landing_job: add method to show pr landing status (bug 2032164)

Author: zzzeid

src/lando/api/views.py

@@ -1,5 +1,4 @@
 import json
-from collections import defaultdict
 from datetime import datetime
 from functools import wraps
 from typing import Callable
@@ -21,7 +20,7 @@
     Revision,
     add_revisions_to_job,
 )
-from lando.main.models.landing_job import get_jobs_for_pull
+from lando.main.models.landing_job import get_pull_request_last_landing_job_status
 from lando.main.models.revision import DiffWarning, DiffWarningStatus
 from lando.main.scm import SCMType
 from lando.utils.github import GitHubAPIClient, PullRequest, PullRequestPatchHelper
@@ -200,26 +199,9 @@ def get(
         self, request: WSGIRequest, repo_name: int, pull_number: int
     ) -> JsonResponse:
         """Return the status of a pull request based on landing job counts."""
-
-        target_repo = Repo.objects.get(name=repo_name)
-        landing_jobs = get_jobs_for_pull(target_repo, pull_number)
-        landing_jobs_by_status = defaultdict(list)
-        for landing_job in landing_jobs:
-            landing_jobs_by_status[landing_job.status].append(landing_job.id)
-
-        status = None
-        # Return the first encountered status in this list.
-        for _status in [
-            JobStatus.LANDED,
-            JobStatus.CREATED,
-            JobStatus.SUBMITTED,
-            JobStatus.IN_PROGRESS,
-            JobStatus.FAILED,
-        ]:
-            if landing_jobs_by_status[_status]:
-                status = str(_status).lower()
-                break
-
+        status = str(
+            get_pull_request_last_landing_job_status(repo_name, pull_number)
+        ).lower()
         return JsonResponse({"status": status}, status=200)
 
     @method_decorator(require_authenticated_user)

src/lando/main/models/landing_job.py

@@ -1,5 +1,6 @@
 import datetime
 import logging
+from collections import defaultdict
 from collections.abc import Iterable
 from pathlib import Path
 from typing import Any
@@ -10,7 +11,7 @@
 from mots.config import FileConfig
 from mots.directory import Directory
 
-from lando.main.models.jobs import BaseJob
+from lando.main.models.jobs import BaseJob, JobStatus
 from lando.main.models.repo import Repo
 from lando.main.models.revision import Revision, RevisionLandingJob
 
@@ -304,6 +305,41 @@ def add_revisions_to_job(revisions: list[Revision], job: LandingJob):
     job.sort_revisions(revisions)
 
 
+def get_pull_request_last_landing_job_status(
+    repo_name: str, pull_number: int
+) -> JobStatus:
+    """Return a heuristically determined status based on related jobs."""
+    target_repo = Repo.objects.get(name=repo_name)
+    landing_jobs = get_jobs_for_pull(target_repo, pull_number)
+    landing_jobs_by_status = defaultdict(list)
+    for landing_job in landing_jobs:
+        landing_jobs_by_status[landing_job.status].append(landing_job.id)
+
+    # A LANDED status implies that the pull request has landed. A
+    # DEFERRED status implies that the last job has been deferred.
+    # For all other cases, there may be other permanently failed landing
+    # jobs that are no longer relevant to the status of the pull request as
+    # a whole.
+
+    # A CREATED status implies that the latest landing job is created.
+    # A SUBMITTED status implies that the latest landing job is submitted.
+    # An IN_PROGRESS status implies that the latest landing job is in progress.
+    # A FAILED status implies that the latest landing job has failed.
+
+    # Return the first encountered status in this list.
+    for _status in [
+        JobStatus.LANDED,
+        JobStatus.CREATED,
+        JobStatus.SUBMITTED,
+        JobStatus.IN_PROGRESS,
+        JobStatus.DEFERRED,
+        JobStatus.FAILED,
+        JobStatus.CANCELLED,
+    ]:
+        if landing_jobs_by_status[_status]:
+            return _status
+
+
 def get_jobs_for_pull(target_repo: Repo, pull_number: int) -> QuerySet[LandingJob]:
     """Given a target repo and a pull number, return all landing jobs."""
     revisions = Revision.objects.filter(