Feedback Workflows

Feedback Workflows

Feedback workflows react to events in a repository (like PRs being merged or issues being created) and perform actions in response.

Overview

Unlike core.workflow which synchronizes code, core.feedback triggers actions based on repository events.

core.feedback(
    name = "notify-on-merge",
    origin = git.github_trigger(...),
    destination = git.github_api(...),
    actions = [...],
)

Use Cases

• Notify internal systems when external PRs are merged
• Create tracking issues when code is synced
• Update labels or milestones automatically
• Post comments on related PRs/issues
• Trigger downstream workflows

GitHub Trigger Origin

Listen to GitHub events:

origin = git.github_trigger(
    url = "https://github.com/org/repo",
    events = ["pull_request", "push"],
)

Supported Events

Event	Trigger
pull_request	PR opened, closed, merged, etc.
push	Commits pushed to a branch
issue	Issue opened, closed, etc.
issue_comment	Comment on issue or PR

GitHub API Destination

Perform actions via the GitHub API:

destination = git.github_api(
    url = "https://github.com/org/internal-repo",
)

Custom Actions

Define actions using Starlark functions:

def _notify_internal(ctx):
    """Notify internal team when external PR is merged."""
    for change in ctx.origin.get_changes():
        if change.labels.get("merged"):
            ctx.destination.create_issue(
                title = "External contribution merged: " + change.ref,
                body = "PR " + change.ref + " was merged. Please sync.",
            )
    return ctx.success()

core.action(
    impl = _notify_internal,
    params = {},
)

Complete Example

copy.bara.sky

# Workflow to notify when external PRs are merged
core.feedback(
    name = "notify-on-external-merge",

    origin = git.github_trigger(
        url = "https://github.com/myorg/public-repo",
        events = ["pull_request"],
    ),

    destination = git.github_api(
        url = "https://github.com/myorg/internal-repo",
    ),

    actions = [
        core.action(
            impl = _handle_pr_event,
            params = {},
        ),
    ],
)

def _handle_pr_event(ctx):
    for pr in ctx.origin.get_pull_requests():
        if pr.merged:
            # Create an issue in the internal repo
            ctx.destination.create_issue(
                title = "[External] PR merged: " + pr.title,
                body = """\
An external contribution was merged.

**PR**: """ + pr.url + """
**Author**: """ + pr.author + """
**Description**: """ + pr.body + """

Please run Copybara to import these changes.
""",
                labels = ["external-contribution", "needs-import"],
            )

            ctx.console.info("Created issue for PR: " + pr.number)

    return ctx.success()

Action Context

The ctx object provides:

Property	Description
ctx.origin	Access to origin events/data
ctx.destination	API to perform actions
ctx.console	Logging methods (info, warn, error)
ctx.success()	Return successful result
ctx.noop(msg)	Return no-op result
ctx.error(msg)	Return error result

Origin Methods

# Get all changes/events
changes = ctx.origin.get_changes()

# Get pull requests
prs = ctx.origin.get_pull_requests()

# Access event data
for change in changes:
    ref = change.ref
    labels = change.labels
    author = change.author

Destination Methods

# Create an issue
ctx.destination.create_issue(
    title = "Issue title",
    body = "Issue body",
    labels = ["label1", "label2"],
    assignees = ["user1"],
)

# Add a comment
ctx.destination.add_comment(
    number = 123,  # Issue or PR number
    body = "Comment text",
)

# Update labels
ctx.destination.add_labels(
    number = 123,
    labels = ["reviewed"],
)

Running Feedback Workflows

# Validate
java -jar copybara.jar validate copy.bara.sky notify-on-external-merge

# Run (typically triggered by webhooks in CI)
java -jar copybara.jar feedback copy.bara.sky notify-on-external-merge

Note

Feedback workflows are typically triggered by CI/CD systems in response to webhooks, not run manually.

Webhook Integration

Set up a GitHub webhook to trigger the feedback workflow:

1. Go to repo Settings → Webhooks
2. Add webhook URL pointing to your CI
3. Select events (e.g., “Pull requests”)
4. CI runs Copybara feedback workflow on webhook

Combining with Sync Workflows

A common pattern:

1. External contributor opens PR on public repo
2. PR gets merged
3. Feedback workflow creates internal issue
4. Team reviews and approves import
5. Sync workflow (import) runs to bring changes internal

# Feedback: notify on merge
core.feedback(
    name = "notify-on-merge",
    origin = git.github_trigger(url = public_url, events = ["pull_request"]),
    ...
)

# Sync: import external contributions
core.workflow(
    name = "import",
    origin = git.github_pr_origin(url = public_url, branch = "main"),
    destination = git.gerrit_destination(url = internal_url, ...),
    mode = "CHANGE_REQUEST_FROM_SOT",
    ...
)

Next Steps

• GitHub integration
• Gerrit integration