Ensure current user's token is not lost on refetch

Author: andrewimm

src/ParseObject.js

@@ -1361,7 +1361,14 @@ export default class ParseObject {
       if (otherAttributes.objectId) {
         o.id = otherAttributes.objectId;
       }
+      let preserved = null;
+      if (typeof o._preserveFieldsOnFetch === 'function') {
+        preserved = o._preserveFieldsOnFetch();
+      }
       o._clearServerData();
+      if (preserved) {
+        o._finishFetch(preserved);
+      }
     }
     o._finishFetch(otherAttributes);
     if (json.objectId) {

src/ParseUser.js

@@ -249,6 +249,16 @@ export default class ParseUser extends ParseObject {
     }
   }
 
+  /**
+   * Class instance method used to maintain specific keys when a fetch occurs.
+   * Used to ensure that the session token is not lost.
+   */
+  _preserveFieldsOnFetch(): AttributeMap {
+    return {
+      sessionToken: this.get('sessionToken'),
+    };
+  }
+
   /**
    * Returns true if <code>current</code> would return this user.
    * @method isCurrent

src/__tests__/ParseUser-test.js

@@ -615,4 +615,38 @@ describe('ParseUser', () => {
     expect(user.getUsername()).toBe('test');
     expect(user.get('authData').anonymous).toBe(null);
   });
+
+  it('maintains the session token when refetched', asyncHelper((done) => {
+    ParseUser.enableUnsafeCurrentUser();
+    ParseUser._clearCache();
+    Storage._clear();
+    CoreManager.setRESTController({
+      request() {
+        return ParsePromise.as({
+          objectId: 'uidfetch',
+          username: 'temporary',
+          number: 123,
+          sessionToken: 'abc141',
+        }, 201);
+      },
+      ajax() {}
+    });
+
+    ParseUser.signUp('temporary', 'password').then((u) => {
+      expect(u.getSessionToken()).toBe('abc141');
+      expect(u.get('number')).toBe(123);
+      ParseUser._clearCache();
+
+      let u2 = ParseObject.fromJSON({
+        objectId: 'uidfetch',
+        className: '_User',
+        username: 'temporary',
+      }, true);
+      expect(u.getSessionToken()).toBe('abc141');
+      expect(u2.getSessionToken()).toBe('abc141');
+      expect(u.get('number')).toBe(undefined);
+      expect(u2.get('number')).toBe(undefined);
+      done();
+    });
+  }));
 });