Use defined inactiveListId constant when needed

On the boards store, "0" is used to deactivate a list, this replaces
that magic number with a defined constant.

app/assets/javascripts/boards/stores/state.js

+import { inactiveListId } from '~/boards/constants';
+
 export default () => ({
   isShowingLabels: true,
-  activeListId: 0,
+  activeListId: inactiveListId,
 });

ee/app/assets/javascripts/boards/components/board_settings_sidebar.vue

@@ -15,6 +15,7 @@ import boardsStoreEE from '../stores/boards_store_ee';
 import eventHub from '~/sidebar/event_hub';
 import flash from '~/flash';
 import { isScopedLabel } from '~/lib/utils/common_utils';
+import { inactiveListId } from '~/boards/constants';
 
 // NOTE: need to revisit how we handle headerHeight, because we have so many different header and footer options.
 export default {
@@ -60,7 +61,7 @@ export default {
       return boardsStoreEE.store.state.lists.find(({ id }) => id === this.activeListId);
     },
     isSidebarOpen() {
-      return this.activeListId > 0;
+      return this.activeListId !== inactiveListId;
     },
     activeListLabel() {
       return this.activeList.label;
@@ -110,7 +111,7 @@ export default {
     ...mapActions(['setActiveListId', 'updateListWipLimit']),
     closeSidebar() {
       this.edit = false;
-      this.setActiveListId(0);
+      this.setActiveListId(inactiveListId);
     },
     showInput() {
       this.edit = true;
@@ -136,7 +137,7 @@ export default {
           })
           .catch(() => {
             this.resetStateAfterUpdate();
-            this.setActiveListId(0);
+            this.setActiveListId(inactiveListId);
             flash(__('Something went wrong while updating your list settings'));
           });
       } else {
@@ -151,7 +152,7 @@ export default {
         })
         .catch(() => {
           this.resetStateAfterUpdate();
-          this.setActiveListId(0);
+          this.setActiveListId(inactiveListId);
           flash(__('Something went wrong while updating your list settings'));
         });
     },

ee/spec/frontend/boards/components/board_settings_sidebar_spec.js

@@ -11,6 +11,7 @@ import bs from '~/boards/stores/boards_store';
 import sidebarEventHub from '~/sidebar/event_hub';
 import flash from '~/flash';
 import waitForPromises from 'helpers/wait_for_promises';
+import { inactiveListId } from '~/boards/constants';
 
 jest.mock('~/flash');
 // NOTE: needed for calling boardsStore.addList
@@ -28,7 +29,11 @@ describe('BoardSettingsSideBar', () => {
   const listId = 1;
   const currentWipLimit = 1; // Needs to be other than null to trigger requests.
 
-  const createComponent = (state = { activeListId: 0 }, actions = {}, localState = {}) => {
+  const createComponent = (
+    state = { activeListId: inactiveListId },
+    actions = {},
+    localState = {},
+  ) => {
     storeActions = actions;
 
     const store = new Vuex.Store({
@@ -88,28 +93,28 @@ describe('BoardSettingsSideBar', () => {
     describe('on close', () => {
       it('calls closeSidebar', () => {
         const spy = jest.fn();
-        createComponent({ activeListId: 0 }, { setActiveListId: spy });
+        createComponent({ activeListId: inactiveListId }, { setActiveListId: spy });
 
         wrapper.find(GlDrawer).vm.$emit('close');
 
         return wrapper.vm.$nextTick().then(() => {
           expect(storeActions.setActiveListId).toHaveBeenCalledWith(
             expect.anything(),
-            0,
+            inactiveListId,
             undefined,
           );
         });
       });
 
       it('calls closeSidebar on sidebar.closeAll event', () => {
-        createComponent({ activeListId: 0 }, { setActiveListId: jest.fn() });
+        createComponent({ activeListId: inactiveListId }, { setActiveListId: jest.fn() });
 
         sidebarEventHub.$emit('sidebar.closeAll');
 
         return wrapper.vm.$nextTick().then(() => {
           expect(storeActions.setActiveListId).toHaveBeenCalledWith(
             expect.anything(),
-            0,
+            inactiveListId,
             undefined,
           );
         });
@@ -178,7 +183,7 @@ describe('BoardSettingsSideBar', () => {
 
         boardsStore.store.addList({ id: listId, label: { title: labelTitle, color: labelColor } });
 
-        createComponent({ activeListId: 0 });
+        createComponent({ activeListId: inactiveListId });
       });
 
       afterEach(() => {

ee/spec/frontend/boards/stores/actions_spec.js

@@ -3,6 +3,7 @@ import boardsStoreEE from 'ee/boards/stores/boards_store_ee';
 import actions from 'ee/boards/stores/actions';
 import * as types from 'ee/boards/stores/mutation_types';
 import testAction from 'helpers/vuex_action_helper';
+import { inactiveListId } from '~/boards/constants';
 
 jest.mock('axios');
 
@@ -25,7 +26,7 @@ describe('toggleShowLabels', () => {
 describe('setActiveListId', () => {
   it('should commit mutation SET_ACTIVE_LIST_ID', done => {
     const state = {
-      activeListId: 0,
+      activeListId: inactiveListId,
     };
 
     testAction(

ee/spec/frontend/boards/stores/mutations_spec.js

 import mutations from 'ee/boards/stores/mutations';
+import { inactiveListId } from '~/boards/constants';
 
 const expectNotImplemented = action => {
   it('is not implemented', () => {
@@ -32,7 +33,7 @@ describe('SET_ACTIVE_LIST_ID', () => {
   it('updates aciveListId to be the value that is passed', () => {
     const expectedId = 1;
     const state = {
-      activeListId: 0,
+      activeListId: inactiveListId,
     };
 
     mutations.SET_ACTIVE_LIST_ID(state, expectedId);