Issue Description

Performing a query for objects located in the local datastore sometimes returns other local object attributes or no attributes when there should be attributes for the local object.

Steps to reproduce

Add multiple items with attributes of the same class to the local datastore. Quit and restart the RN app and perform a query for a subset of objects.

Expected Results

The expectation is that the query results contain the matching objects for the query parameters and each object contains the attributes for the object when it was pinned to the local datastore.

Actual Outcome

The query will return fewer objects than it should due to ParseQuery._handleOfflineQuery setting the object._localId after ParseObject.fromJSON. This causes the static cache reference for the object to now point to null or the attributes of another object.

Environment Setup

• JS SDK
  • JS SDK version: 2.6.0
  • Application? (Browser, Node, React-Native, etc): React-Native

More Info on Solution

I was able to fix this with two changes and I’m asking for feedback or commentary on what other side-effects this may introduce:

Change 1:

In ParseObject._finishFetch the first thing this function does is to set the id of the object if it isn’t set already. There’s already a check here for the serverData.objectId. I added an additional check for the _localId and set the object’s id to the localId of the object if it doesn’t have an objectId in the case of locally stored objects only.

if (!this.id && serverData.objectId) {
    this.id = serverData.objectId;
} else if (!this.id && serverData._localId) {
    this.id = serverData._localId;
}

This seems to be the right place to do this. Without this set here, AFTER the parse object is created using ParseObject.fromJSON during the _handleOfflineQuery operation the next step will then check the object’s localId and objectId and reset the _localId to match the attribute of _localId. However, by doing this outside of the .fromJSON call, this has a side effect of changing the reference to the cache attributes and thus returns another object’s attributes or empty object for attributes.

Change 2:

The second issue is how attribute values are getting encoded into the cache.

In ObjectStateMutations.js the commitServerChanges function was limiting the attributes to only objects. Thus, if an attribute was a string, it wouldn’t be saved to the cache. I changed the check on the val to encode objects and just store the rest as-is. This I’m not clear on what other side-effects this may introduce, but it is now working in my app for strings and bools for attributes.

export function commitServerChanges(serverData
/*: AttributeMap*/
, objectCache
/*: ObjectCache*/
, changes
/*: AttributeMap*/
) {
  for (const attr in changes) {
    const val = changes[attr];
    serverData[attr] = val;

    if (val && !(val instanceof ParseObject) && !(val instanceof ParseFile) && !(val instanceof ParseRelation)) {
      if (typeof val === 'object') {
        const json = encode(val, false, true);
        objectCache[attr] = JSON.stringify(json);
      } else {
        objectCache[attr] = val;
      }
    }
  }
}