Revert hack regarding Babbage→Conway ledger state translation

ouroboros-consensus-cardano/changelog.d/20241030_190550_alexander.esgen_remove_babbage_conway_hfc_tick_hack.md

@@ -0,0 +1,3 @@
+### Non-Breaking
+
+- Removed now-redundant hack in Babbage→Conway translation.

ouroboros-consensus-cardano/src/ouroboros-consensus-cardano/Ouroboros/Consensus/Cardano/CanHardFork.hs

@@ -33,27 +33,20 @@ import qualified Cardano.Chain.Genesis as CC.Genesis
 import qualified Cardano.Chain.Update as CC.Update
 import           Cardano.Crypto.DSIGN (Ed25519DSIGN)
 import           Cardano.Crypto.Hash.Blake2b (Blake2b_224, Blake2b_256)
-import qualified Cardano.Ledger.BaseTypes as SL
-import qualified Cardano.Ledger.Core as Core
 import           Cardano.Ledger.Crypto (ADDRHASH, Crypto, DSIGN, HASH)
 import qualified Cardano.Ledger.Era as SL
 import qualified Cardano.Ledger.Genesis as SL
 import           Cardano.Ledger.Hashes (EraIndependentTxBody)
 import           Cardano.Ledger.Keys (DSignable, Hash)
 import qualified Cardano.Ledger.Shelley.API as SL
-import qualified Cardano.Ledger.Shelley.LedgerState as SL
 import           Cardano.Ledger.Shelley.Translation
                      (toFromByronTranslationContext)
 import qualified Cardano.Protocol.TPraos.API as SL
 import qualified Cardano.Protocol.TPraos.Rules.Prtcl as SL
 import qualified Cardano.Protocol.TPraos.Rules.Tickn as SL
-import           Cardano.Slotting.EpochInfo (epochInfoFirst)
 import           Control.Monad
 import           Control.Monad.Except (runExcept, throwError)
-import qualified Control.State.Transition as STS
 import           Data.Coerce (coerce)
-import           Data.Function ((&))
-import           Data.Functor.Identity
 import qualified Data.Map.Strict as Map
 import           Data.Maybe (listToMaybe, mapMaybe)
 import           Data.Proxy
@@ -62,11 +55,8 @@ import           Data.SOP.InPairs (RequiringBoth (..), ignoringBoth)
 import qualified Data.SOP.Strict as SOP
 import           Data.SOP.Tails (Tails (..))
 import qualified Data.SOP.Tails as Tails
-import           Data.Void
 import           Data.Word
 import           GHC.Generics (Generic)
-import           Lens.Micro ((.~))
-import           Lens.Micro.Extras (view)
 import           NoThunks.Class (NoThunks)
 import           Ouroboros.Consensus.Block
 import           Ouroboros.Consensus.Byron.Ledger
@@ -719,66 +709,16 @@ translateValidatedTxAlonzoToBabbageWrapper ctxt = InjectValidatedTx $
 -------------------------------------------------------------------------------}
 
 translateLedgerStateBabbageToConwayWrapper ::
-     forall c. (Praos.PraosCrypto c)
+     (Praos.PraosCrypto c)
   => RequiringBoth
        WrapLedgerConfig
        (Translate LedgerState)
        (ShelleyBlock (Praos c) (BabbageEra c))
        (ShelleyBlock (Praos c) (ConwayEra c))
 translateLedgerStateBabbageToConwayWrapper =
-    RequireBoth $ \cfgBabbage cfgConway ->
-      Translate $ \epochNo ->
-        let -- It would be cleaner to just pass in the entire 'Bound' instead of
-            -- just the 'EpochNo'.
-            firstSlotNewEra = runIdentity $ epochInfoFirst ei epochNo
-              where
-                ei =
-                    SL.epochInfoPure
-                  $ shelleyLedgerGlobals
-                  $ unwrapLedgerConfig cfgConway
-
-            -- HACK to make sure protocol parameters get properly updated on the
-            -- era transition from Babbage to Conway. This will be replaced by a
-            -- more principled refactoring in the future.
-            --
-            -- Pre-Conway, protocol parameters (like the ledger protocol
-            -- version) were updated by the UPEC rule, which is executed while
-            -- ticking across an epoch boundary. If sufficiently many Genesis
-            -- keys submitted the same update proposal, it will update the
-            -- governance state accordingly.
-            --
-            -- Conway has a completely different governance scheme (CIP-1694),
-            -- and thus has no representation for pre-Conway update proposals,
-            -- which are hence discarded by 'SL.translateEra'' below. Therefore,
-            -- we monkey-patch the governance state by ticking across the
-            -- era/epoch boundary using Babbage logic, and set the governance
-            -- state to the updated one /before/ translating.
-            patchGovState ::
-                 LedgerState (ShelleyBlock proto (BabbageEra c))
-              -> LedgerState (ShelleyBlock proto (BabbageEra c))
-            patchGovState st =
-                st { shelleyLedgerState = shelleyLedgerState st
-                       & SL.newEpochStateGovStateL .~ newGovState
-                   }
-              where
-                newGovState =
-                    view SL.newEpochStateGovStateL
-                  . tickedShelleyLedgerState
-                  . applyChainTick
-                      (unwrapLedgerConfig cfgBabbage)
-                      firstSlotNewEra
-                  $ st
-
-            -- The UPEC rule emits no ledger events, hence this hack is not
-            -- swallowing anything.
-            _upecNoLedgerEvents ::
-                 STS.Event (Core.EraRule "UPEC" (BabbageEra c)) :~: Void
-            _upecNoLedgerEvents = Refl
-
-        in    unComp
-            . SL.translateEra' (getConwayTranslationContext cfgConway)
-            . Comp
-            . patchGovState
+    RequireBoth $ \_cfgBabbage cfgConway ->
+      Translate $ \_epochNo ->
+        unComp . SL.translateEra' (getConwayTranslationContext cfgConway) . Comp
 
 getConwayTranslationContext ::
      WrapLedgerConfig (ShelleyBlock (Praos c) (ConwayEra c))