feat: add locale normalization and merging utilities

package.json

@@ -40,7 +40,8 @@
     "prepare": "husky"
   },
   "dependencies": {
-    "tslib": "^2.3.1"
+    "tslib": "^2.3.1",
+    "weekstart": "^2.0.0"
   },
   "devDependencies": {
     "@cloudscape-design/browser-test-tools": "^3.0.0",

src/index.ts

@@ -4,5 +4,10 @@
 export { default as useContainerQuery } from './container-queries/use-container-query';
 export { default as useControllableState } from './use-controllable-state/use-controllable-state';
 
-export type { PropertyDescriptions } from './use-controllable-state/interfaces';
 export type { ContainerQueryEntry } from './container-queries/interfaces';
+export type { PropertyDescriptions } from './use-controllable-state/interfaces';
+
+// Locale utils
+export { mergeLocales } from './locale/merge-locales';
+export { normalizeLocale } from './locale/normalize-locale';
+export { normalizeStartOfWeek, DayIndex } from './locale/normalize-start-of-week';

src/locale/__tests__/merge-locales.test.ts

@@ -0,0 +1,16 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import { mergeLocales } from '../merge-locales';
+
+test('should return the first locale if it is fully specified', () => {
+  expect(mergeLocales('en-US', 'fr-CA')).toEqual('en-US');
+});
+
+test('should return the second locale if it extends the first', () => {
+  expect(mergeLocales('en', 'en-US')).toEqual('en-US');
+});
+
+test('should return the first locale if the second is different', () => {
+  expect(mergeLocales('en', 'fr-CA')).toEqual('en');
+});

src/locale/__tests__/normalize-locale.test.ts

@@ -0,0 +1,75 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import { normalizeLocale } from '../normalize-locale';
+import setOptions from './utils/intl-polyfill';
+
+function withDocumentLang(lang: string, callback: () => void) {
+  const htmlElement = document.querySelector('html');
+  htmlElement!.setAttribute('lang', lang);
+  callback();
+  htmlElement!.removeAttribute('lang');
+}
+
+describe('normalizeLocale', () => {
+  let consoleSpy: jest.SpyInstance;
+  beforeEach(() => {
+    consoleSpy = jest.spyOn(console, 'warn');
+    setOptions({ locale: 'en-US' });
+  });
+
+  afterEach(() => {
+    expect(consoleSpy).not.toHaveBeenCalled();
+  });
+
+  test('should return the provided value', () => {
+    expect(normalizeLocale('DatePickerTest', 'en-US')).toBe('en-US');
+  });
+
+  test('should extend provided value if it is short form', () => {
+    expect(normalizeLocale('DatePickerTest', 'en')).toBe('en-US');
+    setOptions({ locale: 'en-GB' });
+    expect(normalizeLocale('DatePickerTest', 'en')).toBe('en-GB');
+  });
+
+  test('should not extend the provided value if it starts from different language', () => {
+    expect(normalizeLocale('DatePickerTest', 'fr')).toBe('fr');
+  });
+
+  test('should replace underscores with dashes', () => {
+    expect(normalizeLocale('DatePickerTest', 'zh_CN')).toBe('zh-CN');
+  });
+
+  test('should warn if the provided value is in invalid format', () => {
+    expect(normalizeLocale('DatePickerTest', 'not-locale')).toBe('en-US');
+    expect(consoleSpy).toHaveBeenCalledWith(
+      '[AwsUi] [DatePickerTest] Invalid locale provided: not-locale. Falling back to default'
+    );
+    consoleSpy.mockReset();
+  });
+
+  test('should return document language by default', () => {
+    withDocumentLang('en', () => {
+      expect(normalizeLocale('DatePickerTest', null)).toBe('en-US');
+    });
+  });
+
+  test('should not extend document language with locale if they do not match', () => {
+    withDocumentLang('fr', () => {
+      expect(normalizeLocale('DatePickerTest', null)).toBe('fr');
+    });
+  });
+
+  test('should combine values from document lang and browser locale', () => {
+    setOptions({ locale: 'fr-CA' });
+    withDocumentLang('fr', () => {
+      expect(normalizeLocale('DatePickerTest', null)).toBe('fr-CA');
+    });
+  });
+
+  test('should replace underscores with dashes in document lang', () => {
+    withDocumentLang('zh_CN', () => {
+      expect(normalizeLocale('DatePickerTest', null)).toBe('zh-CN');
+    });
+  });
+});

src/locale/__tests__/utils/intl-polyfill.ts

@@ -0,0 +1,10 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+// We use resolvedOptions to detect browser locale. This method allows us to override the value for testing.
+export default function setResolvedOptions(newValue: { locale: string }): void {
+  const dateTimeFormat = new Intl.DateTimeFormat(newValue.locale);
+  const resolvedOptions = dateTimeFormat.resolvedOptions();
+
+  window.Intl.DateTimeFormat.prototype.resolvedOptions = () => ({ ...resolvedOptions, ...newValue });
+}

src/locale/merge-locales.ts

@@ -0,0 +1,10 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+export function mergeLocales(locale: string, fullLocale: string) {
+  const isShort = locale.length === 2;
+  if (isShort && fullLocale.indexOf(locale) === 0) {
+    return fullLocale;
+  }
+  return locale;
+}

src/locale/normalize-locale.ts

@@ -0,0 +1,43 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import { warnOnce } from '../internal/logging';
+
+import { mergeLocales } from './merge-locales';
+
+export function normalizeLocale(component: string, locale: string | null): string {
+  locale = checkLocale(component, locale);
+  const browserLocale = getBrowserLocale();
+  if (locale) {
+    return mergeLocales(locale, browserLocale);
+  }
+  const htmlLocale = checkLocale(component, getHtmlElement()?.getAttribute('lang'));
+  if (htmlLocale) {
+    return mergeLocales(htmlLocale, browserLocale);
+  }
+  return browserLocale;
+}
+
+function checkLocale(component: string, locale: string | null | undefined): string {
+  if (!locale || locale === '') {
+    return '';
+  }
+
+  // Support underscore-delimited locales
+  locale = locale && locale.replace(/^([a-z]{2})_/, '$1-');
+  // Check that the value matches aa-BB pattern
+  // TODO: support full BCP 47 spec?
+  if (locale && !locale.match(/^[a-z]{2}(-[A-Z]{2})?$/)) {
+    warnOnce(component, `Invalid locale provided: ${locale}. Falling back to default`);
+    locale = '';
+  }
+  return locale;
+}
+
+function getHtmlElement() {
+  return typeof document !== 'undefined' ? document.querySelector('html') : null;
+}
+
+function getBrowserLocale() {
+  return new Intl.DateTimeFormat().resolvedOptions().locale;
+}

src/locale/normalize-start-of-week.ts

@@ -0,0 +1,10 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import { getWeekStartByLocale } from 'weekstart';
+
+export type DayIndex = 0 | 1 | 2 | 3 | 4 | 5 | 6;
+
+export function normalizeStartOfWeek(startOfWeek: number | undefined, locale: string) {
+  return (typeof startOfWeek === 'number' ? startOfWeek % 7 : getWeekStartByLocale(locale)) as DayIndex;
+}