Merge pull request Textualize#5190 from Textualize/fix-focus-within

fixed focus-within

Author: willmcgugan

CHANGELOG.md

@@ -5,6 +5,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## Unreleased
+
+- Fixed broken focus-within https://github.com/Textualize/textual/pull/5190
+
 ## [0.85.1] - 2024-10-26
 
 ### Fixed

src/textual/css/stylesheet.py

@@ -5,7 +5,7 @@
 from itertools import chain
 from operator import itemgetter
 from pathlib import Path, PurePath
-from typing import Iterable, NamedTuple, Sequence, cast
+from typing import Final, Iterable, NamedTuple, Sequence, cast
 
 import rich.repr
 from rich.console import Console, ConsoleOptions, RenderableType, RenderResult
@@ -433,13 +433,14 @@ def _check_rule(
             if _check_selectors(selector_set.selectors, css_path_nodes):
                 yield selector_set.specificity
 
-    # pseudo classes which iterate over many nodes
-    # these have the potential to be slow, and shouldn't be used in a cache key
-    EXPENSIVE_PSEUDO_CLASSES = {
+    # pseudo classes which iterate over multiple nodes
+    # These shouldn't be used in a cache key
+    _EXCLUDE_PSEUDO_CLASSES_FROM_CACHE: Final[set[str]] = {
         "first-of-type",
         "last-of_type",
         "odd",
         "even",
+        "focus-within",
     }
 
     def apply(
@@ -487,7 +488,7 @@ def apply(
         cache_key: tuple | None = None
 
         if cache is not None and all_pseudo_classes.isdisjoint(
-            self.EXPENSIVE_PSEUDO_CLASSES
+            self._EXCLUDE_PSEUDO_CLASSES_FROM_CACHE
         ):
             cache_key = (
                 node._parent,

src/textual/dom.py

@@ -1592,9 +1592,9 @@ def set_class(self, add: bool, *class_names: str, update: bool = True) -> Self:
             Self.
         """
         if add:
-            self.add_class(*class_names, update=update)
+            self.add_class(*class_names, update=update and self.is_attached)
         else:
-            self.remove_class(*class_names, update=update)
+            self.remove_class(*class_names, update=update and self.is_attached)
         return self
 
     def set_classes(self, classes: str | Iterable[str]) -> Self:

src/textual/message_pump.py

@@ -237,7 +237,10 @@ def app(self) -> "App[object]":
     @property
     def is_attached(self) -> bool:
         """Is this node linked to the app through the DOM?"""
-        if self.app._exit:
+        try:
+            if self.app._exit:
+                return False
+        except NoActiveAppError:
             return False
         node: MessagePump | None = self
         while (node := node._parent) is not None: