Mark unique constraint error checks as no cover

Author: jchristgit

pydis_site/apps/api/viewsets/bot/infraction.py

@@ -284,7 +284,12 @@ def create(self, request: HttpRequest, *args, **kwargs) -> Response:
         """
         try:
             return super().create(request, *args, **kwargs)
-        except IntegrityError as err:
+        except IntegrityError as err:  # pragma: no cover - see below
+            # Not covered: DRF handles this via `UniqueTogetherValidator` these
+            # days, which means it's hard to test this branch specifically.
+            # However, in a productive deployment, it's still very much
+            # possible for two concurrent inserts to run into IntegrityError.
+
             # We need to use `__cause__` here, as Django reraises the internal
             # UniqueViolation emitted by psycopg2 (which contains the attribute
             # that we actually need)

pydis_site/apps/api/viewsets/bot/user.py

@@ -395,7 +395,14 @@ def add_alt(self, request: Request, pk: str) -> Response:
                     raise ParseError(detail={
                         "source": ["The user may not be an alternate account of itself"]
                     })
-                if err.__cause__.diag.constraint_name == 'api_useraltrelationship_unique_relationships':
+                if (
+                    err.__cause__.diag.constraint_name == 'api_useraltrelationship_unique_relationships'
+                ):  # pragma: no cover - see below
+                    # This is not covered because newer DRF versions automatically validate this,
+                    # however the validation is done via a SELECT query which may race concurrent
+                    # inserts in prod. The only correct way is e.g. what Ecto does which is
+                    # associating the validators to the unique constraint errors to match in
+                    # errors, anything else may race.
                     raise ParseError(detail={
                         "source": ["This relationship has already been established"]
                     })