test(responses): fold the empty-choices regression tests into the mapped streaming iterator test file

tests/test_litellm/responses/litellm_completion_transformation/test_empty_choices_streaming_iterator.py

@@ -1,91 +0,0 @@
-"""
-Regression tests for LIT-4767.
-
-When an upstream OpenAI-compatible provider emits a chunk with ``choices: []``
-(the trailing usage-only chunk every provider sends when ``include_usage`` is
-set, or Azure's leading ``prompt_filter_results`` chunk), the Responses bridge
-iterator used to index ``choices[0]`` unguarded and die with
-``IndexError: list index out of range``, killing the whole stream.
-
-The empty-choices chunk must be tolerated without crashing, and the usage it
-carries must still reach ``response.completed``.
-"""
-
-from unittest.mock import AsyncMock
-
-from litellm.responses.litellm_completion_transformation.streaming_iterator import (
-    LiteLLMCompletionStreamingIterator,
-)
-from litellm.types.llms.openai import ResponsesAPIStreamEvents
-from litellm.types.utils import (
-    Delta,
-    ModelResponseStream,
-    StreamingChoices,
-    Usage,
-)
-
-
-def _iterator() -> LiteLLMCompletionStreamingIterator:
-    return LiteLLMCompletionStreamingIterator(
-        model="gpt-4o",
-        litellm_custom_stream_wrapper=AsyncMock(),
-        request_input="hi",
-        responses_api_request={},
-        custom_llm_provider="openai",
-    )
-
-
-def _empty_choices_usage_chunk() -> ModelResponseStream:
-    chunk = ModelResponseStream(id="chunk-usage", model="gpt-4o", choices=[])
-    chunk.usage = Usage(prompt_tokens=10, completion_tokens=5, total_tokens=15)
-    return chunk
-
-
-def test_ensure_output_item_for_empty_choices_chunk_does_not_crash():
-    """First chunk with no choices must not raise (traceback frame in the ticket)."""
-    iterator = _iterator()
-    # Would raise IndexError before the fix.
-    assert iterator._ensure_output_item_for_chunk(_empty_choices_usage_chunk()) is None
-    assert iterator.sent_output_item_added_event is False
-
-
-def test_transform_empty_choices_chunk_returns_no_delta():
-    """The mid/trailing usage chunk flows through transform without crashing."""
-    iterator = _iterator()
-    # Would raise IndexError in _get_delta_string_from_streaming_choices before the fix.
-    assert iterator._transform_chat_completion_chunk_to_response_api_chunk(_empty_choices_usage_chunk()) is None
-
-
-def test_is_reasoning_end_false_for_empty_choices_chunk():
-    iterator = _iterator()
-    assert iterator._is_reasoning_end(_empty_choices_usage_chunk()) is False
-
-
-def test_empty_choices_usage_chunk_still_reaches_response_completed():
-    """End-to-end: a text chunk followed by a choices=[] usage chunk must emit
-    response.completed carrying the usage rather than dying mid-stream."""
-
-    class _SyncWrapper:
-        def __init__(self, chunks):
-            self._it = iter(chunks)
-            self.logging_obj = None
-            self.stream_options = {"include_usage": True}
-
-        def __next__(self):
-            return next(self._it)
-
-    text_chunk = ModelResponseStream(
-        id="chunk-1",
-        model="gpt-4o",
-        choices=[StreamingChoices(index=0, delta=Delta(role="assistant", content="Hi"), finish_reason=None)],
-    )
-    iterator = _iterator()
-    iterator.litellm_logging_obj = None
-    iterator.litellm_custom_stream_wrapper = _SyncWrapper([text_chunk, _empty_choices_usage_chunk()])
-
-    events = list(iterator)
-
-    completed = [e for e in events if getattr(e, "type", None) == ResponsesAPIStreamEvents.RESPONSE_COMPLETED]
-    assert len(completed) == 1
-    assert completed[0].response.usage is not None
-    assert completed[0].response.usage.total_tokens == 15

tests/test_litellm/responses/litellm_completion_transformation/test_streaming_iterator_transformation.py

@@ -752,6 +752,49 @@ def test_completed_event_restores_usage_hidden_by_stream_options_none():
     assert completed.response.usage.output_tokens == 5
 
 
+def _empty_choices_chunk(usage: Usage | None = None) -> ModelResponseStream:
+    return ModelResponseStream(id=CHAT_COMPLETION_ID, model="claude-haiku-4-5", choices=[], usage=usage)
+
+
+@pytest.mark.asyncio
+async def test_leading_empty_choices_chunk_does_not_kill_the_stream():
+    """
+    Azure leads some streams with a `prompt_filter_results` chunk whose `choices` is empty.
+    The bridge used to index `choices[0]` on it and die before the first token.
+    """
+    iterator = _build_iterator([_empty_choices_chunk(), _chunk("Hello"), _chunk("!", finish_reason="stop")])
+
+    events = [event async for event in iterator]
+
+    event_types = [getattr(event, "type", None) for event in events]
+    assert event_types.count(ResponsesAPIStreamEvents.OUTPUT_ITEM_ADDED) == 1
+    assert "".join(event.delta for event in events if event.type == ResponsesAPIStreamEvents.OUTPUT_TEXT_DELTA) == "Hello!"
+    assert event_types[-1] == ResponsesAPIStreamEvents.RESPONSE_COMPLETED
+
+
+@pytest.mark.asyncio
+async def test_trailing_empty_choices_usage_chunk_reaches_response_completed():
+    """
+    With `stream_options.include_usage` (which the bridge always sets) the last upstream chunk
+    carries only usage and an empty `choices`. It must not crash the stream, and its usage must
+    still land on `response.completed`.
+    """
+    usage: Final = Usage(prompt_tokens=10, completion_tokens=5, total_tokens=15)
+    iterator = _build_iterator([_chunk("Hello"), _chunk("", finish_reason="stop"), _empty_choices_chunk(usage)])
+
+    events = [event async for event in iterator]
+
+    completed = next(
+        event for event in events if getattr(event, "type", None) == ResponsesAPIStreamEvents.RESPONSE_COMPLETED
+    )
+    assert completed.response.usage.input_tokens == 10
+    assert completed.response.usage.output_tokens == 5
+
+
+def test_is_reasoning_end_ignores_empty_choices_chunk():
+    assert _build_iterator([])._is_reasoning_end(_empty_choices_chunk()) is False
+
+
 def test_object_tool_call_arguments_stream_as_valid_json():
     """A provider that sends decoded object arguments must still stream valid JSON.