refactor(material/tree): docs updates and rename variables (#28238)

Make miscelaneous fixes to documentation. Rename variables. Responding
to PR feedback.

 * remove comment about API contract of CdkTreeNodeToggle
 * rename CdkTree#_groups to CdkTree#_ariaSets
 * move documentation about default key manager configuration from
   TreeKeyManagerStrategy interface to TreeKeyManager class.
 * add JSDoc style comments for NoopTreeKeyManager

src/cdk/a11y/key-manager/noop-tree-key-manager.ts

@@ -22,6 +22,13 @@ import {
 /**
  * @docs-private
  *
+ * Opt-out of Tree of key manager behavior.
+ *
+ * When provided, Tree has same focus management behavior as before TreeKeyManager was introduced.
+ *  - Tree does not respond to keyboard interaction
+ *  - Tree node allows tabindex to be set by Input binding
+ *  - Tree node allows tabindex to be set by attribute binding
+ *
  * @deprecated NoopTreeKeyManager deprecated. Use TreeKeyManager or inject a
  * TreeKeyManagerStrategy instead. To be removed in a future version.
  *
@@ -62,6 +69,13 @@ export class NoopTreeKeyManager<T extends TreeKeyManagerItem> implements TreeKey
 /**
  * @docs-private
  *
+ * Opt-out of Tree of key manager behavior.
+ *
+ * When provided, Tree has same focus management behavior as before TreeKeyManager was introduced.
+ *  - Tree does not respond to keyboard interaction
+ *  - Tree node allows tabindex to be set by Input binding
+ *  - Tree node allows tabindex to be set by attribute binding
+ *
  * @deprecated NoopTreeKeyManager deprecated. Use TreeKeyManager or inject a
  * TreeKeyManagerStrategy instead. To be removed in a future version.
  *
@@ -76,6 +90,13 @@ export function NOOP_TREE_KEY_MANAGER_FACTORY<
 /**
  * @docs-private
  *
+ * Opt-out of Tree of key manager behavior.
+ *
+ * When provided, Tree has same focus management behavior as before TreeKeyManager was introduced.
+ *  - Tree does not respond to keyboard interaction
+ *  - Tree node allows tabindex to be set by Input binding
+ *  - Tree node allows tabindex to be set by attribute binding
+ *
  * @deprecated NoopTreeKeyManager deprecated. Use TreeKeyManager or inject a
  * TreeKeyManagerStrategy instead. To be removed in a future version.
  *

src/cdk/a11y/key-manager/tree-key-manager-strategy.ts

@@ -52,21 +52,20 @@ export interface TreeKeyManagerItem {
 export interface TreeKeyManagerOptions<T extends TreeKeyManagerItem> {
   /**
    * If true, then the key manager will call `activate` in addition to calling `focus` when a
-   * particular item is focused. By default, this is false.
+   * particular item is focused.
    */
-  activationFollowsFocus?: boolean;
+  shouldActivationFollowFocus?: boolean;
 
   /**
    * The direction in which the tree items are laid out horizontally. This influences which key
-   * will be interpreted as expand or collapse. Defaults to 'ltr'.
+   * will be interpreted as expand or collapse.
    */
   horizontalOrientation?: 'rtl' | 'ltr';
 
   /**
-   * Sets the predicate function that determines which items should be skipped by the tree key
-   * manager. By default, disabled items are skipped.
+   * If provided, navigation "skips" over items that pass the given predicate.
    *
-   * If the item is to be skipped, this function should return false.
+   * If the item is to be skipped, predicate function should return false.
    */
   skipPredicate?: (item: T) => boolean;
 

src/cdk/a11y/key-manager/tree-key-manager.ts

@@ -43,8 +43,8 @@ function coerceObservable<T>(data: T | Observable<T>): Observable<T> {
 export class TreeKeyManager<T extends TreeKeyManagerItem> implements TreeKeyManagerStrategy<T> {
   private _activeItemIndex = -1;
   private _activeItem: T | null = null;
-  private _activationFollowsFocus = false;
-  private _horizontal: 'ltr' | 'rtl' = 'ltr';
+  private _shouldActivationFollowFocus = false;
+  private _horizontalOrientation: 'ltr' | 'rtl' = 'ltr';
 
   // Keep tree items focusable when disabled. Align with
   // https://www.w3.org/WAI/ARIA/apg/practices/keyboard-interface/#focusabilityofdisabledcontrols.
@@ -85,6 +85,14 @@ export class TreeKeyManager<T extends TreeKeyManagerItem> implements TreeKeyMana
     this._hasInitialFocused = true;
   }
 
+  /**
+   *
+   * @param items List of TreeKeyManager options. Can be synchronous or asynchronous.
+   * @param config Optional configuration options. By default, use 'ltr' horizontal orientation. By
+   * default, do not skip any nodes. By default, key manager only calls `focus` method when items
+   * are focused and does not call `activate`. If `typeaheadDefaultInterval` is `true`, use a
+   * default interval of 200ms.
+   */
   constructor(items: Observable<T[]> | QueryList<T> | T[], config: TreeKeyManagerOptions<T>) {
     // We allow for the items to be an array or Observable because, in some cases, the consumer may
     // not have access to a QueryList of the items they want to manage (e.g. when the
@@ -109,11 +117,11 @@ export class TreeKeyManager<T extends TreeKeyManagerItem> implements TreeKeyMana
       this._initialFocus();
     }
 
-    if (typeof config.activationFollowsFocus === 'boolean') {
-      this._activationFollowsFocus = config.activationFollowsFocus;
+    if (typeof config.shouldActivationFollowFocus === 'boolean') {
+      this._shouldActivationFollowFocus = config.shouldActivationFollowFocus;
     }
     if (config.horizontalOrientation) {
-      this._horizontal = config.horizontalOrientation;
+      this._horizontalOrientation = config.horizontalOrientation;
     }
     if (config.skipPredicate) {
       this._skipPredicateFn = config.skipPredicate;
@@ -157,11 +165,15 @@ export class TreeKeyManager<T extends TreeKeyManagerItem> implements TreeKeyMana
         break;
 
       case RIGHT_ARROW:
-        this._horizontal === 'rtl' ? this._collapseCurrentItem() : this._expandCurrentItem();
+        this._horizontalOrientation === 'rtl'
+          ? this._collapseCurrentItem()
+          : this._expandCurrentItem();
         break;
 
       case LEFT_ARROW:
-        this._horizontal === 'rtl' ? this._expandCurrentItem() : this._collapseCurrentItem();
+        this._horizontalOrientation === 'rtl'
+          ? this._expandCurrentItem()
+          : this._collapseCurrentItem();
         break;
 
       case HOME:
@@ -264,11 +276,10 @@ export class TreeKeyManager<T extends TreeKeyManagerItem> implements TreeKeyMana
     previousActiveItem?.unfocus();
 
     if (options.emitChangeEvent) {
-      // Emit to `change` stream as required by TreeKeyManagerStrategy interface.
       this.change.next(this._activeItem);
     }
 
-    if (this._activationFollowsFocus) {
+    if (this._shouldActivationFollowFocus) {
       this._activateCurrentItem();
     }
   }

src/cdk/tree/toggle.ts

@@ -12,9 +12,6 @@ import {CdkTree, CdkTreeNode} from './tree';
 
 /**
  * Node toggle to expand and collapse the node.
- *
- * CdkTreeNodeToggle is intended only to be used on native button elements, elements with button role,
- * or elements with treeitem role.
  */
 @Directive({
   selector: '[cdkTreeNodeToggle]',

src/cdk/tree/tree.ts

@@ -132,16 +132,14 @@ export class CdkTree<T, K = T>
   private _parents: Map<K, T | null> = new Map<K, T | null>();
 
   /**
-   * The internal node groupings for each node; we use this to determine where
-   * a particular node is within each group. This allows us to compute the
-   * correct aria attribute values.
+   * Nodes grouped into each set, which is a list of nodes displayed together in the DOM.
    *
-   * The structure of this is that:
-   * - the outer index is the level
-   * - the inner index is the parent node for this particular group. If there is no parent node, we
-   *   use `null`.
+   * Lookup key is the parent of a set. Root nodes have key of null.
+   *
+   * Values is a 'set' of tree nodes. Each tree node maps to a treeitem element. Sets are in the
+   * order that it is rendered. Each set maps directly to aria-posinset and aria-setsize attributes.
    */
-  private _groups: Map<K | null, T[]> = new Map<K | null, T[]>();
+  private _ariaSets: Map<K | null, T[]> = new Map<K | null, T[]>();
 
   /**
    * Provides a stream containing the latest data array to render. Influenced by the tree's
@@ -500,10 +498,10 @@ export class CdkTree<T, K = T>
           this.insertNode(data[currentIndex!], currentIndex!, viewContainer, parentData);
         } else if (currentIndex == null) {
           viewContainer.remove(adjustedPreviousIndex!);
-          const group = this._getNodeGroup(item.item);
+          const set = this._getAriaSet(item.item);
           const key = this._getExpansionKey(item.item);
-          group.splice(
-            group.findIndex(groupItem => this._getExpansionKey(groupItem) === key),
+          set.splice(
+            set.findIndex(groupItem => this._getExpansionKey(groupItem) === key),
             1,
           );
         } else {
@@ -784,8 +782,8 @@ export class CdkTree<T, K = T>
    * This is intended to be used for `aria-setsize`.
    */
   _getSetSize(dataNode: T) {
-    const group = this._getNodeGroup(dataNode);
-    return group.length;
+    const set = this._getAriaSet(dataNode);
+    return set.length;
   }
 
   /**
@@ -794,9 +792,9 @@ export class CdkTree<T, K = T>
    * This is intended to be used for `aria-posinset`.
    */
   _getPositionInSet(dataNode: T) {
-    const group = this._getNodeGroup(dataNode);
+    const set = this._getAriaSet(dataNode);
     const key = this._getExpansionKey(dataNode);
-    return group.findIndex(node => this._getExpansionKey(node) === key) + 1;
+    return set.findIndex(node => this._getExpansionKey(node) === key) + 1;
   }
 
   /** Given a CdkTreeNode, gets the node that renders that node's parent's data. */
@@ -902,12 +900,12 @@ export class CdkTree<T, K = T>
     return this.expansionKey?.(dataNode) ?? (dataNode as unknown as K);
   }
 
-  private _getNodeGroup(node: T) {
+  private _getAriaSet(node: T) {
     const key = this._getExpansionKey(node);
     const parent = this._parents.get(key);
     const parentKey = parent ? this._getExpansionKey(parent) : null;
-    const group = this._groups.get(parentKey);
-    return group ?? [node];
+    const set = this._ariaSets.get(parentKey);
+    return set ?? [node];
   }
 
   /**
@@ -963,7 +961,7 @@ export class CdkTree<T, K = T>
           children.pipe(
             take(1),
             tap(childNodes => {
-              this._groups.set(parentKey, [...(childNodes ?? [])]);
+              this._ariaSets.set(parentKey, [...(childNodes ?? [])]);
               for (const child of childNodes ?? []) {
                 const childKey = this._getExpansionKey(child);
                 this._parents.set(childKey, node);
@@ -1006,7 +1004,7 @@ export class CdkTree<T, K = T>
     // nested.
     if (this.childrenAccessor && nodeType === 'flat') {
       // This flattens children into a single array.
-      this._groups.set(null, [...nodes]);
+      this._ariaSets.set(null, [...nodes]);
       return this._flattenNestedNodesWithExpansion(nodes).pipe(
         map(flattenedNodes => ({
           renderNodes: flattenedNodes,
@@ -1039,7 +1037,7 @@ export class CdkTree<T, K = T>
     } else {
       // For nested nodes, we still need to perform the node flattening in order
       // to maintain our caches for various tree operations.
-      this._groups.set(null, [...nodes]);
+      this._ariaSets.set(null, [...nodes]);
       return this._flattenNestedNodesWithExpansion(nodes).pipe(
         map(flattenedNodes => ({
           renderNodes: nodes,
@@ -1065,7 +1063,7 @@ export class CdkTree<T, K = T>
     }
 
     this._parents.clear();
-    this._groups.clear();
+    this._ariaSets.clear();
 
     for (let index = 0; index < flattenedNodes.length; index++) {
       const dataNode = flattenedNodes[index];
@@ -1075,9 +1073,9 @@ export class CdkTree<T, K = T>
       this._parents.set(key, parent);
       const parentKey = parent ? this._getExpansionKey(parent) : null;
 
-      const group = this._groups.get(parentKey) ?? [];
+      const group = this._ariaSets.get(parentKey) ?? [];
       group.splice(index, 0, dataNode);
-      this._groups.set(parentKey, group);
+      this._ariaSets.set(parentKey, group);
     }
   }
 }

tools/public_api_guard/cdk/a11y.md

@@ -505,8 +505,8 @@ export interface TreeKeyManagerItem {
 
 // @public
 export interface TreeKeyManagerOptions<T extends TreeKeyManagerItem> {
-    activationFollowsFocus?: boolean;
     horizontalOrientation?: 'rtl' | 'ltr';
+    shouldActivationFollowFocus?: boolean;
     skipPredicate?: (item: T) => boolean;
     trackBy?: (treeItem: T) => unknown;
     typeAheadDebounceInterval?: true | number;