Allow adding labels when a backport fails

patchback/_utils.py

@@ -0,0 +1,20 @@
+"""
+Misc. utility functions
+"""
+
+from __future__ import annotations
+
+from typing import TypeVar
+
+_T1 = TypeVar("_T1")
+_T2 = TypeVar("_T2")
+
+
+def strip_nones(mapping: dict[_T1, _T2 | None]) -> dict[_T1, _T2]:
+    """
+    Remove keys set to None from a dictionary
+
+    Returns:
+        A new dictionary instance
+    """
+    return {key: value for key, value in mapping.items() if value is not None}

patchback/config.py

@@ -11,6 +11,7 @@
 DEFAULT_BACKPORT_BRANCH_PREFIX = 'patchback/backports/'
 DEFAULT_BACKPORT_LABEL_PREFIX = 'backport-'
 DEFAULT_TARGET_BRANCH_PREFIX = ''
+DEFAULT_FAILED_BACKPORT_LABEL_PREFIX = 'failed-backport-'
 
 
 @attr.dataclass
@@ -30,6 +31,24 @@ class PatchbackConfig:
     )
     """Prefix that the older/stable version branch has."""
 
+    failed_label_prefix: str | None = attr.ib(default=DEFAULT_FAILED_BACKPORT_LABEL_PREFIX)
+    """
+    Add {failed_label_prefix}-{target_branch} label when backport fails.
+    {target_branch_prefix} is stripped from {target_branch}.
+    Set to None to disable adding a label on failure.
+    """
+
+    @failed_label_prefix.validator
+    def _v_failed_label_prefix(self, _, value: str | None) -> None:
+        """
+        Ensure backport_label_prefix and failed_label_prefix are different
+        to avoid infinite loops
+        """
+        if value == self.backport_label_prefix:
+            raise ValueError(
+                'failed_label_prefix and backport_label_prefix must be unique values'
+            )
+
 
 async def get_patchback_config(
         *,

patchback/event_handlers.py

@@ -1,10 +1,14 @@
 """Webhook event handlers."""
 
+from __future__ import annotations
+
 import http
+import functools
 import logging
 import pathlib
 import tempfile
 from subprocess import CalledProcessError, check_output, check_call
+from typing import Any
 
 from anyio import run_in_thread
 from gidgethub import BadRequest, ValidationError
@@ -18,6 +22,7 @@
 from .locking_api import LockingAPI
 from .config import get_patchback_config
 from .github_reporter import PullRequestReporter
+from .labels_api import IssueLabelsAPI, RepoLabelsAPI
 
 
 logger = logging.getLogger(__name__)
@@ -282,6 +287,9 @@ async def on_merge_of_labeled_pr(
             repository['pulls_url'],
             repository['full_name'],
             repository['clone_url'],
+            repo_config.backport_label_prefix,
+            repo_config.target_branch_prefix,
+            repo_config.failed_label_prefix,
         )
 
 
@@ -332,6 +340,9 @@ async def on_label_added_to_merged_pr(
         repository['pulls_url'],
         repository['full_name'],
         repository['clone_url'],
+        repo_config.backport_label_prefix,
+        repo_config.target_branch_prefix,
+        repo_config.failed_label_prefix,
     )
 
 
@@ -348,6 +359,9 @@ async def process_pr_backport_labels(
         backport_branch_prefix,
         pr_api_url, repo_slug,
         git_url,
+        backport_label_prefix: str,
+        target_branch_prefix: str,
+        failed_label_prefix: str | None,
 ) -> None:
     gh_api = RUNTIME_CONTEXT.app_installation_client
     checks_api = ChecksAPI(
@@ -366,6 +380,17 @@ async def process_pr_backport_labels(
         locking_api=locking_api,
         branch_name=target_branch,
     )
+    labels_api = RepoLabelsAPI(api=gh_api, repo_slug=repo_slug)
+    issue_labels_api = IssueLabelsAPI(api=gh_api, repo_slug=repo_slug, number=pr_number)
+    failed_label_cb = functools.partial(
+        add_failure_label,
+        labels_api=labels_api,
+        issue_labels_api=issue_labels_api,
+        backport_label_prefix=backport_label_prefix,
+        failed_label_prefix=failed_label_prefix,
+        target_branch_prefix=target_branch_prefix,
+        target_branch=target_branch,
+    )
 
     await pr_reporter.start_reporting(pr_head_sha, pr_number, pr_merge_commit)
 
@@ -396,6 +421,7 @@ async def process_pr_backport_labels(
             subtitle='💔 cherry-picking failed — target branch does not exist',
             summary=f'❌ {lu_err!s}',
         )
+        await failed_label_cb()
         return
     except ValueError as val_err:
         logger.info(
@@ -409,6 +435,7 @@ async def process_pr_backport_labels(
             text=manual_backport_guide,
             summary=f'❌ {val_err!s}',
         )
+        await failed_label_cb()
         return
     except PermissionError as perm_err:
         logger.info(
@@ -423,6 +450,7 @@ async def process_pr_backport_labels(
             text=manual_backport_guide,
             summary=f'❌ {perm_err!s}',
         )
+        await failed_label_cb()
         return
     else:
         logger.info('Backport PR branch: `%s`', backport_pr_branch)
@@ -461,6 +489,7 @@ async def process_pr_backport_labels(
             text=manual_backport_guide,
             summary=f'❌ {backport_pr_branch_msg}\n\n{val_err!s}',
         )
+        await failed_label_cb()
         return
     except BadRequest as bad_req_err:
         if (
@@ -480,6 +509,7 @@ async def process_pr_backport_labels(
             text=manual_backport_guide,
             summary=f'❌ {backport_pr_branch_msg}\n\n{bad_req_err!s}',
         )
+        await failed_label_cb()
         return
     else:
         logger.info('Created a PR @ %s', pr_resp['html_url'])
@@ -490,3 +520,31 @@ async def process_pr_backport_labels(
         text=f'Backported as {pr_resp["html_url"]}',
         summary=f'✅ {backport_pr_branch_msg!s}',
     )
+
+async def add_failure_label(
+    *,
+    labels_api: RepoLabelsAPI,
+    issue_labels_api: IssueLabelsAPI,
+    backport_label_prefix: str,
+    failed_label_prefix: str | None,
+    target_branch_prefix: str,
+    target_branch: str,
+) -> dict[str, Any] | None:
+    if failed_label_prefix is None:
+        return None
+    stripped_branch = target_branch[len(target_branch_prefix):]
+    label: str = failed_label_prefix + stripped_branch
+    backport_label = backport_label_prefix + stripped_branch
+    # Create label if it doesn't exist
+    try:
+        await labels_api.get_label(label)
+    except BadRequest as exc:
+        if exc.status_code != 404:
+            raise
+        await labels_api.create_label(
+            label, f'Failed to backport PR to {target_branch}.'
+        )
+    # Add failed label
+    await issue_labels_api.add_labels(label)
+    # Delete backport label
+    await issue_labels_api.remove_label(backport_label)

patchback/labels_api.py

@@ -0,0 +1,52 @@
+"""
+Wrappers around repository and issue label APIs
+"""
+
+from __future__ import annotations
+
+from collections.abc import AsyncIterator
+from typing import Any
+
+from gidgethub.abc import GitHubAPI
+
+from patchback._utils import strip_nones
+
+
+class RepoLabelsAPI:
+    def __init__(self, *, api: GitHubAPI, repo_slug: str) -> None:
+        self._api: GitHubAPI = api
+        self._labels_api = f"/repos/{repo_slug}/labels"
+
+    async def create_label(
+        self, name: str, description: str | None = None, color: str | None = None
+    ) -> dict[str, Any]:
+        return await self._api.post(
+            self._labels_api,
+            data=strip_nones(
+                {"name": name, "description": description, "color": color}
+            ),
+        )
+
+    def list_labels(self) -> AsyncIterator[dict[str, Any]]:
+        return self._api.getiter(self._labels_api)
+
+    async def get_label(self, name: str) -> dict[str, Any]:
+        return await self._api.getitem(f"{self._labels_api}/{name}")
+
+
+class IssueLabelsAPI:
+    def __init__(self, *, api: GitHubAPI, repo_slug: str, number: int) -> None:
+        self._api: GitHubAPI = api
+        self._issue_labels_api = f"/repos/{repo_slug}/issues/{number}/labels"
+
+    async def add_labels(self, *labels: str) -> list[dict[str, Any]]:
+        return await self._api.post(
+            self._issue_labels_api,
+            data={"labels": labels},
+        )
+
+    def list_labels(self) -> AsyncIterator[dict[str, Any]]:
+        return self._api.getiter(self._issue_labels_api)
+
+    async def remove_label(self, label: str) -> None:
+        return await self._api.delete(f"{self._issue_labels_api}/{label}")