amplify-preview: set amplify job info to github outputs

tools/amplify-preview/github.go

@@ -27,6 +27,8 @@ import (
 	"github.com/gravitational/shared-workflows/libs/github"
 )
 
+var errGithubOutputNotAvailable = errors.New("GITHUB_OUTPUT is not available")
+
 func postPreviewURL(ctx context.Context, commentBody string) error {
 	const prRefNameSuffix = "/merge"
 	refName := os.Getenv("GITHUB_REF_NAME")
@@ -69,3 +71,24 @@ func postPreviewURL(ctx context.Context, commentBody string) error {
 
 	return gh.UpdateComment(ctx, currentPR, comment.GetID(), commentBody)
 }
+
+func setGithubOutputs(kv map[string]string) error {
+	githubOutput := os.Getenv(github.OutputEnv)
+	if githubOutput == "" {
+		return errGithubOutputNotAvailable
+	}
+
+	file, err := os.OpenFile(githubOutput, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0o644)
+	if err != nil {
+		return fmt.Errorf("failed to open file %s: %w", githubOutput, err)
+	}
+	defer file.Close()
+
+	for key, value := range kv {
+		if _, err := fmt.Fprintf(file, "%s=%s\n", key, value); err != nil {
+			return fmt.Errorf("failed to write to file %s: %w", githubOutput, err)
+		}
+	}
+
+	return nil
+}

tools/amplify-preview/main.go

@@ -98,6 +98,8 @@ func run(ctx context.Context) error {
 		return fmt.Errorf("failed to post preview URL: %w", err)
 	}
 
+	setAmplifyInfoToGithubOutputs(branch, currentJob)
+
 	slog.Info("Successfully posted PR comment")
 
 	if *wait {
@@ -148,6 +150,30 @@ func ensureAmplifyDeployment(ctx context.Context, amp AmplifyPreview, branch *ty
 	}
 }
 
+func setAmplifyInfoToGithubOutputs(branch *types.Branch, job *types.JobSummary) {
+	kv := make(map[string]string)
+
+	if branch.BranchName != nil {
+		kv["AMPLIFY_BRANCH"] = *branch.BranchName
+	}
+
+	if branch.BranchArn != nil {
+		if appId, err := appIDFromBranchARN(*branch.BranchArn); err != nil {
+			slog.Error("failed to extract app ID from branch ARN", "branch_arn", *branch.BranchArn, "error", err)
+		} else {
+			kv["AMPLIFY_APP_ID"] = appId
+		}
+	}
+
+	if job.JobId != nil {
+		kv["AMPLIFY_JOB_ID"] = *job.JobId
+	}
+
+	if err := setGithubOutputs(kv); err != nil {
+		slog.Error("failed to set Amplify info to GitHub outputs", "error", err)
+	}
+}
+
 func handleInterruption(ctx context.Context) (context.Context, context.CancelFunc) {
 	ctx, cancel := context.WithCancel(ctx)
 	c := make(chan os.Signal, 1)