feat(librariangen): add bazel package (#3940)

Based on https://github.com/googleapis/google-cloud-go/tree/main/internal/librariangen/bazel with adaptation for Java.

Author: meltsufin

internal/librariangen/bazel/parser.go

@@ -0,0 +1,126 @@
+// Copyright 2025 Google LLC
+//
+// 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 (
+"errors"
+"fmt"
+"log/slog"
+"os"
+"path/filepath"
+"regexp"
+"strconv"
+"strings"
+"sync"
+)
+
+// Config holds configuration extracted from a googleapis BUILD.bazel file.
+type Config struct {
+grpcServiceConfig string
+restNumericEnums bool
+serviceYAML string
+transport string
+hasGAPIC bool
+}
+
+// HasGAPIC indicates whether the GAPIC generator should be run.
+func (c *Config) HasGAPIC() bool { return c.hasGAPIC }
+
+// ServiceYAML is the client config file in the API version directory in googleapis.
+func (c *Config) ServiceYAML() string { return c.serviceYAML }
+
+// GRPCServiceConfig is name of the gRPC service config JSON file.
+func (c *Config) GRPCServiceConfig() string { return c.grpcServiceConfig }
+
+// Transport is typically one of "grpc", "rest" or "grpc+rest".
+func (c *Config) Transport() string { return c.transport }
+
+// HasRESTNumericEnums indicates whether the generated client should support numeric enums.
+func (c *Config) HasRESTNumericEnums() bool { return c.restNumericEnums }
+
+// Validate ensures that the configuration is valid.
+func (c *Config) Validate() error {
+if c.hasGAPIC {
+if c.serviceYAML == "" {
+return errors.New("librariangen: serviceYAML is not set")
+}
+}
+return nil
+}
+
+var javaGapicLibraryRE = regexp.MustCompile(`java_gapic_library\((?s:.)*?\)`)
+// Parse reads a BUILD.bazel file from the given directory and extracts the
+// relevant configuration from the java_gapic_library rule.
+func Parse(dir string) (*Config, error) {
+c := &Config{}
+fp := filepath.Join(dir, "BUILD.bazel")
+data, err := os.ReadFile(fp)
+if err != nil {
+return nil, fmt.Errorf("librariangen: failed to read BUILD.bazel file %s: %w", fp, err)
+}
+content := string(data)
+
+gapicLibraryBlock := javaGapicLibraryRE.FindString(content)
+if gapicLibraryBlock != "" {
+c.hasGAPIC = true
+c.grpcServiceConfig = findString(gapicLibraryBlock, "grpc_service_config")
+c.serviceYAML = strings.TrimPrefix(findString(gapicLibraryBlock, "service_yaml"), ":")
+c.transport = findString(gapicLibraryBlock, "transport")
+if c.restNumericEnums, err = findBool(gapicLibraryBlock, "rest_numeric_enums"); err != nil {
+return nil, fmt.Errorf("librariangen: failed to parse BUILD.bazel file %s: %w", fp, err)
+}
+}
+if err := c.Validate(); err != nil {
+return nil, fmt.Errorf("librariangen: invalid bazel config in %s: %w", dir, err)
+}
+slog.Debug("librariangen: bazel config loaded", "conf", c)
+return c, nil
+}
+
+var reCache = &sync.Map{}
+
+func getRegexp(key, pattern string) *regexp.Regexp {
+val, ok := reCache.Load(key)
+if !ok {
+val = regexp.MustCompile(pattern)
+reCache.Store(key, val)
+}
+return val.(*regexp.Regexp)
+}
+
+func findString(content, name string) string {
+re := getRegexp("findString_"+name, fmt.Sprintf(`%s\s*=\s*(?:"([^"]+)"|'([^']+)'){1}`, name))
+match := re.FindStringSubmatch(content)
+if len(match) > 2 {
+if match[1] != "" {
+return match[1] // Double-quoted
+}
+return match[2] // Single-quoted
+}
+slog.Debug("librariangen: failed to find string attr in BUILD.bazel", "name", name)
+return ""
+}
+
+func findBool(content, name string) (bool, error) {
+re := getRegexp("findBool_"+name, fmt.Sprintf(`%s\s*=\s*(\w+)`, name))
+if match := re.FindStringSubmatch(content); len(match) > 1 {
+if b, err := strconv.ParseBool(match[1]); err == nil {
+return b, nil
+}
+return false, fmt.Errorf("librariangen: failed to parse bool attr in BUILD.bazel: %q, got: %q", name, match[1])
+}
+slog.Debug("librariangen: failed to find bool attr in BUILD.bazel", "name", name)
+return false, nil
+}

internal/librariangen/bazel/parser_test.go

@@ -0,0 +1,248 @@
+// Copyright 2025 Google LLC
+//
+// 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 (
+"os"
+"path/filepath"
+"testing"
+)
+
+func TestParse(t *testing.T) {
+content := `
+java_grpc_library(
+ name = "asset_java_grpc",
+ srcs = [":asset_proto"],
+ deps = [":asset_java_proto"],
+)
+
+java_gapic_library(
+ name = "asset_java_gapic",
+ srcs = [":asset_proto_with_info"],
+ grpc_service_config = "cloudasset_grpc_service_config.json",
+ rest_numeric_enums = True,
+ service_yaml = "cloudasset_v1.yaml",
+ test_deps = [
+ ":asset_java_grpc",
+ "//google/iam/v1:iam_java_grpc",
+ ],
+ transport = 'grpc+rest',
+ deps = [
+ ":asset_java_proto",
+ "//google/api:api_java_proto",
+ "//google/iam/v1:iam_java_proto",
+ ],
+)
+`
+tmpDir := t.TempDir()
+buildPath := filepath.Join(tmpDir, "BUILD.bazel")
+if err := os.WriteFile(buildPath, []byte(content), 0644); err != nil {
+t.Fatalf("failed to write test file: %v", err)
+}
+
+got, err := Parse(tmpDir)
+if err != nil {
+t.Fatalf("Parse() failed: %v", err)
+}
+
+t.Run("HasGAPIC", func(t *testing.T) {
+if !got.HasGAPIC() {
+t.Error("HasGAPIC() = false; want true")
+}
+})
+t.Run("ServiceYAML", func(t *testing.T) {
+if want := "cloudasset_v1.yaml"; got.ServiceYAML() != want {
+t.Errorf("ServiceYAML() = %q; want %q", got.ServiceYAML(), want)
+}
+})
+t.Run("GRPCServiceConfig", func(t *testing.T) {
+if want := "cloudasset_grpc_service_config.json"; got.GRPCServiceConfig() != want {
+t.Errorf("GRPCServiceConfig() = %q; want %q", got.GRPCServiceConfig(), want)
+}
+})
+t.Run("Transport", func(t *testing.T) {
+if want := "grpc+rest"; got.Transport() != want {
+t.Errorf("Transport() = %q; want %q", got.Transport(), want)
+}
+})
+t.Run("HasRESTNumericEnums", func(t *testing.T) {
+if !got.HasRESTNumericEnums() {
+t.Error("HasRESTNumericEnums() = false; want true")
+}
+})
+}
+
+func TestParse_serviceConfigIsTarget(t *testing.T) {
+content := `
+java_grpc_library(
+ name = "asset_java_grpc",
+ srcs = [":asset_proto"],
+ deps = [":asset_java_proto"],
+)
+
+java_gapic_library(
+ name = "asset_java_gapic",
+ srcs = [":asset_proto_with_info"],
+ grpc_service_config = "cloudasset_grpc_service_config.json",
+ rest_numeric_enums = True,
+ service_yaml = ":cloudasset_v1.yaml",
+ test_deps = [
+ ":asset_java_grpc",
+ "//google/iam/v1:iam_java_grpc",
+ ],
+ transport = "grpc+rest",
+ deps = [
+ ":asset_java_proto",
+ "//google/api:api_java_proto",
+ "//google/iam/v1:iam_java_proto",
+ ],
+)
+`
+tmpDir := t.TempDir()
+buildPath := filepath.Join(tmpDir, "BUILD.bazel")
+if err := os.WriteFile(buildPath, []byte(content), 0644); err != nil {
+t.Fatalf("failed to write test file: %v", err)
+}
+
+got, err := Parse(tmpDir)
+if err != nil {
+t.Fatalf("Parse() failed: %v", err)
+}
+
+if want := "cloudasset_v1.yaml"; got.ServiceYAML() != want {
+t.Errorf("ServiceYAML() = %q; want %q", got.ServiceYAML(), want)
+}
+}
+
+func TestConfig_Validate(t *testing.T) {
+tests := []struct {
+name string
+cfg *Config
+wantErr bool
+}{
+{
+name: "valid GAPIC",
+cfg: &Config{
+hasGAPIC: true,
+serviceYAML: "b",
+grpcServiceConfig: "c",
+transport: "d",
+},
+wantErr: false,
+},
+{
+name: "valid non-GAPIC",
+cfg: &Config{},
+wantErr: false,
+},
+{
+name: "gRPC service config and transport are optional",
+cfg: &Config{hasGAPIC: true, serviceYAML: "b"},
+wantErr: false,
+},
+{
+name: "missing serviceYAML",
+cfg: &Config{hasGAPIC: true, grpcServiceConfig: "c", transport: "d"},
+wantErr: true,
+},
+}
+for _, tt := range tests {
+t.Run(tt.name, func(t *testing.T) {
+if err := tt.cfg.Validate(); (err != nil) != tt.wantErr {
+t.Errorf("Config.Validate() error = %v, wantErr %v", err, tt.wantErr)
+}
+})
+}
+}
+
+func TestParse_noGapic(t *testing.T) {
+content := `
+java_grpc_library(
+ name = "asset_java_grpc",
+ srcs = [":asset_proto"],
+ deps = [":asset_java_proto"],
+)
+`
+tmpDir := t.TempDir()
+buildPath := filepath.Join(tmpDir, "BUILD.bazel")
+if err := os.WriteFile(buildPath, []byte(content), 0644); err != nil {
+t.Fatalf("failed to write test file: %v", err)
+}
+
+got, err := Parse(tmpDir)
+if err != nil {
+t.Fatalf("Parse() failed: %v", err)
+}
+
+if got.HasGAPIC() {
+t.Error("HasGAPIC() = true; want false")
+}
+}
+
+func TestParse_missingSomeAttrs(t *testing.T) {
+content := `
+java_gapic_library(
+ name = "asset_java_gapic",
+ service_yaml = "cloudasset_v1.yaml",
+)
+`
+tmpDir := t.TempDir()
+buildPath := filepath.Join(tmpDir, "BUILD.bazel")
+if err := os.WriteFile(buildPath, []byte(content), 0644); err != nil {
+t.Fatalf("failed to write test file: %v", err)
+}
+
+got, err := Parse(tmpDir)
+if err != nil {
+t.Fatalf("Parse() failed: %v", err)
+}
+
+if got.GRPCServiceConfig() != "" {
+t.Errorf("GRPCServiceConfig() = %q; want \"\"", got.GRPCServiceConfig())
+}
+if got.Transport() != "" {
+t.Errorf("Transport() = %q; want \"\"", got.Transport())
+}
+if got.HasRESTNumericEnums() {
+t.Error("HasRESTNumericEnums() = true; want false")
+}
+}
+
+func TestParse_invalidBoolAttr(t *testing.T) {
+content := `
+java_gapic_library(
+ name = "asset_java_gapic",
+ rest_numeric_enums = "not-a-bool",
+)
+`
+tmpDir := t.TempDir()
+buildPath := filepath.Join(tmpDir, "BUILD.bazel")
+if err := os.WriteFile(buildPath, []byte(content), 0644); err != nil {
+t.Fatalf("failed to write test file: %v", err)
+}
+
+_, err := Parse(tmpDir)
+if err == nil {
+t.Error("Parse() succeeded; want error")
+}
+}
+
+func TestParse_noBuildFile(t *testing.T) {
+tmpDir := t.TempDir()
+_, err := Parse(tmpDir)
+if err == nil {
+t.Error("Parse() succeeded; want error")
+}
+}