fix(cherry-pick): prevent label duplication on merged PRs

webhook_server/libs/handlers/issue_comment_handler.py

@@ -329,6 +329,36 @@ async def _add_reviewer_by_user_comment(self, pull_request: PullRequest, reviewe
     async def process_cherry_pick_command(
         self, pull_request: PullRequest, command_args: str, reviewed_user: str
     ) -> None:
+        """Process cherry-pick command for pull requests.
+
+        This method handles cherry-pick requests for both unmerged and merged PRs.
+        Cherry-pick labels (cherry-pick/<branch-name>) are added in BOTH scenarios:
+
+        **Unmerged PRs:**
+        - Labels indicate which branches need cherry-picking after the PR is merged
+        - Labels act as a TODO list for automatic cherry-picking
+        - When the PR is merged, the PR handler detects these labels and triggers cherry-picks
+
+        **Merged PRs:**
+        - Cherry-picks are executed immediately for all target branches
+        - Labels are added to track which branches have been cherry-picked to
+        - Labels serve as a historical record of completed cherry-pick operations
+        - Helps with auditing and tracking which releases include this change
+
+        Args:
+            pull_request: The pull request to cherry-pick
+            command_args: Space-separated list of target branches (e.g., "v1.0 v2.0")
+            reviewed_user: User who requested the cherry-pick
+
+        Example:
+            # Unmerged PR: /cherry-pick v1.0 v2.0
+            # - Adds labels: cherry-pick/v1.0, cherry-pick/v2.0
+            # - Posts comment explaining labels will trigger auto cherry-pick on merge
+
+            # Merged PR: /cherry-pick v1.0 v2.0
+            # - Executes cherry-pick to v1.0 and v2.0 immediately
+            # - Adds labels: cherry-pick/v1.0, cherry-pick/v2.0 to track completion
+        """
         _target_branches: list[str] = command_args.split()
         _exits_target_branches: set[str] = set()
         _non_exits_target_branches_msg: str = ""
@@ -349,19 +379,19 @@ async def process_cherry_pick_command(
             self.logger.info(f"{self.log_prefix} {_non_exits_target_branches_msg}")
             await asyncio.to_thread(pull_request.create_issue_comment, _non_exits_target_branches_msg)
 
+        cp_labels: list[str] = [
+            f"{CHERRY_PICK_LABEL_PREFIX}{_target_branch}" for _target_branch in _exits_target_branches
+        ]
+
         if _exits_target_branches:
             if not await asyncio.to_thread(pull_request.is_merged):
-                cp_labels: list[str] = [
-                    f"{CHERRY_PICK_LABEL_PREFIX}{_target_branch}" for _target_branch in _exits_target_branches
-                ]
                 info_msg: str = f"""
 Cherry-pick requested for PR: `{pull_request.title}` by user `{reviewed_user}`
 Adding label/s `{" ".join([_cp_label for _cp_label in cp_labels])}` for automatic cheery-pick once the PR is merged
 """
+
                 self.logger.info(f"{self.log_prefix} {info_msg}")
                 await asyncio.to_thread(pull_request.create_issue_comment, info_msg)
-                for _cp_label in cp_labels:
-                    await self.labels_handler._add_label(pull_request=pull_request, label=_cp_label)
             else:
                 for _exits_target_branch in _exits_target_branches:
                     await self.runner_handler.cherry_pick(
@@ -370,6 +400,9 @@ async def process_cherry_pick_command(
                         reviewed_user=reviewed_user,
                     )
 
+            for _cp_label in cp_labels:
+                await self.labels_handler._add_label(pull_request=pull_request, label=_cp_label)
+
     async def process_retest_command(
         self, pull_request: PullRequest, command_args: str, reviewed_user: str, automerge: bool = False
     ) -> None:

webhook_server/tests/test_issue_comment_handler.py

@@ -656,12 +656,65 @@ async def test_process_cherry_pick_command_merged_pr(self, issue_comment_handler
                 with patch.object(
                     issue_comment_handler.runner_handler, "cherry_pick", new_callable=AsyncMock
                 ) as mock_cherry_pick:
-                    await issue_comment_handler.process_cherry_pick_command(
-                        pull_request=mock_pull_request, command_args="branch1", reviewed_user="test-user"
-                    )
-                    mock_cherry_pick.assert_called_once_with(
-                        pull_request=mock_pull_request, target_branch="branch1", reviewed_user="test-user"
-                    )
+                    with patch.object(
+                        issue_comment_handler.labels_handler, "_add_label", new_callable=AsyncMock
+                    ) as mock_add_label:
+                        await issue_comment_handler.process_cherry_pick_command(
+                            pull_request=mock_pull_request, command_args="branch1", reviewed_user="test-user"
+                        )
+                        mock_cherry_pick.assert_called_once_with(
+                            pull_request=mock_pull_request, target_branch="branch1", reviewed_user="test-user"
+                        )
+                        mock_add_label.assert_called_once_with(
+                            pull_request=mock_pull_request, label="cherry-pick-branch1"
+                        )
+
+    @pytest.mark.asyncio
+    async def test_process_cherry_pick_command_merged_pr_multiple_branches(
+        self, issue_comment_handler: IssueCommentHandler
+    ) -> None:
+        """Test processing cherry pick command for merged PR with multiple branches.
+
+        This test verifies that when cherry-picking to multiple branches on a merged PR:
+        1. cherry_pick is called for each target branch
+        2. Labels are added exactly once for each branch (not duplicated)
+        """
+        mock_pull_request = Mock()
+        mock_pull_request.title = "Test PR"
+
+        # Patch is_merged to return True (merged PR)
+        with patch.object(mock_pull_request, "is_merged", new=Mock(return_value=True)):
+            with patch.object(issue_comment_handler.repository, "get_branch"):
+                with patch.object(
+                    issue_comment_handler.runner_handler, "cherry_pick", new_callable=AsyncMock
+                ) as mock_cherry_pick:
+                    with patch.object(
+                        issue_comment_handler.labels_handler, "_add_label", new_callable=AsyncMock
+                    ) as mock_add_label:
+                        # Execute cherry-pick command with multiple branches
+                        await issue_comment_handler.process_cherry_pick_command(
+                            pull_request=mock_pull_request,
+                            command_args="branch1 branch2 branch3",
+                            reviewed_user="test-user",
+                        )
+
+                        # Verify cherry_pick was called for each branch
+                        assert mock_cherry_pick.call_count == 3
+                        mock_cherry_pick.assert_any_call(
+                            pull_request=mock_pull_request, target_branch="branch1", reviewed_user="test-user"
+                        )
+                        mock_cherry_pick.assert_any_call(
+                            pull_request=mock_pull_request, target_branch="branch2", reviewed_user="test-user"
+                        )
+                        mock_cherry_pick.assert_any_call(
+                            pull_request=mock_pull_request, target_branch="branch3", reviewed_user="test-user"
+                        )
+
+                        # Verify labels were added exactly once for each branch (not duplicated)
+                        assert mock_add_label.call_count == 3
+                        mock_add_label.assert_any_call(pull_request=mock_pull_request, label="cherry-pick-branch1")
+                        mock_add_label.assert_any_call(pull_request=mock_pull_request, label="cherry-pick-branch2")
+                        mock_add_label.assert_any_call(pull_request=mock_pull_request, label="cherry-pick-branch3")
 
     @pytest.mark.asyncio
     async def test_process_retest_command_no_target_tests(self, issue_comment_handler: IssueCommentHandler) -> None: