Fix render str (#3920)

* Fix text render

* changelog

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 
 - `Widget.move_child` would break if `before`/`after` is set to the index of the widget in `child` https://github.com/Textualize/textual/issues/1743
+- Fixed auto width text not processing markup https://github.com/Textualize/textual/issues/3918
 
 ### Changed
 

src/textual/widget.py

@@ -3227,7 +3227,7 @@ def _render(self) -> ConsoleRenderable | RichCast:
         """
         renderable = self.render()
         if isinstance(renderable, str):
-            return Text(renderable)
+            return Text.from_markup(renderable)
         return renderable
 
     async def run_action(self, action: str) -> None:

tests/test_widget.py

@@ -421,3 +421,17 @@ def compose(self) -> ComposeResult:
     with pytest.raises(MountError):
         async with app.run_test():
             pass
+
+
+async def test_render_returns_text():
+    """Test that render processes console markup when returning a string."""
+
+    # Regression test for https://github.com/Textualize/textual/issues/3918
+    class SimpleWidget(Widget):
+        def render(self) -> str:
+            return "Hello [b]World[/b]!"
+
+    widget = SimpleWidget()
+    render_result = widget._render()
+    assert isinstance(render_result, Text)
+    assert render_result.plain == "Hello World!"