try to improve code coverage

google/cloud/bigquery/_job_helpers.py

@@ -169,26 +169,27 @@ def do_query():
         else:
             return query_job
 
-    if job_retry is None:
-        future = do_query()
-    else:
-        # Per https://github.com/googleapis/python-bigquery/issues/2134, sometimes
-        # we get a 404 error. In this case, if we get this far, assume that the job
-        # doesn't actually exist and try again. We can't add 404 to the default
-        # job_retry because that happens for errors like "this table does not
-        # exist", which probably won't resolve with a retry.
+    if job_retry is not None:
+
         def do_query_predicate(exc) -> bool:
             if isinstance(exc, core_exceptions.RetryError):
                 exc = exc.cause
 
+            # Per https://github.com/googleapis/python-bigquery/issues/2134, sometimes
+            # we get a 404 error. In this case, if we get this far, assume that the job
+            # doesn't actually exist and try again. We can't add 404 to the default
+            # job_retry because that happens for errors like "this table does not
+            # exist", which probably won't resolve with a retry.
             if isinstance(exc, core_exceptions.NotFound):
                 return True
 
             # Reference the original job_retry to avoid recursion.
             return job_retry._predicate(exc)
 
         do_query_retry = job_retry.with_predicate(do_query_predicate)
-        future = do_query_retry(do_query)()
+        do_query = do_query_retry(do_query)
+
+    future = do_query()
 
     # The future might be in a failed state now, but if it's
     # unrecoverable, we'll find out when we ask for it's result, at which

tests/unit/test_client.py

@@ -5311,6 +5311,36 @@ def test_query_job_rpc_fail_w_conflict_random_id_job_fetch_fails(self):
             with pytest.raises(DataLoss, match="we lost your job, sorry"):
                 client.query("SELECT 1;", job_id=None)
 
+    def test_query_job_rpc_fail_w_conflict_random_id_job_fetch_fails_no_retries(self):
+        from google.api_core.exceptions import Conflict
+        from google.api_core.exceptions import DataLoss
+        from google.cloud.bigquery.job import QueryJob
+
+        creds = _make_credentials()
+        http = object()
+        client = self._make_one(project=self.PROJECT, credentials=creds, _http=http)
+
+        job_create_error = Conflict("Job already exists.")
+        job_begin_patcher = mock.patch.object(
+            QueryJob, "_begin", side_effect=job_create_error
+        )
+        get_job_patcher = mock.patch.object(
+            client, "get_job", side_effect=DataLoss("we lost your job, sorry")
+        )
+
+        with job_begin_patcher, get_job_patcher:
+            # If get job request fails but supposedly there does exist a job
+            # with this ID already, raise the exception explaining why we
+            # couldn't recover the job.
+            with pytest.raises(DataLoss, match="we lost your job, sorry"):
+                client.query(
+                    "SELECT 1;",
+                    job_id=None,
+                    # Explicitly test with no retries to make sure those branches are covered.
+                    retry=None,
+                    job_retry=None,
+                )
+
     def test_query_job_rpc_fail_w_conflict_random_id_job_fetch_retries_404(self):
         """Regression test for https://github.com/googleapis/python-bigquery/issues/2134