fix(nodejs): freeze v1small generation and prevent deletion (#5540)

Configure `librarian` and the `migrate` to prevent the deletion,
regeneration, or metadata update of the `v1small` package for
`google-cloud-compute`.


This effectively freezes the package in its current state as it
approaches deprecation.

For #4751

Author: quirogas

internal/librarian/nodejs/generate.go

@@ -53,6 +53,13 @@ func Generate(ctx context.Context, cfg *config.Config, library *config.Library,
 	}
 	repoRoot := filepath.Dir(filepath.Dir(outdir))
 	for _, api := range library.APIs {
+		// TODO(https://github.com/googleapis/librarian/issues/4751): Do not
+		// generate v1small. This package is not meant to be used and will be
+		// deprecated in the future, but for now (during the migration period) it
+		// will be set to not be maintained.
+		if api.Path == "google/cloud/compute/v1small" {
+			continue
+		}
 		if err := generateAPI(ctx, api, library, googleapisDir, repoRoot); err != nil {
 			return fmt.Errorf("failed to generate api %q: %w", api.Path, err)
 		}
@@ -543,6 +550,13 @@ func updateSnippetMetadataVersion(outDir, version string) error {
 		return fmt.Errorf("failed to glob snippet metadata files: %w", err)
 	}
 	for _, path := range matches {
+		// TODO(https://github.com/googleapis/librarian/issues/4751): Do not
+		// update v1small. This package is not meant to be used and will be
+		// deprecated in the future, but for now (during the migration period) it
+		// will be set to not be maintained.
+		if filepath.Base(filepath.Dir(path)) == "v1small" {
+			continue
+		}
 		if err := updateVersionInFile(path, version); err != nil {
 			return fmt.Errorf("failed to update %s: %w", path, err)
 		}

tool/cmd/migrate/nodejs.go

@@ -180,8 +180,16 @@ func buildNodejsLibrary(googleapisDir, packagesDir, libraryName string) (*config
 		if err != nil {
 			return nil, fmt.Errorf("parsing API paths for %s: %w", libraryName, err)
 		}
-		library.APIs = apis
-		library.Nodejs.NodejsAPIs = buildNodejsLibraryAPIs(googleapisDir, apis)
+
+		var filteredAPIs []*config.API
+		for _, api := range apis {
+			if libraryName == "google-cloud-compute" && api.Path == "google/cloud/compute/v1small" {
+				continue
+			}
+			filteredAPIs = append(filteredAPIs, api)
+		}
+		library.APIs = filteredAPIs
+		library.Nodejs.NodejsAPIs = buildNodejsLibraryAPIs(googleapisDir, filteredAPIs)
 	}
 
 	// Extract copyright year from existing generated source files.
@@ -240,9 +248,54 @@ func buildNodejsLibrary(googleapisDir, packagesDir, libraryName string) (*config
 		library.Keep = append(library.Keep, dirKeep...)
 	}
 
+	if libraryName == "google-cloud-compute" {
+		v1smallKeep, err := nodejsV1SmallKeep(pkgDir)
+		if err != nil {
+			return nil, fmt.Errorf("collecting keep files for v1small: %w", err)
+		}
+		library.Keep = append(library.Keep, v1smallKeep...)
+	}
+
 	return library, nil
 }
 
+// TODO(https://github.com/googleapis/librarian/issues/4751): Do not
+// generate or delete v1small. This package is not meant to be used and
+// will be deprecated in the future, but for now (during the migration
+// period) it will be set to not be maintained.
+//
+// We explicitly add these files to the keep list to prevent the clean
+// phase from deleting them, as the generation phase skips v1small.
+func nodejsV1SmallKeep(pkgDir string) ([]string, error) {
+	var paths []string
+	err := filepath.WalkDir(pkgDir, func(path string, d os.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() {
+			if d.Name() == "node_modules" || d.Name() == "owl-bot-staging" {
+				return filepath.SkipDir
+			}
+			return nil
+		}
+		rel, err := filepath.Rel(pkgDir, path)
+		if err != nil {
+			return err
+		}
+		if strings.Contains(rel, "v1small") {
+			paths = append(paths, rel)
+		}
+		return nil
+	})
+	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			return nil, nil
+		}
+		return nil, err
+	}
+	return paths, nil
+}
+
 func buildNodejsLibraryAPIs(googleapisDir string, apis []*config.API) []*config.NodejsAPI {
 	var nodejsAPIs []*config.NodejsAPI
 	for _, api := range apis {