feat(core): refactor gas refund logic in state transition (#148)

core/state_transition.go

@@ -424,14 +424,12 @@ func (st *StateTransition) TransitionDb() (*ExecutionResult, error) {
 		st.state.SetNonce(msg.From, st.state.GetNonce(sender.Address())+1)
 		ret, st.gasRemaining, vmerr = st.evm.Call(sender, st.to(), msg.Data, st.gasRemaining, msg.Value)
 	}
-	if !st.msg.IsAnchor {
-		if !rules.IsLondon {
-			// Before EIP-3529: refunds were capped to gasUsed / 2
-			st.refundGas(params.RefundQuotient)
-		} else {
-			// After EIP-3529: refunds are capped to gasUsed / 5
-			st.refundGas(params.RefundQuotientEIP3529)
-		}
+	if !rules.IsLondon {
+		// Before EIP-3529: refunds were capped to gasUsed / 2
+		st.refundGas(params.RefundQuotient)
+	} else {
+		// After EIP-3529: refunds are capped to gasUsed / 5
+		st.refundGas(params.RefundQuotientEIP3529)
 	}
 	effectiveTip := msg.GasPrice
 	if rules.IsLondon {
@@ -469,11 +467,12 @@ func (st *StateTransition) refundGas(refundQuotient uint64) {
 		refund = st.state.GetRefund()
 	}
 	st.gasRemaining += refund
-
-	// Return ETH for remaining gas, exchanged at the original rate.
-	remaining := new(big.Int).Mul(new(big.Int).SetUint64(st.gasRemaining), st.msg.GasPrice)
-	st.state.AddBalance(st.msg.From, remaining)
-
+	// Do not change the balance in anchor transactions.
+	if !st.msg.IsAnchor {
+		// Return ETH for remaining gas, exchanged at the original rate.
+		remaining := new(big.Int).Mul(new(big.Int).SetUint64(st.gasRemaining), st.msg.GasPrice)
+		st.state.AddBalance(st.msg.From, remaining)
+	}
 	// Also return remaining gas to the block gas counter so it is
 	// available for the next transaction.
 	st.gp.AddGas(st.gasRemaining)