feat(internal/librarian/dart): add generate (#3585)

Add generate functionality for Dart.

For #3581

Author: julieqiu

.github/workflows/dart.yaml

@@ -0,0 +1,40 @@
+# Copyright 2026 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
+#
+#     https://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.
+name: Dart
+on: [push, pull_request, merge_group]
+permissions:
+  contents: read
+jobs:
+  test:
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v5
+      - uses: actions/setup-go@v6
+        with:
+          go-version-file: "go.mod"
+      - uses: ./.github/actions/install-protoc
+      - name: Display Go version
+        run: go version
+      - name: Install Dart SDK
+        uses: dart-lang/setup-dart@e51d8e571e22473a2ddebf0ef8a2123f0ab2c02c
+        with:
+          sdk: 3.6.0
+      - name: Display Dart version
+        run: dart --version
+      - name: Verify git is available
+        run: git --version
+      - name: Run internal/sidekick/dart tests
+        run: go test -race ./internal/sidekick/dart
+      - name: Run internal/librarian/dart tests
+        run: go test -race ./internal/librarian/dart

internal/config/config.go

@@ -121,14 +121,19 @@ type Default struct {
 	// ReleaseLevel is either "stable" or "preview".
 	ReleaseLevel string `yaml:"release_level,omitempty"`
 
-	// Rust contains Rust-specific default configuration.
-	Rust *RustDefault `yaml:"rust,omitempty"`
-
 	// TagFormat is the template for git tags, such as "{name}/v{version}".
 	TagFormat string `yaml:"tag_format,omitempty"`
 
 	// Transport is the transport protocol, such as "grpc+rest" or "grpc".
 	Transport string `yaml:"transport,omitempty"`
+
+	// Language-specific fields are below.
+
+	// Dart contains Dart-specific default configuration.
+	Dart *DartPackage `yaml:"dart,omitempty"`
+
+	// Rust contains Rust-specific default configuration.
+	Rust *RustDefault `yaml:"rust,omitempty"`
 }
 
 // Library represents a library configuration.
@@ -153,29 +158,20 @@ type Library struct {
 	// DescriptionOverride overrides the library description.
 	DescriptionOverride string `yaml:"description_override,omitempty"`
 
-	// Go contains Go-specific library configuration.
-	Go *GoModule `yaml:"go,omitempty"`
-
 	// Keep lists files and directories to preserve during regeneration.
 	Keep []string `yaml:"keep,omitempty"`
 
 	// Output is the directory where code is written. This overrides
 	// Default.Output.
 	Output string `yaml:"output,omitempty"`
 
-	// Python contains Python-specific library configuration.
-	Python *PythonPackage `yaml:"python,omitempty"`
-
 	// ReleaseLevel is the release level, such as "stable" or "preview". This
 	// overrides Default.ReleaseLevel.
 	ReleaseLevel string `yaml:"release_level,omitempty"`
 
 	// Roots specifies the source roots to use for generation. Defaults to googleapis.
 	Roots []string `yaml:"roots,omitempty"`
 
-	// Rust contains Rust-specific library configuration.
-	Rust *RustCrate `yaml:"rust,omitempty"`
-
 	// SkipGenerate disables code generation for this library.
 	SkipGenerate bool `yaml:"skip_generate,omitempty"`
 
@@ -198,6 +194,20 @@ type Library struct {
 	// configuration (e.g., rust.modules) instead of generating a complete crate
 	// from channels.
 	Veneer bool `yaml:"veneer,omitempty"`
+
+	// Language-specific fields are below.
+
+	// Dart contains Dart-specific library configuration.
+	Dart *DartPackage `yaml:"dart,omitempty"`
+
+	// Go contains Go-specific library configuration.
+	Go *GoModule `yaml:"go,omitempty"`
+
+	// Python contains Python-specific library configuration.
+	Python *PythonPackage `yaml:"python,omitempty"`
+
+	// Rust contains Rust-specific library configuration.
+	Rust *RustCrate `yaml:"rust,omitempty"`
 }
 
 // Channel describes a Channel to include in a library.

internal/config/language.go

@@ -271,3 +271,52 @@ type PythonPackage struct {
 	// Example: {"google/cloud/secrets/v1beta": ["python-gapic-name=secretmanager"]}
 	OptArgsByChannel map[string][]string `yaml:"opt_args_by_channel,omitempty"`
 }
+
+// DartPackage contains Dart-specific library configuration.
+type DartPackage struct {
+	// APIKeysEnvironmentVariables is a comma-separated list of environment variable names
+	// that can contain API keys (e.g., "GOOGLE_API_KEY,GEMINI_API_KEY").
+	APIKeysEnvironmentVariables string `yaml:"api_keys_environment_variables,omitempty"`
+
+	// Dependencies is a comma-separated list of dependencies.
+	Dependencies string `yaml:"dependencies,omitempty"`
+
+	// DevDependencies is a comma-separated list of development dependencies.
+	DevDependencies string `yaml:"dev_dependencies,omitempty"`
+
+	// ExtraImports is additional imports to include in the generated library.
+	ExtraImports string `yaml:"extra_imports,omitempty"`
+
+	// IssueTrackerURL is the URL for the issue tracker.
+	IssueTrackerURL string `yaml:"issue_tracker_url,omitempty"`
+
+	// LibraryPathOverride overrides the library path.
+	LibraryPathOverride string `yaml:"library_path_override,omitempty"`
+
+	// NotForPublication indicates whether this package should not be published.
+	NotForPublication string `yaml:"not_for_publication,omitempty"`
+
+	// Packages maps Dart package names to version constraints.
+	// Keys are in the format "package:googleapis_auth" and values are version strings like "^2.0.0".
+	Packages map[string]string `yaml:"packages,omitempty"`
+
+	// PartFile is the path to a part file to include in the generated library.
+	PartFile string `yaml:"part_file,omitempty"`
+
+	// Prefixes maps protobuf package names to Dart import prefixes.
+	// Keys are in the format "prefix:google.protobuf" and values are the prefix names.
+	Prefixes map[string]string `yaml:"prefixes,omitempty"`
+
+	// Protos maps protobuf package names to Dart import paths.
+	// Keys are in the format "proto:google.api" and values are import paths like "package:google_cloud_api/api.dart".
+	Protos map[string]string `yaml:"protos,omitempty"`
+
+	// ReadmeAfterTitleText is text to insert in the README after the title.
+	ReadmeAfterTitleText string `yaml:"readme_after_title_text,omitempty"`
+
+	// ReadmeQuickstartText is text to use for the quickstart section in the README.
+	ReadmeQuickstartText string `yaml:"readme_quickstart_text,omitempty"`
+
+	// RepositoryURL is the URL to the repository for this package.
+	RepositoryURL string `yaml:"repository_url,omitempty"`
+}

internal/librarian/dart/generate.go

@@ -0,0 +1,133 @@
+// Copyright 2026 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
+//
+//     https://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 dart provides functionality for generating and releasing Dart client
+// libraries.
+package dart
+
+import (
+	"context"
+
+	"github.com/googleapis/librarian/internal/command"
+	"github.com/googleapis/librarian/internal/config"
+	"github.com/googleapis/librarian/internal/serviceconfig"
+	sidekickconfig "github.com/googleapis/librarian/internal/sidekick/config"
+	sidekickdart "github.com/googleapis/librarian/internal/sidekick/dart"
+	"github.com/googleapis/librarian/internal/sidekick/parser"
+)
+
+// Generate generates a Dart client library.
+func Generate(ctx context.Context, library *config.Library, googleapisDir string) error {
+	sidekickConfig, err := toSidekickConfig(library, library.Channels[0], googleapisDir)
+	if err != nil {
+		return err
+	}
+	model, err := parser.CreateModel(sidekickConfig)
+	if err != nil {
+		return err
+	}
+	if err := sidekickdart.Generate(ctx, model, library.Output, sidekickConfig); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Format formats a generated Dart library.
+func Format(ctx context.Context, library *config.Library) error {
+	if err := command.Run(ctx, "dart", "format", library.Output); err != nil {
+		return err
+	}
+	return nil
+}
+
+func toSidekickConfig(library *config.Library, ch *config.Channel, googleapisDir string) (*sidekickconfig.Config, error) {
+	source := map[string]string{
+		"googleapis-root": googleapisDir,
+	}
+
+	channel, err := serviceconfig.Find(googleapisDir, ch.Path)
+	if err != nil {
+		return nil, err
+	}
+
+	sidekickCfg := &sidekickconfig.Config{
+		General: sidekickconfig.GeneralConfig{
+			Language:            "dart",
+			SpecificationFormat: "protobuf",
+			ServiceConfig:       channel.ServiceConfig,
+			SpecificationSource: ch.Path,
+		},
+		Source: source,
+		Codec:  buildCodec(library),
+	}
+	return sidekickCfg, nil
+}
+
+func buildCodec(library *config.Library) map[string]string {
+	codec := make(map[string]string)
+	if library.CopyrightYear != "" {
+		codec["copyright-year"] = library.CopyrightYear
+	}
+	if library.Version != "" {
+		codec["version"] = library.Version
+	}
+	if library.Dart == nil {
+		return codec
+	}
+
+	dart := library.Dart
+	if dart.APIKeysEnvironmentVariables != "" {
+		codec["api-keys-environment-variables"] = dart.APIKeysEnvironmentVariables
+	}
+	if dart.Dependencies != "" {
+		codec["dependencies"] = dart.Dependencies
+	}
+	if dart.DevDependencies != "" {
+		codec["dev-dependencies"] = dart.DevDependencies
+	}
+	if dart.ExtraImports != "" {
+		codec["extra-imports"] = dart.ExtraImports
+	}
+	if dart.IssueTrackerURL != "" {
+		codec["issue-tracker-url"] = dart.IssueTrackerURL
+	}
+	if dart.LibraryPathOverride != "" {
+		codec["library-path-override"] = dart.LibraryPathOverride
+	}
+	if dart.NotForPublication != "" {
+		codec["not-for-publication"] = dart.NotForPublication
+	}
+	if dart.PartFile != "" {
+		codec["part-file"] = dart.PartFile
+	}
+	if dart.ReadmeAfterTitleText != "" {
+		codec["readme-after-title-text"] = dart.ReadmeAfterTitleText
+	}
+	if dart.ReadmeQuickstartText != "" {
+		codec["readme-quickstart-text"] = dart.ReadmeQuickstartText
+	}
+	if dart.RepositoryURL != "" {
+		codec["repository-url"] = dart.RepositoryURL
+	}
+	for key, value := range dart.Packages {
+		codec["package:"+key] = value
+	}
+	for key, value := range dart.Prefixes {
+		codec["prefix:"+key] = value
+	}
+	for key, value := range dart.Protos {
+		codec["proto:"+key] = value
+	}
+	return codec
+}