jsonrescue 1.0.3

A library to parse and repair malformed JSON-like text.

JSON Rescue

Overview

JSON Rescue is a robust Python library designed to parse and repair malformed JSON-like text, specifically targeting common errors found in AI model responses that fail to return valid JSON. The library employs heuristics to identify, fix, and validate JSON structures against a provided schema, ensuring data consistency and correctness.

Features

• Bracket Matching and Extraction: Uses advanced regex patterns to identify JSON-like structures within a text, even when nested.
• Schema Validation: Ensures the parsed JSON adheres to a defined schema using a customizable Schema class.
• Error Recovery: Attempts to fix common JSON errors, including:
  • Missing or unquoted keys.
  • Unquoted or improperly formatted string values.
  • Missing or extra brackets.
  • Escaping illegal characters.
• Customizable Fixes: Implements modular methods for fixing specific JSON issues.

Installation

pip install jsonrescue

Usage

Example

from jsonrescue.custom_schema import Schema
from jsonrescue.parser import Parser

# Define a schema for validation
schema = Schema(
    type='object',
    properties={
        'name': Schema(type='string'),
        'age': Schema(type='number'),
        'emails': Schema(type='array', items=Schema(type='string'))
    },
    required=['name', 'age']
)

parser = Parser(schema)

malformed_json = """
{
    name: John Doe,
    age: 30,
    emails: ['[e-mail]']
}
"""

parsed_data = parser.rescue(malformed_json)

if parsed_data:
    print("Valid JSON:", parsed_data)
else:
    print("Failed to parse JSON")

Examples of Errors Handled

1. Missing Quotes Around Keys or Values:
   • Input: {name: John Doe, age: 22}
   • Output: {"name": "John Doe", "age": 22}
2. Additional Text Around Object:
   • Input: Here is your result:\n{name: John Doe, age: 22}\n\nThank you!
   • Output: {"name": "John Doe", "age": 22}
3. Unescaped Quotes Within Values:
   • Input: {"name": "John "Deere" Doe", "age": 30}
   • Output: {"name": "John \"Deere\" Doe", "age": 30}
4. Fixing Broken Endings - adds missing double-quotes as well as ending brackets:
   • Input: {"name": "Bob", "age": 35, "emails": ["[e-mail]
   • Output: {"name": "Bob", "age": 35, "emails": ["[e-mail]"]}
5. Handling Multiple Objects in Text: - even when without commas seperating the objects
   • Input: {"name": "Dana", "age": 27}{"name": "Chris", "age": 35}
   • Output: {"name": "Dana", "age": 27} (Picks first valid object parsed if schema was an object) or
   • Alternative Output: [{"name": "Dana", "age": 27},{"name": "Chris", "age": 35}] (if schema was an array or if no schema was provided)
6. Handling Arrays When Object Expected:
   • Input: [{"name": "Alice", "age": 28}]
   • Output: {"name": "Alice", "age": 28}
7. Handling Object When Array Expected:
   • Input: {"name": "Alice", "age": 28}
   • Output: [{"name": "Alice", "age": 28}]

Key Components

Class: Parser

Initialization

Parser(schema: Schema)

• schema: An instance of the Schema class defining the expected JSON structure. To parse the text for JSON without any expected structure, simply skip defining the Schema

Methods

1. rescue(text: str) -> Any

   • Attempts to parse the input text as JSON.
   • Validates against the provided schema.

2. extract_json_candidates(text: str) -> List[str]

   • Extracts potential JSON substrings from the input text using a bracket-matching regex.

3. fix_json(json_str: str) -> str

   • Applies a sequence of fixes to a JSON string.

4. fix_keys(json_str: str) -> str

   • Quotes unquoted object keys.

5. fix_string_values(json_str: str) -> str

   • Quotes unquoted string values.

6. escape_illegal_characters(json_str: str) -> str

   • Escapes problematic characters like newlines, tabs, and unescaped quotes.

7. ensure_ending_brackets(json_str: str) -> str

   • Fixes mismatched or missing brackets.

8. insert_missing_commas(json_str: str) -> str

   • Insert commas between adjacent objects/arrays

Advanced Configuration

The library allows customization and extension by overriding its methods for specific JSON-repair scenarios. For example, you can add custom regex patterns or post-processing logic as needed.

Limitations

• The parser assumes input text contains at least one valid JSON-like structure. Extremely malformed input may result in parsing failures.
• It relies on heuristics to fix errors, which may not always produce the intended results.

Testing

The project includes a suite of unit tests to validate its functionality. To run the tests:

python -m unittest test.py

Example Test Cases

• Proper JSON:

  input_text = '{"name": "John Doe", "age": 30, "emails": ["[e-mail]"]}'
  expected = {"name": "John Doe", "age": 30, "emails": ["[e-mail]"]}
  

• Missing Required Field:

  input_text = '{"name": "Test", "emails": ["[e-mail]"]}'
  assert parser_with_schema.rescue(input_text) is None
  

• Incomplete Brackets:

  input_text = 'Start {"name": "Bob", "age": 35, "emails": ["[e-mail]"'
  expected = {"name": "Bob", "age": 35, "emails": ["[e-mail]"]}
  

Contributing

Contributions are welcome! Please fork the repository and submit a pull request with your changes.

License

This project is licensed under the MIT License.