TIM-435: Prevent whitespace-only submissions

apps/openassessment/xblock/static/js/spec/oa_response.js

@@ -65,6 +65,13 @@ describe("OpenAssessment.ResponseView", function() {
         expect(view.saveEnabled()).toBe(false);
         expect(view.saveStatus()).toContain('Unsaved draft');
 
+        // Response is whitespace --> save/submit buttons disabled
+        view.response('               \n      \n      ');
+        view.responseChanged();
+        expect(view.submitEnabled()).toBe(false);
+        expect(view.saveEnabled()).toBe(false);
+        expect(view.saveStatus()).toContain('Unsaved draft');
+
         // Response is not blank --> submit button enabled
         view.response('Test response');
         view.responseChanged();

apps/openassessment/xblock/static/js/src/oa_response.js

@@ -170,12 +170,12 @@ OpenAssessment.ResponseView.prototype = {
     **/
     responseChanged: function() {
         // Enable the save/submit button only for non-blank responses
-        var currentResponse = this.response();
+        var currentResponse = $.trim(this.response());
         var isBlank = (currentResponse !== '');
         this.submitEnabled(isBlank);
 
         // Update the save button and status only if the response has changed
-        if (this.savedResponse !== currentResponse) {
+        if ($.trim(this.savedResponse) !== currentResponse) {
             this.saveEnabled(isBlank);
             this.saveStatus('Unsaved draft');
         }