Mempool rule

[teodanciu]

Description

Introduces Mempool rule and calls it from Ledger rule for transactions in the mempool.

The first commit adds the predicate failure to ConwayLedgerPredFailure, which breaks node-to-client protocol.
If the rest of the PR requires much rework, which would detract too much from Issues discovered in Conway and fixed during the bootstrap phase, then we can just merge the first commit and put the rest on hold for after the intra-era HF.

Closes #4622

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated
• All visible changes are prepended to the latest section of a CHANGELOG.md for the affected packages.
  New section is never added with the code changes. (See RELEASING.md)
• When applicable, versions are updated in .cabal and CHANGELOG.md files according to the
  versioning process.
• The version bounds in .cabal files for all affected packages are updated.
  If you change the bounds in a cabal file, that package itself must have a version increase. (See RELEASING.md)
• Code is formatted with fourmolu (use scripts/fourmolize.sh)
• Cabal files are formatted (use scripts/cabal-format.sh)
• hie.yaml has been updated (use scripts/gen-hie.sh)
• Self-reviewed the diff

[teodanciu]

EDIT: NEVERMIND!!! I realized it's not possible to get events out of applyTxs anyway! Everything I wrote below assumes the opposite, so nevermind! I will leave the comment in order to avoid confusion if an email was sent already.

I tried to write this test:

    it "Mempool events should be emitted via applyTxs" $ do
      let tx = mkBasicTx mkBasicTxBody
      globals <- use impGlobalsL
      slotNo <- use impLastTickG
      nes <- use impNESL

      _ <-  $ applyTxs globals slotNo (Seq.singleton tx) nes   -- and try to get events somehow

But in order to use applyTxs, it appears that I need a MonadError (ApplyTxError era) (ImpTestM era) instance .

I tried to write it, but failed and gave up!
Tried something like this:

  (Era era, Show (PredicateFailure (EraRule "LEDGER" era))) =>
     MonadError (ApplyTxError era) (ImpTestM era)
  where
  throwError (ApplyTxError predFailures) = fail (show predFailures)

  catchError (ImpTestM action) handler =  action  --  I don't know how to thread in the predFailures from the handler   

I don't know 1) whether all of this is worth it, or 2) whether it's all misguided and there is some straightforward way to call applyTxs within ImpTestM or 3) whether it should make sense at all to call applyTxs within ImptestM.

[lehins]

whether it's all misguided and there is some straightforward way to call applyTxs within ImpTestM or

What you need is use runExcept in order to get applyTx out of MonadError

[lehins]

Or even simpler just restrict it to Either:

case applyTxs globals slotNo (Seq.singleton tx) nes of
  Left err -> error $ show err
  Right (st, vTx) -> ...