textattack-nlp-transformer/textattack/constraints/grammaticality/language_tool.py

import language_tool_python

from textattack.constraints import Constraint


class LanguageTool(Constraint):
    """ 
        Uses languagetool to determine if two sentences have the same
        number of grammatical erors. 
        (https://languagetool.org/)
        
        Args:
            grammar_error_threshold (int): the number of additional errors permitted in x_adv
                relative to x
    """

    def __init__(self, grammar_error_threshold=0):
        self.lang_tool = language_tool_python.LanguageTool("en-US")
        self.grammar_error_threshold = grammar_error_threshold
        self.grammar_error_cache = {}

    def get_errors(self, tokenized_text, use_cache=False):
        text = tokenized_text.clean_text()
        if use_cache:
            if text not in self.grammar_error_cache:
                self.grammar_error_cache[text] = len(self.lang_tool.check(text))
            return self.grammar_error_cache[text]
        else:
            return len(self.lang_tool.check(text))

    def _check_constraint(self, transformed_text, current_text, original_text=None):
        original_num_errors = self.get_errors(original_text, use_cache=True)
        errors_added = self.get_errors(transformed_text) - original_num_errors
        return errors_added <= self.grammar_error_threshold

    def extra_repr_keys(self):
        return ["grammar_error_threshold"]