fix(switch): handle aria-checked correctly. (#5202)

packages/mdc-switch/README.md

@@ -43,7 +43,7 @@ npm install @material/switch
   <div class="mdc-switch__track"></div>
   <div class="mdc-switch__thumb-underlay">
     <div class="mdc-switch__thumb"></div>
-    <input type="checkbox" id="basic-switch" class="mdc-switch__native-control" role="switch">
+    <input type="checkbox" id="basic-switch" class="mdc-switch__native-control" role="switch" aria-checked="false">
   </div>
 </div>
 <label for="basic-switch">off/on</label>
@@ -78,7 +78,7 @@ Add the `mdc-switch--disabled` class to the `mdc-switch` element, and the `disab
   <div class="mdc-switch__track"></div>
   <div class="mdc-switch__thumb-underlay">
     <div class="mdc-switch__thumb"></div>
-    <input type="checkbox" id="another-basic-switch" class="mdc-switch__native-control" role="switch" disabled>
+    <input type="checkbox" id="another-basic-switch" class="mdc-switch__native-control" role="switch" aria-checked="false" disabled>
   </div>
 </div>
 <label for="another-basic-switch">off/on</label>
@@ -93,7 +93,7 @@ Add the `mdc-switch--checked` class to the `mdc-switch` element, and the `checke
   <div class="mdc-switch__track"></div>
   <div class="mdc-switch__thumb-underlay">
     <div class="mdc-switch__thumb"></div>
-    <input type="checkbox" id="another-basic-switch" class="mdc-switch__native-control" role="switch" checked>
+    <input type="checkbox" id="another-basic-switch" class="mdc-switch__native-control" role="switch" aria-checked="false" checked>
   </div>
 </div>
 <label for="another-basic-switch">off/on</label>
@@ -152,6 +152,7 @@ If you are using a JavaScript framework, such as React or Angular, you can creat
 | `removeClass(className: string) => void` | Removes a class from the root element. |
 | `setNativeControlChecked(checked: boolean)` | Sets the checked state of the native control. |
 | `setNativeControlDisabled(disabled: boolean)` | Sets the disabled state of the native control. |
+| `setNativeControlAttr(attr: string, value: string)` | Sets an HTML attribute to the given value on the native input element. |
 
 ### `MDCSwitchFoundation`
 

packages/mdc-switch/adapter.ts

@@ -48,4 +48,9 @@ export interface MDCSwitchAdapter {
    * Sets the disabled state of the native HTML control underlying the switch.
    */
   setNativeControlDisabled(disabled: boolean): void;
+
+  /**
+   * Set an attribute value of the native HTML control underlying the switch.
+   */
+  setNativeControlAttr(attr: string, value: string): void;
 }

packages/mdc-switch/component.ts

@@ -69,6 +69,7 @@ export class MDCSwitch extends MDCComponent<MDCSwitchFoundation> implements MDCR
       removeClass: (className) => this.root_.classList.remove(className),
       setNativeControlChecked: (checked) => this.nativeControl_.checked = checked,
       setNativeControlDisabled: (disabled) => this.nativeControl_.disabled = disabled,
+      setNativeControlAttr: (attr, value) => this.nativeControl_.setAttribute(attr, value),
     };
     return new MDCSwitchFoundation(adapter);
   }

packages/mdc-switch/constants.ts

@@ -31,6 +31,12 @@ const cssClasses = {
 
 /** String constants used by the switch. */
 const strings = {
+  /** Aria attribute for checked or unchecked state of switch */
+  ARIA_CHECKED_ATTR: 'aria-checked',
+  /** Aria attribute value for checked state of switch */
+  ARIA_CHECKED_CHECKED_VALUE: 'true',
+  /** Aria attribute value for unchecked state of switch */
+  ARIA_CHECKED_UNCHECKED_VALUE: 'false',
   /** A CSS selector used to locate the native HTML control for the switch.  */
   NATIVE_CONTROL_SELECTOR: '.mdc-switch__native-control',
   /** A CSS selector used to locate the ripple surface element for the switch. */

packages/mdc-switch/foundation.ts

@@ -43,6 +43,7 @@ export class MDCSwitchFoundation extends MDCFoundation<MDCSwitchAdapter> {
       removeClass: () => undefined,
       setNativeControlChecked: () => undefined,
       setNativeControlDisabled: () => undefined,
+      setNativeControlAttr: () => undefined,
     };
   }
 
@@ -53,6 +54,7 @@ export class MDCSwitchFoundation extends MDCFoundation<MDCSwitchAdapter> {
   /** Sets the checked state of the switch. */
   setChecked(checked: boolean) {
     this.adapter_.setNativeControlChecked(checked);
+    this.updateAriaChecked_(checked);
     this.updateCheckedStyling_(checked);
   }
 
@@ -69,6 +71,7 @@ export class MDCSwitchFoundation extends MDCFoundation<MDCSwitchAdapter> {
   /** Handles the change event for the switch native control. */
   handleChange(evt: Event) {
     const nativeControl = evt.target as HTMLInputElement;
+    this.updateAriaChecked_(nativeControl.checked);
     this.updateCheckedStyling_(nativeControl.checked);
   }
 
@@ -80,6 +83,14 @@ export class MDCSwitchFoundation extends MDCFoundation<MDCSwitchAdapter> {
       this.adapter_.removeClass(cssClasses.CHECKED);
     }
   }
+
+  private updateAriaChecked_(checked: boolean) {
+    this.adapter_.setNativeControlAttr(
+        strings.ARIA_CHECKED_ATTR,
+        checked ?
+            strings.ARIA_CHECKED_CHECKED_VALUE :
+            strings.ARIA_CHECKED_UNCHECKED_VALUE);
+  }
 }
 
 // tslint:disable-next-line:no-default-export Needed for backward compatibility with MDC Web v0.44.0 and earlier.

test/unit/mdc-switch/foundation.test.js

@@ -41,7 +41,13 @@ test('defaultAdapter returns a complete adapter implementation', () => {
   const methods = Object.keys(defaultAdapter).filter((k) => typeof defaultAdapter[k] === 'function');
 
   assert.equal(methods.length, Object.keys(defaultAdapter).length, 'Every adapter key must be a function');
-  assert.deepEqual(methods, ['addClass', 'removeClass', 'setNativeControlChecked', 'setNativeControlDisabled']);
+  assert.deepEqual(methods, [
+    'addClass',
+    'removeClass',
+    'setNativeControlChecked',
+    'setNativeControlDisabled',
+    'setNativeControlAttr',
+  ]);
   methods.forEach((m) => assert.doesNotThrow(defaultAdapter[m]));
 });
 
@@ -72,6 +78,22 @@ test('#setChecked removes mdc-switch--checked from the switch element when set t
   td.verify(mockAdapter.removeClass(MDCSwitchFoundation.cssClasses.CHECKED));
 });
 
+test('#setChecked sets aria-checked to true when set to true', () => {
+  const {foundation, mockAdapter} = setupTest();
+  foundation.setChecked(true);
+  td.verify(mockAdapter.setNativeControlAttr(
+    MDCSwitchFoundation.strings.ARIA_CHECKED_ATTR,
+    MDCSwitchFoundation.strings.ARIA_CHECKED_CHECKED_VALUE));
+});
+
+test('#setChecked sets aria-checked to false when set to false', () => {
+  const {foundation, mockAdapter} = setupTest();
+  foundation.setChecked(false);
+  td.verify(mockAdapter.setNativeControlAttr(
+    MDCSwitchFoundation.strings.ARIA_CHECKED_ATTR,
+    MDCSwitchFoundation.strings.ARIA_CHECKED_UNCHECKED_VALUE));
+});
+
 test('#setDisabled updates the disabled state', () => {
   const {foundation, mockAdapter} = setupTest();
   foundation.setDisabled(true);
@@ -106,3 +128,21 @@ test('#handleChange removes mdc-switch--checked from the switch when it is an un
   foundation.handleChange({target: {checked: false}});
   td.verify(mockAdapter.removeClass(MDCSwitchFoundation.cssClasses.CHECKED));
 });
+
+test('#handleChange sets aria-checked to true when the swith is a checked state', () => {
+  const {foundation, mockAdapter} = setupTest();
+
+  foundation.handleChange({target: {checked: true}});
+  td.verify(mockAdapter.setNativeControlAttr(
+    MDCSwitchFoundation.strings.ARIA_CHECKED_ATTR,
+    MDCSwitchFoundation.strings.ARIA_CHECKED_CHECKED_VALUE));
+});
+
+test('#handleChange sets aria-checked to false when the swith is a checked state', () => {
+  const {foundation, mockAdapter} = setupTest();
+
+  foundation.handleChange({target: {checked: false}});
+  td.verify(mockAdapter.setNativeControlAttr(
+    MDCSwitchFoundation.strings.ARIA_CHECKED_ATTR,
+    MDCSwitchFoundation.strings.ARIA_CHECKED_UNCHECKED_VALUE));
+});

test/unit/mdc-switch/mdc-switch.test.js

@@ -111,6 +111,19 @@ test('get/set disabled updates the component styles', () => {
   assert.isNotOk(root.classList.contains(MDCSwitchFoundation.cssClasses.DISABLED));
 });
 
+test('get/set checked updates the aria-checked of the native switch input element', () => {
+  const {root, component} = setupTest();
+  const inputEl = root.querySelector(NATIVE_CONTROL_SELECTOR);
+  component.checked = true;
+  assert.equal(
+    inputEl.getAttribute(MDCSwitchFoundation.strings.ARIA_CHECKED_ATTR),
+    MDCSwitchFoundation.strings.ARIA_CHECKED_CHECKED_VALUE);
+  component.checked = false;
+  assert.equal(
+    inputEl.getAttribute(MDCSwitchFoundation.strings.ARIA_CHECKED_ATTR),
+    MDCSwitchFoundation.strings.ARIA_CHECKED_UNCHECKED_VALUE);
+});
+
 test('get ripple returns a MDCRipple instance', () => {
   const {component} = setupTest();
   assert.isOk(component.ripple instanceof MDCRipple);