[Responses] Decouple SSE event helpers from Harmony context (#35148)

Signed-off-by: sfeng33 <4florafeng@gmail.com>

tests/entrypoints/openai/responses/conftest.py

@@ -39,6 +39,7 @@ def pairs_of_event_types() -> dict[str, str]:
         "response.mcp_call.completed": "response.mcp_call.in_progress",
         "response.function_call_arguments.done": "response.function_call_arguments.delta", # noqa: E501
         "response.code_interpreter_call_code.done": "response.code_interpreter_call_code.delta", # noqa: E501
+        "response.code_interpreter_call.completed": "response.code_interpreter_call.in_progress", # noqa: E501
         "response.web_search_call.completed": "response.web_search_call.in_progress",
     }
     # fmt: on
@@ -108,29 +109,19 @@ def events_contain_type(events: list, type_substring: str) -> bool:
     return any(type_substring in getattr(e, "type", "") for e in events)
 
 
-def validate_streaming_event_stack(
-    events: list, pairs_of_event_types: dict[str, str]
-) -> None:
-    """Validate that streaming events are properly nested/paired."""
+def _validate_event_pairing(events: list, pairs_of_event_types: dict[str, str]) -> None:
+    """Validate that streaming events are properly nested/paired.
+
+    Derives push/pop sets from *pairs_of_event_types* so that every
+    start/end pair in the dict is handled automatically.
+    """
+    start_events = set(pairs_of_event_types.values())
+    end_events = set(pairs_of_event_types.keys())
+
     stack: list[str] = []
     for event in events:
         etype = event.type
-        if etype == "response.created":
-            stack.append(etype)
-        elif etype == "response.completed":
-            assert stack and stack[-1] == pairs_of_event_types[etype], (
-                f"Unexpected stack top for {etype}: "
-                f"got {stack[-1] if stack else '<empty>'}"
-            )
-            stack.pop()
-        elif etype.endswith("added") or etype == "response.mcp_call.in_progress":
-            stack.append(etype)
-        elif etype.endswith("delta"):
-            if stack and stack[-1] == etype:
-                continue
-            stack.append(etype)
-        elif etype.endswith("done") or etype == "response.mcp_call.completed":
-            assert etype in pairs_of_event_types, f"Unknown done event: {etype}"
+        if etype in end_events:
             expected_start = pairs_of_event_types[etype]
             assert stack and stack[-1] == expected_start, (
                 f"Stack mismatch for {etype}: "
@@ -138,9 +129,180 @@ def validate_streaming_event_stack(
                 f"got {stack[-1] if stack else '<empty>'}"
             )
             stack.pop()
+        elif etype in start_events:
+            # Consecutive deltas of the same type share a single stack slot.
+            if etype.endswith("delta") and stack and stack[-1] == etype:
+                continue
+            stack.append(etype)
+        # else: passthrough event (e.g. response.in_progress,
+        # web_search_call.searching, code_interpreter_call.interpreting)
     assert len(stack) == 0, f"Unclosed events on stack: {stack}"
 
 
+def _validate_event_ordering(events: list) -> None:
+    """Validate that envelope events appear in the correct positions."""
+    assert len(events) >= 2, f"Expected at least 2 events, got {len(events)}"
+
+    # First event must be response.created
+    assert events[0].type == "response.created", (
+        f"First event must be response.created, got {events[0].type}"
+    )
+    # Last event must be response.completed
+    assert events[-1].type == "response.completed", (
+        f"Last event must be response.completed, got {events[-1].type}"
+    )
+
+    # response.in_progress, if present, must be the second event
+    in_progress_indices = [
+        i for i, e in enumerate(events) if e.type == "response.in_progress"
+    ]
+    if in_progress_indices:
+        assert in_progress_indices == [1], (
+            f"response.in_progress must be the second event, "
+            f"found at indices {in_progress_indices}"
+        )
+
+    # Exactly one created and one completed
+    created_count = sum(1 for e in events if e.type == "response.created")
+    completed_count = sum(1 for e in events if e.type == "response.completed")
+    assert created_count == 1, (
+        f"Expected exactly 1 response.created, got {created_count}"
+    )
+    assert completed_count == 1, (
+        f"Expected exactly 1 response.completed, got {completed_count}"
+    )
+
+
+def _validate_field_consistency(events: list) -> None:
+    """Validate item_id, output_index, and content_index consistency.
+
+    Tracks the active output item established by ``output_item.added``
+    and verifies that all subsequent events for that item carry matching
+    identifiers until ``output_item.done`` closes it.
+    """
+    _SESSION_EVENTS = {
+        "response.created",
+        "response.in_progress",
+        "response.completed",
+    }
+
+    active_item_id: str | None = None
+    active_output_index: int | None = None
+    last_output_index: int = -1
+    active_content_index: int | None = None
+
+    for event in events:
+        etype = event.type
+
+        if etype in _SESSION_EVENTS:
+            continue
+
+        # --- output_item.added: opens a new item ------------------
+        if etype == "response.output_item.added":
+            item = getattr(event, "item", None)
+            output_index = getattr(event, "output_index", None)
+
+            assert item is not None, "output_item.added must have an item"
+            item_id = getattr(item, "id", None)
+            assert item_id, "output_item.added item must have an id"
+
+            # output_index must be non-decreasing across items
+            if output_index is not None:
+                assert output_index >= last_output_index, (
+                    f"output_index went backwards: {output_index} < {last_output_index}"
+                )
+                last_output_index = output_index
+
+            active_item_id = item_id
+            active_output_index = output_index
+            active_content_index = None
+            continue
+
+        # --- output_item.done: closes the active item -------------
+        if etype == "response.output_item.done":
+            item = getattr(event, "item", None)
+            output_index = getattr(event, "output_index", None)
+
+            assert item is not None, "output_item.done must have an item"
+            done_item_id = getattr(item, "id", None)
+
+            if active_item_id is not None and done_item_id:
+                assert done_item_id == active_item_id, (
+                    f"output_item.done item.id mismatch: "
+                    f"expected {active_item_id}, got {done_item_id}"
+                )
+            if active_output_index is not None and output_index is not None:
+                assert output_index == active_output_index, (
+                    f"output_item.done output_index mismatch: "
+                    f"expected {active_output_index}, got {output_index}"
+                )
+
+            active_item_id = None
+            active_output_index = None
+            active_content_index = None
+            continue
+
+        # --- content_part / reasoning_part added: sets content_index
+        if etype in (
+            "response.content_part.added",
+            "response.reasoning_part.added",
+        ):
+            _assert_item_fields(event, etype, active_item_id, active_output_index)
+            active_content_index = getattr(event, "content_index", None)
+            continue
+
+        # --- all other item-level events --------------------------
+        _assert_item_fields(event, etype, active_item_id, active_output_index)
+
+        # content_index (only meaningful on events that carry it)
+        content_index = getattr(event, "content_index", None)
+        if content_index is not None and active_content_index is not None:
+            assert content_index == active_content_index, (
+                f"{etype} content_index mismatch: "
+                f"expected {active_content_index}, got {content_index}"
+            )
+
+
+def _assert_item_fields(
+    event,
+    etype: str,
+    active_item_id: str | None,
+    active_output_index: int | None,
+) -> None:
+    """Check that *event*'s item_id and output_index match the active item."""
+    event_item_id = getattr(event, "item_id", None)
+    output_index = getattr(event, "output_index", None)
+
+    if active_item_id is not None and event_item_id is not None:
+        assert event_item_id == active_item_id, (
+            f"{etype} item_id mismatch: expected {active_item_id}, got {event_item_id}"
+        )
+    if active_output_index is not None and output_index is not None:
+        assert output_index == active_output_index, (
+            f"{etype} output_index mismatch: "
+            f"expected {active_output_index}, got {output_index}"
+        )
+
+
+def validate_streaming_event_stack(
+    events: list, pairs_of_event_types: dict[str, str]
+) -> None:
+    """Validate streaming events: pairing, ordering, and field consistency.
+
+    Checks three aspects:
+    1. **Event pairing** — start/end events are properly nested
+       (stack-based matching derived from *pairs_of_event_types*).
+    2. **Event ordering** — envelope events (``created``,
+       ``in_progress``, ``completed``) appear at the correct positions.
+    3. **Field consistency** — ``item_id``, ``output_index``, and
+       ``content_index`` are consistent across related events within
+       each output item's lifecycle.
+    """
+    _validate_event_pairing(events, pairs_of_event_types)
+    _validate_event_ordering(events)
+    _validate_field_consistency(events)
+
+
 def log_response_diagnostics(
     response,
     *,