flake8_patch_decorator.py

import ast
import tokenize

from sys import stdin

__version__ = '1.0.0'

PATCH_DECORATOR_ERROR_CODE = 'T002'
PATCH_DECORATOR_ERROR_MESSAGE = 'use of @patch found (use context manager instead)'


class PatchDecoratorChecker(object):
    name = 'flake8-patch-decorator'
    version = __version__
    ignores = ()

    def __init__(self, tree, filename='(none)', builtins=None):
        self.tree = tree
        self.filename = (filename == 'stdin' and stdin) or filename

    def run(self):
        # Get lines to ignore
        if self.filename == stdin:
            noqa = _get_noqa_lines(self.filename)
        else:
            with open(self.filename, 'r') as file_to_check:
                noqa = _get_noqa_lines(file_to_check.readlines())

        errors = []
        for node in ast.walk(self.tree):
            if isinstance(node, ast.FunctionDef) and hasattr(node, 'decorator_list') and node.decorator_list:
                for decorator in node.decorator_list:
                    if isinstance(decorator, ast.Call) and isinstance(decorator.func, ast.Name) and \
                            decorator.func.id == 'patch' and decorator.lineno not in noqa:
                        errors.append({
                            "message": '{0} {1}'.format(PATCH_DECORATOR_ERROR_CODE, PATCH_DECORATOR_ERROR_MESSAGE),
                            "line": decorator.lineno,
                            "col": decorator.col_offset
                        })

        # Yield the found errors
        for error in errors:
            yield (error.get("line"), error.get("col"), error.get("message"), type(self))


def _get_noqa_lines(code):
    tokens = tokenize.generate_tokens(lambda L=iter(code): next(L))
    return [token[2][0] for token in tokens if token[0] == tokenize.COMMENT and
            (token[1].endswith('noqa') or (isinstance(token[0], str) and token[0].endswith('noqa')))]