internal/ethapi: add CallArgs.ToMessage method (ethereum#20854)

ToMessage is used to convert between ethapi.CallArgs and types.Message.
It reduces the length of the DoCall method by about half by abstracting out
the conversion between the CallArgs and the Message. This should improve the
code's maintainability and reusability.

internal/ethapi/api.go

@@ -739,6 +739,42 @@ type CallArgs struct {
 	Data     *hexutil.Bytes  `json:"data"`
 }
 
+// ToMessage converts CallArgs to the Message type used by the core evm
+func (args *CallArgs) ToMessage(globalGasCap *big.Int) types.Message {
+	// Set sender address or use zero address if none specified.
+	var addr common.Address
+	if args.From != nil {
+		addr = *args.From
+	}
+
+	// Set default gas & gas price if none were set
+	gas := uint64(math.MaxUint64 / 2)
+	if args.Gas != nil {
+		gas = uint64(*args.Gas)
+	}
+	if globalGasCap != nil && globalGasCap.Uint64() < gas {
+		log.Warn("Caller gas above allowance, capping", "requested", gas, "cap", globalGasCap)
+		gas = globalGasCap.Uint64()
+	}
+	gasPrice := new(big.Int)
+	if args.GasPrice != nil {
+		gasPrice = args.GasPrice.ToInt()
+	}
+
+	value := new(big.Int)
+	if args.Value != nil {
+		value = args.Value.ToInt()
+	}
+
+	var data []byte
+	if args.Data != nil {
+		data = []byte(*args.Data)
+	}
+
+	msg := types.NewMessage(addr, args.To, 0, value, gas, gasPrice, data, false)
+	return msg
+}
+
 // account indicates the overriding fields of account during the execution of
 // a message call.
 // Note, state and stateDiff can't be specified at the same time. If state is
@@ -761,12 +797,6 @@ func DoCall(ctx context.Context, b Backend, args CallArgs, blockNrOrHash rpc.Blo
 		return nil, 0, false, err
 	}
 
-	// Set sender address or use zero address if none specified.
-	var addr common.Address
-	if args.From != nil {
-		addr = *args.From
-	}
-
 	// Override the fields of specified contracts before execution.
 	for addr, account := range overrides {
 		// Override account nonce.
@@ -795,32 +825,6 @@ func DoCall(ctx context.Context, b Backend, args CallArgs, blockNrOrHash rpc.Blo
 			}
 		}
 	}
-	// Set default gas & gas price if none were set
-	gas := uint64(math.MaxUint64 / 2)
-	if args.Gas != nil {
-		gas = uint64(*args.Gas)
-	}
-	if globalGasCap != nil && globalGasCap.Uint64() < gas {
-		log.Warn("Caller gas above allowance, capping", "requested", gas, "cap", globalGasCap)
-		gas = globalGasCap.Uint64()
-	}
-	gasPrice := new(big.Int)
-	if args.GasPrice != nil {
-		gasPrice = args.GasPrice.ToInt()
-	}
-
-	value := new(big.Int)
-	if args.Value != nil {
-		value = args.Value.ToInt()
-	}
-
-	var data []byte
-	if args.Data != nil {
-		data = []byte(*args.Data)
-	}
-
-	// Create new call message
-	msg := types.NewMessage(addr, args.To, 0, value, gas, gasPrice, data, false)
 
 	// Setup context so it may be cancelled the call has completed
 	// or, in case of unmetered gas, setup a context with a timeout.
@@ -835,6 +839,7 @@ func DoCall(ctx context.Context, b Backend, args CallArgs, blockNrOrHash rpc.Blo
 	defer cancel()
 
 	// Get a new instance of the EVM.
+	msg := args.ToMessage(globalGasCap)
 	evm, vmError, err := b.GetEVM(ctx, msg, state, header)
 	if err != nil {
 		return nil, 0, false, err