Add public access to a TreeNode's label

This adds public support to reading a TreeNode's label, and also setting it
too.

See Textualize#1396.

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 public `TreeNode` label access via `TreeNode.label` https://github.com/Textualize/textual/issues/1396
+
 ## [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

@@ -163,6 +163,17 @@ def toggle(self) -> None:
         self._updates += 1
         self._tree._invalidate()
 
+    @property
+    def label(self) -> TextType:
+        """TextType: The label for the node."""
+        return self._label
+
+    @label.setter
+    def label(self, new_label: TextType) -> TextType:
+        """TextType: The label for the node."""
+        self.set_label(new_label)
+        return self.label
+
     def set_label(self, label: TextType) -> None:
         """Set a new label for the node.
 

tests/test_tree.py

@@ -0,0 +1,17 @@
+from textual.widgets import Tree, TreeNode
+from rich.text import Text
+
+def test_tree_node_label() -> None:
+    """It should be possible to modify a TreeNode's label."""
+    node = TreeNode(Tree[None]("Xenomorph Lifecycle"), None, 0, "Facehugger")
+    assert node.label == Text("Facehugger")
+    node.label = "Chestbuster"
+    assert node.label == Text("Chestbuster")
+
+def test_tree_node_label_via_tree() -> None:
+    """It should be possible to modify a TreeNode's label when created via a Tree."""
+    tree = Tree[None]("Xenomorph Lifecycle")
+    node = tree.root.add("Facehugger")
+    assert node.label == Text("Facehugger")
+    node.label = "Chestbuster"
+    assert node.label == Text("Chestbuster")