chore(release): process backports as part of creating RC (#3896)

Automatically process pending backports when `/create-rc` is called.

If any backport fails to process (e.g. due to cherry-pick conflicts),
the RC creation will abort.
Additionally, support `--triggering-comment` option to react with a
thumbs-down emoji on the triggering comment if the command fails.

- Call `ProcessBackports` in `CreateRc` before proceeding with RC
tagging.
- Refactor `CreateRc.run` to handle exceptions and reactions.
- Update GitHub Actions workflows to pass `comment_id` to
`release_create_rc` workflow.
- Add unit tests for the new integration and reaction behavior.

Author: rickeylev

.github/workflows/on_issue_comment.yaml

@@ -73,6 +73,7 @@ jobs:
     uses: ./.github/workflows/release_create_rc.yaml
     with:
       issue: ${{ needs.parse_comment.outputs.issue_number }}
+      comment_id: "${{ github.event.comment.id }}"
     secrets: inherit
 
   call_prepare:

.github/workflows/release_create_rc.yaml

@@ -7,12 +7,20 @@ on:
         description: 'The Release Tracking Issue Number (e.g., 142)'
         required: true
         type: string
+      comment_id:
+        description: 'The ID of the comment that triggered this run (optional)'
+        required: false
+        type: string
   workflow_call:
     inputs:
       issue:
         description: 'The Release Tracking Issue Number (e.g., 142)'
         required: true
         type: string
+      comment_id:
+        description: 'The ID of the comment that triggered this run (optional)'
+        required: false
+        type: string
 
 permissions:
   contents: write
@@ -44,9 +52,14 @@ jobs:
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           ISSUE: ${{ inputs.issue }}
+          COMMENT_ID: ${{ inputs.comment_id }}
         run: |
+          ARGS=()
+          if [ -n "$COMMENT_ID" ]; then
+            ARGS+=("--triggering-comment=$COMMENT_ID")
+          fi
           bazel run //tools/private/release -- \
-            create-rc --issue "$ISSUE" --remote origin
+            create-rc --issue "$ISSUE" --remote origin "${ARGS[@]}"
 
   call_release:
     needs: tag_rc

RELEASING.md

@@ -33,8 +33,9 @@ Release Tracking Issue and automated workflows triggered by comments or issue ed
 3.  **Add Backports (if needed)**: If there are backports, add them following
     the [How to add backports](#how-to-add-backports) steps.
 
-4.  **Create an RC**: Comment `/create-rc` on the tracking issue. All pending
-    backports must be successfully processed before creating the RC.
+4.  **Create an RC**: Comment `/create-rc` on the tracking issue. This will
+    automatically process pending backports before creating the RC. If any
+    backport fails, the RC creation will abort.
 
 5.  **Iterate**: Repeat steps 3 and 4 until backports and RCs are no longer
     needed.

news/process-backports-before-rc.changed.md

@@ -0,0 +1,3 @@
+Changed `/create-rc` command to automatically process pending backports before
+creating the RC, and react with a thumbs-down emoji on failure if triggered by
+a comment.

tests/tools/private/release/create_rc_test.py

@@ -253,6 +253,130 @@ def test_create_rc_auto_add_task(self):
             call2_args[1],
         )
 
+    @patch("tools.private.release.create_rc.ProcessBackports")
+    def test_create_rc_calls_process_backports(self, mock_pb_class):
+        # Arrange
+        mock_pb = mock_pb_class.return_value
+        mock_pb.run.return_value = 0
+
+        args = MagicMock(issue=123, remote="my-remote")
+        self.mock_gh.get_issue_title.return_value = "Release 2.0.0"
+        self.mock_gh.get_issue_body.return_value = """
+## Checklist
+- [x] Prepare Release | status=done pr=#122 commit=abcdef12
+- [x] Create Release branch | status=done branch=release/2.0 commit=abcdef12
+- [ ] Tag RC0 | status=pending
+"""
+        self.mock_git.get_remote_tags.return_value = []
+        self.mock_git.get_commit_sha.return_value = "1234567890"
+
+        # Act
+        result = CreateRc(args, self.mock_git, self.mock_gh).run()
+
+        # Assert
+        self.assertEqual(result, 0)
+        mock_pb_class.assert_called_once()
+        called_args = mock_pb_class.call_args[0][0]
+        self.assertEqual(called_args.issue, 123)
+        self.assertEqual(called_args.remote, "my-remote")
+        self.assertFalse(called_args.dry_run)
+        self.assertIsNone(called_args.add)
+        self.assertIsNone(called_args.triggering_comment)
+        mock_pb.run.assert_called_once()
+
+    @patch("tools.private.release.create_rc.ProcessBackports")
+    def test_create_rc_aborts_on_process_backports_failure(self, mock_pb_class):
+        # Arrange
+        mock_pb = mock_pb_class.return_value
+        mock_pb.run.return_value = 1
+
+        args = MagicMock(issue=123, remote="my-remote")
+
+        # Act
+        result = CreateRc(args, self.mock_git, self.mock_gh).run()
+
+        # Assert
+        self.assertEqual(result, 1)
+        mock_pb_class.assert_called_once()
+        mock_pb.run.assert_called_once()
+        self.mock_gh.get_issue_body.assert_not_called()
+        self.mock_git.tag.assert_not_called()
+
+    @patch("tools.private.release.create_rc.ProcessBackports")
+    def test_create_rc_failure_reacts_to_comment(self, mock_pb_class):
+        # Arrange
+        mock_pb = mock_pb_class.return_value
+        mock_pb.run.return_value = 1  # Simulate failure
+
+        args = MagicMock(issue=123, remote="my-remote", triggering_comment=456)
+
+        # Act
+        result = CreateRc(args, self.mock_git, self.mock_gh).run()
+
+        # Assert
+        self.assertEqual(result, 1)
+        self.mock_gh.add_comment_reaction.assert_called_once_with(456, "-1")
+
+    @patch("tools.private.release.create_rc.ProcessBackports")
+    def test_create_rc_failure_no_comment_no_reaction(self, mock_pb_class):
+        # Arrange
+        mock_pb = mock_pb_class.return_value
+        mock_pb.run.return_value = 1  # Simulate failure
+
+        args = MagicMock(issue=123, remote="my-remote", triggering_comment=None)
+
+        # Act
+        result = CreateRc(args, self.mock_git, self.mock_gh).run()
+
+        # Assert
+        self.assertEqual(result, 1)
+        self.mock_gh.add_comment_reaction.assert_not_called()
+
+    @patch("tools.private.release.create_rc.ProcessBackports")
+    def test_create_rc_success_with_comment_no_reaction(self, mock_pb_class):
+        # Arrange
+        mock_pb = mock_pb_class.return_value
+        mock_pb.run.return_value = 0
+
+        args = MagicMock(issue=123, remote="my-remote", triggering_comment=456)
+        self.mock_gh.get_issue_title.return_value = "Release 2.0.0"
+        self.mock_gh.get_issue_body.return_value = """
+## Checklist
+- [x] Prepare Release | status=done pr=#122 commit=abcdef12
+- [x] Create Release branch | status=done branch=release/2.0 commit=abcdef12
+- [ ] Tag RC0 | status=pending
+"""
+        self.mock_git.get_remote_tags.return_value = []
+        self.mock_git.get_commit_sha.return_value = "1234567890"
+
+        # Act
+        result = CreateRc(args, self.mock_git, self.mock_gh).run()
+
+        # Assert
+        self.assertEqual(result, 0)
+        self.mock_gh.add_comment_reaction.assert_not_called()
+
+    @patch("tools.private.release.create_rc.ProcessBackports")
+    def test_create_rc_precondition_failure_reacts_to_comment(self, mock_pb_class):
+        # Arrange
+        mock_pb = mock_pb_class.return_value
+        mock_pb.run.return_value = 0  # Backports succeed
+
+        args = MagicMock(issue=123, remote="my-remote", triggering_comment=456)
+        self.mock_gh.get_issue_body.return_value = """
+## Checklist
+- [ ] Prepare Release | status=pending
+- [ ] Create Release branch | status=pending
+- [ ] Tag RC0 | status=pending
+"""
+
+        # Act
+        result = CreateRc(args, self.mock_git, self.mock_gh).run()
+
+        # Assert
+        self.assertEqual(result, 1)
+        self.mock_gh.add_comment_reaction.assert_called_once_with(456, "-1")
+
 
 if __name__ == "__main__":
     unittest.main()

tools/private/release/create_rc.py

@@ -1,7 +1,11 @@
 """Subcommand to tag and push the next release candidate."""
 
-from tools.private.release.gh import GitHub
+import traceback
+from argparse import Namespace
+
+from tools.private.release.gh import GH_REACTION_THUMBS_DOWN, GitHub
 from tools.private.release.git import Git
+from tools.private.release.process_backports import ProcessBackports
 from tools.private.release.release_issue import (
     RELEASE_TITLE_RE,
     add_rc_task_to_body,
@@ -26,6 +30,44 @@ def __init__(self, args, git: Git, gh: GitHub):
     def run(self) -> int:
         """Executes the create-rc subcommand."""
         args = self.args
+        exit_code = 0
+        try:
+            exit_code = self._run_internal()
+        except Exception as e:
+            print(f"Unexpected error: {e}")
+            traceback.print_exc()
+            exit_code = 1
+
+        if exit_code != 0 and args.triggering_comment:
+            print(f"Reacting with thumbs-down to comment {args.triggering_comment}...")
+            try:
+                self.gh.add_comment_reaction(
+                    args.triggering_comment, GH_REACTION_THUMBS_DOWN
+                )
+            except Exception as e:
+                print(f"Failed to add reaction to comment: {e}")
+
+        return exit_code
+
+    def _run_internal(self) -> int:
+        """Internal implementation of create-rc."""
+        args = self.args
+
+        # Try to process pending backports first
+        print("Processing pending backports before creating RC...")
+        backport_args = Namespace(
+            issue=args.issue,
+            remote=args.remote,
+            add=None,
+            triggering_comment=None,
+            dry_run=False,
+        )
+        pb = ProcessBackports(backport_args, self.git, self.gh)
+        backports_exit_code = pb.run()
+        if backports_exit_code != 0:
+            print("Error: Processing backports failed. Aborting RC creation.")
+            return backports_exit_code
+
         body = self.gh.get_issue_body(args.issue)
         state = parse_checklist_state(body)
 
@@ -153,6 +195,11 @@ def add_parser(cls, subparsers):
             required=True,
             help="The git remote to push the RC tag to (required).",
         )
+        parser.add_argument(
+            "--triggering-comment",
+            type=int,
+            help="The ID of the comment that triggered this run (optional).",
+        )
         parser.set_defaults(command=cls.run_from_args)
 
     @classmethod