fix(librarian): resolve issue where commits cannot be fetched for new library (#2631)

Fixes #2628

Author: parthea

internal/librarian/mocks_test.go

@@ -333,6 +333,7 @@ type MockRepository struct {
 	GetCommitsForPathsSinceTagValue        []*gitrepo.Commit
 	GetCommitsForPathsSinceTagValueByTag   map[string][]*gitrepo.Commit
 	GetCommitsForPathsSinceTagError        error
+	GetCommitsForPathsSinceTagLastTagName  string
 	GetCommitsForPathsSinceLastGenValue    []*gitrepo.Commit
 	GetCommitsForPathsSinceLastGenByCommit map[string][]*gitrepo.Commit
 	GetCommitsForPathsSinceLastGenByPath   map[string][]*gitrepo.Commit
@@ -420,6 +421,7 @@ func (m *MockRepository) GetLatestCommit(path string) (*gitrepo.Commit, error) {
 }
 
 func (m *MockRepository) GetCommitsForPathsSinceTag(paths []string, tagName string) ([]*gitrepo.Commit, error) {
+	m.GetCommitsForPathsSinceTagLastTagName = tagName
 	if m.GetCommitsForPathsSinceTagError != nil {
 		return nil, m.GetCommitsForPathsSinceTagError
 	}

internal/librarian/release_init.go

@@ -202,8 +202,11 @@ func (r *initRunner) runInitCommand(ctx context.Context, outputDir string) error
 // processLibrary wrapper to process the library for release. Helps retrieve latest commits
 // since the last release and passing the changes to updateLibrary.
 func (r *initRunner) processLibrary(library *config.LibraryState) error {
-	tagFormat := config.DetermineTagFormat(library.ID, library, r.librarianConfig)
-	tagName := config.FormatTag(tagFormat, library.ID, library.Version)
+	var tagName string
+	if library.Version != "0.0.0" {
+		tagFormat := config.DetermineTagFormat(library.ID, library, r.librarianConfig)
+		tagName = config.FormatTag(tagFormat, library.ID, library.Version)
+	}
 	commits, err := getConventionalCommitsSinceLastRelease(r.repo, library, tagName)
 	if err != nil {
 		return fmt.Errorf("failed to fetch conventional commits for library, %s: %w", library.ID, err)

internal/librarian/release_init_test.go

@@ -1322,6 +1322,14 @@ func TestProcessLibrary(t *testing.T) {
 			wantErr:    true,
 			wantErrMsg: "failed to fetch conventional commits for library",
 		},
+		{
+			name: "does not search for git tag for 0.0.0 version",
+			libraryState: &config.LibraryState{
+				ID:      "one-id",
+				Version: "0.0.0",
+			},
+			repo: &MockRepository{},
+		},
 	} {
 		state := &config.LibrarianState{
 			Libraries: []*config.LibraryState{
@@ -1345,6 +1353,9 @@ func TestProcessLibrary(t *testing.T) {
 		if err != nil {
 			t.Errorf("failed to run processLibrary(): %q", err.Error())
 		}
+		if test.libraryState.Version == "0.0.0" && test.repo.(*MockRepository).GetCommitsForPathsSinceTagLastTagName != "" {
+			t.Errorf("GetCommitsForPathsSinceTag should be called with an empty tag name for version 0.0.0, got %q", test.repo.(*MockRepository).GetCommitsForPathsSinceTagLastTagName)
+		}
 	}
 }