Merge branch 'main' into fix-1351

CHANGELOG.md

@@ -27,6 +27,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Fixed visibility not affecting children https://github.com/Textualize/textual/issues/1313
 - Fixed issue with auto width/height and relative children https://github.com/Textualize/textual/issues/1319
 - Fixed issue with offset applied to containers https://github.com/Textualize/textual/issues/1256
+- Fixed default CSS retrieval for widgets with no `DEFAULT_CSS` that inherited from widgets with `DEFAULT_CSS` https://github.com/Textualize/textual/issues/1335
 
 ## [0.5.0] - 2022-11-20
 

src/textual/app.py

@@ -1996,9 +1996,9 @@ class App(Generic[ReturnType], DOMNode):
                 await self._prune_nodes(widgets)
             finally:
                 finished_event.set()
+                self.refresh(layout=True)
 
         removed_widgets = self._detach_from_dom(widgets)
-        self.refresh(layout=True)
 
         finished_event = asyncio.Event()
         asyncio.create_task(prune_widgets_task(removed_widgets, finished_event))

src/textual/dom.py

@@ -266,7 +266,7 @@ class DOMNode(MessagePump):
                 return f"{base.__name__}"
 
         for tie_breaker, base in enumerate(self._node_bases):
-            css = base.DEFAULT_CSS.strip()
+            css = base.__dict__.get("DEFAULT_CSS", "").strip()
             if css:
                 css_stack.append((get_path(base), css, -tie_breaker))
 

tests/test_dom.py

@@ -78,6 +78,43 @@ def test_inherited_bindings():
     assert list(e._bindings.keys.keys()) == ["e"]
 
 
+def test_get_default_css():
+    class A(DOMNode):
+        pass
+    class B(A):
+        pass
+    class C(B):
+        DEFAULT_CSS = "C"
+    class D(C):
+        pass
+    class E(D):
+        DEFAULT_CSS = "E"
+    node = DOMNode()
+    node_css = node.get_default_css()
+    a = A()
+    a_css = a.get_default_css()
+    b = B()
+    b_css = b.get_default_css()
+    c = C()
+    c_css = c.get_default_css()
+    d = D()
+    d_css = d.get_default_css()
+    e = E()
+    e_css = e.get_default_css()
+
+    # Descendants that don't assign to DEFAULT_CSS don't add new CSS to the stack.
+    assert len(node_css) == len(a_css) == len(b_css) == 0
+    assert len(c_css) == len(d_css) == 1
+    assert len(e_css) == 2
+
+    # Descendants do push the priority of the ancestors' rules down.
+    assert c_css[0][2] == d_css[0][2] + 1 == 0
+
+    # The CSS on the stack is the correct one.
+    assert e_css[0][1:] == ("E", 0)
+    assert e_css[1][1:] == ("C", -2)
+
+
 @pytest.fixture
 def search():
     """