Fix building of Alonzo transaction in Babbage era.

[newhoggy]

This is achieved by auto-converting from Babbage field protocolParamUTxOCostPerByte to Alonzo field protocolParamUTxOCostPerWord, which is a multiplication by 8.

Fixes #4164

[newhoggy]

The conversion occurs here.

[Jimbo4350]

So in the interest of time we should probably let this through but we need a long term solution otherwise we will always be adding ad hoc fixes like this. What about the following for a long term solution:

In the case of build-raw we don't know what era the node is in (and we can't because this is meant to be a completely offline transaction construction command). The protocol parameters varies between eras and will likely continue to vary in the future. So I propose the following:

We:

• Create a GADT wrapper type as follows:

data ProtocolParameters' txEra where
   ProtocolParameters' :: ShelleyBasedEra pparamsEra -> ProtocolParameters -> ProtocolParameters' txEra

• Create a function as follows (I use the if then else clause just as a crude example):

determinePParamsEra :: ProtocolParameters -> ProtocolParameters' era
determinePParamsEra pp = 
  if True
  then ProtocolParameters' ShelleyBasedEraShelley pp
  else ProtocolParameters' ShelleyBasedEraAlonzo pp

We can check for the existence of the era relevant ProtocolParameters fields (in determinePParamsEra) and return the appropriate ShelleyBasedEra pparamsEra in the ProtocolParameters' txEra type.

When we eventually call toLedgerPParams :: ShelleyBasedEra era -> ProtocolParameters -> Ledger.PParams (ShelleyLedgerEra era) in transaction construction we can provide the correct ShelleyBasedEra era and avoid having to modify the individual toAlonzoPParams, toBabbagePParams etc in the future.

I think this is the path of least resistance as we avoid modifying ProtocolParameters era whilst resolving compatibility issues. Open to other long term suggestions. We also need to think of better names.

#4186

[Jimbo4350]

One minor adjustment then I will approve

[Jimbo4350]

This module should not be here

comments addressed

[newhoggy]

bors r+

[iohk-bors]

Build succeeded:

• buildkite/cardano-node
• ci/hydra-build:required