feat(librarian): add ability to open pull request as a draft (#2604)

Fixes #2588

Author: chingor13

internal/github/github.go

@@ -152,7 +152,7 @@ func (c *Client) GetRawContent(ctx context.Context, path, ref string) ([]byte, e
 // CreatePullRequest creates a pull request in the remote repo.
 // At the moment this requires a single remote to be configured,
 // which must have a GitHub HTTPS URL. We assume a base branch of "main".
-func (c *Client) CreatePullRequest(ctx context.Context, repo *Repository, remoteBranch, baseBranch, title, body string) (*PullRequestMetadata, error) {
+func (c *Client) CreatePullRequest(ctx context.Context, repo *Repository, remoteBranch, baseBranch, title, body string, isDraft bool) (*PullRequestMetadata, error) {
 	if body == "" {
 		slog.Warn("Provided PR body is empty, setting default.")
 		body = "Regenerated all changed APIs. See individual commits for details."
@@ -166,6 +166,7 @@ func (c *Client) CreatePullRequest(ctx context.Context, repo *Repository, remote
 		Base:                &baseBranch,
 		Body:                github.Ptr(body),
 		MaintainerCanModify: github.Ptr(true),
+		Draft:               github.Ptr(isDraft),
 	}
 	pr, _, err := c.PullRequests.Create(ctx, repo.Owner, repo.Name, newPR)
 	if err != nil {

internal/github/github_test.go

@@ -321,7 +321,7 @@ func TestCreatePullRequest(t *testing.T) {
 			client := newClientWithHTTP("fake-token", repo, server.Client())
 			client.BaseURL, _ = url.Parse(server.URL + "/")
 
-			metadata, err := client.CreatePullRequest(t.Context(), repo, test.remoteBranch, test.remoteBase, test.title, test.body)
+			metadata, err := client.CreatePullRequest(t.Context(), repo, test.remoteBranch, test.remoteBase, test.title, test.body, false)
 
 			if test.wantErr {
 				if err == nil {

internal/librarian/command.go

@@ -79,7 +79,7 @@ var globalPreservePatterns = []string{
 // GitHubClient is an abstraction over the GitHub client.
 type GitHubClient interface {
 	GetRawContent(ctx context.Context, path, ref string) ([]byte, error)
-	CreatePullRequest(ctx context.Context, repo *github.Repository, remoteBranch, remoteBase, title, body string) (*github.PullRequestMetadata, error)
+	CreatePullRequest(ctx context.Context, repo *github.Repository, remoteBranch, remoteBase, title, body string, isDraft bool) (*github.PullRequestMetadata, error)
 	AddLabelsToIssue(ctx context.Context, repo *github.Repository, number int, labels []string) error
 	GetLabels(ctx context.Context, number int) ([]string, error)
 	ReplaceLabels(ctx context.Context, number int, labels []string) error
@@ -126,8 +126,11 @@ type commitInfo struct {
 	// api is the api path of a library, only set this value during api onboarding.
 	api string
 	// library is the ID of a library, only set this value during api onboarding.
-	library       string
+	library string
+	// prBodyBuilder is a callback function for building the pull request body
 	prBodyBuilder func() (string, error)
+	// isDraft declares whether or not to create the pull request as a draft.
+	isDraft bool
 }
 
 type commandRunner struct {
@@ -423,7 +426,7 @@ func commitAndPush(ctx context.Context, info *commitInfo) error {
 		return fmt.Errorf("failed to create pull request body: %w", err)
 	}
 
-	pullRequestMetadata, err := info.ghClient.CreatePullRequest(ctx, gitHubRepo, branch, info.branch, title, prBody)
+	pullRequestMetadata, err := info.ghClient.CreatePullRequest(ctx, gitHubRepo, branch, info.branch, title, prBody, info.isDraft)
 	if err != nil {
 		return fmt.Errorf("failed to create pull request: %w", err)
 	}

internal/librarian/mocks_test.go

@@ -66,7 +66,7 @@ func (m *mockGitHubClient) GetRawContent(ctx context.Context, path, ref string)
 	return m.rawContent, m.rawErr
 }
 
-func (m *mockGitHubClient) CreatePullRequest(ctx context.Context, repo *github.Repository, remoteBranch, remoteBase, title, body string) (*github.PullRequestMetadata, error) {
+func (m *mockGitHubClient) CreatePullRequest(ctx context.Context, repo *github.Repository, remoteBranch, remoteBase, title, body string, isDraft bool) (*github.PullRequestMetadata, error) {
 	m.createPullRequestCalls++
 	if m.createPullRequestErr != nil {
 		return nil, m.createPullRequestErr

internal/librarian/update_image.go

@@ -133,7 +133,6 @@ func (r *updateImageRunner) run(ctx context.Context) error {
 		return formatUpdateImagePRBody(r.image, failedGenerations)
 	}
 	commitMessage := fmt.Sprintf("feat: update image to %s", r.image)
-	// TODO(#2588): open PR as draft if there are failures
 	return commitAndPush(ctx, &commitInfo{
 		branch:            r.branch,
 		commit:            r.commit,
@@ -148,6 +147,7 @@ func (r *updateImageRunner) run(ctx context.Context) error {
 		workRoot:          r.workRoot,
 		failedGenerations: len(failedGenerations),
 		prBodyBuilder:     prBodyBuilder,
+		isDraft:           len(failedGenerations) > 0,
 	})
 }
 

system_test.go

@@ -175,7 +175,7 @@ func TestPullRequestSystem(t *testing.T) {
 
 	// Create a pull request
 	client := github.NewClient(testToken, repo)
-	createdPullRequest, err := client.CreatePullRequest(t.Context(), repo, branchName, "main", "test: integration test", "do not merge")
+	createdPullRequest, err := client.CreatePullRequest(t.Context(), repo, branchName, "main", "test: integration test", "do not merge", true)
 	if err != nil {
 		t.Fatalf("unexpected error in CreatePullRequest() %s", err)
 	}
@@ -259,6 +259,10 @@ func TestPullRequestSystem(t *testing.T) {
 				if pullRequest.GetComments() == 0 {
 					t.Fatalf("Expected to have created a comment on the pull request.")
 				}
+
+				if !pullRequest.GetDraft() {
+					t.Fatalf("Expected created pull request to have been a draft.")
+				}
 				break
 			}
 		}