Revert "fix(material/tree): aria-expanded attribute should not appear in the leaf node (#29096)"

src/cdk/tree/tree.spec.ts

@@ -145,14 +145,20 @@ describe('CdkTree', () => {
         let data = dataSource.data;
         dataSource.addChild(data[2]);
         fixture.detectChanges();
-        let ariaExpandedStates = getNodes(treeElement).map(n => n.getAttribute('aria-expanded'));
-        expect(ariaExpandedStates).toEqual([null, null, 'false', null]);
+        expect(
+          getNodes(treeElement).every(node => {
+            return node.getAttribute('aria-expanded') === 'false';
+          }),
+        ).toBe(true);
 
         component.treeControl.expandAll();
         fixture.detectChanges();
 
-        ariaExpandedStates = getNodes(treeElement).map(n => n.getAttribute('aria-expanded'));
-        expect(ariaExpandedStates).toEqual([null, null, 'true', null]);
+        expect(
+          getNodes(treeElement).every(node => {
+            return node.getAttribute('aria-expanded') === 'true';
+          }),
+        ).toBe(true);
       });
 
       it('with the right data', () => {
@@ -799,8 +805,11 @@ describe('CdkTree', () => {
       });
 
       it('with the right aria-expanded attrs', () => {
-        let ariaExpandedStates = getNodes(treeElement).map(n => n.getAttribute('aria-expanded'));
-        expect(ariaExpandedStates).toEqual([null, null, null]);
+        expect(
+          getNodes(treeElement).every(node => {
+            return node.getAttribute('aria-expanded') === 'false';
+          }),
+        ).toBe(true);
 
         component.toggleRecursively = false;
         fixture.changeDetectorRef.markForCheck();
@@ -813,7 +822,7 @@ describe('CdkTree', () => {
         fixture.detectChanges();
 
         const ariaExpanded = getNodes(treeElement).map(n => n.getAttribute('aria-expanded'));
-        expect(ariaExpanded).toEqual([null, 'true', 'false', null]);
+        expect(ariaExpanded).toEqual(['false', 'true', 'false', 'false']);
       });
 
       it('should expand/collapse the node multiple times', () => {
@@ -877,7 +886,6 @@ describe('CdkTree', () => {
       });
 
       it('should expand/collapse the node recursively', () => {
-        fixture.changeDetectorRef.markForCheck();
         let data = dataSource.data;
         const child = dataSource.addChild(data[1], false);
         dataSource.addChild(child, false);

src/cdk/tree/tree.ts

@@ -324,7 +324,7 @@ export class CdkTree<T, K = T> implements AfterContentChecked, CollectionViewer,
   exportAs: 'cdkTreeNode',
   host: {
     'class': 'cdk-tree-node',
-    '[attr.aria-expanded]': 'isLeafNode ? null : isExpanded',
+    '[attr.aria-expanded]': 'isExpanded',
   },
   standalone: true,
 })
@@ -375,26 +375,6 @@ export class CdkTreeNode<T, K = T> implements FocusableOption, OnDestroy, OnInit
     return this._tree.treeControl.isExpanded(this._data);
   }
 
-  /* If leaf node, return true to not assign aria-expanded attribute */
-  get isLeafNode(): boolean {
-    // If flat tree node data returns false for expandable property, it's a leaf node
-    if (
-      this._tree.treeControl.isExpandable !== undefined &&
-      !this._tree.treeControl.isExpandable(this._data)
-    ) {
-      return true;
-
-      // If nested tree node data returns 0 descendants, it's a leaf node
-    } else if (
-      this._tree.treeControl.isExpandable === undefined &&
-      this._tree.treeControl.getDescendants(this._data).length === 0
-    ) {
-      return true;
-    }
-
-    return false;
-  }
-
   get level(): number {
     // If the treeControl has a getLevel method, use it to get the level. Otherwise read the
     // aria-level off the parent node and use it as the level for this node (note aria-level is

src/material/tree/tree.spec.ts

@@ -78,14 +78,20 @@ describe('MatTree', () => {
         const data = underlyingDataSource.data;
         underlyingDataSource.addChild(data[2]);
         fixture.detectChanges();
-        let ariaExpandedStates = getNodes(treeElement).map(n => n.getAttribute('aria-expanded'));
-        expect(ariaExpandedStates).toEqual([null, null, 'false']);
+        expect(
+          getNodes(treeElement).every(node => {
+            return node.getAttribute('aria-expanded') === 'false';
+          }),
+        ).toBe(true);
 
         component.treeControl.expandAll();
         fixture.detectChanges();
 
-        ariaExpandedStates = getNodes(treeElement).map(n => n.getAttribute('aria-expanded'));
-        expect(ariaExpandedStates).toEqual([null, null, 'true', null]);
+        expect(
+          getNodes(treeElement).every(node => {
+            return node.getAttribute('aria-expanded') === 'true';
+          }),
+        ).toBe(true);
       });
 
       it('with the right data', () => {
@@ -464,8 +470,11 @@ describe('MatTree', () => {
       });
 
       it('with the right aria-expanded attrs', () => {
-        let ariaExpandedStates = getNodes(treeElement).map(n => n.getAttribute('aria-expanded'));
-        expect(ariaExpandedStates).toEqual([null, null, null]);
+        expect(
+          getNodes(treeElement).every(node => {
+            return node.getAttribute('aria-expanded') === 'false';
+          }),
+        ).toBe(true);
 
         component.toggleRecursively = false;
         const data = underlyingDataSource.data;
@@ -477,7 +486,7 @@ describe('MatTree', () => {
         fixture.detectChanges();
 
         const ariaExpanded = getNodes(treeElement).map(n => n.getAttribute('aria-expanded'));
-        expect(ariaExpanded).toEqual([null, 'true', 'false', null]);
+        expect(ariaExpanded).toEqual(['false', 'true', 'false', 'false']);
       });
 
       it('should expand/collapse the node', () => {

tools/public_api_guard/cdk/tree.md

@@ -127,8 +127,6 @@ export class CdkTreeNode<T, K = T> implements FocusableOption, OnDestroy, OnInit
     // (undocumented)
     get isExpanded(): boolean;
     // (undocumented)
-    get isLeafNode(): boolean;
-    // (undocumented)
     get level(): number;
     static mostRecentTreeNode: CdkTreeNode<any> | null;
     // (undocumented)