feat(librariangen): add protoc package

internal/librariangen/protoc/protoc.go

@@ -0,0 +1,100 @@
+// 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 protoc
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+)
+
+// ConfigProvider is an interface that describes the configuration needed
+// by the Build function. This allows the protoc package to be decoupled
+// from the source of the configuration (e.g., Bazel files, JSON, etc.).
+type ConfigProvider interface {
+	ServiceYAML() string
+	GapicYAML() string
+	GRPCServiceConfig() string
+	Transport() string
+	HasRESTNumericEnums() bool
+	HasGAPIC() bool
+}
+
+// Build constructs the full protoc command arguments for a given API.
+func Build(apiServiceDir string, config ConfigProvider, sourceDir, outputDir string) ([]string, error) {
+	// Gather all .proto files in the API's source directory.
+	entries, err := os.ReadDir(apiServiceDir)
+	if err != nil {
+		return nil, fmt.Errorf("librariangen: failed to read API source directory %s: %w", apiServiceDir, err)
+	}
+
+	var protoFiles []string
+	for _, entry := range entries {
+		if !entry.IsDir() && filepath.Ext(entry.Name()) == ".proto" {
+			protoFiles = append(protoFiles, filepath.Join(apiServiceDir, entry.Name()))
+		}
+	}
+
+	if len(protoFiles) == 0 {
+		return nil, fmt.Errorf("librariangen: no .proto files found in %s", apiServiceDir)
+	}
+
+	// Construct the protoc command arguments.
+	var gapicOpts []string
+	if config.HasGAPIC() {
+		if config.ServiceYAML() != "" {
+			gapicOpts = append(gapicOpts, fmt.Sprintf("api-service-config=%s", filepath.Join(apiServiceDir, config.ServiceYAML())))
+		}
+		if config.GapicYAML() != "" {
+			gapicOpts = append(gapicOpts, fmt.Sprintf("gapic-config=%s", filepath.Join(apiServiceDir, config.GapicYAML())))
+		}
+		if config.GRPCServiceConfig() != "" {
+			gapicOpts = append(gapicOpts, fmt.Sprintf("grpc-service-config=%s", filepath.Join(apiServiceDir, config.GRPCServiceConfig())))
+		}
+		if config.Transport() != "" {
+			gapicOpts = append(gapicOpts, fmt.Sprintf("transport=%s", config.Transport()))
+		}
+		if config.HasRESTNumericEnums() {
+			gapicOpts = append(gapicOpts, "rest-numeric-enums")
+		}
+	}
+
+	args := []string{
+		"protoc",
+		"--experimental_allow_proto3_optional",
+	}
+
+	args = append(args, fmt.Sprintf("--java_out=%s", outputDir))
+	if config.HasGAPIC() {
+		args = append(args, fmt.Sprintf("--java_gapic_out=metadata:%s", filepath.Join(outputDir, "java_gapic.zip")))
+
+		if len(gapicOpts) > 0 {
+			args = append(args, "--java_gapic_opt="+strings.Join(gapicOpts, ","))
+		}
+	}
+
+	args = append(args,
+		// The -I flag specifies the import path for protoc. All protos
+		// and their dependencies must be findable from this path.
+		// The /source mount contains the complete googleapis repository.
+		"-I="+sourceDir,
+	)
+
+	args = append(args, protoFiles...)
+
+	return args, nil
+}

internal/librariangen/protoc/protoc_test.go

@@ -0,0 +1,141 @@
+// 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 protoc
+
+import (
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+// mockConfigProvider is a mock implementation of the ConfigProvider interface for testing.
+type mockConfigProvider struct {
+	serviceYAML       string
+	gapicYAML         string
+	grpcServiceConfig string
+	transport         string
+	restNumericEnums  bool
+	hasGAPIC          bool
+}
+
+func (m *mockConfigProvider) ServiceYAML() string       { return m.serviceYAML }
+func (m *mockConfigProvider) GapicYAML() string         { return m.gapicYAML }
+func (m *mockConfigProvider) GRPCServiceConfig() string { return m.grpcServiceConfig }
+func (m *mockConfigProvider) Transport() string         { return m.transport }
+func (m *mockConfigProvider) HasRESTNumericEnums() bool { return m.restNumericEnums }
+func (m *mockConfigProvider) HasGAPIC() bool            { return m.hasGAPIC }
+
+func TestBuild(t *testing.T) {
+	// The testdata directory is a curated version of a valid protoc
+	// import path that contains all the necessary proto definitions.
+	sourceDir, err := filepath.Abs("../testdata/generate/source")
+	if err != nil {
+		t.Fatalf("failed to get absolute path for sourceDir: %v", err)
+	}
+	tests := []struct {
+		name          string
+		apiPath       string
+		reqID         string
+		config        mockConfigProvider
+		want          []string
+	}{
+		{
+			name:    "java_grpc_library rule",
+			apiPath: "google/cloud/workflows/v1",
+			reqID:   "workflows",
+			config: mockConfigProvider{
+				transport:         "grpc",
+				grpcServiceConfig: "workflows_grpc_service_config.json",
+				gapicYAML:         "workflows_gapic.yaml",
+				serviceYAML:       "workflows_v1.yaml",
+				restNumericEnums:  true,
+				hasGAPIC:          true,
+			},
+			want: []string{
+				"protoc",
+				"--experimental_allow_proto3_optional",
+				"--java_out=/output",
+				"--java_gapic_out=metadata:/output/java_gapic.zip",
+				"--java_gapic_opt=" + strings.Join([]string{
+					"api-service-config=" + filepath.Join(sourceDir, "google/cloud/workflows/v1/workflows_v1.yaml"),
+					"gapic-config=" + filepath.Join(sourceDir, "google/cloud/workflows/v1/workflows_gapic.yaml"),
+					"grpc-service-config=" + filepath.Join(sourceDir, "google/cloud/workflows/v1/workflows_grpc_service_config.json"),
+					"transport=grpc",
+					"rest-numeric-enums",
+				}, ","),
+				"-I=" + sourceDir,
+				filepath.Join(sourceDir, "google/cloud/workflows/v1/workflows.proto"),
+			},
+		},
+		{
+			name:    "java_proto_library rule with legacy gRPC",
+			apiPath: "google/cloud/secretmanager/v1beta2",
+			reqID:   "secretmanager",
+			config: mockConfigProvider{
+				transport:         "grpc",
+				grpcServiceConfig: "secretmanager_grpc_service_config.json",
+				serviceYAML:       "secretmanager_v1beta2.yaml",
+				restNumericEnums:  true,
+				hasGAPIC:          true,
+			},
+			want: []string{
+				"protoc",
+				"--experimental_allow_proto3_optional",
+				"--java_out=/output",
+				"--java_gapic_out=metadata:/output/java_gapic.zip",
+				"--java_gapic_opt=" + strings.Join([]string{
+					"api-service-config=" + filepath.Join(sourceDir, "google/cloud/secretmanager/v1beta2/secretmanager_v1beta2.yaml"),
+					"grpc-service-config=" + filepath.Join(sourceDir, "google/cloud/secretmanager/v1beta2/secretmanager_grpc_service_config.json"),
+					"transport=grpc",
+					"rest-numeric-enums",
+				}, ","),
+				"-I=" + sourceDir,
+				filepath.Join(sourceDir, "google/cloud/secretmanager/v1beta2/secretmanager.proto"),
+			},
+		},
+		{
+			// Note: we don't have a separate test directory with a proto-only library;
+			// the config is used to say "don't generate GAPIC".
+			name:    "proto-only",
+			apiPath: "google/cloud/secretmanager/v1beta2",
+			reqID:   "secretmanager",
+			config: mockConfigProvider{
+				hasGAPIC:  false,
+			},
+			want: []string{
+				"protoc",
+				"--experimental_allow_proto3_optional",
+				"--java_out=/output",
+				"-I=" + sourceDir,
+				filepath.Join(sourceDir, "google/cloud/secretmanager/v1beta2/secretmanager.proto"),
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := Build(filepath.Join(sourceDir, tt.apiPath), &tt.config, sourceDir, "/output")
+			if err != nil {
+				t.Fatalf("Build() failed: %v", err)
+			}
+
+			if diff := cmp.Diff(tt.want, got); diff != "" {
+				t.Errorf("Build() mismatch (-want +got):\n%s", diff)
+			}
+		})
+	}
+}

internal/librariangen/testdata/generate/source/google/api/annotations.proto

@@ -0,0 +1,46 @@
+// 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.
+
+syntax = "proto3";
+
+package google.api;
+
+import "google/protobuf/descriptor.proto";
+
+option java_multiple_files = true;
+option java_outer_classname = "AnnotationsProto";
+option java_package = "com.google.api";
+
+extend google.protobuf.MethodOptions {
+  HttpRule http = 72295728;
+}
+
+message HttpRule {
+  string selector = 1;
+  oneof pattern {
+    string get = 2;
+    string put = 3;
+    string post = 4;
+    string delete = 5;
+    string patch = 6;
+    CustomHttpPattern custom = 8;
+  }
+  string body = 7;
+  repeated HttpRule additional_bindings = 11;
+}
+
+message CustomHttpPattern {
+  string kind = 1;
+  string path = 2;
+}

internal/librariangen/testdata/generate/source/google/cloud/secretmanager/v1beta2/BUILD.bazel

@@ -0,0 +1,53 @@
+java_proto_library(
+    name = "secretmanager_java_proto",
+    deps = [":secretmanager_proto"],
+)
+
+java_grpc_library(
+    name = "secretmanager_java_grpc",
+    srcs = [":secretmanager_proto"],
+    deps = [":secretmanager_java_proto"],
+)
+
+java_gapic_library(
+    name = "secretmanager_java_gapic",
+    srcs = [":secretmanager_proto_with_info"],
+    gapic_yaml = None,
+    grpc_service_config = "secretmanager_grpc_service_config.json",
+    rest_numeric_enums = True,
+    service_yaml = "secretmanager_v1beta2.yaml",
+    test_deps = [
+        "//google/cloud/location:location_java_grpc",
+        "//google/iam/v1:iam_java_grpc",
+        ":secretmanager_java_grpc",
+    ],
+    transport = "grpc+rest",
+    deps = [
+        ":secretmanager_java_proto",
+        "//google/api:api_java_proto",
+        "//google/cloud/location:location_java_proto",
+        "//google/iam/v1:iam_java_proto",
+    ],
+)
+
+java_gapic_test(
+    name = "secretmanager_java_gapic_test_suite",
+    test_classes = [
+        "com.google.cloud.secretmanager.v1beta2.SecretManagerServiceClientHttpJsonTest",
+        "com.google.cloud.secretmanager.v1beta2.SecretManagerServiceClientTest",
+    ],
+    runtime_deps = [":secretmanager_java_gapic_test"],
+)
+
+# Open Source Packages
+java_gapic_assembly_gradle_pkg(
+    name = "google-cloud-secretmanager-v1beta2-java",
+    transport = "grpc+rest",
+    deps = [
+        ":secretmanager_java_gapic",
+        ":secretmanager_java_grpc",
+        ":secretmanager_java_proto",
+        ":secretmanager_proto",
+    ],
+    include_samples = True,
+)

internal/librariangen/testdata/generate/source/google/cloud/secretmanager/v1beta2/secretmanager.proto

@@ -0,0 +1,48 @@
+// 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.
+
+syntax = "proto3";
+
+package google.cloud.secretmanager.v1beta2;
+
+import "google/api/annotations.proto";
+
+option java_multiple_files = true;
+option java_outer_classname = "ServiceProto";
+option java_package = "com.google.cloud.secretmanager.v1beta2";
+
+// A Secret is a secret value.
+message Secret {
+  string name = 1;
+}
+
+// Request for the `ListSecrets` method.
+message ListSecretsRequest {
+  string parent = 1;
+}
+
+// Response for the `ListSecrets` method.
+message ListSecretsResponse {
+  repeated Secret Secrets = 1;
+}
+
+// Service for managing secrets.
+service Secrets {
+  // Lists Secrets in a given project and location.
+  rpc ListSecrets(ListSecretsRequest) returns (ListSecretsResponse) {
+    option (google.api.http) = {
+      get: "/v1/{parent=projects/*/locations/*}/Secrets"
+    };
+  }
+}