Implement correctly cosmos account sequence

[NicolasMahe]

Conversation started on #1267 (comment).

The account sequence is currently hardcoded and only work when transactions have different content.
But if 2 transactions have the same content, then they generate the same hash and thus the second is rejected.

The sequence should be always be different.

• Must the sequence number be incremented?
• Maybe use the last block height at a starting point?

[krhubert]

https://forum.cosmos.network/t/account-sequence-number/1610/2

[antho1404]

We should use the GetSequence from the AccountKeeper https://github.com/cosmos/cosmos-sdk/blob/fb3e0af0b6320838c1da8531deba6c6a542c376a/x/auth/keeper/keeper.go#L61

[NicolasMahe]

I think the Account SDK should return data from the Account Keeper. It looks like the AccountKeeper has all the data needed.
If we do this, then the functions NewTxBuilder and client.BuildAndBroadcastMsg could also accept the AccountKeeper to directly get the sequence, and account number ;)

[krhubert]

Will use GetSequence and GetAccountNumber then.

[NicolasMahe]

The SetSequence is already managed by cosmos when applying a transaction:

https://github.com/cosmos/cosmos-sdk/blob/02c6c9fafd58da88550ab4d7d494724a477c8a68/x/auth/ante/sigverify.go#L252

[antho1404]

With that, we should be able to simply use GetSequence all the time and not have to manage the sequence at all.

[krhubert]

This is not that simple. We need to have cosmos context to get the account.

I've used auth.NewAccountRetriver to get account number and sequence via rest api.