User: Add getCurrentUserLocale state selector

client/state/current-user/selectors.js

@@ -16,3 +16,18 @@ export function getCurrentUser( state ) {
 
 	return getUser( state, state.currentUser.id );
 }
+
+/**
+ * Returns the locale slug for the current user.
+ *
+ * @param  {Object}  state  Global state tree
+ * @return {?String}        Current user locale
+ */
+export function getCurrentUserLocale( state ) {
+	const user = getCurrentUser( state );
+	if ( ! user ) {
+		return null;
+	}
+
+	return user.localeSlug || null;
+}

client/state/current-user/test/selectors.js

@@ -6,7 +6,10 @@ import { expect } from 'chai';
 /**
  * Internal dependencies
  */
-import { getCurrentUser } from '../selectors';
+import {
+	getCurrentUser,
+	getCurrentUserLocale
+} from '../selectors';
 
 describe( 'selectors', () => {
 	describe( '#getCurrentUser()', () => {
@@ -35,4 +38,46 @@ describe( 'selectors', () => {
 			expect( selected ).to.eql( { ID: 73705554, login: 'testonesite2014' } );
 		} );
 	} );
+
+	describe( '#getCurrentUserLocale', () => {
+		it( 'should return null if the current user is not set', () => {
+			const locale = getCurrentUserLocale( {
+				currentUser: {
+					id: null
+				}
+			} );
+
+			expect( locale ).to.be.null;
+		} );
+
+		it( 'should return null if the current user locale slug is not set', () => {
+			const locale = getCurrentUserLocale( {
+				users: {
+					items: {
+						73705554: { ID: 73705554, login: 'testonesite2014' }
+					}
+				},
+				currentUser: {
+					id: 73705554
+				}
+			} );
+
+			expect( locale ).to.be.null;
+		} );
+
+		it( 'should return the current user locale slug', () => {
+			const locale = getCurrentUserLocale( {
+				users: {
+					items: {
+						73705554: { ID: 73705554, login: 'testonesite2014', localeSlug: 'fr' }
+					}
+				},
+				currentUser: {
+					id: 73705554
+				}
+			} );
+
+			expect( locale ).to.equal( 'fr' );
+		} );
+	} );
 } );