Hot fix for #1237 and #1202

[ananfang]

1. Fix typo PFPreconditionFailOnError and PFPreconditionFailAndSetError.

2. If there is a new object in OfflineStore, should not send the exception when the saved object update its OfflineStore cache:

change the assert condition in function - (void)updateObjectIdForObject:oldObjectId:newObjectId: of PFOfflineStore.m

// If this object is just saved, update local store without exception.
BOOL isNewlySaved = (oldObjectId == nil) && (object.createdAt != nil);
PFConsistencyAssert(isNewlySaved || existing == nil || existing == object,
                    @"Attempted to change an objectId to one that's already known to the OfflineStore. className: %@ old: %@, new: %@",
                    className, oldObjectId, newObjectId);

[flovilmart]

@ananfang thanks for the PR, PFPreconditionFailOnError doesn’t exist I’m not even sure how it compiles, can you revert to PFPreconditionFailOnError? This seem unrelated to that PR.

[ananfang]

@flovilmart
I just reverted PFPreconditionBailOnError and PFPreconditionBailAndSetError.

[flovilmart]

Let's try it, let's hope it doesn't yield any corruption issue.

[ananfang]

@flovilmart
Thanks for your help 👍

This hotfix is just a workaround, the actual problem is SDK assigns twice (or more) objectId to newly saved object. The first time objectId is assigned, existing == nil, pass the assert. But the second time, existing != nil && existing != object, raises the exception.

[flovilmart]

DO you have some code that reproduces the issue?

[ananfang]

Followings are my scenario:

1. A chat view with two users.
2. Use ParseLiveQuery to listen messages created.
3. User sends message as a PFObject, save it by saveInBackground() method.

It will not always crash, about 50/50.

[flovilmart]

Are you saving/mutating the received messages from liveQuery?

…

On Feb 8, 2018, 06:30 -0500, ananfang ***@***.***>, wrote: Followings are my scenario: 1. A chat view with two users. 2. Use ParseLiveQuery to listen messages created. 3. User sends message as a PFObject, save it by saveInBackground() method. It will not always crash, about 50/50. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

[ananfang]

No, I don't mutate messages from LiveQuery

[flovilmart]

Would you be able to share a demo project that reproduces the issue? I believe it’s related to liveQuery

[brianyyz]

+1

[ananfang]

@flovilmart
Demo Project

Run and tap "Add Message" button, it will crash all the time by "Attempted to change an objectId to one that's already known to the Offline Store"

[ananfang]

I found a PFObject Equality bug comes from my "isNewlySaved" workaround.

Following is scenario:

1. Enable Local Datastore
2. Use Live Query to listen new Message object (PFObject) created.
3. Save a new Message object.
4. There will be two Message objects assigned the same new objectId.
5. Without "isNewlySaved" condition, raise assert Attempted to change an objectId to one that's already known to the Offline Store. With "isNewlySaved" condition, it will only store the last of two Message objects in the local datastore.
6. If we check these two newly saved objects with same objectId, they are not equal. (But they are supposedly equal when enable locale datastore)

Thus, DO NOT use my "isNewlySaved" workaround.

Instead, we should find out why Parse / LiveQuery assign the new objectId into two (or more) different objects.

[flovilmart]

Ok so basically, creating and receiving an object through liveQuery will yield the issue. I need to either update LiveQuery or make sure the liveQUery received objects are treated the same as the ones fetched.

[ananfang]

Yes, you can try this Chat demo project

[ananfang]

@flovilmart
Should we open a new issue for this?
Or it was already fixed in release 1.17.0?

I found you already fixed it in release 1.17.0, I'll check if there is any new issue. If there is, I'll open a new one, thanks for your effort.

[flovilmart]

Thanks! Please use the release-1.17.1 branch in the meantime as 1.17.0 is broken.