Merge pull request #3002 from davep/early-show-root

Fix a crash when setting `DirectoryTree.show_root` before DOM is ready

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 
 - Parameter `animate` from `DataTable.move_cursor` was being ignored https://github.com/Textualize/textual/issues/3840
+- Fixed a crash if `DirectoryTree.show_root` was set before the DOM was fully available https://github.com/Textualize/textual/issues/2363
 
 
 ## [0.47.1] - 2023-01-05

src/textual/widgets/_directory_tree.py

@@ -295,6 +295,11 @@ def render_label(
         node_label = node._label.copy()
         node_label.stylize(style)
 
+        # If the tree isn't mounted yet we can't use component classes to stylize
+        # the label fully, so we return early.
+        if not self.is_mounted:
+            return node_label
+
         if node._allow_expand:
             prefix = ("📂 " if node.is_expanded else "📁 ", base_style + TOGGLE_STYLE)
             node_label.stylize_before(

tests/directory_tree/test_early_show_root.py

@@ -0,0 +1,16 @@
+from textual.app import App, ComposeResult
+from textual.widgets import DirectoryTree
+
+
+class DirectoryTreeApp(App[None]):
+    def compose(self) -> ComposeResult:
+        tree = DirectoryTree(".")
+        tree.show_root = True
+        yield tree
+
+
+async def test_managed_to_set_show_root_before_mounted() -> None:
+    """https://github.com/Textualize/textual/issues/2363"""
+    async with DirectoryTreeApp().run_test() as pilot:
+        assert isinstance(pilot.app.query_one(DirectoryTree), DirectoryTree)
+        assert pilot.app.query_one(DirectoryTree).show_root is True