i18n: add new APIs for React bindings

packages/i18n/CHANGELOG.md

@@ -2,6 +2,13 @@
 
 ## Unreleased
 
+### Enhancements
+
+- Export the default `I18n` instance as `defaultI18n`, in addition to already exported bound methods.
+- Add new `getLocaleData` method to get the internal Tannin locale data object.
+- Add new `subscribe` method to subscribe to changes in the internal locale data.
+- Add new `hasTranslation` method to determine whether a translation for a string is available.
+
 ## 3.17.0 (2020-12-17)
 
 ### Enhancements

packages/i18n/README.md

@@ -35,12 +35,46 @@ _Parameters_
 
 -   _initialData_ `[LocaleData]`: Locale data configuration.
 -   _initialDomain_ `[string]`: Domain for which configuration applies.
--   _hooks_ `[ApplyFiltersInterface]`: Hooks implementation.
+-   _hooks_ `[Hooks]`: Hooks implementation.
 
 _Returns_
 
 -   `I18n`: I18n instance
 
+<a name="defaultI18n" href="#defaultI18n">#</a> **defaultI18n**
+
+Default, singleton instance of `I18n`.
+
+<a name="getLocaleData" href="#getLocaleData">#</a> **getLocaleData**
+
+Returns locale data by domain in a Jed-formatted JSON object shape.
+
+_Related_
+
+-   <http://messageformat.github.io/Jed/>
+
+_Parameters_
+
+-   _domain_ `[string]`: Domain for which to get the data.
+
+_Returns_
+
+-   `LocaleData`: Locale data.
+
+<a name="hasTranslation" href="#hasTranslation">#</a> **hasTranslation**
+
+Check if there is a translation for a given string (in singular form).
+
+_Parameters_
+
+-   _single_ `string`: Singular form of the string to look up.
+-   _context_ `[string]`: Context information for the translators.
+-   _domain_ `[string]`: Domain to retrieve the translated text.
+
+_Returns_
+
+-   `boolean`: Whether the translation exists or not.
+
 <a name="isRTL" href="#isRTL">#</a> **isRTL**
 
 Check if current locale is RTL.
@@ -86,6 +120,18 @@ _Returns_
 
 -   `string`: The formatted string.
 
+<a name="subscribe" href="#subscribe">#</a> **subscribe**
+
+Subscribes to changes of locale data
+
+_Parameters_
+
+-   _callback_ `SubscribeCallback`: Subscription callback
+
+_Returns_
+
+-   `UnsubscribeCallback`: Unsubscribe callback
+
 <a name="_n" href="#_n">#</a> **\_n**
 
 Translates and retrieves the singular or plural form based on the supplied

packages/i18n/src/create-i18n.js

@@ -22,13 +22,35 @@ const DEFAULT_LOCALE_DATA = {
 	},
 };
 
+/*
+ * Regular expression that matches i18n hooks like `i18n.gettext`, `i18n.ngettext`,
+ * `i18n.gettext_domain` or `i18n.ngettext_with_context`
+ */
+const I18N_HOOK_REGEXP = /^i18n\.(n?)gettext(_|$)/;
+
+/**
+ * @typedef {(domain?: string) => LocaleData} GetLocaleData
+ *
+ * Returns locale data by domain in a
+ * Jed-formatted JSON object shape.
+ *
+ * @see http://messageformat.github.io/Jed/
+ */
 /**
  * @typedef {(data?: LocaleData, domain?: string) => void} SetLocaleData
+ *
  * Merges locale data into the Tannin instance by domain. Accepts data in a
  * Jed-formatted JSON object shape.
  *
  * @see http://messageformat.github.io/Jed/
  */
+/** @typedef {() => void} SubscribeCallback */
+/** @typedef {() => void} UnsubscribeCallback */
+/**
+ * @typedef {(callback: SubscribeCallback) => UnsubscribeCallback} Subscribe
+ *
+ * Subscribes to changes of locale data
+ */
 /**
  * @typedef {(domain?: string) => string} GetFilterDomain
  * Retrieve the domain to use when calling domain-specific filters.
@@ -74,30 +96,36 @@ const DEFAULT_LOCALE_DATA = {
  * including English (`en`, `en-US`, `en-GB`, etc.), Spanish (`es`), and French (`fr`).
  */
 /**
- * @typedef {{ applyFilters: (hookName:string, ...args: unknown[]) => unknown}} ApplyFiltersInterface
+ * @typedef {(single: string, context?: string, domain?: string) => boolean} HasTranslation
+ *
+ * Check if there is a translation for a given string in singular form.
  */
+/** @typedef {import('@wordpress/hooks').Hooks} Hooks */
 
 /**
  * An i18n instance
  *
  * @typedef I18n
+ * @property {GetLocaleData} getLocaleData Returns locale data by domain in a Jed-formatted JSON object shape.
  * @property {SetLocaleData} setLocaleData Merges locale data into the Tannin instance by domain. Accepts data in a
  *                                         Jed-formatted JSON object shape.
+ * @property {Subscribe} subscribe         Subscribes to changes of Tannin locale data.
  * @property {__} __                       Retrieve the translation of text.
  * @property {_x} _x                       Retrieve translated string with gettext context.
  * @property {_n} _n                       Translates and retrieves the singular or plural form based on the supplied
  *                                         number.
  * @property {_nx} _nx                     Translates and retrieves the singular or plural form based on the supplied
  *                                         number, with gettext context.
  * @property {IsRtl} isRTL                 Check if current locale is RTL.
+ * @property {HasTranslation} hasTranslation Check if there is a translation for a given string.
  */
 
 /**
  * Create an i18n instance
  *
  * @param {LocaleData} [initialData]    Locale data configuration.
  * @param {string}     [initialDomain]  Domain for which configuration applies.
- * @param {ApplyFiltersInterface} [hooks]     Hooks implementation.
+ * @param {Hooks} [hooks]     Hooks implementation.
  * @return {I18n}                       I18n instance
  */
 export const createI18n = ( initialData, initialDomain, hooks ) => {
@@ -108,8 +136,31 @@ export const createI18n = ( initialData, initialDomain, hooks ) => {
 	 */
 	const tannin = new Tannin( {} );
 
-	/** @type {SetLocaleData} */
-	const setLocaleData = ( data, domain = 'default' ) => {
+	const listeners = new Set();
+
+	const notifyListeners = () => {
+		listeners.forEach( ( listener ) => listener() );
+	};
+
+	/**
+	 * Subscribe to changes of locale data.
+	 *
+	 * @param {SubscribeCallback} callback Subscription callback.
+	 * @return {UnsubscribeCallback} Unsubscribe callback.
+	 */
+	const subscribe = ( callback ) => {
+		listeners.add( callback );
+		return () => listeners.delete( callback );
+	};
+
+	/** @type {GetLocaleData} */
+	const getLocaleData = ( domain = 'default' ) => tannin.data[ domain ];
+
+	/**
+	 * @param {LocaleData} [data]
+	 * @param {string} [domain]
+	 */
+	const doSetLocaleData = ( data, domain = 'default' ) => {
 		tannin.data[ domain ] = {
 			...DEFAULT_LOCALE_DATA,
 			...tannin.data[ domain ],
@@ -124,6 +175,12 @@ export const createI18n = ( initialData, initialDomain, hooks ) => {
 		};
 	};
 
+	/** @type {SetLocaleData} */
+	const setLocaleData = ( data, domain ) => {
+		doSetLocaleData( data, domain );
+		notifyListeners();
+	};
+
 	/**
 	 * Wrapper for Tannin's `dcnpgettext`. Populates default locale data if not
 	 * otherwise previously assigned.
@@ -147,7 +204,8 @@ export const createI18n = ( initialData, initialDomain, hooks ) => {
 		number
 	) => {
 		if ( ! tannin.data[ domain ] ) {
-			setLocaleData( undefined, domain );
+			// use `doSetLocaleData` to set silently, without notifying listeners
+			doSetLocaleData( undefined, domain );
 		}
 
 		return tannin.dcnpgettext( domain, context, single, plural, number );
@@ -320,16 +378,69 @@ export const createI18n = ( initialData, initialDomain, hooks ) => {
 		return 'rtl' === _x( 'ltr', 'text direction' );
 	};
 
+	/** @type {HasTranslation} */
+	const hasTranslation = ( single, context, domain ) => {
+		const key = context ? context + '\u0004' + single : single;
+		let result = !! tannin.data?.[ domain ?? 'default' ]?.[ key ];
+		if ( hooks ) {
+			/**
+			 * Filters the presence of a translation in the locale data.
+			 *
+			 * @param {boolean} hasTranslation Whether the translation is present or not..
+			 * @param {string} single The singular form of the translated text (used as key in locale data)
+			 * @param {string} context Context information for the translators.
+			 * @param {string} domain Text domain. Unique identifier for retrieving translated strings.
+			 */
+			result = /** @type { boolean } */ (
+				/** @type {*} */ hooks.applyFilters(
+					'i18n.has_translation',
+					result,
+					single,
+					context,
+					domain
+				)
+			);
+
+			result = /** @type { boolean } */ (
+				/** @type {*} */ hooks.applyFilters(
+					'i18n.has_translation_' + getFilterDomain( domain ),
+					result,
+					single,
+					context,
+					domain
+				)
+			);
+		}
+		return result;
+	};
+
 	if ( initialData ) {
 		setLocaleData( initialData, initialDomain );
 	}
 
+	if ( hooks ) {
+		/**
+		 * @param {string} hookName
+		 */
+		const onHookAddedOrRemoved = ( hookName ) => {
+			if ( I18N_HOOK_REGEXP.test( hookName ) ) {
+				notifyListeners();
+			}
+		};
+
+		hooks.addAction( 'hookAdded', 'core/i18n', onHookAddedOrRemoved );
+		hooks.addAction( 'hookRemoved', 'core/i18n', onHookAddedOrRemoved );
+	}
+
 	return {
+		getLocaleData,
 		setLocaleData,
+		subscribe,
 		__,
 		_x,
 		_n,
 		_nx,
 		isRTL,
+		hasTranslation,
 	};
 };

packages/i18n/src/default-i18n.js

@@ -1,14 +1,19 @@
 /**
- * WordPress dependencies
+ * Internal dependencies
  */
-import { applyFilters } from '@wordpress/hooks';
+import { createI18n } from './create-i18n';
 
 /**
- * Internal dependencies
+ * WordPress dependencies
  */
-import { createI18n } from './create-i18n';
+import { defaultHooks } from '@wordpress/hooks';
 
-const i18n = createI18n( undefined, undefined, { applyFilters } );
+const i18n = createI18n( undefined, undefined, defaultHooks );
+
+/**
+ * Default, singleton instance of `I18n`.
+ */
+export default i18n;
 
 /*
  * Comments in this file are duplicated from ./i18n due to
@@ -17,7 +22,19 @@ const i18n = createI18n( undefined, undefined, { applyFilters } );
 
 /**
  * @typedef {import('./create-i18n').LocaleData} LocaleData
+ * @typedef {import('./create-i18n').SubscribeCallback} SubscribeCallback
+ * @typedef {import('./create-i18n').UnsubscribeCallback} UnsubscribeCallback
+ */
+
+/**
+ * Returns locale data by domain in a Jed-formatted JSON object shape.
+ *
+ * @see http://messageformat.github.io/Jed/
+ *
+ * @param {string} [domain] Domain for which to get the data.
+ * @return {LocaleData} Locale data.
  */
+export const getLocaleData = i18n.getLocaleData.bind( i18n );
 
 /**
  * Merges locale data into the Tannin instance by domain. Accepts data in a
@@ -30,6 +47,14 @@ const i18n = createI18n( undefined, undefined, { applyFilters } );
  */
 export const setLocaleData = i18n.setLocaleData.bind( i18n );
 
+/**
+ * Subscribes to changes of locale data
+ *
+ * @param {SubscribeCallback} callback Subscription callback
+ * @return {UnsubscribeCallback} Unsubscribe callback
+ */
+export const subscribe = i18n.subscribe.bind( i18n );
+
 /**
  * Retrieve the translation of text.
  *
@@ -99,3 +124,13 @@ export const _nx = i18n._nx.bind( i18n );
  * @return {boolean} Whether locale is RTL.
  */
 export const isRTL = i18n.isRTL.bind( i18n );
+
+/**
+ * Check if there is a translation for a given string (in singular form).
+ *
+ * @param {string} single Singular form of the string to look up.
+ * @param {string} [context] Context information for the translators.
+ * @param {string} [domain] Domain to retrieve the translated text.
+ * @return {boolean} Whether the translation exists or not.
+ */
+export const hasTranslation = i18n.hasTranslation.bind( i18n );

packages/i18n/src/index.js

@@ -1,3 +1,14 @@
 export { sprintf } from './sprintf';
 export * from './create-i18n';
-export { setLocaleData, __, _x, _n, _nx, isRTL } from './default-i18n';
+export {
+	default as defaultI18n,
+	setLocaleData,
+	getLocaleData,
+	subscribe,
+	__,
+	_x,
+	_n,
+	_nx,
+	isRTL,
+	hasTranslation,
+} from './default-i18n';