langchain_openai: Make sure the response from the async client in the astream method of ChatOpenAI is properly awaited in case of "include_response_headers=True" (#26031)

- **Description:** This is a **one line change**. the
`self.async_client.with_raw_response.create(**payload)` call is not
properly awaited within the `_astream` method. In `_agenerate` this is
done already, but likely forgotten in the other method.
  - **Issue:** Not applicable
  - **Dependencies:** No dependencies required.

(If no one reviews your PR within a few days, please @-mention one of
baskaryan, efriis, eyurtsev, ccurme, vbarda, hwchase17.)

---------

Co-authored-by: Chester Curme <chester.curme@gmail.com>

libs/partners/openai/langchain_openai/chat_models/base.py

@@ -757,7 +757,7 @@ class BaseChatOpenAI(BaseChatModel):
             )
             return
         if self.include_response_headers:
-            raw_response = self.async_client.with_raw_response.create(**payload)
+            raw_response = await self.async_client.with_raw_response.create(**payload)
             response = raw_response.parse()
             base_generation_info = {"headers": dict(raw_response.headers)}
         else:

libs/partners/openai/tests/integration_tests/chat_models/test_base.py

@@ -686,15 +686,47 @@ def test_openai_proxy() -> None:
         assert proxy.port == 8080
 
 
-def test_openai_response_headers_invoke() -> None:
+def test_openai_response_headers() -> None:
     """Test ChatOpenAI response headers."""
     chat_openai = ChatOpenAI(include_response_headers=True)
-    result = chat_openai.invoke("I'm Pickle Rick")
+    query = "I'm Pickle Rick"
+    result = chat_openai.invoke(query, max_tokens=10)
     headers = result.response_metadata["headers"]
     assert headers
     assert isinstance(headers, dict)
     assert "content-type" in headers
 
+    # Stream
+    full: Optional[BaseMessageChunk] = None
+    for chunk in chat_openai.stream(query, max_tokens=10):
+        full = chunk if full is None else full + chunk
+    assert isinstance(full, AIMessage)
+    headers = full.response_metadata["headers"]
+    assert headers
+    assert isinstance(headers, dict)
+    assert "content-type" in headers
+
+
+async def test_openai_response_headers_async() -> None:
+    """Test ChatOpenAI response headers."""
+    chat_openai = ChatOpenAI(include_response_headers=True)
+    query = "I'm Pickle Rick"
+    result = await chat_openai.ainvoke(query, max_tokens=10)
+    headers = result.response_metadata["headers"]
+    assert headers
+    assert isinstance(headers, dict)
+    assert "content-type" in headers
+
+    # Stream
+    full: Optional[BaseMessageChunk] = None
+    async for chunk in chat_openai.astream(query, max_tokens=10):
+        full = chunk if full is None else full + chunk
+    assert isinstance(full, AIMessage)
+    headers = full.response_metadata["headers"]
+    assert headers
+    assert isinstance(headers, dict)
+    assert "content-type" in headers
+
 
 def test_image_token_counting_jpeg() -> None:
     model = ChatOpenAI(model="gpt-4o", temperature=0)