Update cache to be immutable

app/assets/javascripts/alert_management/components/sidebar/sidebar_todo.vue

 <script>
+import produce from 'immer';
 import { s__ } from '~/locale';
 import Todo from '~/sidebar/components/todo_toggle/todo.vue';
 import createAlertTodoMutation from '../../graphql/mutations/alert_todo_create.mutation.graphql';
@@ -109,12 +110,15 @@ export default {
         });
     },
     updateCache(store) {
-      const data = store.readQuery({
+      const sourceData = store.readQuery({
         query: alertQuery,
         variables: this.getAlertQueryVariables,
       });
 
-      data.project.alertManagementAlerts.nodes[0].todos.nodes.shift();
+      const data = produce(sourceData, draftData => {
+        // eslint-disable-next-line no-param-reassign
+        draftData.project.alertManagementAlerts.nodes[0].todos.nodes = [];
+      });
 
       store.writeQuery({
         query: alertQuery,

app/assets/javascripts/alert_management/details.js

 import Vue from 'vue';
 import VueApollo from 'vue-apollo';
+import produce from 'immer';
 import { defaultDataIdFromObject } from 'apollo-cache-inmemory';
 import createDefaultClient from '~/lib/graphql';
 import createRouter from './router';
@@ -16,8 +17,11 @@ export default selector => {
   const resolvers = {
     Mutation: {
       toggleSidebarStatus: (_, __, { cache }) => {
-        const data = cache.readQuery({ query: sidebarStatusQuery });
-        data.sidebarStatus = !data.sidebarStatus;
+        const sourceData = cache.readQuery({ query: sidebarStatusQuery });
+        const data = produce(sourceData, draftData => {
+          // eslint-disable-next-line no-param-reassign
+          draftData.sidebarStatus = !draftData.sidebarStatus;
+        });
         cache.writeQuery({ query: sidebarStatusQuery, data });
       },
     },
@@ -34,6 +38,7 @@ export default selector => {
           return defaultDataIdFromObject(object);
         },
       },
+      assumeImmutableResults: true,
     }),
   });