[core, langchain] modelio code improvements (#15277)

libs/core/langchain_core/example_selectors/base.py

@@ -8,7 +8,7 @@ class BaseExampleSelector(ABC):
 
     @abstractmethod
     def add_example(self, example: Dict[str, str]) -> Any:
-        """Add new example to store for a key."""
+        """Add new example to store."""
 
     @abstractmethod
     def select_examples(self, input_variables: Dict[str, str]) -> List[dict]:

libs/core/langchain_core/output_parsers/__init__.py

@@ -3,7 +3,7 @@ from langchain_core.output_parsers.base import (
     BaseLLMOutputParser,
     BaseOutputParser,
 )
-from langchain_core.output_parsers.json import SimpleJsonOutputParser
+from langchain_core.output_parsers.json import JsonOutputParser, SimpleJsonOutputParser
 from langchain_core.output_parsers.list import (
     CommaSeparatedListOutputParser,
     ListOutputParser,
@@ -30,4 +30,5 @@ __all__ = [
     "BaseCumulativeTransformOutputParser",
     "SimpleJsonOutputParser",
     "XMLOutputParser",
+    "JsonOutputParser",
 ]

libs/core/langchain_core/output_parsers/format_instructions.py

@@ -0,0 +1,11 @@
+# flake8: noqa
+
+JSON_FORMAT_INSTRUCTIONS = """The output should be formatted as a JSON instance that conforms to the JSON schema below.
+
+As an example, for the schema {{"properties": {{"foo": {{"title": "Foo", "description": "a list of strings", "type": "array", "items": {{"type": "string"}}}}}}, "required": ["foo"]}}
+the object {{"foo": ["bar", "baz"]}} is a well-formatted instance of the schema. The object {{"properties": {{"foo": ["bar", "baz"]}}}} is not well-formatted.
+
+Here is the output schema:
+```
+{schema}
+```"""

libs/core/langchain_core/output_parsers/json.py

@@ -3,12 +3,14 @@ from __future__ import annotations
 import json
 import re
 from json import JSONDecodeError
-from typing import Any, Callable, List, Optional
+from typing import Any, Callable, List, Optional, Type
 
 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.pydantic_v1 import BaseModel
 
 
 def _replace_new_line(match: re.Match[str]) -> str:
@@ -170,7 +172,7 @@ def parse_and_check_json_markdown(text: str, expected_keys: List[str]) -> dict:
     return json_obj
 
 
-class SimpleJsonOutputParser(BaseCumulativeTransformOutputParser[Any]):
+class JsonOutputParser(BaseCumulativeTransformOutputParser[Any]):
     """Parse the output of an LLM call to a JSON object.
 
     When used in streaming mode, it will yield partial JSON objects containing
@@ -180,6 +182,8 @@ class SimpleJsonOutputParser(BaseCumulativeTransformOutputParser[Any]):
     describing the difference between the previous and the current object.
     """
 
+    pydantic_object: Optional[Type[BaseModel]] = None
+
     def _diff(self, prev: Optional[Any], next: Any) -> Any:
         return jsonpatch.make_patch(prev, next).patch
 
@@ -190,6 +194,26 @@ class SimpleJsonOutputParser(BaseCumulativeTransformOutputParser[Any]):
         except JSONDecodeError as e:
             raise OutputParserException(f"Invalid json output: {text}") from e
 
+    def get_format_instructions(self) -> str:
+        if self.pydantic_object is None:
+            return "Return a JSON object."
+        else:
+            schema = self.pydantic_object.schema()
+
+            # Remove extraneous fields.
+            reduced_schema = schema
+            if "title" in reduced_schema:
+                del reduced_schema["title"]
+            if "type" in reduced_schema:
+                del reduced_schema["type"]
+            # Ensure json in context is well-formed with double quotes.
+            schema_str = json.dumps(reduced_schema)
+            return JSON_FORMAT_INSTRUCTIONS.format(schema=schema_str)
+
     @property
     def _type(self) -> str:
         return "simple_json_output_parser"
+
+
+# For backwards compatibility
+SimpleJsonOutputParser = JsonOutputParser

libs/core/langchain_core/output_parsers/xml.py

@@ -34,7 +34,11 @@ class XMLOutputParser(BaseTransformOutputParser):
         return XML_FORMAT_INSTRUCTIONS.format(tags=self.tags)
 
     def parse(self, text: str) -> Dict[str, List[Any]]:
-        text = text.strip("`").strip("xml")
+        # Try to find XML string within triple backticks
+        match = re.search(r"```(xml)?(.*)```", text, re.DOTALL)
+        if match is not None:
+            # If match found, use the content within the backticks
+            text = match.group(2)
         encoding_match = self.encoding_matcher.search(text)
         if encoding_match:
             text = encoding_match.group(2)

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

@@ -13,6 +13,7 @@ EXPECTED_ALL = [
     "BaseCumulativeTransformOutputParser",
     "SimpleJsonOutputParser",
     "XMLOutputParser",
+    "JsonOutputParser",
 ]
 
 

libs/langchain/langchain/output_parsers/datetime.py

@@ -39,8 +39,12 @@ class DatetimeOutputParser(BaseOutputParser[datetime]):
 
     def get_format_instructions(self) -> str:
         examples = comma_list(_generate_random_datetime_strings(self.format))
-        return f"""Write a datetime string that matches the 
+        return (
-            following pattern: "{self.format}". Examples: {examples}"""
+            f"Write a datetime string that matches the "
+            f"following pattern: '{self.format}'.\n\n"
+            f"Examples: {examples}\n\n"
+            f"Return ONLY this string, no other words!"
+        )
 
     def parse(self, response: str) -> datetime:
         try: