Add async tests and comments

libs/langchain/langchain/output_parsers/json.py

@@ -205,8 +205,10 @@ class PartialFunctionsJsonOutputParser(BaseCumulativeTransformOutputParser[Any])
     def _diff(self, prev: Optional[Any], next: Any) -> Any:
         return jsonpatch.make_patch(prev, next).patch
 
+    # This method would be called by the default implementation of `parse_result`
+    # but we're overriding that method so it's not needed.
     def parse(self, text: str) -> Any:
-        pass
+        raise NotImplementedError()
 
 
 class PartialJsonOutputParser(BaseCumulativeTransformOutputParser[Any]):

libs/langchain/langchain/schema/output_parser.py

@@ -340,6 +340,8 @@ class BaseCumulativeTransformOutputParser(BaseTransformOutputParser[T]):
     diff: bool = False
 
     def _diff(self, prev: Optional[T], next: T) -> T:
+        """Convert parsed outputs into a diff format. The semantics of this are
+        up to the output parser."""
         raise NotImplementedError()
 
     def _transform(self, input: Iterator[Union[str, BaseMessage]]) -> Iterator[Any]:

libs/langchain/tests/unit_tests/output_parsers/test_json.py

@@ -1,5 +1,5 @@
 import json
-from typing import Any, Iterator, Tuple
+from typing import Any, AsyncIterator, Iterator, Tuple
 
 import pytest
 
@@ -492,3 +492,51 @@ def test_partial_functions_json_output_parser_diff() -> None:
     chain = input_iter | PartialFunctionsJsonOutputParser(diff=True)
 
     assert list(chain.stream(None)) == EXPECTED_STREAMED_JSON_DIFF
+
+
+@pytest.mark.asyncio
+async def test_partial_text_json_output_parser_async() -> None:
+    async def input_iter(_: Any) -> AsyncIterator[str]:
+        for token in STREAMED_TOKENS:
+            yield token
+
+    chain = input_iter | PartialJsonOutputParser()
+
+    assert [p async for p in chain.astream(None)] == EXPECTED_STREAMED_JSON
+
+
+@pytest.mark.asyncio
+async def test_partial_functions_json_output_parser_async() -> None:
+    async def input_iter(_: Any) -> AsyncIterator[AIMessageChunk]:
+        for token in STREAMED_TOKENS:
+            yield AIMessageChunk(
+                content="", additional_kwargs={"function_call": {"arguments": token}}
+            )
+
+    chain = input_iter | PartialFunctionsJsonOutputParser()
+
+    assert [p async for p in chain.astream(None)] == EXPECTED_STREAMED_JSON
+
+
+@pytest.mark.asyncio
+async def test_partial_text_json_output_parser_diff_async() -> None:
+    async def input_iter(_: Any) -> AsyncIterator[str]:
+        for token in STREAMED_TOKENS:
+            yield token
+
+    chain = input_iter | PartialJsonOutputParser(diff=True)
+
+    assert [p async for p in chain.astream(None)] == EXPECTED_STREAMED_JSON_DIFF
+
+
+@pytest.mark.asyncio
+async def test_partial_functions_json_output_parser_diff_async() -> None:
+    async def input_iter(_: Any) -> AsyncIterator[AIMessageChunk]:
+        for token in STREAMED_TOKENS:
+            yield AIMessageChunk(
+                content="", additional_kwargs={"function_call": {"arguments": token}}
+            )
+
+    chain = input_iter | PartialFunctionsJsonOutputParser(diff=True)
+
+    assert [p async for p in chain.astream(None)] == EXPECTED_STREAMED_JSON_DIFF