Immutable cache update in `submit_content_changes` resolver

app/assets/javascripts/static_site_editor/graphql/index.js

@@ -21,6 +21,7 @@ const createApolloProvider = appData => {
     },
     {
       typeDefs,
+      assumeImmutableResults: true,
     },
   );
 

app/assets/javascripts/static_site_editor/graphql/resolvers/has_submitted_changes.js

+import { produce } from 'immer';
 import query from '../queries/app_data.query.graphql';
 
 const hasSubmittedChangesResolver = (_, { input: { hasSubmittedChanges } }, { cache }) => {
-  const { appData } = cache.readQuery({ query });
-  cache.writeQuery({
-    query,
-    data: {
+  const oldData = cache.readQuery({ query });
+
+  const data = produce(oldData, draftState => {
+    // punctually modifying draftState as per immer docs upsets our linters
+    return {
+      ...draftState,
       appData: {
         __typename: 'AppData',
-        ...appData,
+        ...draftState.appData,
         hasSubmittedChanges,
       },
-    },
+    };
+  });
+
+  cache.writeQuery({
+    query,
+    data,
   });
 };
 

app/assets/javascripts/static_site_editor/graphql/resolvers/submit_content_changes.js

+import { produce } from 'immer';
 import submitContentChanges from '../../services/submit_content_changes';
 import savedContentMetaQuery from '../queries/saved_content_meta.query.graphql';
 
@@ -14,14 +15,18 @@ const submitContentChangesResolver = (
     images,
     mergeRequestMeta,
   }).then(savedContentMeta => {
-    cache.writeQuery({
-      query: savedContentMetaQuery,
-      data: {
+    const data = produce(savedContentMeta, draftState => {
+      return {
         savedContentMeta: {
           __typename: 'SavedContentMeta',
-          ...savedContentMeta,
+          ...draftState,
         },
-      },
+      };
+    });
+
+    cache.writeQuery({
+      query: savedContentMetaQuery,
+      data,
     });
   });
 };

spec/frontend/static_site_editor/graphql/resolvers/has_submitted_changes_spec.js

+import appDataQuery from '~/static_site_editor/graphql/queries/app_data.query.graphql';
+import hasSubmittedChanges from '~/static_site_editor/graphql/resolvers/has_submitted_changes';
+
+describe('static_site_editor/graphql/resolvers/has_submitted_changes', () => {
+  it('updates the cache with the data passed in input', () => {
+    const cachedData = { appData: { original: 'foo' } };
+    const newValue = { input: { hasSubmittedChanges: true } };
+
+    const cache = {
+      readQuery: jest.fn().mockReturnValue(cachedData),
+      writeQuery: jest.fn(),
+    };
+    hasSubmittedChanges(null, newValue, { cache });
+
+    expect(cache.readQuery).toHaveBeenCalledWith({ query: appDataQuery });
+    expect(cache.writeQuery).toHaveBeenCalledWith({
+      query: appDataQuery,
+      data: {
+        appData: {
+          __typename: 'AppData',
+          original: 'foo',
+          hasSubmittedChanges: true,
+        },
+      },
+    });
+  });
+});