feat(widget): add is_mounted property (#3709)

* feat(widget): add is_mounted property Co-authored-by: Darren Burns <[email protected]> * fix property docstring * add simple test * update changelog --------- Co-authored-by: Darren Burns <[email protected]>
Textualize · Nov 20, 2023 · ca68b86 · ca68b86
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -34,6 +34,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Added `restrict`, `type`, `max_length`, and `valid_empty` to Input https://github.com/Textualize/textual/pull/3657
 - Added `Pilot.mouse_down` to simulate `MouseDown` events https://github.com/Textualize/textual/pull/3495
 - Added `Pilot.mouse_up` to simulate `MouseUp` events https://github.com/Textualize/textual/pull/3495
+- Added `Widget.is_mounted` property https://github.com/Textualize/textual/pull/3709
 
 ### Changed
 

diff --git a/src/textual/widget.py b/src/textual/widget.py
@@ -393,6 +393,11 @@ def __init__(
     border_subtitle: str | Text | None = _BorderTitle()  # type: ignore
     """A title to show in the bottom border (if there is one)."""
 
+    @property
+    def is_mounted(self) -> bool:
+        """Check if this widget is mounted."""
+        return self._mounted_event.is_set()
+
     @property
     def siblings(self) -> list[Widget]:
         """Get the widget's siblings (self is removed from the return list).

diff --git a/tests/test_widget.py b/tests/test_widget.py
@@ -383,3 +383,14 @@ def compose(self) -> ComposeResult:
         label.loading = False  # Setting to same value is a null-op
         await pilot.pause()
         assert len(label.query(LoadingIndicator)) == 0
+
+
+async def test_is_mounted_property():
+    class TestWidgetIsMountedApp(App):
+        pass
+
+    async with TestWidgetIsMountedApp().run_test() as pilot:
+        widget = Widget()
+        assert widget.is_mounted is False
+        await pilot.app.mount(widget)
+        assert widget.is_mounted is True