GraphQL API doesn't update optional values

[chris-mds]

Describe the bug
Im trying to implement AppSync API and it doesn't update optional Values, when updating on the client app side.

To Reproduce
Steps to reproduce the behavior:

1. Create a DataModel with optional fields
2. Create on your app an item of this model with any optional key filled with value 'nil'
3. Now we can see in our Table that this key is from type 'NULL' and his value is true.
4. Now update on your app this key with the value it should be, when it is not nil. E.g. string.
5. The Xcode console will show that the operation was successfull and the item was updated. But in the success data you can see, that this value wasn't updated
6. Refresh the table and you will see, that nothing happened. The key is still from type 'NULL' and set to true

Expected behavior
Update the key with its given new value

Screenshots

Environment(please complete the following information):

• Dependency Manager: [ Cocoapods]
• Swift Version : [ 5.3]

Device Information (please complete the following information):

• Device: [Simulator]
• iOS Version: [iOS 14]

[lawmicha]

Hi @chris-mds

Sorry you are running into this issue, can you please verify which Amplify pod versions you are using?

I was not able to reproduce using Amplify 1.3.1 on Xcode 12

let post = Post(title: "title", content: "content", createdAt: .now(), updatedAt: nil, draft: nil, rating: nil, status: nil, finishedFrom: nil, isFinished: nil, finishedAt: nil, comments: [])
                Amplify.API.mutate(request: .create(post)) { (result) in
                    switch result {
                    case .success(let result):
                        print(result)
                    case .failure(let apiError):
                        print(apiError)
                    }
                }

_ = Amplify.API.query(request: .get(Post.self, byId: "BF95FF22-8620-4758-B048-D843BFCEB8E8")) { (result) in
                    switch result {
                    case .success(let result):
                        print(result)
                        switch result {
                        case .success(let post):
                            if var post = post {
                                post.finishedFrom = "Chris"
                                post.isFinished = true
                                post.comments = []
                                Amplify.API.mutate(request: .update(post)) { (result) in
                                    switch result {
                                    case .success(let result):
                                        print(result)
                                    case .failure(let apiError):
                                        print(apiError)
                                    }
                                }
                            }
                        case .failure(let graphQLError):
                            print(graphQLError)
                        }
                        
                    case .failure(let apiError):
                        print(apiError)
                    }
                }

I suspect that this might be related, depending on your set up, there was known issue fixed in 1.2.0 and later #752

the issue affected users using Xcode12 and amplify versions less than 1.2.0

[lawmicha]

Also what is you pod file like? I suspect from #821 that you may be interpolating different ways to persist data.

[chris-mds]

Since I was mixing APIPlugin and DataStorePlugin and I haven't handled versions, the conflict detection rejected any updates. Now with a clean API and no mixes it works like expected, thanks!