ChargeAssetTxPayment Should Handle Fee Withdrawal Better When an Account Does Not Exist in System

[joepetrowski]

Right now, when an asset is converted to the native asset for fee payment, it must create the account for the transaction's execution. This means, if the account doesn't already exist, it actually converts the existential deposit plus the fee in order to have enough balance.

At the end of the transation, in post_dispatch, the ED plus any fee refund are converted back into the asset selected by the user.

This requires the user to have a liquid balance of the asset much greater than the potential transaction fee. It would be better to handle this by only withdrawing the amount needed for the fee.

To consider though: Asset Conversion does not obviate the need for sufficiency. An account should only exist without the ED if an asset it holds is sufficient. If paying in that asset, one could argue that if it cannot be converted to the ED of the native asset, then the minimum balance of the asset class is too low. However, the user could be paying via asset conversion with another, non-sufficient asset.

[muharem]

this now should be possible with swap credit implementation

[joepetrowski]

@muharem can we close this now with swap credit in the runtimes?

[muharem]

@joepetrowski yes, this can be closed

[muharem]

ChargeAssetTxPayment now uses credit swap impl for swaps, which drops the ED requirement

[joepetrowski]

Reopening for the SignedExtension impl