eth, eth/tracers: expose gas used in tx to js tracer

eth/api_tracer.go

@@ -794,7 +794,7 @@ func (api *PrivateDebugAPI) traceTx(ctx context.Context, message core.Message, v
 			}
 		}
 		// Constuct the JavaScript tracer to execute with
-		if tracer, err = tracers.New(*config.Tracer); err != nil {
+		if tracer, err = tracers.New(*config.Tracer, txContext); err != nil {
 			return nil, err
 		}
 		// Handle timeouts and RPC cancellations

eth/tracers/internal/tracers/prestate_tracer.js

@@ -55,7 +55,7 @@
 		var toBal   = bigInt(this.prestate[toHex(ctx.to)].balance.slice(2), 16);
 
 		this.prestate[toHex(ctx.to)].balance   = '0x'+toBal.subtract(ctx.value).toString(16);
-		this.prestate[toHex(ctx.from)].balance = '0x'+fromBal.add(ctx.value).toString(16);
+		this.prestate[toHex(ctx.from)].balance = '0x'+fromBal.add(ctx.value).add((ctx.gasUsed + ctx.intrinsicGas) * ctx.gasPrice).toString(16);
 
 		// Decrement the caller's nonce, and remove empty create targets
 		this.prestate[toHex(ctx.from)].nonce--;

eth/tracers/tracer.go

@@ -27,10 +27,11 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/log"
-	"gopkg.in/olebedev/go-duktape.v3"
+	duktape "gopkg.in/olebedev/go-duktape.v3"
 )
 
 // bigIntegerJS is the minified version of https://github.com/peterolson/BigInteger.js.
@@ -316,7 +317,7 @@ type Tracer struct {
 // New instantiates a new tracer instance. code specifies a Javascript snippet,
 // which must evaluate to an expression returning an object with 'step', 'fault'
 // and 'result' functions.
-func New(code string) (*Tracer, error) {
+func New(code string, txCtx vm.TxContext) (*Tracer, error) {
 	// Resolve any tracers by name and assemble the tracer object
 	if tracer, ok := tracer(code); ok {
 		code = tracer
@@ -335,6 +336,8 @@ func New(code string) (*Tracer, error) {
 		depthValue:      new(uint),
 		refundValue:     new(uint),
 	}
+	tracer.ctx["gasPrice"] = txCtx.GasPrice
+
 	// Set up builtins for this environment
 	tracer.vm.PushGlobalGoFunction("toHex", func(ctx *duktape.Context) int {
 		ctx.PushString(hexutil.Encode(popSlice(ctx)))
@@ -546,6 +549,18 @@ func (jst *Tracer) CaptureState(env *vm.EVM, pc uint64, op vm.OpCode, gas, cost
 		// Initialize the context if it wasn't done yet
 		if !jst.inited {
 			jst.ctx["block"] = env.Context.BlockNumber.Uint64()
+			// Compute intrinsic gas
+			isHomestead := env.ChainConfig().IsHomestead(env.Context.BlockNumber)
+			isIstanbul := env.ChainConfig().IsIstanbul(env.Context.BlockNumber)
+			var input []byte
+			if data, ok := jst.ctx["input"].([]byte); ok {
+				input = data
+			}
+			intrinsicGas, err := core.IntrinsicGas(input, jst.ctx["type"] == "CREATE", isHomestead, isIstanbul)
+			if err != nil {
+				return err
+			}
+			jst.ctx["intrinsicGas"] = intrinsicGas
 			jst.inited = true
 		}
 		// If tracing was interrupted, set the error and stop
@@ -597,8 +612,8 @@ func (jst *Tracer) CaptureFault(env *vm.EVM, pc uint64, op vm.OpCode, gas, cost
 // CaptureEnd is called after the call finishes to finalize the tracing.
 func (jst *Tracer) CaptureEnd(output []byte, gasUsed uint64, t time.Duration, err error) error {
 	jst.ctx["output"] = output
-	jst.ctx["gasUsed"] = gasUsed
 	jst.ctx["time"] = t.String()
+	jst.ctx["gasUsed"] = gasUsed
 
 	if err != nil {
 		jst.ctx["error"] = err.Error()