playwright/packages/playwright-core/src/server/webkit/wkAccessibility.ts

/**
 * Copyright (c) Microsoft Corporation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import * as accessibility from '../accessibility';
import { WKSession } from './wkConnection';
import { Protocol } from './protocol';
import * as dom from '../dom';
import * as types from '../types';

export async function getAccessibilityTree(session: WKSession, needle?: dom.ElementHandle) {
  const objectId = needle ? needle._objectId : undefined;
  const { axNode } = await session.send('Page.accessibilitySnapshot', { objectId });
  const tree = new WKAXNode(axNode);
  return {
    tree,
    needle: needle ? tree._findNeedle() : null
  };
}

const WKRoleToARIARole = new Map(Object.entries({
  'TextField': 'textbox',
}));

// WebKit localizes role descriptions on mac, but the english versions only add noise.
const WKUnhelpfulRoleDescriptions = new Map(Object.entries({
  'WebArea': 'HTML content',
  'Summary': 'summary',
  'DescriptionList': 'description list',
  'ImageMap': 'image map',
  'ListMarker': 'list marker',
  'Video': 'video playback',
  'Mark': 'highlighted',
  'contentinfo': 'content information',
  'Details': 'details',
  'DescriptionListDetail': 'description',
  'DescriptionListTerm': 'term',
  'alertdialog': 'web alert dialog',
  'dialog': 'web dialog',
  'status': 'application status',
  'tabpanel': 'tab panel',
  'application': 'web application',
}));

class WKAXNode implements accessibility.AXNode {
  private _payload: Protocol.Page.AXNode;
  private _children: WKAXNode[];

  constructor(payload: Protocol.Page.AXNode) {
    this._payload = payload;

    this._children = [];
    for (const payload of this._payload.children || [])
      this._children.push(new WKAXNode(payload));
  }

  children() {
    return this._children;
  }

  _findNeedle(): WKAXNode | null {
    if (this._payload.found)
      return this;
    for (const child of this._children) {
      const found = child._findNeedle();
      if (found)
        return found;
    }
    return null;
  }

  isControl(): boolean {
    switch (this._payload.role) {
      case 'button':
      case 'checkbox':
      case 'ColorWell':
      case 'combobox':
      case 'DisclosureTriangle':
      case 'listbox':
      case 'menu':
      case 'menubar':
      case 'menuitem':
      case 'menuitemcheckbox':
      case 'menuitemradio':
      case 'radio':
      case 'scrollbar':
      case 'searchbox':
      case 'slider':
      case 'spinbutton':
      case 'switch':
      case 'tab':
      case 'textbox':
      case 'TextField':
      case 'tree':
        return true;
      default:
        return false;
    }
  }

  _isTextControl(): boolean {
    switch (this._payload.role) {
      case 'combobox':
      case 'searchfield':
      case 'textbox':
      case 'TextField':
        return true;
    }
    return false;
  }

  _name(): string {
    if (this._payload.role === 'text')
      return this._payload.value || '';
    return this._payload.name || '';
  }

  isInteresting(insideControl: boolean): boolean {
    const { role, focusable } = this._payload;
    const name = this._name();
    if (role === 'ScrollArea')
      return false;
    if (role === 'WebArea')
      return true;

    if (focusable || role === 'MenuListOption')
      return true;

    // If it's not focusable but has a control role, then it's interesting.
    if (this.isControl())
      return true;

    // A non focusable child of a control is not interesting
    if (insideControl)
      return false;

    return this.isLeafNode() && !!name;
  }

  _hasRendundantTextChild() {
    if (this._children.length !== 1)
      return false;
    const child = this._children[0];
    return child._payload.role === 'text' && this._payload.name === child._payload.value;
  }

  isLeafNode(): boolean {
    if (!this._children.length)
      return true;
      // WebKit on Linux ignores everything inside text controls, normalize this behavior
    if (this._isTextControl())
      return true;
      // WebKit for mac has text nodes inside heading, li, menuitem, a, and p nodes
    if (this._hasRendundantTextChild())
      return true;
    return false;
  }

  serialize(): types.SerializedAXNode {
    const node: types.SerializedAXNode = {
      role: WKRoleToARIARole.get(this._payload.role) || this._payload.role,
      name: this._name(),
    };

    if ('description' in this._payload && this._payload.description !== node.name)
      node.description = this._payload.description;

    if ('roledescription' in this._payload) {
      const roledescription = this._payload.roledescription;
      if (roledescription !== this._payload.role && WKUnhelpfulRoleDescriptions.get(this._payload.role) !== roledescription)
        node.roledescription = roledescription;
    }

    if ('value' in this._payload && this._payload.role !== 'text') {
      if (typeof this._payload.value === 'string')
        node.valueString = this._payload.value;
      else if (typeof this._payload.value === 'number')
        node.valueNumber = this._payload.value;
    }

    if ('checked' in this._payload)
      node.checked = this._payload.checked === 'true' ? 'checked' : this._payload.checked === 'false' ? 'unchecked' : 'mixed';

    if ('pressed' in this._payload)
      node.pressed = this._payload.pressed === 'true' ? 'pressed' : this._payload.pressed === 'false' ? 'released' : 'mixed';

    const userStringProperties: Array<keyof types.SerializedAXNode & keyof Protocol.Page.AXNode> = [
      'keyshortcuts',
      'valuetext'
    ];
    for (const userStringProperty of userStringProperties) {
      if (!(userStringProperty in this._payload))
        continue;
      (node as any)[userStringProperty] = this._payload[userStringProperty];
    }

    const booleanProperties: Array<keyof types.SerializedAXNode & keyof Protocol.Page.AXNode> = [
      'disabled',
      'expanded',
      'focused',
      'modal',
      'multiline',
      'multiselectable',
      'readonly',
      'required',
      'selected',
    ];
    for (const booleanProperty of booleanProperties) {
      // WebArea and ScorllArea treat focus differently than other nodes. They report whether their frame  has focus,
      // not whether focus is specifically on the root node.
      if (booleanProperty === 'focused' && (this._payload.role === 'WebArea' || this._payload.role === 'ScrollArea'))
        continue;
      const value = this._payload[booleanProperty];
      if (!value)
        continue;
      (node as any)[booleanProperty] = value;
    }

    const numericalProperties: Array<keyof types.SerializedAXNode & keyof Protocol.Page.AXNode> = [
      'level',
      'valuemax',
      'valuemin',
    ];
    for (const numericalProperty of numericalProperties) {
      if (!(numericalProperty in this._payload))
        continue;
      (node as any)[numericalProperty] = (this._payload as any)[numericalProperty];
    }
    const tokenProperties: Array<keyof types.SerializedAXNode & keyof Protocol.Page.AXNode> = [
      'autocomplete',
      'haspopup',
      'invalid',
    ];
    for (const tokenProperty of tokenProperties) {
      const value = (this._payload as any)[tokenProperty];
      if (!value || value === 'false')
        continue;
      (node as any)[tokenProperty] = value;
    }

    const orientationIsApplicable = new Set([
      'ScrollArea',
      'scrollbar',
      'listbox',
      'combobox',
      'menu',
      'tree',
      'separator',
      'slider',
      'tablist',
      'toolbar',
    ]);
    if (this._payload.orientation && orientationIsApplicable.has(this._payload.role))
      node.orientation = this._payload.orientation;

    return node;
  }
}