revert cleanup: harmonize old and new consensus engine creation

core/genesis.go

@@ -373,6 +373,40 @@ func SetupGenesisBlockWithOverride(db ethdb.Database, triedb *trie.Database, gen
 	return newcfg, stored, nil
 }
 
+// LoadChainConfig loads the stored chain config if it is already present in
+// database, otherwise, return the config in the provided genesis specification.
+// LG: this is replicated for now to satisfy the divergent interfaces between 1.11 and after
+func LoadChainConfig(db ethdb.Database, genesis *Genesis) (*params.ChainConfig, error) {
+	// Load the stored chain config from the database. It can be nil
+	// in case the database is empty. Notably, we only care about the
+	// chain config corresponds to the canonical chain.
+	stored := rawdb.ReadCanonicalHash(db, 0)
+	if stored != (common.Hash{}) {
+		storedcfg := rawdb.ReadChainConfig(db, stored)
+		if storedcfg != nil {
+			return storedcfg, nil
+		}
+	}
+	// Load the config from the provided genesis specification
+	if genesis != nil {
+		// Reject invalid genesis spec without valid chain config
+		if genesis.Config == nil {
+			return nil, errGenesisNoConfig
+		}
+		// If the canonical genesis header is present, but the chain
+		// config is missing(initialize the empty leveldb with an
+		// external ancient chain segment), ensure the provided genesis
+		// is matched.
+		if stored != (common.Hash{}) && genesis.ToBlock().Hash() != stored {
+			return nil, &GenesisMismatchError{stored, genesis.ToBlock().Hash()}
+		}
+		return genesis.Config, nil
+	}
+	// There is no stored chain config and no new config provided,
+	// In this case the default chain config(mainnet) will be used
+	return params.MainnetChainConfig, nil
+}
+
 // LoadCliqueConfig loads the stored clique config if the chain config
 // is already present in database, otherwise, return the config in the
 // provided genesis specification. Note the returned clique config can

eth/backend.go

@@ -151,13 +151,20 @@ func New(stack *node.Node, config *ethconfig.Config) (*Ethereum, error) {
 		return nil, err
 	}
 
+	// Transfer mining-related config to the ethash config.
+	chainConfig, err := core.LoadChainConfig(chainDb, config.Genesis)
+	if err != nil {
+		return nil, err
+	}
+	engine := ethconfig.CreateConsensusEngine(stack, &ethashConfig, cliqueConfig, config.Miner.Notify, config.Miner.Noverify, chainDb)
+	if err != nil {
+		return nil, err
+	}
 	networkID := config.NetworkId
 	if networkID == 0 {
 		networkID = chainConfig.ChainID.Uint64()
 	}
 
-	engine := ethconfig.CreateConsensusEngine(stack, &ethashConfig, cliqueConfig, config.Miner.Notify, config.Miner.Noverify, chainDb)
-
 	eth := &Ethereum{
 		config:            config,
 		merger:            consensus.NewMerger(chainDb),