feat(all): Implement stubs for lit-localize support

PiperOrigin-RevId: 474657115

localization/localize.ts

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+/**
+ * @license
+ * Copyright 2022 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {TemplateResult} from 'lit';
+
+/** Options object to the `msg()` function */
+export interface MsgOptions {
+  id?: string;
+  desc?: string;
+}
+
+/** stand-in for lit-localize str function */
+export function str(
+    strings: TemplateStringsArray, ...values: unknown[]): string {
+  let out = strings[0];
+  for (let i = 1; i < strings.length; i++) {
+    out += String(values[i - 1]) + strings[i];
+  }
+  return out;
+}
+
+/** stand-in for lit-localize msg function */
+export function msg<T extends(string | TemplateResult)>(
+    template: T, options?: MsgOptions): T {
+  return template;
+}

localization/localize_test.ts

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+/**
+ * @license
+ * Copyright 2022 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import 'jasmine';
+
+import {html} from 'lit';
+
+import {msg, str} from './localize.js';
+
+
+describe('localize test', () => {
+  it('passes through TemplateResults', () => {
+    const expression = html`<span>world!</span>`
+    const result = msg(html`<div tmpl>Hello ${expression}</div>`);
+    expect(msg(result)).toEqual(result);
+  });
+
+  it('passes through strings', () => {
+    expect(msg('Hello!')).toEqual('Hello!');
+  });
+
+  it('converts str templates to strings', () => {
+    const expression = 'world';
+    expect(msg(str`Hello ${expression}!`)).toEqual('Hello world!');
+  });
+});