fix(redux-devtools-core): don't mutate source object during stringification (#627)

* Add failing test case for stringifyJSON

* Mutate clone of value in stringifyJSON instead of original

Co-authored-by: Nathan Bierema <nbierema@gmail.com>

Author: wms

packages/redux-devtools-core/src/app/utils/stringifyJSON.js

@@ -4,9 +4,10 @@ import { DATA_TYPE_KEY, DATA_REF_KEY } from '../constants/dataTypes';
 function replacer(key, value) {
   if (typeof value === 'object' && value !== null && DATA_TYPE_KEY in value) {
     const __serializedType__ = value[DATA_TYPE_KEY];
-    delete value[DATA_TYPE_KEY]; // eslint-disable-line no-param-reassign
-    const r = { data: value, __serializedType__ };
-    if (DATA_REF_KEY in value) r.__serializedRef__ = value[DATA_REF_KEY];
+    const clone = { ...value };
+    delete clone[DATA_TYPE_KEY]; // eslint-disable-line no-param-reassign
+    const r = { data: clone, __serializedType__ };
+    if (DATA_REF_KEY in value) r.__serializedRef__ = clone[DATA_REF_KEY];
     return r;
   }
   return value;

packages/redux-devtools-core/test/app.spec.js

@@ -7,6 +7,8 @@ import App from '../src/app/containers/App';
 import api from '../src/app/middlewares/api';
 import exportState from '../src/app/middlewares/exportState';
 import rootReducer from '../src/app/reducers';
+import { DATA_TYPE_KEY } from '../src/app/constants/dataTypes';
+import stringifyJSON from '../src/app/utils/stringifyJSON';
 
 let wrapper;
 
@@ -43,3 +45,25 @@ describe('App container', () => {
     ).toMatch(/<div class="actionListRows-\d-\d-\d+"><\/div>/);
   });
 });
+
+describe('stringifyJSON', () => {
+  it('should not mutate the source object', () => {
+    const src = {
+      isTest: true,
+      [DATA_TYPE_KEY]: 'Test',
+    };
+
+    const result = {
+      data: {
+        isTest: true,
+      },
+      __serializedType__: 'Test',
+    };
+
+    expect(stringifyJSON(src, true)).toEqual(JSON.stringify(result));
+    expect(src).toEqual({
+      isTest: true,
+      [DATA_TYPE_KEY]: 'Test',
+    });
+  });
+});