Fixed error handling

app/assets/javascripts/droplab/plugins/ajax.js

 /* eslint-disable */
 
-function droplabAjaxException(message) {
-  this.message = message;
-}
-
 const Ajax = {
   _loadUrlData: function _loadUrlData(url) {
     var self = this;
@@ -58,9 +54,7 @@ const Ajax = {
       this._loadUrlData(config.endpoint)
         .then(function(d) {
           self._loadData(d, config, self);
-        }, config.onError).catch(function(e) {
-          throw new droplabAjaxException(e.message || e);
-        });
+        }, config.onError).catch(config.onError);
     }
   },
   destroy: function() {

app/assets/javascripts/droplab/plugins/ajax_filter.js

@@ -68,7 +68,7 @@ const AjaxFilter = {
       this._loadUrlData(url)
         .then(function(data) {
           self._loadData(data, config, self);
-        }, config.onError);
+        }, config.onError).catch(config.onError);
     }
   },
 

app/assets/javascripts/filtered_search/dropdown_non_user.js

+/* global Flash */
+
 import Ajax from '~/droplab/plugins/ajax';
 import Filter from '~/droplab/plugins/filter';
 
@@ -13,6 +15,11 @@ require('./filtered_search_dropdown');
           endpoint,
           method: 'setData',
           loadingTemplate: this.loadingTemplate,
+          onError() {
+            /* eslint-disable no-new */
+            new Flash('An error occured fetching the dropdown data.');
+            /* eslint-enable no-new */
+          },
         },
         Filter: {
           filterFunction: gl.DropdownUtils.filterWithSymbol.bind(null, this.symbol, input),

app/assets/javascripts/filtered_search/dropdown_user.js

+/* global Flash */
+
 import AjaxFilter from '~/droplab/plugins/ajax_filter';
 
 require('./filtered_search_dropdown');
@@ -18,6 +20,11 @@ require('./filtered_search_dropdown');
           },
           searchValueFunction: this.getSearchInput.bind(this),
           loadingTemplate: this.loadingTemplate,
+          onError() {
+            /* eslint-disable no-new */
+            new Flash('An error occured fetching the dropdown data.');
+            /* eslint-enable no-new */
+          },
         },
       };
     }

spec/features/issues/filtered_search/dropdown_milestone_spec.rb

@@ -65,7 +65,7 @@ describe 'Dropdown milestone', :feature, :js do
     it 'should load all the milestones when opened' do
       filtered_search.set('milestone:')
 
-      expect(dropdown_milestone_size).to be > 0
+      expect(filter_dropdown).to have_selector('.filter-dropdown .filter-dropdown-item', count: 6)
     end
   end
 
@@ -84,37 +84,37 @@ describe 'Dropdown milestone', :feature, :js do
     it 'filters by name' do
       filtered_search.send_keys('v1')
 
-      expect(dropdown_milestone_size).to eq(1)
+      expect(filter_dropdown).to have_selector('.filter-dropdown .filter-dropdown-item', count: 1)
     end
 
     it 'filters by case insensitive name' do
       filtered_search.send_keys('V1')
 
-      expect(dropdown_milestone_size).to eq(1)
+      expect(filter_dropdown).to have_selector('.filter-dropdown .filter-dropdown-item', count: 1)
     end
 
     it 'filters by name with symbol' do
       filtered_search.send_keys('%v1')
 
-      expect(dropdown_milestone_size).to eq(1)
+      expect(filter_dropdown).to have_selector('.filter-dropdown .filter-dropdown-item', count: 1)
     end
 
     it 'filters by case insensitive name with symbol' do
       filtered_search.send_keys('%V1')
 
-      expect(dropdown_milestone_size).to eq(1)
+      expect(filter_dropdown).to have_selector('.filter-dropdown .filter-dropdown-item', count: 1)
     end
 
     it 'filters by special characters' do
       filtered_search.send_keys('(+')
 
-      expect(dropdown_milestone_size).to eq(1)
+      expect(filter_dropdown).to have_selector('.filter-dropdown .filter-dropdown-item', count: 1)
     end
 
     it 'filters by special characters with symbol' do
       filtered_search.send_keys('%(+')
 
-      expect(dropdown_milestone_size).to eq(1)
+      expect(filter_dropdown).to have_selector('.filter-dropdown .filter-dropdown-item', count: 1)
     end
   end