fix(BA-585): Empty tag image scan error in docker registry (#3533)

changes/3513.fix.md

@@ -0,0 +1 @@
+Fix empty tag image scan error in docker registry.

src/ai/backend/manager/container_registry/base.py

@@ -185,9 +185,12 @@ async def _scan_image(
         while tag_list_url is not None:
             async with sess.get(tag_list_url, **rqst_args) as resp:
                 data = json.loads(await resp.read())
-                if "tags" in data:
-                    # sometimes there are dangling image names in the hub.
-                    tags.extend(data["tags"])
+                tags_data = data.get("tags", [])
+                # sometimes there are dangling image names in the hub.
+                if not tags_data:
+                    break
+
+                tags.extend(tags_data)
                 tag_list_url = None
                 next_page_link = resp.links.get("next")
                 if next_page_link:

src/ai/backend/testutils/mock.py

@@ -1,6 +1,9 @@
+from typing import Any, Callable
 from unittest import mock
 from unittest.mock import AsyncMock
 
+from aioresponses import CallbackResult
+
 
 def mock_corofunc(return_value):
     """
@@ -155,3 +158,26 @@ async def __aenter__(self):
 
     async def __aexit__(self, exc_type, exc_val, exc_tb):
         pass
+
+
+def mock_aioresponses_sequential_payloads(
+    mock_responses: list[Any],
+) -> Callable[..., CallbackResult]:
+    """
+    Creates a callback function for aioresponses that sequentially returns mock responses.
+    On each invocation, the callback function returns the next mock response from the 'mock_value' list.
+    If the number of calls exceeds the length of 'mock_value', it raises an Exception to indicate that no more responses are available.
+    """
+    cb_call_counter = 0
+
+    def _callback(*args, **kwargs) -> CallbackResult:
+        nonlocal cb_call_counter
+
+        if cb_call_counter >= len(mock_responses):
+            raise Exception("No more mock responses left")
+
+        data = mock_responses[cb_call_counter]
+        cb_call_counter += 1
+        return CallbackResult(status=200, payload=data)
+
+    return _callback