Comment on the source PR when a backport fails

ddev/changelog.d/24872.added

@@ -0,0 +1 @@
+Include a comment on the source PR listing each failed base when a backport fails.

ddev/src/ddev/cli/release/port_commit_workflow.py

@@ -1011,6 +1011,8 @@ def run_backport_from_pr(
         options=options,
     )
     _display_backport_summary(app, pr_number, results)
+    if not options.dry_run:
+        _comment_on_backport_failures(app, pr_number, results)
     return all(result.status is not BackportStatus.FAILED for result in results)
 
 
@@ -1106,3 +1108,48 @@ def _display_backport_summary(app: Application, pr_number: int, results: list[Ba
         ),
         stderr=True,
     )
+
+
+def _comment_on_backport_failures(app: Application, pr_number: int, results: list[BackportResult]) -> None:
+    """Post a comment on the source PR when one or more bases failed to backport.
+
+    The pre-`--from-pr` automation commented on the merged PR when a backport failed; without this a
+    failure is only visible as a red workflow run, never on the PR the developer merged. Posting is
+    best-effort: a comment failure must not mask the backport failure it is reporting, so any error
+    here is warned, not raised.
+    """
+    failures = [result for result in results if result.status is BackportStatus.FAILED]
+    if not failures:
+        return
+    token = app.config.github.token
+    if not token:
+        app.display_warning(f'No GitHub token configured; skipping backport-failure comment on PR #{pr_number}.')
+        return
+
+    owner, repo = resolve_owner_repo(app)
+    lines = [f'⚠️ Automatic backport of this PR failed for {len(failures)} target branch(es):', '']
+    for result in failures:
+        reason = f': {result.detail}' if result.detail else ''
+        lines.append(
+            f'- `{result.base}`{reason} — retry manually with '
+            f'`ddev release port-commit PR-{pr_number} --target-branch {result.base}`.'
+        )
+    body = '\n'.join(lines)
+
+    try:
+        _post_issue_comment(token, owner, repo, pr_number, body)
+    except Exception as e:  # noqa: BLE001 - best-effort comment; never mask the backport result
+        app.display_warning(f'Could not post backport-failure comment on PR #{pr_number}: {e}')
+
+
+def _post_issue_comment(token: str, owner: str, repo: str, issue_number: int, body: str) -> None:
+    """Create a comment on the given issue or pull request."""
+    import asyncio
+
+    from ddev.utils.github_async import async_github_client
+
+    async def _post() -> None:
+        async with async_github_client(token=token) as client:
+            await client.create_issue_comment(owner=owner, repo=repo, issue_number=issue_number, body=body)
+
+    asyncio.run(_post())

ddev/tests/cli/release/test_port_commit.py

@@ -1159,6 +1159,55 @@ def test_command_from_pr_aggregates_failures_and_continues(
     assert bases == ['7.62.x', '7.61.x']
 
 
+def test_command_from_pr_comments_on_source_pr_when_a_base_fails(
+    ddev: CliRunner, mocker: MockerFixture, fake_async_github: FakeAsyncGitHubClient
+) -> None:
+    """A failed base posts a comment on the merged PR so the failure is visible off the workflow run."""
+    import httpx
+
+    _setup_command_mocks(mocker, commit_sha=FULL_SHA_FOR_TESTS)
+    fake_async_github.mock_response(
+        'get_pull_request',
+        _merged_pr(number=23703, backport_bases=['7.62.x', '7.61.x']),
+    )
+    fake_async_github.mock_response(
+        'create_pull_request',
+        httpx.HTTPStatusError('boom', request=httpx.Request('POST', 'https://x'), response=httpx.Response(500)),
+        base='7.62.x',
+    )
+    mocker.patch.dict('os.environ', {'DD_GITHUB_USER': 'alice'})
+
+    result = ddev('release', 'port-commit', '--from-pr', '23703')
+
+    assert result.exit_code == 1, result.output
+    comment_calls = fake_async_github.calls_to('create_issue_comment')
+    assert len(comment_calls) == 1
+    comment_call = comment_calls[0]
+    assert comment_call.kwargs['issue_number'] == 23703
+    body = comment_call.kwargs['body']
+    assert '7.62.x' in body
+    assert 'retry manually' in body
+    # Only the failed base is named; the base that ported cleanly is not mentioned.
+    assert '7.61.x' not in body
+
+
+def test_command_from_pr_does_not_comment_when_all_bases_succeed(
+    ddev: CliRunner, mocker: MockerFixture, fake_async_github: FakeAsyncGitHubClient
+) -> None:
+    """The happy path leaves no comment on the source PR."""
+    _setup_command_mocks(mocker, commit_sha=FULL_SHA_FOR_TESTS)
+    fake_async_github.mock_response(
+        'get_pull_request',
+        _merged_pr(number=23703, backport_bases=['7.62.x', '7.61.x']),
+    )
+    mocker.patch.dict('os.environ', {'DD_GITHUB_USER': 'alice'})
+
+    result = ddev('release', 'port-commit', '--from-pr', '23703')
+
+    assert result.exit_code == 0, result.output
+    fake_async_github.assert_not_called('create_issue_comment')
+
+
 def test_command_from_pr_summary_reports_every_status(
     ddev: CliRunner, mocker: MockerFixture, fake_async_github: FakeAsyncGitHubClient
 ) -> None:

ddev/tests/helpers/github_async.py

@@ -46,6 +46,7 @@ def test_thing(fake_async_github):
 from ddev.utils.github_async.models import (
     ArtifactsList,
     CheckRun,
+    IssueComment,
     Label,
     PullRequest,
     WorkflowDispatchResult,
@@ -84,6 +85,10 @@ def _default_response_factories() -> dict[str, Callable[[], Any]]:
             headers={},
         ),
         'add_labels_to_issue': lambda: GitHubResponse.model_validate({'data': [], 'headers': {}}),
+        'create_issue_comment': lambda: GitHubResponse(
+            data=IssueComment(id=1, body='', html_url='https://github.com/test/repo/issues/1#issuecomment-1'),
+            headers={},
+        ),
         # Default to "PR not found" so tests that don't care about PR lookup auto-fall-through
         # to commit resolution. Tests that need a specific PR register their own mock_response.
         'get_pull_request': lambda: httpx.HTTPStatusError(
@@ -284,6 +289,23 @@ async def add_labels_to_issue(
             timeout=timeout,
         )
 
+    async def create_issue_comment(
+        self,
+        owner: str,
+        repo: str,
+        issue_number: int,
+        body: str,
+        timeout: float | None = None,
+    ) -> GitHubResponse[IssueComment]:
+        return self._call(
+            'create_issue_comment',
+            owner=owner,
+            repo=repo,
+            issue_number=issue_number,
+            body=body,
+            timeout=timeout,
+        )
+
     async def create_workflow_dispatch(
         self,
         owner: str,