feat: override vm.NewEVM() args

core/vm/evm.go

@@ -143,6 +143,7 @@ func NewEVM(blockCtx BlockContext, txCtx TxContext, statedb StateDB, chainConfig
 			blockCtx.BlobBaseFee = new(big.Int)
 		}
 	}
+	blockCtx, txCtx, statedb, chainConfig, config = overrideNewEVMArgs(blockCtx, txCtx, statedb, chainConfig, config)
 	evm := &EVM{
 		Context:     blockCtx,
 		TxContext:   txCtx,

core/vm/evm.libevm_test.go

@@ -0,0 +1,32 @@
+package vm
+
+import (
+	"math/big"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/params"
+	"github.com/stretchr/testify/require"
+)
+
+type chainIDOverrider struct {
+	chainID int64
+}
+
+func (o chainIDOverrider) OverrideNewEVMArgs(BlockContext, TxContext, StateDB, *params.ChainConfig, Config) (BlockContext, TxContext, StateDB, *params.ChainConfig, Config) {
+	return BlockContext{}, TxContext{}, nil, &params.ChainConfig{ChainID: big.NewInt(o.chainID)}, Config{}
+}
+
+func TestOverrideNewEVMArgs(t *testing.T) {
+	// The OverrideNewEVMArgs hook accepts and returns all arguments to
+	// NewEVM(), in order. Here we lock in our assumption of that order. If this
+	// breaks then the Hooks.OverrideNewEVMArgs() signature MUST be changed to
+	// match.
+	var _ func(BlockContext, TxContext, StateDB, *params.ChainConfig, Config) *EVM = NewEVM
+
+	const chainID = 13579
+	libevmHooks = nil
+	RegisterHooks(chainIDOverrider{chainID: chainID})
+
+	got := NewEVM(BlockContext{}, TxContext{}, nil, nil, Config{}).ChainConfig().ChainID
+	require.Equal(t, big.NewInt(chainID), got)
+}

core/vm/hooks.libevm.go

@@ -0,0 +1,32 @@
+package vm
+
+import "github.com/ethereum/go-ethereum/params"
+
+// RegisterHooks registers the Hooks. It is expected to be called in an `init()`
+// function and MUST NOT be called more than once.
+func RegisterHooks(h Hooks) {
+	if libevmHooks != nil {
+		panic("already registered")
+	}
+	libevmHooks = h
+}
+
+var libevmHooks Hooks
+
+// Hooks are arbitrary configuration functions to modify default VM behaviour.
+type Hooks interface {
+	OverrideNewEVMArgs(BlockContext, TxContext, StateDB, *params.ChainConfig, Config) (BlockContext, TxContext, StateDB, *params.ChainConfig, Config)
+}
+
+func overrideNewEVMArgs(
+	blockCtx BlockContext,
+	txCtx TxContext,
+	statedb StateDB,
+	chainConfig *params.ChainConfig,
+	config Config,
+) (BlockContext, TxContext, StateDB, *params.ChainConfig, Config) {
+	if libevmHooks == nil {
+		return blockCtx, txCtx, statedb, chainConfig, config
+	}
+	return libevmHooks.OverrideNewEVMArgs(blockCtx, txCtx, statedb, chainConfig, config)
+}