles android.Paths
 		for _, bazelOutputFile := range filePaths {
-			bazelOutputFiles = append(bazelOutputFiles, android.PathForSource(ctx, bazelOutputFile))
+			bazelOutputFiles = append(bazelOutputFiles, android.PathForBazelOut(ctx, bazelOutputFile))
 		}
 		c.outputFiles = bazelOutputFiles
 		c.outputDeps = bazelOutputFiles

genrule/genrule_test.go

@@ -736,7 +736,8 @@ func TestGenruleWithBazel(t *testing.T) {
 	}
 	gen := ctx.ModuleForTests("foo", "").Module().(*Module)
 
-	expectedOutputFiles := []string{"bazelone.txt", "bazeltwo.txt"}
+	expectedOutputFiles := []string{"outputbase/execroot/__main__/bazelone.txt",
+		"outputbase/execroot/__main__/bazeltwo.txt"}
 	if !reflect.DeepEqual(gen.outputFiles.Strings(), expectedOutputFiles) {
 		t.Errorf("Expected output files: %q, actual: %q", expectedOutputFiles, gen.outputFiles)
 	}