@angular/cdk/fesm2022/tree.mjs.map

Angular Material Component Development Kit

{"version":3,"file":"tree.mjs","sources":["../../../../../k8-fastbuild-ST-46c76129e412/bin/src/cdk/tree/control/base-tree-control.ts","../../../../../k8-fastbuild-ST-46c76129e412/bin/src/cdk/tree/control/flat-tree-control.ts","../../../../../k8-fastbuild-ST-46c76129e412/bin/src/cdk/tree/control/nested-tree-control.ts","../../../../../k8-fastbuild-ST-46c76129e412/bin/src/cdk/tree/outlet.ts","../../../../../k8-fastbuild-ST-46c76129e412/bin/src/cdk/tree/node.ts","../../../../../k8-fastbuild-ST-46c76129e412/bin/src/cdk/tree/tree-errors.ts","../../../../../k8-fastbuild-ST-46c76129e412/bin/src/cdk/tree/tree.ts","../../../../../k8-fastbuild-ST-46c76129e412/bin/src/cdk/tree/nested-node.ts","../../../../../k8-fastbuild-ST-46c76129e412/bin/src/cdk/tree/padding.ts","../../../../../k8-fastbuild-ST-46c76129e412/bin/src/cdk/tree/toggle.ts","../../../../../k8-fastbuild-ST-46c76129e412/bin/src/cdk/tree/tree-module.ts"],"sourcesContent":["/**\n * @license\n * Copyright Google LLC All Rights Reserved.\n *\n * Use of this source code is governed by an MIT-style license that can be\n * found in the LICENSE file at https://angular.dev/license\n */\nimport {SelectionModel} from '../../collections';\nimport {Observable} from 'rxjs';\nimport {TreeControl} from './tree-control';\n\n/**\n * Base tree control. It has basic toggle/expand/collapse operations on a single data node.\n *\n * @deprecated Use one of levelAccessor or childrenAccessor. To be removed in a future version.\n * @breaking-change 21.0.0\n */\nexport abstract class BaseTreeControl<T, K = T> implements TreeControl<T, K> {\n  /** Gets a list of descendent data nodes of a subtree rooted at given data node recursively. */\n  abstract getDescendants(dataNode: T): T[];\n\n  /** Expands all data nodes in the tree. */\n  abstract expandAll(): void;\n\n  /** Saved data node for `expandAll` action. */\n  dataNodes: T[];\n\n  /** A selection model with multi-selection to track expansion status. */\n  expansionModel: SelectionModel<K> = new SelectionModel<K>(true);\n\n  /**\n   * Returns the identifier by which a dataNode should be tracked, should its\n   * reference change.\n   *\n   * Similar to trackBy for *ngFor\n   */\n  trackBy?: (dataNode: T) => K;\n\n  /** Get depth of a given data node, return the level number. This is for flat tree node. */\n  getLevel: (dataNode: T) => number;\n\n  /**\n   * Whether the data node is expandable. Returns true if expandable.\n   * This is for flat tree node.\n   */\n  isExpandable: (dataNode: T) => boolean;\n\n  /** Gets a stream that emits whenever the given data node's children change. */\n  getChildren: (dataNode: T) => Observable<T[]> | T[] | undefined | null;\n\n  /** Toggles one single data node's expanded/collapsed state. */\n  toggle(dataNode: T): void {\n    this.expansionModel.toggle(this._trackByValue(dataNode));\n  }\n\n  /** Expands one single data node. */\n  expand(dataNode: T): void {\n    this.expansionModel.select(this._trackByValue(dataNode));\n  }\n\n  /** Collapses one single data node. */\n  collapse(dataNode: T): void {\n    this.expansionModel.deselect(this._trackByValue(dataNode));\n  }\n\n  /** Whether a given data node is expanded or not. Returns true if the data node is expanded. */\n  isExpanded(dataNode: T): boolean {\n    return this.expansionModel.isSelected(this._trackByValue(dataNode));\n  }\n\n  /** Toggles a subtree rooted at `node` recursively. */\n  toggleDescendants(dataNode: T): void {\n    this.expansionModel.isSelected(this._trackByValue(dataNode))\n      ? this.collapseDescendants(dataNode)\n      : this.expandDescendants(dataNode);\n  }\n\n  /** Collapse all dataNodes in the tree. */\n  collapseAll(): void {\n    this.expansionModel.clear();\n  }\n\n  /** Expands a subtree rooted at given data node recursively. */\n  expandDescendants(dataNode: T): void {\n    let toBeProcessed = [dataNode];\n    toBeProcessed.push(...this.getDescendants(dataNode));\n    this.expansionModel.select(...toBeProcessed.map(value => this._trackByValue(value)));\n  }\n\n  /** Collapses a subtree rooted at given data node recursively. */\n  collapseDescendants(dataNode: T): void {\n    let toBeProcessed = [dataNode];\n    toBeProcessed.push(...this.getDescendants(dataNode));\n    this.expansionModel.deselect(...toBeProcessed.map(value => this._trackByValue(value)));\n  }\n\n  protected _trackByValue(value: T | K): K {\n    return this.trackBy ? this.trackBy(value as T) : (value as K);\n  }\n}\n","/**\n * @license\n * Copyright Google LLC All Rights Reserved.\n *\n * Use of this source code is governed by an MIT-style license that can be\n * found in the LICENSE file at https://angular.dev/license\n */\n\nimport {BaseTreeControl} from './base-tree-control';\n\n/** Optional set of configuration that can be provided to the FlatTreeControl. */\nexport interface FlatTreeControlOptions<T, K> {\n  trackBy?: (dataNode: T) => K;\n}\n\n/**\n * Flat tree control. Able to expand/collapse a subtree recursively for flattened tree.\n *\n * @deprecated Use one of levelAccessor or childrenAccessor instead. To be removed in a future\n * version.\n * @breaking-change 21.0.0\n */\nexport class FlatTreeControl<T, K = T> extends BaseTreeControl<T, K> {\n  /** Construct with flat tree data node functions getLevel and isExpandable. */\n  constructor(\n    public override getLevel: (dataNode: T) => number,\n    public override isExpandable: (dataNode: T) => boolean,\n    public options?: FlatTreeControlOptions<T, K>,\n  ) {\n    super();\n\n    if (this.options) {\n      this.trackBy = this.options.trackBy;\n    }\n  }\n\n  /**\n   * Gets a list of the data node's subtree of descendent data nodes.\n   *\n   * To make this working, the `dataNodes` of the TreeControl must be flattened tree nodes\n   * with correct levels.\n   */\n  getDescendants(dataNode: T): T[] {\n    const startIndex = this.dataNodes.indexOf(dataNode);\n    const results: T[] = [];\n\n    // Goes through flattened tree nodes in the `dataNodes` array, and get all descendants.\n    // The level of descendants of a tree node must be greater than the level of the given\n    // tree node.\n    // If we reach a node whose level is equal to the level of the tree node, we hit a sibling.\n    // If we reach a node whose level is greater than the level of the tree node, we hit a\n    // sibling of an ancestor.\n    for (\n      let i = startIndex + 1;\n      i < this.dataNodes.length && this.getLevel(dataNode) < this.getLevel(this.dataNodes[i]);\n      i++\n    ) {\n      results.push(this.dataNodes[i]);\n    }\n    return results;\n  }\n\n  /**\n   * Expands all data nodes in the tree.\n   *\n   * To make this working, the `dataNodes` variable of the TreeControl must be set to all flattened\n   * data nodes of the tree.\n   */\n  expandAll(): void {\n    this.expansionModel.select(...this.dataNodes.map(node => this._trackByValue(node)));\n  }\n}\n","/**\n * @license\n * Copyright Google LLC All Rights Reserved.\n *\n * Use of this source code is governed by an MIT-style license that can be\n * found in the LICENSE file at https://angular.dev/license\n */\nimport {Observable, isObservable} from 'rxjs';\nimport {take, filter} from 'rxjs/operators';\nimport {BaseTreeControl} from './base-tree-control';\n\n/** Optional set of configuration that can be provided to the NestedTreeControl. */\nexport interface NestedTreeControlOptions<T, K> {\n  /** Function to determine if the provided node is expandable. */\n  isExpandable?: (dataNode: T) => boolean;\n  trackBy?: (dataNode: T) => K;\n}\n\n/**\n * Nested tree control. Able to expand/collapse a subtree recursively for NestedNode type.\n *\n * @deprecated Use one of levelAccessor or childrenAccessor instead. To be removed in a future\n * version.\n * @breaking-change 21.0.0\n */\nexport class NestedTreeControl<T, K = T> extends BaseTreeControl<T, K> {\n  /** Construct with nested tree function getChildren. */\n  constructor(\n    public override getChildren: (dataNode: T) => Observable<T[]> | T[] | undefined | null,\n    public options?: NestedTreeControlOptions<T, K>,\n  ) {\n    super();\n\n    if (this.options) {\n      this.trackBy = this.options.trackBy;\n    }\n\n    if (this.options?.isExpandable) {\n      this.isExpandable = this.options.isExpandable;\n    }\n  }\n\n  /**\n   * Expands all dataNodes in the tree.\n   *\n   * To make this working, the `dataNodes` variable of the TreeControl must be set to all root level\n   * data nodes of the tree.\n   */\n  expandAll(): void {\n    this.expansionModel.clear();\n    const allNodes = this.dataNodes.reduce(\n      (accumulator: T[], dataNode) => [...accumulator, ...this.getDescendants(dataNode), dataNode],\n      [],\n    );\n    this.expansionModel.select(...allNodes.map(node => this._trackByValue(node)));\n  }\n\n  /** Gets a list of descendant dataNodes of a subtree rooted at given data node recursively. */\n  getDescendants(dataNode: T): T[] {\n    const descendants: T[] = [];\n\n    this._getDescendants(descendants, dataNode);\n    // Remove the node itself\n    return descendants.splice(1);\n  }\n\n  /** A helper function to get descendants recursively. */\n  protected _getDescendants(descendants: T[], dataNode: T): void {\n    descendants.push(dataNode);\n    const childrenNodes = this.getChildren(dataNode);\n    if (Array.isArray(childrenNodes)) {\n      childrenNodes.forEach((child: T) => this._getDescendants(descendants, child));\n    } else if (isObservable(childrenNodes)) {\n      // TypeScript as of version 3.5 doesn't seem to treat `Boolean` like a function that\n      // returns a `boolean` specifically in the context of `filter`, so we manually clarify that.\n      childrenNodes.pipe(take(1), filter(Boolean as () => boolean)).subscribe(children => {\n        for (const child of children) {\n          this._getDescendants(descendants, child);\n        }\n      });\n    }\n  }\n}\n","/**\n * @license\n * Copyright Google LLC All Rights Reserved.\n *\n * Use of this source code is governed by an MIT-style license that can be\n * found in the LICENSE file at https://angular.dev/license\n */\nimport {Directive, InjectionToken, ViewContainerRef, inject} from '@angular/core';\n\n/**\n * Injection token used to provide a `CdkTreeNode` to its outlet.\n * Used primarily to avoid circular imports.\n * @docs-private\n */\nexport const CDK_TREE_NODE_OUTLET_NODE = new InjectionToken<{}>('CDK_TREE_NODE_OUTLET_NODE');\n\n/**\n * Outlet for nested CdkNode. Put `[cdkTreeNodeOutlet]` on a tag to place children dataNodes\n * inside the outlet.\n */\n@Directive({\n  selector: '[cdkTreeNodeOutlet]',\n})\nexport class CdkTreeNodeOutlet {\n  viewContainer = inject(ViewContainerRef);\n  _node? = inject(CDK_TREE_NODE_OUTLET_NODE, {optional: true});\n\n  constructor(...args: unknown[]);\n  constructor() {}\n}\n","/**\n * @license\n * Copyright Google LLC All Rights Reserved.\n *\n * Use of this source code is governed by an MIT-style license that can be\n * found in the LICENSE file at https://angular.dev/license\n */\n\nimport {Directive, TemplateRef, inject} from '@angular/core';\n\n/** Context provided to the tree node component. */\nexport class CdkTreeNodeOutletContext<T> {\n  /** Data for the node. */\n  $implicit: T;\n\n  /** Depth of the node. */\n  level: number;\n\n  /** Index location of the node. */\n  index?: number;\n\n  /** Length of the number of total dataNodes. */\n  count?: number;\n\n  constructor(data: T) {\n    this.$implicit = data;\n  }\n}\n\n/**\n * Data node definition for the CdkTree.\n * Captures the node's template and a when predicate that describes when this node should be used.\n */\n@Directive({\n  selector: '[cdkTreeNodeDef]',\n  inputs: [{name: 'when', alias: 'cdkTreeNodeDefWhen'}],\n})\nexport class CdkTreeNodeDef<T> {\n  /** @docs-private */\n  template = inject<TemplateRef<any>>(TemplateRef);\n\n  /**\n   * Function that should return true if this node template should be used for the provided node\n   * data and index. If left undefined, this node will be considered the default node template to\n   * use when no other when functions return true for the data.\n   * For every node, there must be at least one when function that passes or an undefined to\n   * default.\n   */\n  when: (index: number, nodeData: T) => boolean;\n\n  constructor(...args: unknown[]);\n  constructor() {}\n}\n","/**\n * @license\n * Copyright Google LLC All Rights Reserved.\n *\n * Use of this source code is governed by an MIT-style license that can be\n * found in the LICENSE file at https://angular.dev/license\n */\n\n/**\n * Returns an error to be thrown when there is no usable data.\n * @docs-private\n */\nexport function getTreeNoValidDataSourceError() {\n  return Error(`A valid data source must be provided.`);\n}\n\n/**\n * Returns an error to be thrown when there are multiple nodes that are missing a when function.\n * @docs-private\n */\nexport function getTreeMultipleDefaultNodeDefsError() {\n  return Error(`There can only be one default row without a when predicate function.`);\n}\n\n/**\n * Returns an error to be thrown when there are no matching node defs for a particular set of data.\n * @docs-private\n */\nexport function getTreeMissingMatchingNodeDefError() {\n  return Error(`Could not find a matching node definition for the provided node data.`);\n}\n\n/**\n * Returns an error to be thrown when there is no tree control.\n * @docs-private\n */\nexport function getTreeControlMissingError() {\n  return Error(`Could not find a tree control, levelAccessor, or childrenAccessor for the tree.`);\n}\n\n/**\n * Returns an error to be thrown when there are multiple ways of specifying children or level\n * provided to the tree.\n * @docs-private\n */\nexport function getMultipleTreeControlsError() {\n  return Error(`More than one of tree control, levelAccessor, or childrenAccessor were provided.`);\n}\n","/**\n * @license\n * Copyright Google LLC All Rights Reserved.\n *\n * Use of this source code is governed by an MIT-style license that can be\n * found in the LICENSE file at https://angular.dev/license\n */\nimport {\n  TREE_KEY_MANAGER,\n  TreeKeyManagerFactory,\n  TreeKeyManagerItem,\n  TreeKeyManagerOptions,\n  TreeKeyManagerStrategy,\n} from '../a11y';\nimport {Directionality} from '../bidi';\nimport {\n  CollectionViewer,\n  DataSource,\n  isDataSource,\n  SelectionChange,\n  SelectionModel,\n} from '../collections';\nimport {\n  AfterContentChecked,\n  AfterContentInit,\n  AfterViewInit,\n  ChangeDetectionStrategy,\n  ChangeDetectorRef,\n  Component,\n  ContentChildren,\n  Directive,\n  ElementRef,\n  EventEmitter,\n  EmbeddedViewRef,\n  Input,\n  IterableChangeRecord,\n  IterableDiffer,\n  IterableDiffers,\n  OnDestroy,\n  OnInit,\n  Output,\n  QueryList,\n  TrackByFunction,\n  ViewChild,\n  ViewContainerRef,\n  ViewEncapsulation,\n  numberAttribute,\n  inject,\n  booleanAttribute,\n} from '@angular/core';\nimport {coerceObservable} from '../coercion/private';\nimport {\n  BehaviorSubject,\n  combineLatest,\n  concat,\n  EMPTY,\n  Observable,\n  Subject,\n  Subscription,\n  isObservable,\n  of as observableOf,\n} from 'rxjs';\nimport {\n  distinctUntilChanged,\n  concatMap,\n  map,\n  reduce,\n  startWith,\n  switchMap,\n  take,\n  takeUntil,\n  tap,\n} from 'rxjs/operators';\nimport {TreeControl} from './control/tree-control';\nimport {CdkTreeNodeDef, CdkTreeNodeOutletContext} from './node';\nimport {CdkTreeNodeOutlet} from './outlet';\nimport {\n  getMultipleTreeControlsError,\n  getTreeControlMissingError,\n  getTreeMissingMatchingNodeDefError,\n  getTreeMultipleDefaultNodeDefsError,\n  getTreeNoValidDataSourceError,\n} from './tree-errors';\n\ntype RenderingData<T> =\n  | {\n      flattenedNodes: null;\n      nodeType: null;\n      renderNodes: readonly T[];\n    }\n  | {\n      flattenedNodes: readonly T[];\n      nodeType: 'nested' | 'flat';\n      renderNodes: readonly T[];\n    };\n\n/**\n * CDK tree component that connects with a data source to retrieve data of type `T` and renders\n * dataNodes with hierarchy. Updates the dataNodes when new data is provided by the data source.\n */\n@Component({\n  selector: 'cdk-tree',\n  exportAs: 'cdkTree',\n  template: `<ng-container cdkTreeNodeOutlet></ng-container>`,\n  host: {\n    'class': 'cdk-tree',\n    'role': 'tree',\n    '(keydown)': '_sendKeydownToKeyManager($event)',\n  },\n  encapsulation: ViewEncapsulation.None,\n  // The \"OnPush\" status for the `CdkTree` component is effectively a noop, so we are removing it.\n  // The view for `CdkTree` consists entirely of templates declared in other views. As they are\n  // declared elsewhere, they are checked when their declaration points are checked.\n  // tslint:disable-next-line:validate-decorators\n  changeDetection: ChangeDetectionStrategy.Default,\n  imports: [CdkTreeNodeOutlet],\n})\nexport class CdkTree<T, K = T>\n  implements\n    AfterContentChecked,\n    AfterContentInit,\n    AfterViewInit,\n    CollectionViewer,\n    OnDestroy,\n    OnInit\n{\n  private _differs = inject(IterableDiffers);\n  private _changeDetectorRef = inject(ChangeDetectorRef);\n  private _elementRef = inject(ElementRef);\n\n  private _dir = inject(Directionality);\n\n  /** Subject that emits when the component has been destroyed. */\n  private readonly _onDestroy = new Subject<void>();\n\n  /** Differ used to find the changes in the data provided by the data source. */\n  private _dataDiffer: IterableDiffer<T>;\n\n  /** Stores the node definition that does not have a when predicate. */\n  private _defaultNodeDef: CdkTreeNodeDef<T> | null;\n\n  /** Data subscription */\n  private _dataSubscription: Subscription | null;\n\n  /** Level of nodes */\n  private _levels: Map<K, number> = new Map<K, number>();\n\n  /** The immediate parents for a node. This is `null` if there is no parent. */\n  private _parents: Map<K, T | null> = new Map<K, T | null>();\n\n  /**\n   * Nodes grouped into each set, which is a list of nodes displayed together in the DOM.\n   *\n   * Lookup key is the parent of a set. Root nodes have key of null.\n   *\n   * Values is a 'set' of tree nodes. Each tree node maps to a treeitem element. Sets are in the\n   * order that it is rendered. Each set maps directly to aria-posinset and aria-setsize attributes.\n   */\n  private _ariaSets: Map<K | null, T[]> = new Map<K | null, T[]>();\n\n  /**\n   * Provides a stream containing the latest data array to render. Influenced by the tree's\n   * stream of view window (what dataNodes are currently on screen).\n   * Data source can be an observable of data array, or a data array to render.\n   */\n  @Input()\n  get dataSource(): DataSource<T> | Observable<T[]> | T[] {\n    return this._dataSource;\n  }\n  set dataSource(dataSource: DataSource<T> | Observable<T[]> | T[]) {\n    if (this._dataSource !== dataSource) {\n      this._switchDataSource(dataSource);\n    }\n  }\n  private _dataSource: DataSource<T> | Observable<T[]> | T[];\n\n  /**\n   * The tree controller\n   *\n   * @deprecated Use one of `levelAccessor` or `childrenAccessor` instead. To be removed in a\n   * future version.\n   * @breaking-change 21.0.0\n   */\n  @Input() treeControl?: TreeControl<T, K>;\n\n  /**\n   * Given a data node, determines what tree level the node is at.\n   *\n   * One of levelAccessor or childrenAccessor must be specified, not both.\n   * This is enforced at run-time.\n   */\n  @Input() levelAccessor?: (dataNode: T) => number;\n\n  /**\n   * Given a data node, determines what the children of that node are.\n   *\n   * One of levelAccessor or childrenAccessor must be specified, not both.\n   * This is enforced at run-time.\n   */\n  @Input() childrenAccessor?: (dataNode: T) => T[] | Observable<T[]>;\n\n  /**\n   * Tracking function that will be used to check the differences in data changes. Used similarly\n   * to `ngFor` `trackBy` function. Optimize node operations by identifying a node based on its data\n   * relative to the function to know if a node should be added/removed/moved.\n   * Accepts a function that takes two parameters, `index` and `item`.\n   */\n  @Input() trackBy: TrackByFunction<T>;\n\n  /**\n   * Given a data node, determines the key by which we determine whether or not this node is expanded.\n   */\n  @Input() expansionKey?: (dataNode: T) => K;\n\n  // Outlets within the tree's template where the dataNodes will be inserted.\n  @ViewChild(CdkTreeNodeOutlet, {static: true}) _nodeOutlet: CdkTreeNodeOutlet;\n\n  /** The tree node template for the tree */\n  @ContentChildren(CdkTreeNodeDef, {\n    // We need to use `descendants: true`, because Ivy will no longer match\n    // indirect descendants if it's left as false.\n    descendants: true,\n  })\n  _nodeDefs: QueryList<CdkTreeNodeDef<T>>;\n\n  // TODO(tinayuangao): Setup a listener for scrolling, emit the calculated view to viewChange.\n  //     Remove the MAX_VALUE in viewChange\n  /**\n   * Stream containing the latest information on what rows are being displayed on screen.\n   * Can be used by the data source to as a heuristic of what data should be provided.\n   */\n  readonly viewChange = new BehaviorSubject<{start: number; end: number}>({\n    start: 0,\n    end: Number.MAX_VALUE,\n  });\n\n  /** Keep track of which nodes are expanded. */\n  private _expansionModel?: SelectionModel<K>;\n\n  /**\n   * Maintain a synchronous cache of flattened data nodes. This will only be\n   * populated after initial render, and in certain cases, will be delayed due to\n   * relying on Observable `getChildren` calls.\n   */\n  private _flattenedNodes: BehaviorSubject<readonly T[]> = new BehaviorSubject<readonly T[]>([]);\n\n  /** The automatically determined node type for the tree. */\n  private _nodeType: BehaviorSubject<'flat' | 'nested' | null> = new BehaviorSubject<\n    'flat' | 'nested' | null\n  >(null);\n\n  /** The mapping between data and the node that is rendered. */\n  private _nodes: BehaviorSubject<Map<K, CdkTreeNode<T, K>>> = new BehaviorSubject(\n    new Map<K, CdkTreeNode<T, K>>(),\n  );\n\n  /**\n   * Synchronous cache of nodes for the `TreeKeyManager`. This is separate\n   * from `_flattenedNodes` so they can be independently updated at different\n   * times.\n   */\n  private _keyManagerNodes: BehaviorSubject<readonly T[]> = new BehaviorSubject<readonly T[]>([]);\n\n  private _keyManagerFactory = inject(TREE_KEY_MANAGER) as TreeKeyManagerFactory<CdkTreeNode<T, K>>;\n\n  /** The key manager for this tree. Handles focus and activation based on user keyboard input. */\n  _keyManager: TreeKeyManagerStrategy<CdkTreeNode<T, K>>;\n  private _viewInit = false;\n\n  constructor(...args: unknown[]);\n  constructor() {}\n\n  ngAfterContentInit() {\n    this._initializeKeyManager();\n  }\n\n  ngAfterContentChecked() {\n    this._updateDefaultNodeDefinition();\n    this._subscribeToDataChanges();\n  }\n\n  ngOnDestroy() {\n    this._nodeOutlet.viewContainer.clear();\n\n    this.viewChange.complete();\n    this._onDestroy.next();\n    this._onDestroy.complete();\n\n    if (this._dataSource && typeof (this._dataSource as DataSource<T>).disconnect === 'function') {\n      (this.dataSource as DataSource<T>).disconnect(this);\n    }\n\n    if (this._dataSubscription) {\n      this._dataSubscription.unsubscribe();\n      this._dataSubscription = null;\n    }\n\n    // In certain tests, the tree might be destroyed before this is initialized\n    // in `ngAfterContentInit`.\n    this._keyManager?.destroy();\n  }\n\n  ngOnInit() {\n    this._checkTreeControlUsage();\n    this._initializeDataDiffer();\n  }\n\n  ngAfterViewInit() {\n    this._viewInit = true;\n  }\n\n  private _updateDefaultNodeDefinition() {\n    const defaultNodeDefs = this._nodeDefs.filter(def => !def.when);\n    if (defaultNodeDefs.length > 1 && (typeof ngDevMode === 'undefined' || ngDevMode)) {\n      throw getTreeMultipleDefaultNodeDefsError();\n    }\n    this._defaultNodeDef = defaultNodeDefs[0];\n  }\n\n  /**\n   * Sets the node type for the tree, if it hasn't been set yet.\n   *\n   * This will be called by the first node that's rendered in order for the tree\n   * to determine what data transformations are required.\n   */\n  _setNodeTypeIfUnset(newType: 'flat' | 'nested') {\n    const currentType = this._nodeType.value;\n\n    if (currentType === null) {\n      this._nodeType.next(newType);\n    } else if ((typeof ngDevMode === 'undefined' || ngDevMode) && currentType !== newType) {\n      console.warn(\n        `Tree is using conflicting node types which can cause unexpected behavior. ` +\n          `Please use tree nodes of the same type (e.g. only flat or only nested). ` +\n          `Current node type: \"${currentType}\", new node type \"${newType}\".`,\n      );\n    }\n  }\n\n  /**\n   * Switch to the provided data source by resetting the data and unsubscribing from the current\n   * render change subscription if one exists. If the data source is null, interpret this by\n   * clearing the node outlet. Otherwise start listening for new data.\n   */\n  private _switchDataSource(dataSource: DataSource<T> | Observable<T[]> | T[]) {\n    if (this._dataSource && typeof (this._dataSource as DataSource<T>).disconnect === 'function') {\n      (this.dataSource as DataSource<T>).disconnect(this);\n    }\n\n    if (this._dataSubscription) {\n      this._dataSubscription.unsubscribe();\n      this._dataSubscription = null;\n    }\n\n    // Remove the all dataNodes if there is now no data source\n    if (!dataSource) {\n      this._nodeOutlet.viewContainer.clear();\n    }\n\n    this._dataSource = dataSource;\n    if (this._nodeDefs) {\n      this._subscribeToDataChanges();\n    }\n  }\n\n  _getExpansionModel() {\n    if (!this.treeControl) {\n      this._expansionModel ??= new SelectionModel<K>(true);\n      return this._expansionModel;\n    }\n    return this.treeControl.expansionModel;\n  }\n\n  /** Set up a subscription for the data provided by the data source. */\n  private _subscribeToDataChanges() {\n    if (this._dataSubscription) {\n      return;\n    }\n\n    let dataStream: Observable<readonly T[]> | undefined;\n\n    if (isDataSource(this._dataSource)) {\n      dataStream = this._dataSource.connect(this);\n    } else if (isObservable(this._dataSource)) {\n      dataStream = this._dataSource;\n    } else if (Array.isArray(this._dataSource)) {\n      dataStream = observableOf(this._dataSource);\n    }\n\n    if (!dataStream) {\n      if (typeof ngDevMode === 'undefined' || ngDevMode) {\n        throw getTreeNoValidDataSourceError();\n      }\n      return;\n    }\n\n    this._dataSubscription = this._getRenderData(dataStream)\n      .pipe(takeUntil(this._onDestroy))\n      .subscribe(renderingData => {\n        this._renderDataChanges(renderingData);\n      });\n  }\n\n  /** Given an Observable containing a stream of the raw data, returns an Observable containing the RenderingData */\n  private _getRenderData(dataStream: Observable<readonly T[]>): Observable<RenderingData<T>> {\n    const expansionModel = this._getExpansionModel();\n    return combineLatest([\n      dataStream,\n      this._nodeType,\n      // We don't use the expansion data directly, however we add it here to essentially\n      // trigger data rendering when expansion changes occur.\n      expansionModel.changed.pipe(\n        startWith(null),\n        tap(expansionChanges => {\n          this._emitExpansionChanges(expansionChanges);\n        }),\n      ),\n    ]).pipe(\n      switchMap(([data, nodeType]) => {\n        if (nodeType === null) {\n          return observableOf({renderNodes: data, flattenedNodes: null, nodeType} as const);\n        }\n\n        // If we're here, then we know what our node type is, and therefore can\n        // perform our usual rendering pipeline, which necessitates converting the data\n        return this._computeRenderingData(data, nodeType).pipe(\n          map(convertedData => ({...convertedData, nodeType}) as const),\n        );\n      }),\n    );\n  }\n\n  private _renderDataChanges(data: RenderingData<T>) {\n    if (data.nodeType === null) {\n      this.renderNodeChanges(data.renderNodes);\n      return;\n    }\n\n    // If we're here, then we know what our node type is, and therefore can\n    // perform our usual rendering pipeline.\n    this._updateCachedData(data.flattenedNodes);\n    this.renderNodeChanges(data.renderNodes);\n    this._updateKeyManagerItems(data.flattenedNodes);\n  }\n\n  private _emitExpansionChanges(expansionChanges: SelectionChange<K> | null) {\n    if (!expansionChanges) {\n      return;\n    }\n\n    const nodes = this._nodes.value;\n    for (const added of expansionChanges.added) {\n      const node = nodes.get(added);\n      node?._emitExpansionState(true);\n    }\n    for (const removed of expansionChanges.removed) {\n      const node = nodes.get(removed);\n      node?._emitExpansionState(false);\n    }\n  }\n\n  private _initializeKeyManager() {\n    const items = combineLatest([this._keyManagerNodes, this._nodes]).pipe(\n      map(([keyManagerNodes, renderNodes]) =>\n        keyManagerNodes.reduce<CdkTreeNode<T, K>[]>((items, data) => {\n          const node = renderNodes.get(this._getExpansionKey(data));\n          if (node) {\n            items.push(node);\n          }\n          return items;\n        }, []),\n      ),\n    );\n\n    const keyManagerOptions: TreeKeyManagerOptions<CdkTreeNode<T, K>> = {\n      trackBy: node => this._getExpansionKey(node.data),\n      skipPredicate: node => !!node.isDisabled,\n      typeAheadDebounceInterval: true,\n      horizontalOrientation: this._dir.value,\n    };\n\n    this._keyManager = this._keyManagerFactory(items, keyManagerOptions);\n  }\n\n  private _initializeDataDiffer() {\n    // Provide a default trackBy based on `_getExpansionKey` if one isn't provided.\n    const trackBy = this.trackBy ?? ((_index: number, item: T) => this._getExpansionKey(item));\n    this._dataDiffer = this._differs.find([]).create(trackBy);\n  }\n\n  private _checkTreeControlUsage() {\n    if (typeof ngDevMode === 'undefined' || ngDevMode) {\n      // Verify that Tree follows API contract of using one of TreeControl, levelAccessor or\n      // childrenAccessor. Throw an appropriate error if contract is not met.\n      let numTreeControls = 0;\n\n      if (this.treeControl) {\n        numTreeControls++;\n      }\n      if (this.levelAccessor) {\n        numTreeControls++;\n      }\n      if (this.childrenAccessor) {\n        numTreeControls++;\n      }\n\n      if (!numTreeControls) {\n        throw getTreeControlMissingError();\n      } else if (numTreeControls > 1) {\n        throw getMultipleTreeControlsError();\n      }\n    }\n  }\n\n  /** Check for changes made in the data and render each change (node added/removed/moved). */\n  renderNodeChanges(\n    data: readonly T[],\n    dataDiffer: IterableDiffer<T> = this._dataDiffer,\n    viewContainer: ViewContainerRef = this._nodeOutlet.viewContainer,\n    parentData?: T,\n  ) {\n    const changes = dataDiffer.diff(data);\n\n    // Some tree consumers expect change detection to propagate to nodes\n    // even when the array itself hasn't changed; we explicitly detect changes\n    // anyways in order for nodes to update their data.\n    //\n    // However, if change detection is called while the component's view is\n    // still initing, then the order of child views initing will be incorrect;\n    // to prevent this, we only exit early if the view hasn't initialized yet.\n    if (!changes && !this._viewInit) {\n      return;\n    }\n\n    changes?.forEachOperation(\n      (\n        item: IterableChangeRecord<T>,\n        adjustedPreviousIndex: number | null,\n        currentIndex: number | null,\n      ) => {\n        if (item.previousIndex == null) {\n          this.insertNode(data[currentIndex!], currentIndex!, viewContainer, parentData);\n        } else if (currentIndex == null) {\n          viewContainer.remove(adjustedPreviousIndex!);\n        } else {\n          const view = viewContainer.get(adjustedPreviousIndex!);\n          viewContainer.move(view!, currentIndex);\n        }\n      },\n    );\n\n    // If the data itself changes, but keeps the same trackBy, we need to update the templates'\n    // context to reflect the new object.\n    changes?.forEachIdentityChange((record: IterableChangeRecord<T>) => {\n      const newData = record.item;\n      if (record.currentIndex != undefined) {\n        const view = viewContainer.get(record.currentIndex);\n        (view as EmbeddedViewRef<any>).context.$implicit = newData;\n      }\n    });\n\n    // Note: we only `detectChanges` from a top-level call, otherwise we risk overflowing\n    // the call stack since this method is called recursively (see #29733.)\n    // TODO: change to `this._changeDetectorRef.markForCheck()`,\n    // or just switch this component to use signals.\n    if (parentData) {\n      this._changeDetectorRef.markForCheck();\n    } else {\n      this._changeDetectorRef.detectChanges();\n    }\n  }\n\n  /**\n   * Finds the matching node definition that should be used for this node data. If there is only\n   * one node definition, it is returned. Otherwise, find the node definition that has a when\n   * predicate that returns true with the data. If none return true, return the default node\n   * definition.\n   */\n  _getNodeDef(data: T, i: number): CdkTreeNodeDef<T> {\n    if (this._nodeDefs.length === 1) {\n      return this._nodeDefs.first!;\n    }\n\n    const nodeDef =\n      this._nodeDefs.find(def => def.when && def.when(i, data)) || this._defaultNodeDef;\n\n    if (!nodeDef && (typeof ngDevMode === 'undefined' || ngDevMode)) {\n      throw getTreeMissingMatchingNodeDefError();\n    }\n\n    return nodeDef!;\n  }\n\n  /**\n   * Create the embedded view for the data node template and place it in the correct index location\n   * within the data node view container.\n   */\n  insertNode(nodeData: T, index: number, viewContainer?: ViewContainerRef, parentData?: T) {\n    const levelAccessor = this._getLevelAccessor();\n\n    const node = this._getNodeDef(nodeData, index);\n    const key = this._getExpansionKey(nodeData);\n\n    // Node context that will be provided to created embedded view\n    const context = new CdkTreeNodeOutletContext<T>(nodeData);\n\n    parentData ??= this._parents.get(key) ?? undefined;\n    // If the tree is flat tree, then use the `getLevel` function in flat tree control\n    // Otherwise, use the level of parent node.\n    if (levelAccessor) {\n      context.level = levelAccessor(nodeData);\n    } else if (parentData !== undefined && this._levels.has(this._getExpansionKey(parentData))) {\n      context.level = this._levels.get(this._getExpansionKey(parentData))! + 1;\n    } else {\n      context.level = 0;\n    }\n    this._levels.set(key, context.level);\n\n    // Use default tree nodeOutlet, or nested node's nodeOutlet\n    const container = viewContainer ? viewContainer : this._nodeOutlet.viewContainer;\n    container.createEmbeddedView(node.template, context, index);\n\n    // Set the data to just created `CdkTreeNode`.\n    // The `CdkTreeNode` created from `createEmbeddedView` will be saved in static variable\n    //     `mostRecentTreeNode`. We get it from static variable and pass the node data to it.\n    if (CdkTreeNode.mostRecentTreeNode) {\n      CdkTreeNode.mostRecentTreeNode.data = nodeData;\n    }\n  }\n\n  /** Whether the data node is expanded or collapsed. Returns true if it's expanded. */\n  isExpanded(dataNode: T): boolean {\n    return !!(\n      this.treeControl?.isExpanded(dataNode) ||\n      this._expansionModel?.isSelected(this._getExpansionKey(dataNode))\n    );\n  }\n\n  /** If the data node is currently expanded, collapse it. Otherwise, expand it. */\n  toggle(dataNode: T): void {\n    if (this.treeControl) {\n      this.treeControl.toggle(dataNode);\n    } else if (this._expansionModel) {\n      this._expansionModel.toggle(this._getExpansionKey(dataNode));\n    }\n  }\n\n  /** Expand the data node. If it is already expanded, does nothing. */\n  expand(dataNode: T): void {\n    if (this.treeControl) {\n      this.treeControl.expand(dataNode);\n    } else if (this._expansionModel) {\n      this._expansionModel.select(this._getExpansionKey(dataNode));\n    }\n  }\n\n  /** Collapse the data node. If it is already collapsed, does nothing. */\n  collapse(dataNode: T): void {\n    if (this.treeControl) {\n      this.treeControl.collapse(dataNode);\n    } else if (this._expansionModel) {\n      this._expansionModel.deselect(this._getExpansionKey(dataNode));\n    }\n  }\n\n  /**\n   * If the data node is currently expanded, collapse it and all its descendants.\n   * Otherwise, expand it and all its descendants.\n   */\n  toggleDescendants(dataNode: T): void {\n    if (this.treeControl) {\n      this.treeControl.toggleDescendants(dataNode);\n    } else if (this._expansionModel) {\n      if (this.isExpanded(dataNode)) {\n        this.collapseDescendants(dataNode);\n      } else {\n        this.expandDescendants(dataNode);\n      }\n    }\n  }\n\n  /**\n   * Expand the data node and all its descendants. If they are already expanded, does nothing.\n   */\n  expandDescendants(dataNode: T): void {\n    if (this.treeControl) {\n      this.treeControl.expandDescendants(dataNode);\n    } else if (this._expansionModel) {\n      const expansionModel = this._expansionModel;\n      expansionModel.select(this._getExpansionKey(dataNode));\n      this._getDescendants(dataNode)\n        .pipe(take(1), takeUntil(this._onDestroy))\n        .subscribe(children => {\n          expansionModel.select(...children.map(child => this._getExpansionKey(child)));\n        });\n    }\n  }\n\n  /** Collapse the data node and all its descendants. If it is already collapsed, does nothing. */\n  collapseDescendants(dataNode: T): void {\n    if (this.treeControl) {\n      this.treeControl.collapseDescendants(dataNode);\n    } else if (this._expansionModel) {\n      const expansionModel = this._expansionModel;\n      expansionModel.deselect(this._getExpansionKey(dataNode));\n      this._getDescendants(dataNode)\n        .pipe(take(1), takeUntil(this._onDestroy))\n        .subscribe(children => {\n          expansionModel.deselect(...children.map(child => this._getExpansionKey(child)));\n        });\n    }\n  }\n\n  /** Expands all data nodes in the tree. */\n  expandAll(): void {\n    if (this.treeControl) {\n      this.treeControl.expandAll();\n    } else if (this._expansionModel) {\n      this._forEachExpansionKey(keys => this._expansionModel?.select(...keys));\n    }\n  }\n\n  /** Collapse all data nodes in the tree. */\n  collapseAll(): void {\n    if (this.treeControl) {\n      this.treeControl.collapseAll();\n    } else if (this._expansionModel) {\n      this._forEachExpansionKey(keys => this._expansionModel?.deselect(...keys));\n    }\n  }\n\n  /** Level accessor, used for compatibility between the old Tree and new Tree */\n  _getLevelAccessor() {\n    return this.treeControl?.getLevel?.bind(this.treeControl) ?? this.levelAccessor;\n  }\n\n  /** Children accessor, used for compatibility between the old Tree and new Tree */\n  _getChildrenAccessor() {\n    return this.treeControl?.getChildren?.bind(this.treeControl) ?? this.childrenAccessor;\n  }\n\n  /**\n   * Gets the direct children of a node; used for compatibility between the old tree and the\n   * new tree.\n   */\n  _getDirectChildren(dataNode: T): Observable<T[]> {\n    const levelAccessor = this._getLevelAccessor();\n    const expansionModel = this._expansionModel ?? this.treeControl?.expansionModel;\n    if (!expansionModel) {\n      return observableOf([]);\n    }\n\n    const key = this._getExpansionKey(dataNode);\n\n    const isExpanded = expansionModel.changed.pipe(\n      switchMap(changes => {\n        if (changes.added.includes(key)) {\n          return observableOf(true);\n        } else if (changes.removed.includes(key)) {\n          return observableOf(false);\n        }\n        return EMPTY;\n      }),\n      startWith(this.isExpanded(dataNode)),\n    );\n\n    if (levelAccessor) {\n      return combineLatest([isExpanded, this._flattenedNodes]).pipe(\n        map(([expanded, flattenedNodes]) => {\n          if (!expanded) {\n            return [];\n          }\n          return this._findChildrenByLevel(levelAccessor, flattenedNodes, dataNode, 1);\n        }),\n      );\n    }\n    const childrenAccessor = this._getChildrenAccessor();\n    if (childrenAccessor) {\n      return coerceObservable(childrenAccessor(dataNode) ?? []);\n    }\n    throw getTreeControlMissingError();\n  }\n\n  /**\n   * Given the list of flattened nodes, the level accessor, and the level range within\n   * which to consider children, finds the children for a given node.\n   *\n   * For example, for direct children, `levelDelta` would be 1. For all descendants,\n   * `levelDelta` would be Infinity.\n   */\n  private _findChildrenByLevel(\n    levelAccessor: (node: T) => number,\n    flattenedNodes: readonly T[],\n    dataNode: T,\n    levelDelta: number,\n  ): T[] {\n    const key = this._getExpansionKey(dataNode);\n    const startIndex = flattenedNodes.findIndex(node => this._getExpansionKey(node) === key);\n    const dataNodeLevel = levelAccessor(dataNode);\n    const expectedLevel = dataNodeLevel + levelDelta;\n    const results: T[] = [];\n\n    // Goes through flattened tree nodes in the `flattenedNodes` array, and get all\n    // descendants within a certain level range.\n    //\n    // If we reach a node whose level is equal to or less than the level of the tree node,\n    // we hit a sibling or parent's sibling, and should stop.\n    for (let i = startIndex + 1; i < flattenedNodes.length; i++) {\n      const currentLevel = levelAccessor(flattenedNodes[i]);\n      if (currentLevel <= dataNodeLevel) {\n        break;\n      }\n      if (currentLevel <= expectedLevel) {\n        results.push(flattenedNodes[i]);\n      }\n    }\n    return results;\n  }\n\n  /**\n   * Adds the specified node component to the tree's internal registry.\n   *\n   * This primarily facilitates keyboard navigation.\n   */\n  _registerNode(node: CdkTreeNode<T, K>) {\n    this._nodes.value.set(this._getExpansionKey(node.data), node);\n    this._nodes.next(this._nodes.value);\n  }\n\n  /** Removes the specified node component from the tree's internal registry. */\n  _unregisterNode(node: CdkTreeNode<T, K>) {\n    this._nodes.value.delete(this._getExpansionKey(node.data));\n    this._nodes.next(this._nodes.value);\n  }\n\n  /**\n   * For the given node, determine the level where this node appears in the tree.\n   *\n   * This is intended to be used for `aria-level` but is 0-indexed.\n   */\n  _getLevel(node: T) {\n    return this._levels.get(this._getExpansionKey(node));\n  }\n\n  /**\n   * For the given node, determine the size of the parent's child set.\n   *\n   * This is intended to be used for `aria-setsize`.\n   */\n  _getSetSize(dataNode: T) {\n    const set = this._getAriaSet(dataNode);\n    return set.length;\n  }\n\n  /**\n   * For the given node, determine the index (starting from 1) of the node in its parent's child set.\n   *\n   * This is intended to be used for `aria-posinset`.\n   */\n  _getPositionInSet(dataNode: T) {\n    const set = this._getAriaSet(dataNode);\n    const key = this._getExpansionKey(dataNode);\n    return set.findIndex(node => this._getExpansionKey(node) === key) + 1;\n  }\n\n  /** Given a CdkTreeNode, gets the node that renders that node's parent's data. */\n  _getNodeParent(node: CdkTreeNode<T, K>) {\n    const parent = this._parents.get(this._getExpansionKey(node.data));\n    return parent && this._nodes.value.get(this._getExpansionKey(parent));\n  }\n\n  /** Given a CdkTreeNode, gets the nodes that renders that node's child data. */\n  _getNodeChildren(node: CdkTreeNode<T, K>) {\n    return this._getDirectChildren(node.data).pipe(\n      map(children =>\n        children.reduce<CdkTreeNode<T, K>[]>((nodes, child) => {\n          const value = this._nodes.value.get(this._getExpansionKey(child));\n          if (value) {\n            nodes.push(value);\n          }\n\n          return nodes;\n        }, []),\n      ),\n    );\n  }\n\n  /** `keydown` event handler; this just passes the event to the `TreeKeyManager`. */\n  protected _sendKeydownToKeyManager(event: KeyboardEvent): void {\n    // Only handle events directly on the tree or directly on one of the nodes, otherwise\n    // we risk interfering with events in the projected content (see #29828).\n    if (event.target === this._elementRef.nativeElement) {\n      this._keyManager.onKeydown(event);\n    } else {\n      const nodes = this._nodes.getValue();\n      for (const [, node] of nodes) {\n        if (event.target === node._elementRef.nativeElement) {\n          this._keyManager.onKeydown(event);\n          break;\n        }\n      }\n    }\n  }\n\n  /** Gets all nested descendants of a given node. */\n  private _getDescendants(dataNode: T): Observable<T[]> {\n    if (this.treeControl) {\n      return observableOf(this.treeControl.getDescendants(dataNode));\n    }\n    if (this.levelAccessor) {\n      const results = this._findChildrenByLevel(\n        this.levelAccessor,\n        this._flattenedNodes.value,\n        dataNode,\n        Infinity,\n      );\n      return observableOf(results);\n    }\n    if (this.childrenAccessor) {\n      return this._getAllChildrenRecursively(dataNode).pipe(\n        reduce((allChildren: T[], nextChildren) => {\n          allChildren.push(...nextChildren);\n          return allChildren;\n        }, []),\n      );\n    }\n    throw getTreeControlMissingError();\n  }\n\n  /**\n   * Gets all children and sub-children of the provided node.\n   *\n   * This will emit multiple times, in the order that the children will appear\n   * in the tree, and can be combined with a `reduce` operator.\n   */\n  private _getAllChildrenRecursively(dataNode: T): Observable<T[]> {\n    if (!this.childrenAccessor) {\n      return observableOf([]);\n    }\n\n    return coerceObservable(this.childrenAccessor(dataNode)).pipe(\n      take(1),\n      switchMap(children => {\n        // Here, we cache the parents of a particular child so that we can compute the levels.\n        for (const child of children) {\n          this._parents.set(this._getExpansionKey(child), dataNode);\n        }\n        return observableOf(...children).pipe(\n          concatMap(child => concat(observableOf([child]), this._getAllChildrenRecursively(child))),\n        );\n      }),\n    );\n  }\n\n  private _getExpansionKey(dataNode: T): K {\n    // In the case that a key accessor function was not provided by the\n    // tree user, we'll default to using the node object itself as the key.\n    //\n    // This cast is safe since:\n    // - if an expansionKey is provided, TS will infer the type of K to be\n    //   the return type.\n    // - if it's not, then K will be defaulted to T.\n    return this.expansionKey?.(dataNode) ?? (dataNode as unknown as K);\n  }\n\n  private _getAriaSet(node: T) {\n    const key = this._getExpansionKey(node);\n    const parent = this._parents.get(key);\n    const parentKey = parent ? this._getExpansionKey(parent) : null;\n    const set = this._ariaSets.get(parentKey);\n    return set ?? [node];\n  }\n\n  /**\n   * Finds the parent for the given node. If this is a root node, this\n   * returns null. If we're unable to determine the parent, for example,\n   * if we don't have cached node data, this returns undefined.\n   */\n  private _findParentForNode(node: T, index: number, cachedNodes: readonly T[]): T | null {\n    // In all cases, we have a mapping from node to level; all we need to do here is backtrack in\n    // our flattened list of nodes to determine the first node that's of a level lower than the\n    // provided node.\n    if (!cachedNodes.length) {\n      return null;\n    }\n    const currentLevel = this._levels.get(this._getExpansionKey(node)) ?? 0;\n    for (let parentIndex = index - 1; parentIndex >= 0; parentIndex--) {\n      const parentNode = cachedNodes[parentIndex];\n      const parentLevel = this._levels.get(this._getExpansionKey(parentNode)) ?? 0;\n\n      if (parentLevel < currentLevel) {\n        return parentNode;\n      }\n    }\n    return null;\n  }\n\n  /**\n   * Given a set of root nodes and the current node level, flattens any nested\n   * nodes into a single array.\n   *\n   * If any nodes are not expanded, then their children will not be added into the array.\n   * This will still traverse all nested children in order to build up our internal data\n   * models, but will not include them in the returned array.\n   */\n  private _flattenNestedNodesWithExpansion(nodes: readonly T[], level = 0): Observable<T[]> {\n    const childrenAccessor = this._getChildrenAccessor();\n    // If we're using a level accessor, we don't need to flatten anything.\n    if (!childrenAccessor) {\n      return observableOf([...nodes]);\n    }\n\n    return observableOf(...nodes).pipe(\n      concatMap(node => {\n        const parentKey = this._getExpansionKey(node);\n        if (!this._parents.has(parentKey)) {\n          this._parents.set(parentKey, null);\n        }\n        this._levels.set(parentKey, level);\n\n        const children = coerceObservable(childrenAccessor(node));\n        return concat(\n          observableOf([node]),\n          children.pipe(\n            take(1),\n            tap(childNodes => {\n              this._ariaSets.set(parentKey, [...(childNodes ?? [])]);\n              for (const child of childNodes ?? []) {\n                const childKey = this._getExpansionKey(child);\n                this._parents.set(childKey, node);\n                this._levels.set(childKey, level + 1);\n              }\n            }),\n            switchMap(childNodes => {\n              if (!childNodes) {\n                return observableOf([]);\n              }\n              return this._fla