Module "textual.app" does not explicitly export attribute "CSSPathType"

[tconbeer]

There was a type checking regression in v0.28.0 that was introduced by this commit, which imported CSSPathType in app.py from _path.py, even though that was defined as a constant lower in the file. Since the import isn't exported, it removes the public interface for CSSPathType, which is needed to subclass App and replace App.__init__():

mypy doesn't like this. This will raise a type checking error in 0.28 (but not 0.27):

from textual.app import App, CSSPathType # error: Module "textual.app" does not explicitly export attribute "CSSPathType"  [attr-defined]

class MyApp(App, inherit_bindings=False):
    def __init__(
        self,
        foo: str,
        driver_class: Union[Type[Driver], None] = None,
        css_path: Union[CSSPathType, None] = None,
        watch_css: bool = False,
    ):
        super().__init__(driver_class, css_path, watch_css)
        self.foo = foo

[davep]

CSSPathType now lives in textual.types. The likes of mypy and pyright seem happy with this kind of code:

from __future__ import annotations

from textual.app import App, ComposeResult
from textual.widgets import Label
from textual.types import CSSPathType

class MyApp(App[None]):

    def __init__(self, css_path: CSSPathType | None ) -> None:
        super().__init__(css_path=css_path)

    def compose(self) -> ComposeResult:
        yield Label("Hello, World!")

if __name__ == "__main__":
    MyApp("foo.css").run()

[tconbeer]

Thanks. Couldn't find it with a code search

[davep]

For what it's worth, I only found the correct location by scanning through the PR you linked. ;-)

Looks like making this change clear was something left out of the CHANGELOG, so easily missed.

[willmcgugan]

Probably because it may have seemed like an internal detail at the time. You're right though. We should document these in the changelog.