Apply suggestions from code review

Co-authored-by: Alexey Kuleshevich <alexey.kuleshevich@iohk.io>

Author: Lucsanszky

eras/alonzo/impl/src/Cardano/Ledger/Alonzo/Genesis.hs

@@ -229,7 +229,11 @@ instance FromJSON AlonzoGenesis where
     agCollateralPercentage <- o .: "collateralPercentage"
     agMaxCollateralInputs <- o .: "maxCollateralInputs"
     agExtraConfig <- o .:? "extraConfig"
-    let agCostModels = costModelsValid cms ! PlutusV1
+    agPlutusV1CostModel <- 
+      case Map.toList (costModelsValid cms) of
+        [] -> fail "Expected \"PlutusV1\" cost model to be supplied"
+        [(PlutusV1, pv1CostModel)] -> pure pv1CostModel
+        _ -> fail $ "Only PlutusV1 CostModel is allowed in the AlonzoGenesis, but " <> List.intercalate ", " (Map.keys cms) <> " were supplied. Use \"extraConfig\" if you need to inject other cost models for testing."
     return AlonzoGenesis {..}
 
 instance ToKeyValuePairs AlonzoGenesis where
@@ -243,4 +247,4 @@ instance ToKeyValuePairs AlonzoGenesis where
     , "collateralPercentage" .= agCollateralPercentage ag
     , "maxCollateralInputs" .= agMaxCollateralInputs ag
     ]
-      ++ ["extraConfig" .= agExtraConfig ag | isJust (agExtraConfig ag)]
+      ++ ["extraConfig" .= extraConfig | Just extraConfig <- [agExtraConfig ag]]

eras/alonzo/impl/src/Cardano/Ledger/Alonzo/Transition.hs

@@ -30,9 +30,13 @@ instance EraTransition AlonzoEra where
 
   mkTransitionConfig = AlonzoTransitionConfig
 
-  injectIntoTestState cfg = case agExtraConfig $ cfg ^. tcTranslationContextL of
-    Nothing -> shelleyRegisterInitialFundsThenStaking cfg
-    Just aec -> shelleyRegisterInitialFundsThenStaking cfg . overrideCostModels (aecCostModels aec)
+  injectIntoTestState cfg = 
+    shelleyRegisterInitialFundsThenStaking cfg . alonzoInjectCostModels cfg
+
+alonzoInjectCostModels cfg =
+  case agExtraConfig $ cfg ^. tcTranslationContextL of
+    Nothing -> id
+    Just aec -> overrideCostModels (aecCostModels aec)
 
   tcPreviousEraConfigL =
     lens atcMaryTransitionConfig (\atc pc -> atc {atcMaryTransitionConfig = pc})
@@ -48,4 +52,6 @@ overrideCostModels ::
   NewEpochState era ->
   NewEpochState era
 overrideCostModels Nothing nes = nes
-overrideCostModels (Just cms) nes = nes & nesEsL . curPParamsEpochStateL . ppCostModelsL %~ (<> cms)
+overrideCostModels = \case 
+  Nothing -> id 
+  Just cms -> nesEsL . curPParamsEpochStateL . ppCostModelsL %~ updateCostModels cms