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Seeing this error, looking into it:

@Gudahtt Yeah, David did implement a solution that used AbortController, you can see it here: deaf1b5

We looked at it together, and the challenge is aborting all the async calls that happen after that first fetch. For instance, aborting await this.timedoutGasReturn(Object.values(newQuotes)[0].approvalNeeded) would be a big challenge, I think? At least, we'd have to get the signal passed through createInfuraMiddleware to the fetch ultimately called in https://github.com/MetaMask/eth-json-rpc-infura/blob/master/src/index.js This would require signal to be serializable, which I don't think it is, or some way to update the infura middleware config after initialization.

Given that not all the async calls here can be aborted, the least we can do is the minimum necessary change of preventing a state update after the calls are complete.

@darkwing Regarding that error, some additional changes are needed so that fetchQuotesAndSetQuoteState in ducks/swaps/swaps, which calls SwapsController.fetchAndSetQuotes, can properly handle the response in the case of this.indexOfNewestCallInFlight !== indexOfCurrentCall

One option would be to throw an error with a custom message, and then check for that message in the catch in fetchQuotesAndSetQuoteState and respond accordingly.

All the code here is looking good and the initial QA is almost perfect. There was some weird behaviour that I saw when radpidly going back and forth between the build quote and loading screen. I think that might be a pre-existing issue though. I am going to QA one more time a little later, and then we should be able to merge this.