fix(worker): fallback to latest known default-branch parent when provider ancestry isn't in DB

apps/worker/services/repository.py

@@ -150,6 +150,31 @@ async def fetch_appropriate_parent_for_commit(
                 closest_parent_without_message = parent.commitid
         elements = parents
 
+    is_default_branch_commit = bool(
+        commit.branch
+        and getattr(commit.repository, "branch", None)
+        and commit.branch == commit.repository.branch
+    )
+
+    if is_default_branch_commit:
+        default_branch_fallback_query = db_session.query(Commit.commitid).filter(
+            Commit.repoid == commit.repoid,
+            Commit.commitid != commit.commitid,
+            Commit.branch == commit.branch,
+            ~Commit.message.is_(None),
+            ~Commit.deleted.is_(True),
+        )
+        if commit.timestamp is not None:
+            default_branch_fallback_query = default_branch_fallback_query.filter(
+                Commit.timestamp < commit.timestamp
+            )
+
+        default_branch_fallback = default_branch_fallback_query.order_by(
+            Commit.timestamp.desc()
+        ).first()
+        if default_branch_fallback:
+            return default_branch_fallback.commitid
+
     log.warning(
         "Unable to find a parent commit that was properly found on Github",
         extra={"commit": commit.commitid, "repoid": commit.repoid},

apps/worker/services/tests/test_repository_service.py

@@ -726,6 +726,81 @@ async def test_fetch_appropriate_parent_for_commit_multiple_parents(
     assert expected_result == result
 
 
+@pytest.mark.asyncio
+async def test_fetch_appropriate_parent_for_default_branch_commit_falls_back_to_latest_previous_known_commit_when_ancestors_unknown(
+    dbsession, mock_repo_provider
+):
+    repository = RepositoryFactory.create(branch="main")
+    latest_known_commit_id = "c" * 40
+    older_known_commit_id = "d" * 40
+
+    older_known_commit = CommitFactory.create(
+        commitid=older_known_commit_id,
+        repository=repository,
+        branch="main",
+        timestamp=datetime(2021, 3, 8),
+    )
+    latest_known_commit = CommitFactory.create(
+        commitid=latest_known_commit_id,
+        repository=repository,
+        branch="main",
+        timestamp=datetime(2021, 3, 9),
+    )
+    commit = CommitFactory.create(
+        parent_commit_id=None,
+        repository=repository,
+        branch="main",
+        timestamp=datetime(2021, 3, 10),
+    )
+    dbsession.add_all([older_known_commit, latest_known_commit, commit])
+    dbsession.flush()
+
+    git_commit = {"parents": ["a" * 40]}
+    mock_repo_provider.get_ancestors_tree.return_value = {
+        "commitid": commit.commitid,
+        "parents": [{"commitid": "a" * 40, "parents": []}],
+    }
+
+    result = await fetch_appropriate_parent_for_commit(
+        mock_repo_provider, commit, git_commit
+    )
+    assert result == latest_known_commit_id
+
+
+@pytest.mark.asyncio
+async def test_fetch_appropriate_parent_for_non_default_branch_commit_does_not_fallback_to_latest_previous_known_commit_when_ancestors_unknown(
+    dbsession, mock_repo_provider
+):
+    repository = RepositoryFactory.create(branch="main")
+    latest_known_commit_id = "c" * 40
+
+    latest_known_commit = CommitFactory.create(
+        commitid=latest_known_commit_id,
+        repository=repository,
+        branch="release",
+        timestamp=datetime(2021, 3, 9),
+    )
+    commit = CommitFactory.create(
+        parent_commit_id=None,
+        repository=repository,
+        branch="release",
+        timestamp=datetime(2021, 3, 10),
+    )
+    dbsession.add_all([latest_known_commit, commit])
+    dbsession.flush()
+
+    git_commit = {"parents": ["a" * 40]}
+    mock_repo_provider.get_ancestors_tree.return_value = {
+        "commitid": commit.commitid,
+        "parents": [{"commitid": "a" * 40, "parents": []}],
+    }
+
+    result = await fetch_appropriate_parent_for_commit(
+        mock_repo_provider, commit, git_commit
+    )
+    assert result is None
+
+
 @freeze_time("2024-03-28T00:00:00")
 def test_upsert_author_doesnt_exist(dbsession):
     service = "github"