gazelle: Add ability to read/write to BUILD.bazel instead of BUILD (#219

)

go/tools/gazelle/gazelle/diff.go

@@ -24,7 +24,7 @@ import (
 )
 
 func diffFile(file *bzl.File) error {
-	f, err := ioutil.TempFile("", "BUILD")
+	f, err := ioutil.TempFile("", *buildName)
 	if err != nil {
 		return err
 	}

go/tools/gazelle/gazelle/main.go

@@ -33,9 +33,15 @@ import (
 )
 
 var (
-	goPrefix = flag.String("go_prefix", "", "go_prefix of the target workspace")
-	repoRoot = flag.String("repo_root", "", "path to a directory which corresponds to go_prefix, otherwise gazelle searches for it.")
-	mode     = flag.String("mode", "fix", "print: prints all of the updated BUILD files\n\tfix: rewrites all of the BUILD files in place\n\tdiff: computes the rewrite but then just does a diff")
+	goPrefix  = flag.String("go_prefix", "", "go_prefix of the target workspace")
+	repoRoot  = flag.String("repo_root", "", "path to a directory which corresponds to go_prefix, otherwise gazelle searches for it.")
+	mode      = flag.String("mode", "fix", "print: prints all of the updated BUILD files\n\tfix: rewrites all of the BUILD files in place\n\tdiff: computes the rewrite but then just does a diff")
+	buildName = flag.String("build_name", "BUILD", "name of output build files to generate, defaults to 'BUILD'")
+
+	validBuildNames = map[string]bool{
+		"BUILD":       true,
+		"BUILD.bazel": true,
+	}
 )
 
 func init() {
@@ -51,7 +57,7 @@ var modeFromName = map[string]func(*bzl.File) error{
 }
 
 func run(dirs []string, emit func(*bzl.File) error) error {
-	g, err := generator.New(*repoRoot, *goPrefix)
+	g, err := generator.New(*repoRoot, *goPrefix, *buildName)
 	if err != nil {
 		return err
 	}
@@ -120,6 +126,10 @@ func main() {
 		}
 	}
 
+	if !validBuildNames[*buildName] {
+		log.Fatalf("-build_name %q must be in: %v", *buildName, validBuildNames)
+	}
+
 	emit := modeFromName[*mode]
 	if emit == nil {
 		log.Fatalf("unrecognized mode %s", *mode)
@@ -135,9 +145,23 @@ func main() {
 	}
 }
 
+func readBuild(root string) (data []byte, location string, _ error) {
+	for n := range validBuildNames {
+		p := filepath.Join(root, n)
+		b, err := ioutil.ReadFile(p)
+		if err != nil {
+			if os.IsNotExist(err) {
+				continue
+			}
+			return nil, "", err
+		}
+		return b, p, nil
+	}
+	return nil, "", fmt.Errorf("no build files found at %q", root)
+}
+
 func loadGoPrefix(repo string) (string, error) {
-	p := filepath.Join(repo, "BUILD")
-	b, err := ioutil.ReadFile(p)
+	b, p, err := readBuild(repo)
 	if err != nil {
 		return "", err
 	}

go/tools/gazelle/generator/generator.go

@@ -39,18 +39,19 @@ var (
 
 // Generator generates BUILD files for a Go repository.
 type Generator struct {
-	repoRoot string
-	goPrefix string
-	bctx     build.Context
-	g        rules.Generator
+	repoRoot  string
+	goPrefix  string
+	buildName string
+	bctx      build.Context
+	g         rules.Generator
 }
 
 // New returns a new Generator which is responsible for a Go repository.
 //
 // "repoRoot" is a path to the root directory of the repository.
 // "goPrefix" is the go_prefix corresponding to the repository root directory.
 // See also https://github.com/bazelbuild/rules_go#go_prefix.
-func New(repoRoot, goPrefix string) (*Generator, error) {
+func New(repoRoot, goPrefix, buildName string) (*Generator, error) {
 	bctx := build.Default
 	// Ignore source files in $GOROOT and $GOPATH
 	bctx.GOROOT = ""
@@ -66,10 +67,11 @@ func New(repoRoot, goPrefix string) (*Generator, error) {
 		return nil, err
 	}
 	return &Generator{
-		repoRoot: filepath.Clean(repoRoot),
-		goPrefix: goPrefix,
-		bctx:     bctx,
-		g:        rules.NewGenerator(goPrefix),
+		repoRoot:  filepath.Clean(repoRoot),
+		goPrefix:  goPrefix,
+		buildName: buildName,
+		bctx:      bctx,
+		g:         rules.NewGenerator(goPrefix),
 	}, nil
 }
 
@@ -99,7 +101,7 @@ func (g *Generator) Generate(dir string) ([]*bzl.File, error) {
 		if len(files) == 0 && rel != "" {
 			// "dir" was not a buildable Go package but still need a BUILD file
 			// for go_prefix.
-			files = append(files, emptyToplevel(g.goPrefix))
+			files = append(files, emptyToplevel(g.goPrefix, g.buildName))
 		}
 
 		file, err := g.generateOne(rel, pkg)
@@ -116,9 +118,9 @@ func (g *Generator) Generate(dir string) ([]*bzl.File, error) {
 	return files, nil
 }
 
-func emptyToplevel(goPrefix string) *bzl.File {
+func emptyToplevel(goPrefix, buildName string) *bzl.File {
 	return &bzl.File{
-		Path: "BUILD",
+		Path: buildName,
 		Stmt: []bzl.Expr{
 			loadExpr("go_prefix"),
 			&bzl.CallExpr{
@@ -137,7 +139,7 @@ func (g *Generator) generateOne(rel string, pkg *build.Package) (*bzl.File, erro
 		return nil, err
 	}
 
-	file := &bzl.File{Path: filepath.Join(rel, "BUILD")}
+	file := &bzl.File{Path: filepath.Join(rel, g.buildName)}
 	for _, r := range rs {
 		file.Stmt = append(file.Stmt, r.Call)
 	}

go/tools/gazelle/generator/generator_test.go

@@ -33,6 +33,14 @@ var (
 )
 
 func TestGenerator(t *testing.T) {
+	testGenerator(t, "BUILD")
+}
+
+func TestGeneratorDotBazel(t *testing.T) {
+	testGenerator(t, "BUILD.bazel")
+}
+
+func testGenerator(t *testing.T, buildName string) {
 	stub := stubRuleGen{
 		goFiles: make(map[string][]string),
 		cFiles:  make(map[string][]string),
@@ -153,7 +161,7 @@ func TestGenerator(t *testing.T) {
 	}
 
 	repo := filepath.Join(testdata.Dir(), "repo")
-	g, err := New(repo, "example.com/repo")
+	g, err := New(repo, "example.com/repo", buildName)
 	if err != nil {
 		t.Errorf(`New(%q, "example.com/repo") failed with %v; want success`, repo, err)
 		return
@@ -172,7 +180,7 @@ func TestGenerator(t *testing.T) {
 
 	want := []*bzl.File{
 		{
-			Path: "BUILD",
+			Path: buildName,
 			Stmt: []bzl.Expr{
 				loadExpr("go_prefix"),
 				&bzl.CallExpr{
@@ -184,38 +192,38 @@ func TestGenerator(t *testing.T) {
 			},
 		},
 		{
-			Path: "lib/BUILD",
+			Path: "lib/" + buildName,
 			Stmt: []bzl.Expr{
 				loadExpr("go_prefix", "go_library"),
 				stub.fixtures["lib"][0].Call,
 				stub.fixtures["lib"][1].Call,
 			},
 		},
 		{
-			Path: "lib/internal/deep/BUILD",
+			Path: "lib/internal/deep/" + buildName,
 			Stmt: []bzl.Expr{
 				loadExpr("go_library", "go_test"),
 				stub.fixtures["lib/internal/deep"][0].Call,
 				stub.fixtures["lib/internal/deep"][1].Call,
 			},
 		},
 		{
-			Path: "lib/relativeimporter/BUILD",
+			Path: "lib/relativeimporter/" + buildName,
 			Stmt: []bzl.Expr{
 				loadExpr("go_library"),
 				stub.fixtures["lib/relativeimporter"][0].Call,
 			},
 		},
 		{
-			Path: "bin/BUILD",
+			Path: "bin/" + buildName,
 			Stmt: []bzl.Expr{
 				loadExpr("go_library", "go_binary"),
 				stub.fixtures["bin"][0].Call,
 				stub.fixtures["bin"][1].Call,
 			},
 		},
 		{
-			Path: "bin_with_tests/BUILD",
+			Path: "bin_with_tests/" + buildName,
 			Stmt: []bzl.Expr{
 				loadExpr("go_library", "go_binary", "go_test"),
 				stub.fixtures["bin_with_tests"][0].Call,
@@ -224,7 +232,7 @@ func TestGenerator(t *testing.T) {
 			},
 		},
 		{
-			Path: "cgolib/BUILD",
+			Path: "cgolib/" + buildName,
 			Stmt: []bzl.Expr{
 				loadExpr("go_library", "go_test", "cgo_library"),
 				stub.fixtures["cgolib"][0].Call,
@@ -233,7 +241,7 @@ func TestGenerator(t *testing.T) {
 			},
 		},
 		{
-			Path: "cgolib_with_build_tags/BUILD",
+			Path: "cgolib_with_build_tags/" + buildName,
 			Stmt: []bzl.Expr{
 				loadExpr("go_library", "go_test", "cgo_library"),
 				stub.fixtures["cgolib"][0].Call,
@@ -242,7 +250,7 @@ func TestGenerator(t *testing.T) {
 			},
 		},
 		{
-			Path: "allcgolib/BUILD",
+			Path: "allcgolib/" + buildName,
 			Stmt: []bzl.Expr{
 				loadExpr("go_library", "go_test", "cgo_library"),
 				stub.fixtures["cgolib"][0].Call,