Source code for langchain_core.utils.json

from __future__ import annotations

import json
import re
from typing import Any, Callable, List

from langchain_core.exceptions import OutputParserException


def _replace_new_line(match: re.Match[str]) -> str:
    value = match.group(2)
    value = re.sub(r"\n", r"\\n", value)
    value = re.sub(r"\r", r"\\r", value)
    value = re.sub(r"\t", r"\\t", value)
    value = re.sub(r'(?<!\\)"', r"\"", value)

    return match.group(1) + value + match.group(3)


def _custom_parser(multiline_string: str) -> str:
    """
    The LLM response for `action_input` may be a multiline
    string containing unescaped newlines, tabs or quotes. This function
    replaces those characters with their escaped counterparts.
    (newlines in JSON must be double-escaped: `\\n`)
    """
    if isinstance(multiline_string, (bytes, bytearray)):
        multiline_string = multiline_string.decode()

    multiline_string = re.sub(
        r'("action_input"\:\s*")(.*?)(")',
        _replace_new_line,
        multiline_string,
        flags=re.DOTALL,
    )

    return multiline_string


# Adapted from https://github.com/KillianLucas/open-interpreter/blob/5b6080fae1f8c68938a1e4fa8667e3744084ee21/interpreter/utils/parse_partial_json.py
# MIT License


[docs]def parse_partial_json(s: str, *, strict: bool = False) -> Any: """Parse a JSON string that may be missing closing braces. Args: s: The JSON string to parse. strict: Whether to use strict parsing. Defaults to False. Returns: The parsed JSON object as a Python dictionary. """ # Attempt to parse the string as-is. try: return json.loads(s, strict=strict) except json.JSONDecodeError: pass # Initialize variables. new_s = "" stack = [] is_inside_string = False escaped = False # Process each character in the string one at a time. for char in s: if is_inside_string: if char == '"' and not escaped: is_inside_string = False elif char == "\n" and not escaped: char = "\\n" # Replace the newline character with the escape sequence. elif char == "\\": escaped = not escaped else: escaped = False else: if char == '"': is_inside_string = True escaped = False elif char == "{": stack.append("}") elif char == "[": stack.append("]") elif char == "}" or char == "]": if stack and stack[-1] == char: stack.pop() else: # Mismatched closing character; the input is malformed. return None # Append the processed character to the new string. new_s += char # If we're still inside a string at the end of processing, # we need to close the string. if is_inside_string: new_s += '"' # Try to parse mods of string until we succeed or run out of characters. while new_s: final_s = new_s # Close any remaining open structures in the reverse # order that they were opened. for closing_char in reversed(stack): final_s += closing_char # Attempt to parse the modified string as JSON. try: return json.loads(final_s, strict=strict) except json.JSONDecodeError: # If we still can't parse the string as JSON, # try removing the last character new_s = new_s[:-1] # If we got here, we ran out of characters to remove # and still couldn't parse the string as JSON, so return the parse error # for the original string. return json.loads(s, strict=strict)
[docs]def parse_json_markdown( json_string: str, *, parser: Callable[[str], Any] = parse_partial_json ) -> dict: """ Parse a JSON string from a Markdown string. Args: json_string: The Markdown string. Returns: The parsed JSON object as a Python dictionary. """ try: return _parse_json(json_string, parser=parser) except json.JSONDecodeError: # Try to find JSON string within triple backticks match = re.search(r"```(json)?(.*)", json_string, re.DOTALL) # If no match found, assume the entire string is a JSON string if match is None: json_str = json_string else: # If match found, use the content within the backticks json_str = match.group(2) return _parse_json(json_str, parser=parser)
def _parse_json( json_str: str, *, parser: Callable[[str], Any] = parse_partial_json ) -> dict: # Strip whitespace and newlines from the start and end json_str = json_str.strip().strip("`") # handle newlines and other special characters inside the returned value json_str = _custom_parser(json_str) # Parse the JSON string into a Python dictionary return parser(json_str)
[docs]def parse_and_check_json_markdown(text: str, expected_keys: List[str]) -> dict: """ Parse a JSON string from a Markdown string and check that it contains the expected keys. Args: text: The Markdown string. expected_keys: The expected keys in the JSON string. Returns: The parsed JSON object as a Python dictionary. """ try: json_obj = parse_json_markdown(text) except json.JSONDecodeError as e: raise OutputParserException(f"Got invalid JSON object. Error: {e}") for key in expected_keys: if key not in json_obj: raise OutputParserException( f"Got invalid return object. Expected key `{key}` " f"to be present, but got {json_obj}" ) return json_obj