Allow overriding the locale for individual translations

addon/services/i18n.js

@@ -18,12 +18,17 @@ export default Parent.extend(Evented, {
   // A list of found locales.
   locales: computed(getLocales),
 
+  // @public
+  // Whether to allow overriding the locale for individual translations.
+  allowLocaleOverride: undefined,
+
   // @public
   //
   // Returns the translation `key` interpolated with `data`
   // in the current `locale`.
   t: function(key, data = {}) {
-    const locale = this.get('_locale');
+    const locale = this._getLocaleWithOverride(data);
+
     assert("I18n: Cannot translate when locale is null", locale);
     const count = get(data, 'count');
 
@@ -41,7 +46,7 @@ export default Parent.extend(Evented, {
 
   // @public
   exists: function(key, data = {}) {
-    const locale = this.get('_locale');
+    const locale = this._getLocaleWithOverride(data);
     assert("I18n: Cannot check existance when locale is null", locale);
     const count = get(data, 'count');
 
@@ -71,6 +76,10 @@ export default Parent.extend(Evented, {
       }
       this.set('locale', defaultLocale);
     }
+
+    if (this.get('allowLocaleOverride') == null) {
+      this.set('allowLocaleOverride', (ENV.i18n || {}).allowLocaleOverride);
+    }
   }),
 
   // @private
@@ -83,6 +92,24 @@ export default Parent.extend(Evented, {
   _locale: computed('locale', function() {
     const locale = this.get('locale');
     return locale ? new Locale(this.get('locale'), getOwner(this)) : null;
-  })
+  }),
+
+  // @private
+  // Retrieves the current locale, allowing it to be overridden by a `locale`
+  // option in the translation data if `allowLocaleOverride` is enabled.
+  _getLocaleWithOverride: function(data) {
+    let locale = this.get('_locale');
+
+    if (data.locale && this.get('allowLocaleOverride') !== false) {
+      warn(
+        'Specifying an interpolation key named `locale` now overrides the target locale for translation. To silence this warning, set ENV.i18n.allowLocaleOverride to true. To disable this behavior and treat `locale` as a normal interpolation key, set ENV.i18n.allowLocaleOverride to false.',
+        (this.get('allowLocaleOverride') !== undefined),
+        { id: 'ember-i18n.locale-override' }
+      );
+      locale = new Locale(data.locale, getOwner(this));
+      delete data.locale;
+    }
 
+    return locale;
+  }
 });

tests/acceptance/t-helper-test.js

@@ -50,3 +50,7 @@ test('updates when the locale changes', function(assert) {
     assert.textIs('.no-interpolations', 'texto sin interpolaciones');
   });
 });
+
+test('can override the target locale', function(assert) {
+  assert.textIs('.locale-override', 'texto sin interpolaciones');
+});

tests/dummy/app/locales/en/translations.js

@@ -3,7 +3,8 @@ export default {
   'no.interpolations.either': 'another text without interpolations',
 
   'with': {
-    interpolations: 'Clicks: {{clicks}}'
+    interpolations: 'Clicks: {{clicks}}',
+    'locale.interpolation': 'Locale: {{locale}}'
   },
 
   'pluralized.translation': {

tests/dummy/app/templates/index.hbs

@@ -21,3 +21,7 @@
 <section>
   <button class='switch-to-es' {{action "switchLocale" "es"}}>Switch to Spanish</button>
 </section>
+
+<section>
+  <span class='locale-override'>{{t "no.interpolations" locale="es"}}</span>
+</section>

tests/unit/i18n-exists-test.js

@@ -33,3 +33,9 @@ test('fallsback to the parent locale', function(assert) {
 
   assert.equal(i18n.exists('no.interpolations.either'), true);
 });
+
+test('allows overriding the locale', function(assert) {
+  const i18n = this.subject({ locale: 'en' });
+
+  assert.equal(i18n.exists('no.interpolations.either', { locale: 'es' }), false);
+});

tests/unit/i18n-t-test.js

@@ -3,8 +3,24 @@ import { moduleFor, test } from 'ember-qunit';
 
 const { run } = Ember;
 
+let originalWarn = null;
+const warnings = Ember.A();
+
 moduleFor('service:i18n', 'I18nService#t', {
-  integration: true
+  integration: true,
+
+  beforeEach: function() {
+    originalWarn = Ember.Logger.warn;
+    Ember.Logger.warn = function(message, ...args) {
+      warnings.pushObject(message);
+      originalWarn(message, ...args);
+    };
+  },
+
+  afterEach: function() {
+    warnings.clear();
+    Ember.Logger.warn = originalWarn;
+  }
 });
 
 test('falls back to parent locale', function(assert) {
@@ -91,3 +107,27 @@ test("check unknown locale", function(assert) {
   const result = this.subject({ locale: 'uy' }).t('not.yet.translated', {count: 2});
   assert.equal('Missing translation: not.yet.translated', result);
 });
+
+test("locale can be overridden and warns by default", function(assert) {
+  const i18n = this.subject({ locale: 'en' });
+
+  const result = i18n.t('no.interpolations', { locale: 'es' });
+  assert.equal(result, 'texto sin interpolaciones');
+  assert.equal(warnings.length, 1);
+});
+
+test("locale can be overridden and does not warn if allowLocaleOverride is true", function(assert) {
+  const i18n = this.subject({ locale: 'en', allowLocaleOverride: true });
+
+  const result = i18n.t('no.interpolations', { locale: 'es' });
+  assert.equal(result, 'texto sin interpolaciones');
+  assert.equal(warnings.length, 0);
+});
+
+test("locale can be used as an interpolation key if allowLocaleOverride is false", function(assert) {
+  const i18n = this.subject({ locale: 'en', allowLocaleOverride: false });
+
+  const result = i18n.t('with.locale.interpolation', { locale: 'es' });
+  assert.equal(result, 'Locale: es');
+  assert.equal(warnings.length, 0);
+});