refactor(config): migrate language string literals to a new config.Language type with defined constants (#4287)

Migrate language string literals to a new `config.Language` type with
defined constants.

Fixes #4010

Author: jameslynnwu

internal/config/config_test.go

@@ -28,7 +28,7 @@ func TestRead(t *testing.T) {
 		t.Fatal(err)
 	}
 	want := &Config{
-		Language: "rust",
+		Language: LanguageRust,
 		Sources: &Sources{
 			Discovery: &Source{
 				Commit: "b27c80574e918a7e2a36eb21864d1d2e45b8c032",

internal/config/language.go

@@ -14,7 +14,38 @@
 
 package config
 
-import "github.com/googleapis/librarian/internal/yaml"
+import (
+	"github.com/googleapis/librarian/internal/yaml"
+)
+
+const (
+	// LanguageUnknown represents an unsupported or unspecified language.
+	LanguageUnknown = "unknown"
+	// LanguageAll is the identifier for all languages.
+	LanguageAll = "all"
+	// LanguageCsharp is the language identifier for C#.
+	LanguageCsharp = "csharp"
+	// LanguageDart is the language identifier for Dart.
+	LanguageDart = "dart"
+	// LanguageFake is the language identifier for Fakes.
+	LanguageFake = "fake"
+	// LanguageGo is the language identifier for Go.
+	LanguageGo = "go"
+	// LanguageJava is the language identifier for Java.
+	LanguageJava = "java"
+	// LanguageNodejs is the language identifier for Node.js.
+	LanguageNodejs = "nodejs"
+	// LanguagePhp is the language identifier for PHP.
+	LanguagePhp = "php"
+	// LanguagePython is the language identifier for Python.
+	LanguagePython = "python"
+	// LanguageRuby is the language identifier for Ruby.
+	LanguageRuby = "ruby"
+	// LanguageRust is the language identifier for Rust.
+	LanguageRust = "rust"
+	// LanguageRustStorage is a variation of the Rust generator for storage.
+	LanguageRustStorage = "rust_storage"
+)
 
 // GoModule represents the Go-specific configuration for a library.
 type GoModule struct {

internal/docuploader/metadata.go

@@ -44,10 +44,7 @@ type DocUploaderMetadata struct {
 	// https://github.com/googleapis/nodejs-storage/issues
 	IssueTracker string `json:"issueTracker,omitempty"`
 
-	// Language is the (programming) language. While this isn't enforced with an
-	// enum, you should use one of the following strings:  python, nodejs, ruby,
-	// dotnet, java, go, php, cpp. In some cases you might need to use something
-	// else, consult the docs team for guidance.
+	// Language is the (programming) language.
 	Language string `json:"language,omitempty"`
 
 	// Name is the product/API name. This *should* match the DNS name of the API

internal/docuploader/metadata_test.go

@@ -19,6 +19,7 @@ import (
 	"time"
 
 	"github.com/google/go-cmp/cmp"
+	"github.com/googleapis/librarian/internal/config"
 	"github.com/googleapis/librarian/internal/repometadata"
 )
 
@@ -38,7 +39,7 @@ func TestFromRepoMetadata(t *testing.T) {
 				DefaultVersion:       "default-version-ignored",
 				DistributionName:     "distribution-name",
 				IssueTracker:         "issue-tracker",
-				Language:             "language",
+				Language:             config.LanguageGo,
 				LibraryType:          "library-type-ignored",
 				Name:                 "name",
 				NamePretty:           "name-pretty-ignored",
@@ -50,7 +51,7 @@ func TestFromRepoMetadata(t *testing.T) {
 				DistributionName: "distribution-name",
 				GithubRepository: "repo",
 				IssueTracker:     "issue-tracker",
-				Language:         "language",
+				Language:         config.LanguageGo,
 				Name:             "name",
 				ProductPage:      "product-documentation",
 			},

internal/librarian/add.go

@@ -70,7 +70,7 @@ func runAdd(ctx context.Context, cfg *config.Config, apis ...string) error {
 
 func resolveDependencies(ctx context.Context, cfg *config.Config, name string) (*config.Config, error) {
 	switch cfg.Language {
-	case languageRust:
+	case config.LanguageRust:
 		lib, err := FindLibrary(cfg, name)
 		if err != nil {
 			return nil, err
@@ -87,15 +87,15 @@ func resolveDependencies(ctx context.Context, cfg *config.Config, name string) (
 
 // deriveLibraryName derives a library name from an API path.
 // The derivation is language-specific.
-func deriveLibraryName(language, api string) string {
+func deriveLibraryName(language string, api string) string {
 	switch language {
-	case languageDart:
+	case config.LanguageDart:
 		return dart.DefaultLibraryName(api)
-	case languageFake:
+	case config.LanguageFake:
 		return fakeDefaultLibraryName(api)
-	case languagePython:
+	case config.LanguagePython:
 		return python.DefaultLibraryName(api)
-	case languageRust:
+	case config.LanguageRust:
 		return rust.DefaultLibraryName(api)
 	default:
 		return strings.ReplaceAll(api, "/", "-")

internal/librarian/add_test.go

@@ -287,15 +287,15 @@ func TestDeriveLibraryName(t *testing.T) {
 		apiPath  string
 		want     string
 	}{
-		{"dart", "google/cloud/secretmanager/v1", "google_cloud_secretmanager_v1"},
-		{"python", "google/cloud/secretmanager/v1", "google-cloud-secretmanager"},
-		{"python", "google/cloud/secretmanager/v1beta2", "google-cloud-secretmanager"},
-		{"python", "google/cloud/storage/v2alpha", "google-cloud-storage"},
-		{"python", "google/maps/addressvalidation/v1", "google-maps-addressvalidation"},
-		{"python", "google/api/v1", "google-api"},
-		{"rust", "google/cloud/secretmanager/v1", "google-cloud-secretmanager-v1"},
-		{"rust", "google/cloud/secretmanager/v1beta2", "google-cloud-secretmanager-v1beta2"},
-		{"fake", "google/cloud/secretmanager/v1", "google-cloud-secretmanager-v1"},
+		{config.LanguageDart, "google/cloud/secretmanager/v1", "google_cloud_secretmanager_v1"},
+		{config.LanguagePython, "google/cloud/secretmanager/v1", "google-cloud-secretmanager"},
+		{config.LanguagePython, "google/cloud/secretmanager/v1beta2", "google-cloud-secretmanager"},
+		{config.LanguagePython, "google/cloud/storage/v2alpha", "google-cloud-storage"},
+		{config.LanguagePython, "google/maps/addressvalidation/v1", "google-maps-addressvalidation"},
+		{config.LanguagePython, "google/api/v1", "google-api"},
+		{config.LanguageRust, "google/cloud/secretmanager/v1", "google-cloud-secretmanager-v1"},
+		{config.LanguageRust, "google/cloud/secretmanager/v1beta2", "google-cloud-secretmanager-v1beta2"},
+		{config.LanguageFake, "google/cloud/secretmanager/v1", "google-cloud-secretmanager-v1"},
 	} {
 		t.Run(test.language+"/"+test.apiPath, func(t *testing.T) {
 			got := deriveLibraryName(test.language, test.apiPath)

internal/librarian/bump.go

@@ -49,7 +49,7 @@ var (
 	// this should be removed. If a language does not have specific needs, a
 	// default [semver.DeriveNextOptions] is returned for default semantics.
 	languageVersioningOptions = map[string]semver.DeriveNextOptions{
-		"rust": {
+		config.LanguageRust: {
 			BumpVersionCore:       true,
 			DowngradePreGAChanges: true,
 		},
@@ -112,7 +112,7 @@ func runBump(ctx context.Context, cfg *config.Config, all bool, libraryName, ver
 	if err := git.AssertGitStatusClean(ctx, gitExe); err != nil {
 		return err
 	}
-	if cfg.Language == languageRust {
+	if cfg.Language == config.LanguageRust {
 		return legacyRustBump(ctx, cfg, all, libraryName, versionOverride, gitExe)
 	}
 
@@ -197,11 +197,11 @@ func bumpLibrary(ctx context.Context, cfg *config.Config, lib *config.Library, g
 	lib.Version = version
 
 	switch cfg.Language {
-	case languageFake:
+	case config.LanguageFake:
 		return fakeBumpLibrary(output, version)
-	case languageGo:
+	case config.LanguageGo:
 		return golang.Bump(lib, output, version)
-	case languagePython:
+	case config.LanguagePython:
 		return python.Bump(output, version)
 	default:
 		return fmt.Errorf("%q does not support bump", cfg.Language)
@@ -211,7 +211,7 @@ func bumpLibrary(ctx context.Context, cfg *config.Config, lib *config.Library, g
 // postBump performs post version bump cleanup and maintenance tasks after libraries have been processed.
 func postBump(ctx context.Context, cfg *config.Config) error {
 	switch cfg.Language {
-	case languageRust:
+	case config.LanguageRust:
 		cargoExe := "cargo"
 		if cfg.Release != nil {
 			cargoExe = command.GetExecutablePath(cfg.Release.Preinstalled, "cargo")
@@ -420,9 +420,9 @@ func legacyRustBumpLibrary(ctx context.Context, cfg *config.Config, lib *config.
 	}
 	output := libraryOutput(cfg.Language, lib, cfg.Default)
 	switch cfg.Language {
-	case languageRust:
+	case config.LanguageRust:
 		return rust.Bump(ctx, lib, output, version, gitExe, lastTag)
-	case languageFake:
+	case config.LanguageFake:
 		lib.Version = version
 		return fakeBumpLibrary(output, version)
 	default:

internal/librarian/bump_test.go

@@ -379,7 +379,7 @@ func TestBumpLibrary_Error(t *testing.T) {
 			name: "unsupported language",
 			cfg: func() *config.Config {
 				c := sample.Config()
-				c.Language = languageRust
+				c.Language = config.LanguageRust
 				return c
 			}(),
 			versionOverride: "2.0.0",
@@ -603,7 +603,7 @@ func TestPostBump(t *testing.T) {
 				}
 			},
 			cfg: &config.Config{
-				Language: languageRust,
+				Language: config.LanguageRust,
 				Release: &config.Release{
 					Preinstalled: map[string]string{
 						"cargo": fakeCargo,
@@ -620,7 +620,7 @@ func TestPostBump(t *testing.T) {
 				}
 			},
 			cfg: &config.Config{
-				Language: languageRust,
+				Language: config.LanguageRust,
 				Release: &config.Release{
 					Preinstalled: map[string]string{
 						"cargo": fakeCargo,
@@ -632,7 +632,7 @@ func TestPostBump(t *testing.T) {
 		{
 			name: "non-rust language does nothing",
 			cfg: &config.Config{
-				Language: languageFake,
+				Language: config.LanguageFake,
 			},
 		},
 	} {
@@ -662,21 +662,21 @@ func TestDeriveNextVersion(t *testing.T) {
 			name: "rust library next non-GA version",
 			cfg: func() *config.Config {
 				c := sample.Config()
-				c.Language = languageRust
+				c.Language = config.LanguageRust
 				c.Libraries[0].Version = sample.RustNonGAVersion
 				return c
 			}(),
-			versionOpts: languageVersioningOptions[languageRust],
+			versionOpts: languageVersioningOptions[config.LanguageRust],
 			wantVersion: sample.RustNextNonGAVersion,
 		},
 		{
 			name: "rust library next GA version",
 			cfg: func() *config.Config {
 				c := sample.Config()
-				c.Language = languageRust
+				c.Language = config.LanguageRust
 				return c
 			}(),
-			versionOpts: languageVersioningOptions[languageRust],
+			versionOpts: languageVersioningOptions[config.LanguageRust],
 			wantVersion: sample.NextVersion,
 		},
 		{

internal/librarian/dart/codec.go

@@ -42,7 +42,7 @@ func toModelConfig(library *config.Library, ch *config.API, sources *sidekickcon
 	if ch.Path == "schema/google/showcase/v1beta1" {
 		root = sources.Showcase
 	}
-	svcConfig, err := serviceconfig.Find(root, ch.Path, serviceconfig.LangDart)
+	svcConfig, err := serviceconfig.Find(root, ch.Path, config.LanguageDart)
 	if err != nil {
 		return nil, err
 	}

internal/librarian/fake_test.go

@@ -33,7 +33,7 @@ func TestGenerateLibraries(t *testing.T) {
 		Output: outputDir,
 	}
 	cfg := &config.Config{
-		Language: languageFake,
+		Language: config.LanguageFake,
 	}
 
 	tmpDir := t.TempDir()