Suggested diff for guardrails error handling

- ValidationError is now a subclass of Exception
- Each OutputParser can now declare its own subclass of ValidationError that people can reference in a catch statement

langchain/output_parsers/base.py

@@ -11,6 +11,12 @@ from langchain.schema import Fixer, Guardrail, PromptValue, ValidationError
 class BaseOutputParser(BaseModel, ABC):
     """Class to parse the output of an LLM call."""
 
+    Exception: ValidationError = ValidationError
+
+    @property
+    def Exception(self) -> ValidationError:
+        return self.__class__.Exception
+
     @abstractmethod
     def parse(self, text: str) -> Any:
         """Parse the output of an LLM call."""
@@ -41,7 +47,7 @@ class OutputGuardrail(Guardrail, BaseModel):
             self.output_parser.parse(result)
             return None
         except Exception as e:
-            return ValidationError(text=e)
+            return self.output_parser.Exception(text=e)
 
     def fix(
         self, prompt_value: PromptValue, result: Any, error: ValidationError

langchain/output_parsers/structured.py

@@ -7,6 +7,7 @@ from pydantic import BaseModel
 
 from langchain.output_parsers.base import BaseOutputParser
 from langchain.output_parsers.format_instructions import STRUCTURED_FORMAT_INSTRUCTIONS
+from langchain.schema import ValidationError
 
 line_template = '\t"{name}": {type}  // {description}'
 
@@ -22,7 +23,13 @@ def _get_sub_string(schema: ResponseSchema) -> str:
     )
 
 
+class StructuredOutputParserException(ValidationError):
+    pass
+
+
 class StructuredOutputParser(BaseOutputParser):
+    Exception = StructuredOutputParserException
+
     response_schemas: List[ResponseSchema]
 
     @classmethod

langchain/schema.py

@@ -5,6 +5,7 @@ from abc import ABC, abstractmethod
 from typing import Any, Dict, List, NamedTuple, Optional
 
 from pydantic import BaseModel, Extra, Field, root_validator
+from pydantic.dataclasses import dataclass
 
 
 class AgentAction(NamedTuple):
@@ -222,7 +223,8 @@ class BaseMemory(BaseModel, ABC):
 Memory = BaseMemory
 
 
-class ValidationError(BaseModel):
+@dataclass
+class ValidationError(Exception):
     error_message: str