feat($i18n): makes the setLocaleData call append to the existing locales

i18n/index.js

@@ -13,12 +13,25 @@ let i18n;
  * @param {Object} data Locale data configuration
  */
 export function setLocaleData( data ) {
-	i18n = new Jed( data );
+	i18n = new Jed( {
+		...(i18n ? i18n.options : {}),
+		...data
+	} );
 }
 
 /**
- * Returns the current Jed instance, initializing with a default configuration
- * if not already assigned.
+ * Resets the Jed instance.
+ *
+ * @see http://messageformat.github.io/Jed/
+ *
+ * @param {Object} data Locale data configuration
+ */
+export function resetLocaleData () {
+	i18n = new Jed( { '': {} });
+}
+
+/**
+ * Returns the current Jed instance.
  *
  * @return {Jed} Jed instance
  */

i18n/test/jed.js

@@ -0,0 +1,55 @@
+import { resetLocaleData, setLocaleData, __, getI18n } from '../index';
+
+describe( 'wp.i18n', () => {
+	describe( '.setLocaleData', () => {
+		it('should set locale data', () => {
+			resetLocaleData();
+
+			setLocaleData({
+				domain: 'gutenberg',
+				locale_data: {
+					gutenberg: {
+						"": {
+							domain: 'gutenberg',
+							lang: 'ro_RO'
+						},
+						Demo: ["Demonstrație"],
+						['Gutenberg Team']: ["Echipa Gutenberg"]
+					}
+				}
+			});
+
+			expect( __('Demo') ).toBe( 'Demonstrație' );
+			expect( __('Gutenberg Team') ).toBe( 'Echipa Gutenberg' );
+		});
+
+		it('should preserve local data between multiple .setLocaleData calls', () => {
+			resetLocaleData();
+
+			setLocaleData({
+				domain: 'gutenberg',
+				locale_data: {
+					gutenberg: {
+						"": {
+							domain: 'gutenberg',
+							lang: 'ro_RO'
+						},
+						Demo: ["Demonstrație"]
+					}
+				}
+			});
+
+			setLocaleData({
+				...getI18n().options,
+				locale_data: {
+					gutenberg: {
+						...getI18n().options.locale_data.gutenberg,
+						['Gutenberg Team']: ["Echipa Gutenberg"]
+					}
+				}
+			});
+
+			expect( __('Gutenberg Team') ).toBe( 'Echipa Gutenberg' );
+		} );
+	} );
+} );