Handle closed PR checkout failures as warnings instead of errors

[Copilot]

When workflows process events on closed PRs (e.g., comments), checkout fails if the branch was deleted. This causes the entire workflow step to fail, preventing any further processing.

Changes

• Detect closed PR state before checkout attempt via pullRequest.state === "closed"
• Modified error handling in checkout_pr_branch.cjs to differentiate between closed and open PRs
• Closed PRs: Log warnings, set checkout_pr_success=true, continue workflow
• Open PRs: Preserve existing behavior - fail on checkout errors

Behavior

Closed PR with deleted branch:

⚠️ Closed PR Checkout Warning
  PR state: closed
  Checkout failed (expected for closed PR): branch not found
  Branch likely deleted: feature-branch
  This is expected behavior when a PR is closed

Step output: checkout_pr_success: "true" (workflow continues)

Open PR with checkout failure:

❌ Checkout Error Details
  Error message: network error

Step output: checkout_pr_success: "false" (workflow fails as before)

Original prompt

The JavaScript code that checks out a pull-request should handle the case where the pull-request is already closed. When it tries to check out the pull-request branch and the pull-request is closed, the branch has likely already been deleted.
If the pull-request is already closed and the checkout fails, this should not be treated as an error. It should be reported as a warning in the output, but it must not cause the step to fail.

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[Copilot]

Pull request overview

Updates the PR-branch checkout GitHub Action script to avoid failing workflows when processing events on closed pull requests whose branches may have been deleted, while preserving failure behavior for open PRs.

Changes:

• Detects pullRequest.state === "closed" and treats checkout failures as warnings (step continues).
• Adds step-summary + grouped warning logs for closed-PR checkout failures.
• Extends unit tests to cover closed-PR warning behavior vs open-PR error behavior.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
actions/setup/js/checkout_pr_branch.cjs	Adds closed-PR detection and warning-only handling for checkout failures, including summary output.
actions/setup/js/checkout_pr_branch.test.cjs	Adds test coverage for closed-PR checkout failures being warnings and open-PR failures remaining errors.
scratchpad/pr-checkout-logic-explained.md	Documents the new closed-PR behavior and expected logs/tests.

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[Copilot]

In the closed-PR warning path, core.summary.addRaw(...).write() is awaited without any protection. If writing the summary throws (filesystem issues, runner limitations, etc.), the script will throw and the step can still fail—negating the intent to treat closed-PR checkout failures as warnings. Consider wrapping the summary write in a try/catch (logging a warning on failure) so the closed-PR path cannot error out.

Suggested change

	await core.summary.addRaw(warningMessage).write();
	try {
	await core.summary.addRaw(warningMessage).write();
	} catch (summaryError) {
	core.warning(`Failed to write closed PR summary: ${getErrorMessage(summaryError)}`);
	}