feat: add a comment to generation PR if generation has a failure (#2291)

Fixes #2287

Author: JoeWang1127

internal/github/github.go

@@ -44,9 +44,6 @@ type PullRequestReview = github.PullRequestReview
 // RepositoryRelease is a type alias for the go-github type.
 type RepositoryRelease = github.RepositoryRelease
 
-// MergeMethodRebase is a constant alias for the go-github constant.
-const MergeMethodRebase = github.MergeMethodRebase
-
 // Client represents this package's abstraction of a GitHub client, including
 // an access token.
 type Client struct {

internal/librarian/command.go

@@ -38,8 +38,12 @@ import (
 )
 
 const (
-	generate = "generate"
-	release  = "release"
+	generate                = "generate"
+	release                 = "release"
+	defaultAPISourceBranch  = "master"
+	failedGenerationComment = `One or more libraries have failed to generate, please review PR description for a list of failed libraries.
+For each failed library, open a ticket in that library’s repository and then you may resolve this comment and merge.
+`
 )
 
 var globalPreservePatterns = []string{
@@ -83,6 +87,7 @@ type commitInfo struct {
 	repo              gitrepo.Repository
 	sourceRepo        gitrepo.Repository
 	state             *config.LibrarianState
+	failedGenerations int
 }
 
 type commandRunner struct {
@@ -96,8 +101,6 @@ type commandRunner struct {
 	workRoot        string
 }
 
-const defaultAPISourceBranch = "master"
-
 func newCommandRunner(cfg *config.Config) (*commandRunner, error) {
 	languageRepo, err := cloneOrOpenRepo(cfg.WorkRoot, cfg.Repo, cfg.APISourceDepth, cfg.Branch, cfg.CI, cfg.GitHubToken)
 	if err != nil {
@@ -375,6 +378,12 @@ func commitAndPush(ctx context.Context, info *commitInfo) error {
 		return fmt.Errorf("failed to create pull request: %w", err)
 	}
 
+	if info.failedGenerations != 0 {
+		if err := info.ghClient.CreateIssueComment(ctx, pullRequestMetadata.Number, failedGenerationComment); err != nil {
+			return fmt.Errorf("failed to add pull request comment: %w", err)
+		}
+	}
+
 	return addLabelsToPullRequest(ctx, info.ghClient, info.pullRequestLabels, pullRequestMetadata)
 }
 

internal/librarian/command_test.go

@@ -1293,15 +1293,16 @@ func TestCompileRegexps(t *testing.T) {
 
 func TestCommitAndPush(t *testing.T) {
 	for _, test := range []struct {
-		name            string
-		setupMockRepo   func(t *testing.T) gitrepo.Repository
-		setupMockClient func(t *testing.T) GitHubClient
-		state           *config.LibrarianState
-		prType          string
-		commit          bool
-		push            bool
-		wantErr         bool
-		expectedErrMsg  string
+		name              string
+		setupMockRepo     func(t *testing.T) gitrepo.Repository
+		setupMockClient   func(t *testing.T) GitHubClient
+		state             *config.LibrarianState
+		prType            string
+		failedGenerations int
+		commit            bool
+		push              bool
+		wantErr           bool
+		expectedErrMsg    string
 	}{
 		{
 			name: "Push flag and Commit flag are not specified",
@@ -1576,19 +1577,48 @@ func TestCommitAndPush(t *testing.T) {
 			prType: "generate",
 			push:   true,
 		},
+		{
+			name: "create_a_comment_on_generation_pr_error",
+			setupMockRepo: func(t *testing.T) gitrepo.Repository {
+				remote := git.NewRemote(memory.NewStorage(), &gogitConfig.RemoteConfig{
+					Name: "origin",
+					URLs: []string{"https://github.com/googleapis/librarian.git"},
+				})
+				status := make(git.Status)
+				status["file.txt"] = &git.FileStatus{Worktree: git.Modified}
+				return &MockRepository{
+					Dir:          t.TempDir(),
+					AddAllStatus: status,
+					RemotesValue: []*git.Remote{remote},
+				}
+			},
+			setupMockClient: func(t *testing.T) GitHubClient {
+				return &mockGitHubClient{
+					createdPR:      &github.PullRequestMetadata{Number: 123, Repo: &github.Repository{Owner: "test-owner", Name: "test-repo"}},
+					createIssueErr: errors.New("simulate comment creation error"),
+				}
+			},
+			state:             &config.LibrarianState{},
+			prType:            "generate",
+			failedGenerations: 1,
+			push:              true,
+			wantErr:           true,
+			expectedErrMsg:    "failed to add pull request comment",
+		},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			repo := test.setupMockRepo(t)
 			client := test.setupMockClient(t)
 
 			commitInfo := &commitInfo{
-				commit:        test.commit,
-				commitMessage: "",
-				ghClient:      client,
-				prType:        test.prType,
-				push:          test.push,
-				repo:          repo,
-				state:         test.state,
+				commit:            test.commit,
+				commitMessage:     "",
+				ghClient:          client,
+				prType:            test.prType,
+				push:              test.push,
+				repo:              repo,
+				state:             test.state,
+				failedGenerations: test.failedGenerations,
 			}
 
 			err := commitAndPush(context.Background(), commitInfo)

internal/librarian/generate.go

@@ -86,8 +86,9 @@ func (r *generateRunner) run(ctx context.Context) error {
 	// The last generated commit is changed after library generation,
 	// use this map to keep the mapping from library id to commit sha before the
 	// generation since we need these commits to create pull request body.
-	idToCommits := make(map[string]string, 0)
+	idToCommits := make(map[string]string)
 	var failedLibraries []string
+	failedGenerations := 0
 	if r.api != "" || r.library != "" {
 		libraryID := r.library
 		if libraryID == "" {
@@ -100,7 +101,6 @@ func (r *generateRunner) run(ctx context.Context) error {
 		idToCommits[libraryID] = oldCommit
 	} else {
 		succeededGenerations := 0
-		failedGenerations := 0
 		blockedGenerations := 0
 		for _, library := range r.state.Libraries {
 			if r.librarianConfig != nil {
@@ -141,17 +141,18 @@ func (r *generateRunner) run(ctx context.Context) error {
 	}
 
 	commitInfo := &commitInfo{
-		branch:          r.branch,
-		commit:          r.commit,
-		commitMessage:   "feat: generate libraries",
-		failedLibraries: failedLibraries,
-		ghClient:        r.ghClient,
-		idToCommits:     idToCommits,
-		prType:          generate,
-		push:            r.push,
-		repo:            r.repo,
-		sourceRepo:      r.sourceRepo,
-		state:           r.state,
+		branch:            r.branch,
+		commit:            r.commit,
+		commitMessage:     "feat: generate libraries",
+		failedLibraries:   failedLibraries,
+		ghClient:          r.ghClient,
+		idToCommits:       idToCommits,
+		prType:            generate,
+		push:              r.push,
+		repo:              r.repo,
+		sourceRepo:        r.sourceRepo,
+		state:             r.state,
+		failedGenerations: failedGenerations,
 	}
 
 	return commitAndPush(ctx, commitInfo)

internal/librarian/mocks_test.go

@@ -41,6 +41,7 @@ type mockGitHubClient struct {
 	searchPullRequestsCalls int
 	getPullRequestCalls     int
 	createReleaseCalls      int
+	createIssueCalls        int
 	createTagCalls          int
 	createPullRequestErr    error
 	addLabelsToIssuesErr    error
@@ -49,6 +50,7 @@ type mockGitHubClient struct {
 	searchPullRequestsErr   error
 	getPullRequestErr       error
 	createReleaseErr        error
+	createIssueErr          error
 	createTagErr            error
 	createdPR               *github.PullRequestMetadata
 	labels                  []string
@@ -104,6 +106,11 @@ func (m *mockGitHubClient) CreateRelease(ctx context.Context, tagName, releaseNa
 	return m.createdRelease, m.createReleaseErr
 }
 
+func (m *mockGitHubClient) CreateIssueComment(ctx context.Context, number int, comment string) error {
+	m.createIssueCalls++
+	return m.createIssueErr
+}
+
 func (m *mockGitHubClient) CreateTag(ctx context.Context, tagName, commitish string) error {
 	m.createTagCalls++
 	return m.createTagErr