[core] add test for json parser (#15297)

this should fail, but isnt

---------

Co-authored-by: Nuno Campos <nuno@langchain.dev>

libs/core/langchain_core/output_parsers/json.py

@@ -10,6 +10,7 @@ import jsonpatch  # type: ignore[import]
 from langchain_core.exceptions import OutputParserException
 from langchain_core.output_parsers.format_instructions import JSON_FORMAT_INSTRUCTIONS
 from langchain_core.output_parsers.transform import BaseCumulativeTransformOutputParser
+from langchain_core.outputs import Generation
 from langchain_core.pydantic_v1 import BaseModel
 
 
@@ -106,11 +107,7 @@ def parse_partial_json(s: str, *, strict: bool = False) -> Any:
         new_s += closing_char
 
     # Attempt to parse the modified string as JSON.
-    try:
-        return json.loads(new_s, strict=strict)
-    except json.JSONDecodeError:
-        # If we still can't parse the string as JSON, return None to indicate failure.
-        return None
+    return json.loads(new_s, strict=strict)
 
 
 def parse_json_markdown(
@@ -187,12 +184,22 @@ class JsonOutputParser(BaseCumulativeTransformOutputParser[Any]):
     def _diff(self, prev: Optional[Any], next: Any) -> Any:
         return jsonpatch.make_patch(prev, next).patch
 
-    def parse(self, text: str) -> Any:
+    def parse_result(self, result: List[Generation], *, partial: bool = False) -> Any:
+        text = result[0].text
         text = text.strip()
-        try:
-            return parse_json_markdown(text.strip())
-        except JSONDecodeError as e:
-            raise OutputParserException(f"Invalid json output: {text}") from e
+        if partial:
+            try:
+                return parse_json_markdown(text)
+            except JSONDecodeError:
+                return None
+        else:
+            try:
+                return parse_json_markdown(text)
+            except JSONDecodeError as e:
+                raise OutputParserException(f"Invalid json output: {text}") from e
+
+    def parse(self, text: str) -> Any:
+        return self.parse_result([Generation(text=text)])
 
     def get_format_instructions(self) -> str:
         if self.pydantic_object is None:

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

@@ -487,3 +487,9 @@ async def test_partial_text_json_output_parser_diff_async() -> None:
     chain = input_iter | SimpleJsonOutputParser(diff=True)
 
     assert [p async for p in chain.astream(None)] == EXPECTED_STREAMED_JSON_DIFF
+
+
+def test_raises_error() -> None:
+    parser = SimpleJsonOutputParser()
+    with pytest.raises(Exception):
+        parser.invoke("hi")

libs/langchain/langchain/output_parsers/openai_functions.py

@@ -78,17 +78,20 @@ class JsonOutputFunctionsParser(BaseCumulativeTransformOutputParser[Any]):
                 raise OutputParserException(f"Could not parse function call: {exc}")
         try:
             if partial:
-                if self.args_only:
-                    return parse_partial_json(
-                        function_call["arguments"], strict=self.strict
-                    )
-                else:
-                    return {
-                        **function_call,
-                        "arguments": parse_partial_json(
+                try:
+                    if self.args_only:
+                        return parse_partial_json(
                             function_call["arguments"], strict=self.strict
-                        ),
-                    }
+                        )
+                    else:
+                        return {
+                            **function_call,
+                            "arguments": parse_partial_json(
+                                function_call["arguments"], strict=self.strict
+                            ),
+                        }
+                except json.JSONDecodeError:
+                    return None
             else:
                 if self.args_only:
                     try: