fix(cdk/testing): TestElement sendKeys method should throw if no keys have been specified

src/cdk/testing/protractor/protractor-element.ts

@@ -9,6 +9,7 @@
 import {
   _getTextWithExcludedElements,
   ElementDimensions,
+  getNoKeysSpecifiedError,
   ModifierKeys,
   TestElement,
   TestKey,
@@ -161,7 +162,7 @@ export class ProtractorElement implements TestElement {
     const first = modifiersAndKeys[0];
     let modifiers: ModifierKeys;
     let rest: (string | TestKey)[];
-    if (typeof first !== 'string' && typeof first !== 'number') {
+    if (first !== undefined && typeof first !== 'string' && typeof first !== 'number') {
       modifiers = first;
       rest = modifiersAndKeys.slice(1);
     } else {
@@ -177,6 +178,12 @@ export class ProtractorElement implements TestElement {
       // so avoid it if no modifier keys are required.
       .map(k => (modifierKeys.length > 0 ? Key.chord(...modifierKeys, k) : k));
 
+    // Throw an error if no keys have been specified. Calling this function with no
+    // keys should not result in a focus event being dispatched unexpectedly.
+    if (keys.length === 0) {
+      throw getNoKeysSpecifiedError();
+    }
+
     return this.element.sendKeys(...keys);
   }
 

src/cdk/testing/public-api.ts

@@ -9,6 +9,7 @@
 export * from './component-harness';
 export * from './harness-environment';
 export * from './test-element';
+export * from './test-element-errors';
 export * from './element-dimensions';
 export * from './text-filtering';
 export * from './change-detection';

src/cdk/testing/selenium-webdriver/selenium-web-driver-element.ts

@@ -10,6 +10,7 @@ import {
   _getTextWithExcludedElements,
   ElementDimensions,
   EventData,
+  getNoKeysSpecifiedError,
   ModifierKeys,
   TestElement,
   TestKey,
@@ -111,7 +112,7 @@ export class SeleniumWebDriverElement implements TestElement {
     const first = modifiersAndKeys[0];
     let modifiers: ModifierKeys;
     let rest: (string | TestKey)[];
-    if (typeof first !== 'string' && typeof first !== 'number') {
+    if (first !== undefined && typeof first !== 'string' && typeof first !== 'number') {
       modifiers = first;
       rest = modifiersAndKeys.slice(1);
     } else {
@@ -127,6 +128,12 @@ export class SeleniumWebDriverElement implements TestElement {
       // so avoid it if no modifier keys are required.
       .map(k => (modifierKeys.length > 0 ? webdriver.Key.chord(...modifierKeys, k) : k));
 
+    // Throw an error if no keys have been specified. Calling this function with no
+    // keys should not result in a focus event being dispatched unexpectedly.
+    if (keys.length === 0) {
+      throw getNoKeysSpecifiedError();
+    }
+
     await this.element().sendKeys(...keys);
     await this._stabilize();
   }

src/cdk/testing/test-element-errors.ts

@@ -0,0 +1,15 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+/**
+ * Returns an error which reports that no keys have been specified.
+ * @docs-private
+ */
+export function getNoKeysSpecifiedError() {
+  return Error('No keys have been specified.');
+}

src/cdk/testing/test-element.ts

@@ -119,12 +119,14 @@ export interface TestElement {
    * Sends the given string to the input as a series of key presses. Also fires input events
    * and attempts to add the string to the Element's value. Note that some environments cannot
    * reproduce native browser behavior for keyboard shortcuts such as Tab, Ctrl + A, etc.
+   * @throws An error if no keys have been specified.
    */
   sendKeys(...keys: (string | TestKey)[]): Promise<void>;
 
   /**
-   * Sends the given string to the input as a series of key presses. Also fires input events
-   * and attempts to add the string to the Element's value.
+   * Sends the given string to the input as a series of key presses. Also fires input
+   * events and attempts to add the string to the Element's value.
+   * @throws An error if no keys have been specified.
    */
   sendKeys(modifiers: ModifierKeys, ...keys: (string | TestKey)[]): Promise<void>;
 

src/cdk/testing/testbed/fake-events/type-in-element.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {ModifierKeys} from '@angular/cdk/testing';
+import {getNoKeysSpecifiedError, ModifierKeys} from '@angular/cdk/testing';
 import {PERIOD} from '@angular/cdk/keycodes';
 import {dispatchFakeEvent, dispatchKeyboardEvent} from './dispatch-events';
 import {triggerFocus} from './element-focus';
@@ -32,7 +32,7 @@ export function isTextInput(element: Element): element is HTMLInputElement | HTM
 }
 
 /**
- * Focuses an input, sets its value and dispatches
+ * If keys have been specified, focuses an input, sets its value and dispatches
  * the `input` event, simulating the user typing.
  * @param element Element onto which to set the value.
  * @param keys The keys to send to the element.
@@ -44,7 +44,7 @@ export function typeInElement(
 ): void;
 
 /**
- * Focuses an input, sets its value and dispatches
+ * If keys have been specified, focuses an input, sets its value and dispatches
  * the `input` event, simulating the user typing.
  * @param element Element onto which to set the value.
  * @param modifiers Modifier keys that are held while typing.
@@ -57,11 +57,16 @@ export function typeInElement(
   ...keys: (string | {keyCode?: number; key?: string})[]
 ): void;
 
-export function typeInElement(element: HTMLElement, ...modifiersAndKeys: any) {
+export function typeInElement(element: HTMLElement, ...modifiersAndKeys: any[]) {
   const first = modifiersAndKeys[0];
   let modifiers: ModifierKeys;
   let rest: (string | {keyCode?: number; key?: string})[];
-  if (typeof first !== 'string' && first.keyCode === undefined && first.key === undefined) {
+  if (
+    first !== undefined &&
+    typeof first !== 'string' &&
+    first.keyCode === undefined &&
+    first.key === undefined
+  ) {
     modifiers = first;
     rest = modifiersAndKeys.slice(1);
   } else {
@@ -78,13 +83,19 @@ export function typeInElement(element: HTMLElement, ...modifiersAndKeys: any) {
     )
     .reduce((arr, k) => arr.concat(k), []);
 
+  // Throw an error if no keys have been specified. Calling this function with no
+  // keys should not result in a focus event being dispatched unexpectedly.
+  if (keys.length === 0) {
+    throw getNoKeysSpecifiedError();
+  }
+
   // We simulate the user typing in a value by incrementally assigning the value below. The problem
   // is that for some input types, the browser won't allow for an invalid value to be set via the
   // `value` property which will always be the case when going character-by-character. If we detect
   // such an input, we have to set the value all at once or listeners to the `input` event (e.g.
   // the `ReactiveFormsModule` uses such an approach) won't receive the correct value.
   const enterValueIncrementally =
-    inputType === 'number' && keys.length > 0
+    inputType === 'number'
       ? // The value can be set character by character in number inputs if it doesn't have any decimals.
         keys.every(key => key.key !== '.' && key.keyCode !== PERIOD)
       : incrementalInputTypes.has(inputType);

src/cdk/testing/tests/cross-environment.spec.ts

@@ -9,6 +9,7 @@
 import {
   ComponentHarness,
   ComponentHarnessConstructor,
+  getNoKeysSpecifiedError,
   HarnessLoader,
   HarnessPredicate,
   parallel,
@@ -345,6 +346,18 @@ export function crossEnvironmentSpecs(
       harness = await getMainComponentHarnessFromEnvironment();
     });
 
+    async function expectAsyncError(fn: () => Promise<void>, expected: Error) {
+      let error: unknown | null = null;
+      try {
+        await fn();
+      } catch (e: unknown) {
+        error = e;
+      }
+      expect(error).not.toBe(null);
+      expect(error instanceof Error).toBe(true);
+      expect((error as Error).message).toBe(expected.message);
+    }
+
     it('should be able to clear', async () => {
       const input = await harness.input();
       await input.sendKeys('Yi');
@@ -354,6 +367,13 @@ export function crossEnvironmentSpecs(
       expect(await input.getProperty<string>('value')).toBe('');
     });
 
+    it('sendKeys method should throw if no keys have been specified', async () => {
+      const input = await harness.input();
+      await expectAsyncError(() => input.sendKeys(), getNoKeysSpecifiedError());
+      await expectAsyncError(() => input.sendKeys(''), getNoKeysSpecifiedError());
+      await expectAsyncError(() => input.sendKeys('', ''), getNoKeysSpecifiedError());
+    });
+
     it('should be able to click', async () => {
       const counter = await harness.counter();
       expect(await counter.text()).toBe('0');

tools/public_api_guard/cdk/testing.md

@@ -76,6 +76,9 @@ export type EventData = string | number | boolean | undefined | null | EventData
     [key: string]: EventData;
 };
 
+// @public
+export function getNoKeysSpecifiedError(): Error;
+
 // @public
 export function _getTextWithExcludedElements(element: Element, excludeSelector: string): string;