api.views: add try push handover functionality (bug 2002566)

- add functionality that adds try_task_config.json file
- update landing worker to process handover jobs
- add PullRequestTryLintAPIView
- add LandingJob.handover_repo field and migrations
- add Repo.is_try helper method

Author: zzzeid

src/lando/api/legacy/workers/landing_worker.py

@@ -1,4 +1,5 @@
 import configparser
+import json
 import logging
 import subprocess
 from pathlib import Path
@@ -168,6 +169,19 @@ def run_job(self, job: LandingJob) -> bool:
 
         return True
 
+    def add_try_task_config(self, scm: AbstractSCM):
+        with (Path(scm.path) / "try_task_config.json").open("x") as f:
+            content = json.dumps(
+                {
+                    "parameters": {
+                        "optimize_target_tasks": True,
+                        "target_tasks_method": "codereview",
+                    },
+                    "version": 2,
+                }
+            )
+            f.write(content)
+
     def convert_patches_to_diff(self, scm: AbstractSCM, job: LandingJob):
         """Generate a unified diff from multiple patches stored in a revision."""
         # NOTE: this only applies to git patches that are downloaded from GitHub
@@ -215,10 +229,31 @@ def apply_patch(revision: Revision):
 
         self.update_repo(repo, job, scm, job.target_commit_hash)
 
+        if job.is_pull_request_job and job.handover_repo and job.handover_repo.is_try:
+            self.add_try_task_config(scm)
+            self.convert_patches_to_diff(scm, job)
+            job.target_repo = job.handover_repo
+            job.handover_repo = None
+            job.save()
+            job.revisions.update(pull_number=None)
+            message = "Job deferred to try repo."
+            job.transition_status(JobAction.DEFER, message=message)
+            raise TemporaryFailureException(message)
+
         if job.is_pull_request_job:
+            if job.handover_repo and job.handover_repo.is_try:
+                self.add_try_task_config(scm)
             self.convert_patches_to_diff(scm, job)
             self.update_repo(repo, job, scm, job.target_commit_hash)
 
+            try:
+                try_repo = Repo.objects.get(name="try")
+            except Repo.DoesNotExist:
+                pass
+            else:
+                if job.target_repo == try_repo:
+                    self.add_try_task_config(job)
+
         # Run through the patches one by one and try to apply them.
         logger.debug(
             f"About to land {job.revisions.count()} revisions: {job.revisions.all()} ..."

src/lando/api/views.py

@@ -287,3 +287,42 @@ def get(self, request: WSGIRequest, repo_name: str, number: int) -> JsonResponse
             target_repo, pull_request, request
         )
         return JsonResponse(warnings_and_blockers)
+
+
+class PullRequestTryLintAPIView(APIView):
+    @method_decorator(require_authenticated_user)
+    def post(
+        self, request: WSGIRequest, repo_name: str, pull_number: int
+    ) -> JsonResponse:
+        try:
+            try_repo = Repo.objects.get(name="try")
+        except Repo.DoesNotExist:
+            return JsonResponse({"errors": ["Try repo does not exist"]}, 500)
+
+        target_repo = Repo.objects.get(name=repo_name)
+        client = GitHubAPIClient(target_repo.url)
+        ldap_username = request.user.email
+        pull_request = client.build_pull_request(pull_number)
+
+        job = LandingJob.objects.create(
+            target_repo=target_repo,
+            handover_repo=try_repo,
+            requester_email=ldap_username,
+        )
+        author_name, author_email = pull_request.author
+        patch_data = {
+            "author_name": author_name,
+            "author_email": author_email,
+            "commit_message": pull_request.commit_message,
+            "timestamp": int(datetime.now().timestamp()),
+        }
+        revision = Revision.objects.create(
+            pull_number=pull_request.number,
+            patches=pull_request.patch,
+            patch_data=patch_data,
+        )
+        add_revisions_to_job([revision], job)
+        job.status = JobStatus.SUBMITTED
+        job.save()
+
+        return JsonResponse({"id": job.id}, status=201)

src/lando/main/migrations/0038_landingjob_handover_repo.py

@@ -0,0 +1,25 @@
+# Generated by Django 5.2.8 on 2025-12-05 19:40
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("main", "0037_repo_pr_enabled"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="landingjob",
+            name="handover_repo",
+            field=models.ForeignKey(
+                blank=True,
+                null=True,
+                on_delete=django.db.models.deletion.SET_NULL,
+                related_name="handover_jobs",
+                to="main.repo",
+            ),
+        ),
+    ]

src/lando/main/models/landing_job.py

@@ -46,6 +46,17 @@ class LandingJob(BaseJob):
         Revision, through="RevisionLandingJob", related_name="landing_jobs"
     )
 
+    # Reference to the handover repo. A handover repo is a repo that a landing
+    # job is handed over to after being processed in a previous state. If this value
+    # is set, the job will be processed twice, but pushed once.
+    handover_repo = models.ForeignKey(
+        Repo,
+        on_delete=models.SET_NULL,
+        null=True,
+        blank=True,
+        related_name="handover_jobs",
+    )
+
     @property
     def is_pull_request_job(self) -> bool:
         """Return True if all revisions in the landing job have a pull_number set."""

src/lando/main/models/repo.py

@@ -97,6 +97,10 @@ class HooksChoices(models.TextChoices):
     def path(self) -> str:
         return str(self.system_path) or self.get_system_path()
 
+    @property
+    def is_try(self) -> bool:
+        return self.name == "try"
+
     # TODO: help text for fields below.
     name = models.CharField(max_length=255, unique=True)
     default_branch = models.CharField(max_length=255, default="", blank=True)

src/lando/urls.py

@@ -23,6 +23,7 @@
     LandingJobPullRequestAPIView,
     LegacyDiffWarningView,
     PullRequestChecksAPIView,
+    PullRequestTryLintAPIView,
     git2hgCommitMapView,
     hg2gitCommitMapView,
 )
@@ -103,6 +104,11 @@
         LandingJobPullRequestAPIView.as_view(),
         name="api-landing-job-pull-request",
     ),
+    path(
+        "api/pulls/<str:repo_name>/<int:pull_number>/try_jobs",
+        PullRequestTryLintAPIView.as_view(),
+        name="api-try-job-pull-request",
+    ),
     path(
         "api/pulls/<str:repo_name>/<int:number>/checks",
         PullRequestChecksAPIView.as_view(),