Make it easy for third party patch to support pyproject.toml

[waketzheng]

I use pyproject-flake8 to make flake8 support pyproject.toml

For flake8>=5.0, code have to be:

class FixFilenames(ast.NodeTransformer):
    tuple_of_interest = ("setup.cfg", "tox.ini", ".flake8")

    modern = sys.version_info[0] >= 3 and sys.version_info[1] > 7

    inner_type = ast.Constant if modern else ast.Str
    inner_type_field = "value" if modern else "s"

    fix_applied = False

    def visit_Tuple(self, node: ast.Tuple) -> ast.Tuple:
        if all(isinstance(el, self.inner_type) for el in node.elts) and set(
            self.tuple_of_interest
        ) == {getattr(el, self.inner_type_field) for el in node.elts}:
            node.elts.append(
                self.inner_type(**{self.inner_type_field: "pyproject.toml"})
            )
            ast.fix_missing_locations(node)
            self.fix_applied = True
        return node
    ...

But if there is a var as: CONFIG_FILES = ("setup.cfg", "tox.ini", ".flake8")
Code of the pyproject-flake8 patch to extend config files can be as simple as:

flake8.options.config.CONFIG_FILES += ('pyproject.toml',)

[asottile]

dupe #1634