Add a public read-only parent property to TreeNode

See Textualize#1397.

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## [0.10.0] - Unreleased
+
+### Added
+
+- Added `TreeNode.parent` -- a read-only property for accessing a node's parent https://github.com/Textualize/textual/issues/1397
+
 ## [0.9.1] - 2022-12-30
 
 ### Added
@@ -23,8 +29,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Widget.render_line now returns a Strip
 - Fix for slow updates on Windows
-- Bumped Rich dependency 
-  
+- Bumped Rich dependency
+
 ## [0.8.2] - 2022-12-28
 
 ### Fixed

src/textual/widgets/_tree.py

@@ -121,6 +121,11 @@ def id(self) -> NodeID:
         """NodeID: Get the node ID."""
         return self._id
 
+    @property
+    def parent(self) -> TreeNode[TreeDataType] | None:
+        """TreeNode[TreeDataType] | None: The parent of the node."""
+        return self._parent
+
     @property
     def is_expanded(self) -> bool:
         """bool: Check if the node is expanded."""

tests/tree/test_tree_node_parent.py

@@ -0,0 +1,10 @@
+from textual.widgets import TreeNode, Tree
+
+def test_tree_node_parent() -> None:
+    """It should be possible to access a TreeNode's parent."""
+    tree = Tree[None]("Anakin")
+    child = tree.root.add("Leia")
+    grandchild = child.add("Ben")
+    assert tree.root.parent is None
+    assert grandchild.parent == child
+    assert child.parent == tree.root