Use a single protocol version across all eras (#1224)

While giving us flexibility, using different protocol versions for all
eras increased the level of complexity and led to several errors in the
past. This PR removes this flexibility by using a single protocol
version, which determines the maximum protocol version Consensus
supports.

See #324 for more background.

Closes #324.
Closes #276.

TODOs:

- [x] Format the code.
- [x] Fix ThreadNet test failure.
- [x] Improve documentation.
- [x] Address all the `FIXME`s.

ouroboros-consensus-cardano/changelog.d/20240823_131440_damian.nadales_324_simplify_protver_arguments.md

@@ -0,0 +1,5 @@
+### Breaking
+
+- ProtocolParams (CardanoBlock c) was monomorphized to `CardanoProtocolParams`
+- Remove `cardanoProtocolParamsPerEra` from `CardanoProtocolParams` in favour of a single `cardanoProtocolVersion`.
+  This patch intentionally removes the flexibility the n-ary product of versions per-era gave us, in favour of a simpler interface, as the current one has caused a lot of confusion and led to several mistakes in the past.

ouroboros-consensus-cardano/src/byron/Ouroboros/Consensus/Byron/Node.hs

@@ -18,7 +18,7 @@ module Ouroboros.Consensus.Byron.Node (
   , mkByronLeaderCredentials
   , mkPBftCanBeLeader
     -- * ProtocolInfo
-  , ProtocolParams (..)
+  , ProtocolParamsByron (..)
   , defaultPBftSignatureThreshold
   , mkByronConfig
   , protocolClientInfoByron
@@ -152,7 +152,7 @@ mkPBftCanBeLeader (ByronLeaderCredentials sk cert nid _) = PBftCanBeLeader {
     }
 
 blockForgingByron :: Monad m
-                  => ProtocolParams ByronBlock
+                  => ProtocolParamsByron
                   -> [BlockForging m ByronBlock]
 blockForgingByron ProtocolParamsByron { byronLeaderCredentials = mLeaderCreds
                                       } =
@@ -169,15 +169,15 @@ defaultPBftSignatureThreshold :: PBftSignatureThreshold
 defaultPBftSignatureThreshold = PBftSignatureThreshold 0.22
 
 -- | Parameters needed to run Byron
-data instance ProtocolParams ByronBlock = ProtocolParamsByron {
+data ProtocolParamsByron = ProtocolParamsByron {
       byronGenesis                :: Genesis.Config
     , byronPbftSignatureThreshold :: Maybe PBftSignatureThreshold
     , byronProtocolVersion        :: Update.ProtocolVersion
     , byronSoftwareVersion        :: Update.SoftwareVersion
     , byronLeaderCredentials      :: Maybe ByronLeaderCredentials
     }
 
-protocolInfoByron :: ProtocolParams ByronBlock
+protocolInfoByron :: ProtocolParamsByron
                   -> ProtocolInfo ByronBlock
 protocolInfoByron ProtocolParamsByron {
                       byronGenesis                = genesisConfig

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

@@ -9,7 +9,6 @@ module Ouroboros.Consensus.Cardano (
   , ProtocolShelley
     -- * Abstract over the various protocols
   , CardanoHardForkTriggers (..)
-  , ProtocolParams (..)
   , module X
   ) where
 

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

@@ -34,9 +34,8 @@
 module Ouroboros.Consensus.Cardano.Node (
     CardanoHardForkConstraints
   , CardanoHardForkTriggers (.., CardanoHardForkTriggers', triggerHardForkShelley, triggerHardForkAllegra, triggerHardForkMary, triggerHardForkAlonzo, triggerHardForkBabbage, triggerHardForkConway)
-  , CardanoProtocolParams
+  , CardanoProtocolParams (..)
   , MaxMajorProtVer (..)
-  , ProtocolParams (.., CardanoProtocolParams, paramsByron, paramsShelleyBased, paramsShelley, paramsAllegra, paramsMary, paramsAlonzo, paramsBabbage, paramsConway, hardForkTriggers, ledgerTransitionConfig, checkpoints)
   , TriggerHardFork (..)
   , protocolClientInfoCardano
   , protocolInfoCardano
@@ -77,7 +76,6 @@ import qualified Data.Map.Strict as Map
 import           Data.SOP.BasicFunctors
 import           Data.SOP.Counting
 import           Data.SOP.Index (Index (..))
-import           Data.SOP.NonEmpty
 import           Data.SOP.OptNP (NonEmptyOptNP, OptNP (OptSkip))
 import qualified Data.SOP.OptNP as OptNP
 import           Data.SOP.Strict
@@ -93,8 +91,6 @@ import           Ouroboros.Consensus.Cardano.Block
 import           Ouroboros.Consensus.Cardano.CanHardFork
 import           Ouroboros.Consensus.Config
 import           Ouroboros.Consensus.HardFork.Combinator
-import           Ouroboros.Consensus.HardFork.Combinator.AcrossEras
-                     (PerEraProtocolParams (..))
 import           Ouroboros.Consensus.HardFork.Combinator.Embed.Nary
 import           Ouroboros.Consensus.HardFork.Combinator.Serialisation
 import qualified Ouroboros.Consensus.HardFork.History as History
@@ -521,61 +517,57 @@ pattern CardanoHardForkTriggers' {
 {-# COMPLETE CardanoHardForkTriggers' #-}
 
 -- | Parameters needed to run Cardano.
-data instance ProtocolParams (CardanoBlock c) = ProtocolParamsCardano {
-    cardanoProtocolParamsPerEra   :: PerEraProtocolParams (CardanoEras c)
+--
+-- __On the relation between 'cardanoHardForkTriggers' and 'cardanoProtocolVersion'__:
+--
+-- The 'cardanoHardForkTriggers' can mention __ledger__ protocol
+-- version versions at which the hard fork will occur. In principle
+-- there is no relation between the versions mentioned in
+-- 'cardanoProtocolVerson' (if any) and 'cardanoHardForkTriggers',
+-- however their relationship might indicate experimental eras or
+-- intra-era hard forks. For instance if the last era in the
+-- 'CardanoHardForkTriggers' is set to @9 0@, ie:
+--
+-- > ... :* TriggerHardForkAtVersion (ProtVer (SL.natVersion @9) 0)
+--
+-- Setting 'cardanoProtocolVersion' to @ProtVer (SL.natVersion @8) 0@
+-- will mark that last era as experimental because the obsolete node
+-- checks determine that the highest version we support is @8 0@.
+--
+-- If, on the other hand, we would set 'cardanoProtocolVersion' to
+-- @ProtVer (SL.natVersion @10) 0@, this indicates that the node is
+-- ready to perform an intra-era hardfork (from version @9@ to version
+-- @10@).
+--
+data CardanoProtocolParams c = CardanoProtocolParams {
+    byronProtocolParams           :: ProtocolParamsByron
   , shelleyBasedProtocolParams    :: ProtocolParamsShelleyBased c
   , cardanoHardForkTriggers       :: CardanoHardForkTriggers
   , cardanoLedgerTransitionConfig :: L.TransitionConfig (L.LatestKnownEra c)
   , cardanoCheckpoints            :: CheckpointsMap (CardanoBlock c)
+    -- | The greatest protocol version that this node's software and config
+    -- files declare to handle correctly.
+    --
+    -- This parameter has three consequences. First, the blocks minted
+    -- will include the protocol version in their header, but
+    -- essentially only for public signaling (eg measuring the
+    -- percentage of adoption of software updates).
+    --
+    -- Second, and more importantly, it's passed to the protocol logic. In
+    -- particular, the node's envelope check will begin rejecting all blocks
+    -- (actually, their headers) if the chain moves to a greater protocol
+    -- version. This should never happen in a node that is using up-to-date
+    -- software and config files. Note that the missing software update is
+    -- not necessarily a 'HardForkBlock' era transition: it might be an
+    -- /intra-era hard fork/ (ie conditionals in the ledger rules).
+    --
+    -- Third, it's passed to the ledger rules---but that's entirely
+    -- vestigial. See
+    -- <https://github.com/IntersectMBO/cardano-ledger/issues/3682>.
+    --
+  , cardanoProtocolVersion        :: ProtVer
   }
 
-type CardanoProtocolParams c = ProtocolParams (CardanoBlock c)
-
-pattern CardanoProtocolParams ::
-     ProtocolParams ByronBlock
-  -> ProtocolParamsShelleyBased c
-  -> ProtocolParams (ShelleyBlock (TPraos c) (ShelleyEra c))
-  -> ProtocolParams (ShelleyBlock (TPraos c) (AllegraEra c))
-  -> ProtocolParams (ShelleyBlock (TPraos c) (MaryEra    c))
-  -> ProtocolParams (ShelleyBlock (TPraos c) (AlonzoEra  c))
-  -> ProtocolParams (ShelleyBlock (Praos  c) (BabbageEra c))
-  -> ProtocolParams (ShelleyBlock (Praos  c) (ConwayEra  c))
-  -> CardanoHardForkTriggers
-  -> L.TransitionConfig (L.LatestKnownEra c)
-  -> CheckpointsMap (CardanoBlock c)
-  -> CardanoProtocolParams c
-pattern CardanoProtocolParams {
-        paramsByron
-      , paramsShelleyBased
-      , paramsShelley
-      , paramsAllegra
-      , paramsMary
-      , paramsAlonzo
-      , paramsBabbage
-      , paramsConway
-      , hardForkTriggers
-      , ledgerTransitionConfig
-      , checkpoints
-      } =
-    ProtocolParamsCardano {
-        cardanoProtocolParamsPerEra = PerEraProtocolParams
-          (  paramsByron
-          :* paramsShelley
-          :* paramsAllegra
-          :* paramsMary
-          :* paramsAlonzo
-          :* paramsBabbage
-          :* paramsConway
-          :* Nil
-          )
-      , shelleyBasedProtocolParams = paramsShelleyBased
-      , cardanoHardForkTriggers = hardForkTriggers
-      , cardanoLedgerTransitionConfig = ledgerTransitionConfig
-      , cardanoCheckpoints = checkpoints
-      }
-
-{-# COMPLETE CardanoProtocolParams #-}
-
 -- | Create a 'ProtocolInfo' for 'CardanoBlock'
 --
 -- NOTE: For testing and benchmarking purposes, the 'ShelleyGenesis' can contain
@@ -607,84 +599,44 @@ protocolInfoCardano paramsCardano
     )
   where
     CardanoProtocolParams {
-        paramsByron
-      , paramsShelleyBased
-      , paramsShelley
-      , paramsAllegra
-      , paramsMary
-      , paramsAlonzo
-      , paramsBabbage
-      , paramsConway
-      , hardForkTriggers = CardanoHardForkTriggers' {
+        byronProtocolParams
+      , shelleyBasedProtocolParams
+      , cardanoHardForkTriggers = CardanoHardForkTriggers' {
           triggerHardForkShelley
         , triggerHardForkAllegra
         , triggerHardForkMary
         , triggerHardForkAlonzo
         , triggerHardForkBabbage
         , triggerHardForkConway
         }
-      , ledgerTransitionConfig
-      , checkpoints
+      , cardanoLedgerTransitionConfig
+      , cardanoCheckpoints
+      , cardanoProtocolVersion
       } = paramsCardano
 
-    genesisShelley = ledgerTransitionConfig ^. L.tcShelleyGenesisL
+    genesisShelley = cardanoLedgerTransitionConfig ^. L.tcShelleyGenesisL
 
     ProtocolParamsByron {
           byronGenesis           = genesisByron
         , byronLeaderCredentials = mCredsByron
-        } = paramsByron
+        } = byronProtocolParams
     ProtocolParamsShelleyBased {
           shelleyBasedInitialNonce      = initialNonceShelley
         , shelleyBasedLeaderCredentials = credssShelleyBased
-        } = paramsShelleyBased
-    ProtocolParamsShelley {
-          shelleyProtVer = protVerShelley
-        } = paramsShelley
-    ProtocolParamsAllegra {
-          allegraProtVer = protVerAllegra
-        } = paramsAllegra
-    ProtocolParamsMary {
-          maryProtVer = protVerMary
-        } = paramsMary
-    ProtocolParamsAlonzo {
-          alonzoProtVer = protVerAlonzo
-        } = paramsAlonzo
-    ProtocolParamsBabbage {
-          babbageProtVer = protVerBabbage
-        } = paramsBabbage
-    ProtocolParamsConway {
-          conwayProtVer = protVerConway
-        } = paramsConway
+        } = shelleyBasedProtocolParams
 
     transitionConfigShelley = transitionConfigAllegra ^. L.tcPreviousEraConfigL
     transitionConfigAllegra = transitionConfigMary    ^. L.tcPreviousEraConfigL
     transitionConfigMary    = transitionConfigAlonzo  ^. L.tcPreviousEraConfigL
     transitionConfigAlonzo  = transitionConfigBabbage ^. L.tcPreviousEraConfigL
     transitionConfigBabbage = transitionConfigConway  ^. L.tcPreviousEraConfigL
-    transitionConfigConway  = ledgerTransitionConfig
+    transitionConfigConway  = cardanoLedgerTransitionConfig
 
     -- The major protocol version of the last era is the maximum major protocol
     -- version we support.
     --
-    -- TODO: use index of CardanoProtocolParams NP
     maxMajorProtVer :: MaxMajorProtVer
-    maxMajorProtVer =
-          MaxMajorProtVer
-        $ pvMajor
-        $ nonEmptyLast
-        $ exactlyWeakenNonEmpty
-        $ protVers
-      where
-        protVers :: Exactly (CardanoShelleyEras StandardCrypto) ProtVer
-        protVers = Exactly $
-          -- ensure that these have the same order as 'CardanoShelleyEras'!
-          K protVerShelley :*
-          K protVerAllegra :*
-          K protVerMary :*
-          K protVerAlonzo :*
-          K protVerBabbage :*
-          K protVerConway :*
-          Nil
+    maxMajorProtVer = MaxMajorProtVer $ pvMajor cardanoProtocolVersion
 
     -- Byron
 
@@ -695,7 +647,7 @@ protocolInfoCardano paramsCardano
           , topLevelConfigBlock    = blockConfigByron
           }
       , pInfoInitLedger = initExtLedgerStateByron
-      } = protocolInfoByron paramsByron
+      } = protocolInfoByron byronProtocolParams
 
     partialConsensusConfigByron :: PartialConsensusConfig (BlockProtocol ByronBlock)
     partialConsensusConfigByron = consensusConfigByron
@@ -744,7 +696,7 @@ protocolInfoCardano paramsCardano
     blockConfigShelley :: BlockConfig (ShelleyBlock (TPraos c) (ShelleyEra c))
     blockConfigShelley =
         Shelley.mkShelleyBlockConfig
-          protVerShelley
+          cardanoProtocolVersion
           genesisShelley
           (shelleyBlockIssuerVKey <$> credssShelleyBased)
 
@@ -767,7 +719,7 @@ protocolInfoCardano paramsCardano
     blockConfigAllegra :: BlockConfig (ShelleyBlock (TPraos c) (AllegraEra c))
     blockConfigAllegra =
         Shelley.mkShelleyBlockConfig
-          protVerAllegra
+          cardanoProtocolVersion
           genesisShelley
           (shelleyBlockIssuerVKey <$> credssShelleyBased)
 
@@ -787,7 +739,7 @@ protocolInfoCardano paramsCardano
     blockConfigMary :: BlockConfig (ShelleyBlock (TPraos c) (MaryEra c))
     blockConfigMary =
         Shelley.mkShelleyBlockConfig
-          protVerMary
+          cardanoProtocolVersion
           genesisShelley
           (shelleyBlockIssuerVKey <$> credssShelleyBased)
 
@@ -807,7 +759,7 @@ protocolInfoCardano paramsCardano
     blockConfigAlonzo :: BlockConfig (ShelleyBlock (TPraos c) (AlonzoEra c))
     blockConfigAlonzo =
         Shelley.mkShelleyBlockConfig
-          protVerAlonzo
+          cardanoProtocolVersion
           genesisShelley
           (shelleyBlockIssuerVKey <$> credssShelleyBased)
 
@@ -827,7 +779,7 @@ protocolInfoCardano paramsCardano
     blockConfigBabbage :: BlockConfig (ShelleyBlock (Praos c) (BabbageEra c))
     blockConfigBabbage =
         Shelley.mkShelleyBlockConfig
-          protVerBabbage
+          cardanoProtocolVersion
           genesisShelley
           (shelleyBlockIssuerVKey <$> credssShelleyBased)
 
@@ -857,7 +809,7 @@ protocolInfoCardano paramsCardano
     blockConfigConway :: BlockConfig (ShelleyBlock (Praos c) (ConwayEra c))
     blockConfigConway =
         Shelley.mkShelleyBlockConfig
-          protVerConway
+          cardanoProtocolVersion
           genesisShelley
           (shelleyBlockIssuerVKey <$> credssShelleyBased)
 
@@ -944,7 +896,7 @@ protocolInfoCardano paramsCardano
             (Shelley.ShelleyStorageConfig tpraosSlotsPerKESPeriod k)
             (Shelley.ShelleyStorageConfig tpraosSlotsPerKESPeriod k)
             (Shelley.ShelleyStorageConfig tpraosSlotsPerKESPeriod k)
-      , topLevelConfigCheckpoints = checkpoints
+      , topLevelConfigCheckpoints = cardanoCheckpoints
       }
 
     -- When the initial ledger state is not in the Byron era, register the

ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Node.hs

@@ -14,7 +14,6 @@
 
 module Ouroboros.Consensus.Shelley.Node (
     MaxMajorProtVer (..)
-  , ProtocolParams (..)
   , ProtocolParamsShelleyBased (..)
   , SL.Nonce (..)
   , SL.ProtVer (..)
@@ -44,7 +43,6 @@ import           Ouroboros.Consensus.Shelley.Ledger
 import           Ouroboros.Consensus.Shelley.Ledger.Inspect ()
 import           Ouroboros.Consensus.Shelley.Ledger.NetworkProtocolVersion ()
 import           Ouroboros.Consensus.Shelley.Node.DiffusionPipelining ()
-import           Ouroboros.Consensus.Shelley.Node.Praos
 import           Ouroboros.Consensus.Shelley.Node.Serialisation ()
 import           Ouroboros.Consensus.Shelley.Node.TPraos
 import           Ouroboros.Consensus.Shelley.Protocol.Abstract (pHeaderIssuer)