Apollo - update() method getting called twice, bot

问题:

I'm completely stuck on an Apollo problem, for which I've opened a GitHub issue and had zero response on.

I'm calling an Apollo mutation, using optimisticResponse. The way it's supposed to work, as I understand it, is that update() gets called twice: first with the optimistic data, then again with the actual data coming in from the network.

But for some reason, my code is not working like this. I'm getting two update() calls, both with the optimistic data.

Here's a repo that demonstrates this behavior: https://github.com/ffxsam/apollo-update-bug

1. yarn && yarn dev
2. Open in browser, open console
3. Enter some text and hit enter
4. Repeat above
5. Notice the error in the console about duplicate keys. This is happening because the temporary ID "??" is not being replaced with the real UUID (optional) You can open Vue DevTools if available and inspect the data to see it's incorrect

回答1:

I was doing some digging and I think I found the source of the problem. Unfortunately, I don't have a solution.

In short, the problem might be with a network link called OfflineLink that is used by aws-appsync.

Explanation

aws-appsync has an ApolloLink called OfflineLink that intervenes with the request function.

What happens is something like this:

1. you call $apollo.mutate(...)
2. ApolloClient.QueryManager initializes the mutation that triggers your update the first time with the optimistic response. That is happening inside ApolloClient data store, markMutationInit calls markMutationResult that calls your update.
3. The graphql operation executes and reaches the OfflineLink in the network chain.
4. OfflineLink creates a new observer and dispatches the mutation info as an action.
5. The next line of OfflineLink calls the observer's next function with the optimisticResponse as if it was the execution result!
6. This triggers your update the second time with the result which is actually the optimisticResponse.
7. OfflineLink calls the observer's complete which resolves your promise.
8. console.log('done!'...

Meanwhile, OfflineLink prevents the original mutation from even sending the request, and a new mutation is generated and sent with the options you've given it.