Fixed Issuable sidebar so it remains closed on mobile/smaller screen devices

Added test to replicate the bug, also added a couple of helpers that can be reused
on the testing suite to resize the browser window, these helpers are located on the
spec/support/mobile_helpers.rb

app/assets/javascripts/application.js

@@ -84,7 +84,6 @@
     var $sidebarGutterToggle = $('.js-sidebar-toggle');
     var $flash = $('.flash-container');
     var bootstrapBreakpoint = bp.getBreakpointSize();
-    var checkInitialSidebarSize;
     var fitSidebarForSize;
 
     // Set the default path for all cookies to GitLab's root directory
@@ -246,19 +245,19 @@
         return $document.trigger('breakpoint:change', [bootstrapBreakpoint]);
       }
     };
-    checkInitialSidebarSize = function () {
-      bootstrapBreakpoint = bp.getBreakpointSize();
-      if (bootstrapBreakpoint === 'xs' || 'sm') {
-        return $document.trigger('breakpoint:change', [bootstrapBreakpoint]);
-      }
-    };
     $window.off('resize.app').on('resize.app', function () {
       return fitSidebarForSize();
     });
+    window.addEventListener('beforeunload', function() {
+      // collapsed_gutter cookie hides the sidebar
+      var bpBreakpoint = bp.getBreakpointSize();
+      if (bpBreakpoint === 'xs' || bpBreakpoint === 'sm') {
+        Cookies.set('collapsed_gutter', true);
+      }
+    });
+
     gl.awardsHandler = new AwardsHandler();
-    checkInitialSidebarSize();
     new Aside();
-
     // bind sidebar events
     new gl.Sidebar();
   });

changelogs/unreleased/issuable-sidebar-bug.yml

+---
+title: Fixed Issuable sidebar not closing on smaller/mobile sized screens
+merge_request: 
+author: 

spec/features/issues/issue_sidebar_spec.rb

 require 'rails_helper'
 
 feature 'Issue Sidebar', feature: true do
-  include WaitForAjax
+  include WaitForAjax, MobileHelpers
 
   let(:project) { create(:project, :public) }
   let(:issue) { create(:issue, project: project) }
@@ -59,6 +59,30 @@ feature 'Issue Sidebar', feature: true do
       end
     end
 
+    context 'sidebar', js: true do
+      it 'changes size when the screen size is smaller' do
+        sidebar_selector = 'aside.right-sidebar.right-sidebar-collapsed'
+        # Resize the window
+        resize_screen_sm
+        # Make sure the sidebar is collapsed
+        expect(page).to have_css(sidebar_selector)
+        # Once is collapsed let's open the sidebard and reload
+        page.within(sidebar_selector) do
+          find('.js-sidebar-toggle').click
+          # we wait a bit so the sidebar finishes it's animation
+          sleep 1
+        end
+        refresh
+        expect(page).to have_css(sidebar_selector)
+        # Restore the window size as it was including the sidebar
+        restore_window_size
+        page.within(sidebar_selector) do
+          find('.js-sidebar-toggle').click
+          sleep 1
+        end
+      end
+    end
+
     context 'creating a new label', js: true do
       it 'shows option to crate a new label is present' do
         page.within('.block.labels') do

spec/support/mobile_helpers.rb

+module MobileHelpers
+  def resize_screen_sm
+    resize_window(900, 768)
+  end
+
+  def restore_window_size
+    resize_window(1366, 768)
+  end
+
+  def resize_window(width, height)
+    page.driver.resize_window width, height
+  end
+end