cardano-ledger can not/no longer parse AlonzoGenesis from JSON / Yaml

[KtorZ]

Hello. The parser for the AlonzoGenesis expects the PlutusV1 cost models to contain keys/values for parameters introduced well after the definition of that genesis configuration. As a result, one cannot decode the genesis config from JSON/Yaml directly.

To make it work, one must patch the PlutusV1's cost model with placeholder values for the missing parameters (which is wrong because those parameters simply did not exist at the time). See for example:

https://github.com/CardanoSolutions/ogmios/blob/master/server/src/Ogmios/App/Configuration.hs#L147-L203

I am not the only person bumping into this, as similar code can be witnessed in the cardano-api which has to work around that too:

https://github.com/IntersectMBO/cardano-api/blob/master/cardano-api/src/Cardano/Api/Genesis/Internal.hs#L372-L440

[lehins]

Hello. I totally agree, AlonzoGenesis, as any other genesis file, is there to provide initial values for new protocol parameters, including the cost model for PlutusV1 as it was when the era was entered upon the hard fork. As, such number of cost model parameters, must match the number that Plutus expected at that moment. We have discovered this exact problem recently when plutus added new primitives for PlutusV1 and have already fixed in #5241. It is no longer wrong and the fix will be included in the upcoming 10.6 release.

It should be impossible to supply new primitives in Alonzo that were added in Conway or Dijkstra on any long running chain like mainnet, preview or preprod, since their genesis files must remain unchanged. That being said, for the purpose of testing and benchmarking it could be useful to abuse AlonzoGenesis to provide cost models for new primitives, since there is desire to start testing or benchmarking in a much later era, say in Conway. We already do provide similar functionality for injecting utxo, delegations, stake pools, dreps, etc. We've discussed this exact point last week internally and we have a plan to add such functionality for CostModels. I've created a ticket #5342 that captures this use case and will be closing this one as already done.