chatperplexity stream-citations in additional kwargs

libs/community/langchain_community/chat_models/perplexity.py

@@ -223,15 +223,21 @@ def _stream(
         stream_resp = self.client.chat.completions.create(
             messages=message_dicts, stream=True, **params
         )
+        first_chunk = True
         for chunk in stream_resp:
             if not isinstance(chunk, dict):
                 chunk = chunk.dict()
             if len(chunk["choices"]) == 0:
                 continue
             choice = chunk["choices"][0]
+            citations = chunk.get("citations", [])
+
             chunk = self._convert_delta_to_message_chunk(
                 choice["delta"], default_chunk_class
             )
+            if first_chunk:
+                chunk.additional_kwargs |= {"citations": citations}
+                first_chunk = False
             finish_reason = choice.get("finish_reason")
             generation_info = (
                 dict(finish_reason=finish_reason) if finish_reason is not None else None

libs/community/tests/unit_tests/chat_models/test_perplexity.py

@@ -1,8 +1,12 @@
 """Test Perplexity Chat API wrapper."""
 
 import os
+from typing import Any, Dict, List, Optional
+from unittest.mock import MagicMock
 
 import pytest
+from langchain_core.messages import AIMessageChunk, BaseMessageChunk
+from pytest_mock import MockerFixture
 
 from langchain_community.chat_models import ChatPerplexity
 
@@ -40,3 +44,58 @@ def test_perplexity_initialization() -> None:
     ]:
         assert model.request_timeout == 1
         assert model.pplx_api_key == "test"
+
+
+@pytest.mark.requires("openai")
+def test_perplexity_stream_includes_citations(mocker: MockerFixture) -> None:
+    """Test that the stream method includes citations in the additional_kwargs."""
+    llm = ChatPerplexity(
+        model="test",
+        timeout=30,
+        verbose=True,
+    )
+    mock_chunk_0 = {
+        "choices": [
+            {
+                "delta": {
+                    "content": "Hello ",
+                },
+                "finish_reason": None,
+            }
+        ],
+        "citations": ["example.com", "example2.com"],
+    }
+    mock_chunk_1 = {
+        "choices": [
+            {
+                "delta": {
+                    "content": "Perplexity",
+                },
+                "finish_reason": None,
+            }
+        ],
+        "citations": ["example.com", "example2.com"],
+    }
+    mock_chunks: List[Dict[str, Any]] = [mock_chunk_0, mock_chunk_1]
+    mock_stream = MagicMock()
+    mock_stream.__iter__.return_value = mock_chunks
+    patcher = mocker.patch.object(
+        llm.client.chat.completions, "create", return_value=mock_stream
+    )
+    stream = llm.stream("Hello langchain")
+    full: Optional[BaseMessageChunk] = None
+    for i, chunk in enumerate(stream):
+        full = chunk if full is None else full + chunk
+        assert chunk.content == mock_chunks[i]["choices"][0]["delta"]["content"]
+        if i == 0:
+            assert chunk.additional_kwargs["citations"] == [
+                "example.com",
+                "example2.com",
+            ]
+        else:
+            assert "citations" not in chunk.additional_kwargs
+    assert isinstance(full, AIMessageChunk)
+    assert full.content == "Hello Perplexity"
+    assert full.additional_kwargs == {"citations": ["example.com", "example2.com"]}
+
+    patcher.assert_called_once()