import rpc transactions sequentially

[seunlanlege]

Previously the ProspectiveSigner marks nonces as used even though they weren't successfully imported into the transaction queue
which caused issues like: #9040

This PR auguments the nonce reservation system such that a reserved nonce is only marked as used if
the PostSign action executes successfully eg transaction is successfully imported into the tx queue

[parity-cla-bot]

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Parity Technologies CLA Bot

[seunlanlege]

There should be some tests that affirm this new behaviour, just how to design them properly 🤔

[tomusdrw]

I don't like the fact that now we have logic splitted into multiple places. Also I think ProspectiveDispatcher is uneccessary complication - let's just add PostSign to ProspectiveSigner instead.

I think PostSign should allow custom IntoFuture to be returned.
The result of that future should then be returned as ProspectiveSigner result.

That would simplify the API, the goal would be to have:

let dispatch_result = dispatcher.sign(accounts, filled, password, |transaction| {
  dispatcher.dispatch(transaction) // this returns a future
});
// in dispatch_result we have whatever was returned by `dispatcher.dispatch`.

[tomusdrw]

Looks good! Couple of minor nitpicks

[tomusdrw]

I know that it's aligned with how currently the state is passed in the ProspectiveSigner, but we might consider refactoring this in a way that the required items are passed in the ProspectiveSignerState enum instead to avoid so many Option< and .expects().
Not required for this PR (or not required at all), unless someone wants to pick it up :)

[niklasad1]

It doesn't make sense that post_sign is an Option anymore because poll assumes that it is always is Some otherwise panic and new requires it too!

Then we can get rid of a couple of expect's

[seunlanlege]

the execute method on PostSign takes self, so inorder to take ownership of post_sign from ProspectiveSigner it needs to be an option. refer to this line

https://github.com/paritytech/parity-ethereum/blob/001a42a98a557edc7c602265a580dd552c871a1d/rpc/src/v1/helpers/dispatch.rs#L592-L599

[niklasad1]

Ok, thanks for clarifying missed that 👍

[niklasad1]

LGTM, but still I would like the field post_sign in ProspectiveSigner struct not to be an Option

You cannot approve and tag it as "grumble" at the same time. Either tag it as "grumble" or approve it and say "mustntgrumble" ... Dismissing this review.

[jam10o-new]

@5chdn we have had many users running into related issues, do you think we could backport this for this or next release?

[5chdn]

yes, label at will