Address review comments.

CHANGELOG.md

@@ -14,7 +14,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Added read-only public access to the children of a `TreeNode` via `TreeNode.children` https://github.com/Textualize/textual/issues/1398
 - Added `Tree.get_node_by_id` to allow getting a node by its ID https://github.com/Textualize/textual/pull/1535
 - Added a `Tree.NodeHighlighted` message, giving a `on_tree_node_highlighted` event handler https://github.com/Textualize/textual/issues/1400
-- Added a `_inherit_component_classes` class variable to control whether or not component classes are inherited from base classes https://github.com/Textualize/textual/issues/1399
+- Added a `inherit_component_classes` subclassing parameter to control whether or not component classes are inherited from base classes https://github.com/Textualize/textual/issues/1399
 - Added `diagnose` as a `textual` command https://github.com/Textualize/textual/issues/1542
 
 ### Changed

src/textual/dom.py

@@ -163,11 +163,15 @@ class DOMNode(MessagePump):
         self.refresh()
 
     def __init_subclass__(
-        cls, inherit_css: bool = True, inherit_bindings: bool = True
+        cls,
+        inherit_css: bool = True,
+        inherit_bindings: bool = True,
+        inherit_component_classes: bool = True,
     ) -> None:
         super().__init_subclass__()
         cls._inherit_css = inherit_css
         cls._inherit_bindings = inherit_bindings
+        cls._inherit_component_classes = inherit_component_classes
         css_type_names: set[str] = set()
         for base in cls._css_bases(cls):
             css_type_names.add(base.__name__)

tests/test_dom.py

@@ -47,6 +47,7 @@ def test_validate():
 
 def test_inherited_bindings():
     """Test if binding merging is done correctly when (not) inheriting bindings."""
+
     class A(DOMNode):
         BINDINGS = [("a", "a", "a")]
 
@@ -81,14 +82,19 @@ def test_inherited_bindings():
 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()
@@ -121,9 +127,8 @@ def test_component_classes_inheritance():
     class A(DOMNode):
         COMPONENT_CLASSES = {"a-1", "a-2"}
 
-    class B(A):
+    class B(A, inherit_component_classes=False):
         COMPONENT_CLASSES = {"b-1"}
-        _inherit_component_classes = False
 
     class C(B):
         COMPONENT_CLASSES = {"c-1", "c-2"}
@@ -134,9 +139,8 @@ def test_component_classes_inheritance():
     class E(D):
         COMPONENT_CLASSES = {"e-1"}
 
-    class F(E):
+    class F(E, inherit_component_classes=False):
         COMPONENT_CLASSES = {"f-1"}
-        _inherit_component_classes = False
 
     node = DOMNode()
     node_cc = node.get_component_classes()