[enhance] Merge changes to resource instances

src/state/__tests__/reducer.ts

@@ -15,6 +15,10 @@ describe('reducer', () => {
         expiresAt: 5000500000,
       },
     };
+    const partialResultAction: ReceiveAction = {
+      ...action,
+      payload: { id, title: 'hello' },
+    };
     const iniState = {
       entities: {},
       results: {},
@@ -33,6 +37,21 @@ describe('reducer', () => {
       expect(nextEntity).not.toBe(prevEntity);
       expect(nextEntity).toBeDefined();
     })
+    it('should merge partial entity with existing entity', () => {
+      const getEntity = (state: any): ArticleResource => state.entities[ArticleResource.getKey()][`${ArticleResource.pk(action.payload)}`]
+      const prevEntity = getEntity(newState);
+      expect(prevEntity).toBeDefined();
+      const nextState = reducer(newState, partialResultAction);
+      const nextEntity = getEntity(nextState);
+      expect(nextEntity).not.toBe(prevEntity);
+      expect(nextEntity).toBeDefined();
+
+      expect(nextEntity.title).not.toBe(prevEntity.title);
+      expect(nextEntity.title).toBe(partialResultAction.payload.title);
+
+      expect(nextEntity.content).toBe(prevEntity.content);
+      expect(nextEntity.content).not.toBe(partialResultAction.payload.content);
+    })
   });
   it('mutate should never change results', () => {
     const id = 20;

src/state/reducer.ts

@@ -1,5 +1,5 @@
 import { normalize } from '../resource';
-import { merge } from 'lodash';
+import { mergeWith } from 'lodash';
 import { Resource } from '../resource';
 import { ActionTypes, State } from '../types';
 
@@ -13,6 +13,13 @@ type Writable<T> = {
   [P in keyof T]: NonNullable<T[P]>;
 }
 
+function resourceCustomizer(a: any, b: any): any {
+  if (a instanceof Resource && b instanceof Resource) {
+    const Static = b.constructor as typeof Resource;
+    return Static.merge(a, b);
+  }
+}
+
 export default function reducer(state: State<Resource>, action: ActionTypes) {
   switch (action.type) {
     case 'receive':
@@ -31,7 +38,7 @@ export default function reducer(state: State<Resource>, action: ActionTypes) {
       }
       const normalized = normalize(action.payload, action.meta.schema);
       return {
-        entities: merge({ ...state.entities }, normalized.entities),
+        entities: mergeWith({ ...state.entities }, normalized.entities, resourceCustomizer),
         results: {
           ...state.results,
           [action.meta.url]: normalized.result,
@@ -49,7 +56,7 @@ export default function reducer(state: State<Resource>, action: ActionTypes) {
       let { entities } = normalize(action.payload, action.meta.schema);
       return {
         ...state,
-        entities: merge({ ...state.entities }, entities),
+        entities: mergeWith({ ...state.entities }, entities, resourceCustomizer),
       };
     case 'purge':
       if (action.error) return state;