eth/tracers: package restructuring (#23857)

* eth/tracers: restructure tracer package

* core/vm/runtime: load js tracers

* eth/tracers: mv bigint js code to own file

* eth/tracers: add method docs for native tracers

* eth/tracers: minor doc fix

* core,eth: cancel evm on nativecalltracer stop

* core/vm: fix failing test

Co-authored-by: Sina Mahmoodi <itz.s1na@gmail.com>

cmd/geth/main.go

@@ -40,7 +40,8 @@ import (
 	"github.com/ethereum/go-ethereum/metrics"
 	"github.com/ethereum/go-ethereum/node"
 
-	// Force-load the native, to trigger registration
+	// Force-load the tracer engines to trigger registration
+	_ "github.com/ethereum/go-ethereum/eth/tracers/js"
 	_ "github.com/ethereum/go-ethereum/eth/tracers/native"
 
 	"gopkg.in/urfave/cli.v1"

core/vm/access_list_tracer.go

@@ -141,7 +141,7 @@ func (a *AccessListTracer) CaptureStart(env *EVM, from common.Address, to common
 }
 
 // CaptureState captures all opcodes that touch storage or addresses and adds them to the accesslist.
-func (a *AccessListTracer) CaptureState(env *EVM, pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, rData []byte, depth int, err error) {
+func (a *AccessListTracer) CaptureState(pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, rData []byte, depth int, err error) {
 	stack := scope.Stack
 	if (op == SLOAD || op == SSTORE) && stack.len() >= 1 {
 		slot := common.Hash(stack.data[stack.len()-1].Bytes32())
@@ -161,7 +161,7 @@ func (a *AccessListTracer) CaptureState(env *EVM, pc uint64, op OpCode, gas, cos
 	}
 }
 
-func (*AccessListTracer) CaptureFault(env *EVM, pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, depth int, err error) {
+func (*AccessListTracer) CaptureFault(pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, depth int, err error) {
 }
 
 func (*AccessListTracer) CaptureEnd(output []byte, gasUsed uint64, t time.Duration, err error) {}

core/vm/interpreter.go

@@ -169,9 +169,9 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
 		defer func() {
 			if err != nil {
 				if !logged {
-					in.cfg.Tracer.CaptureState(in.evm, pcCopy, op, gasCopy, cost, callContext, in.returnData, in.evm.depth, err)
+					in.cfg.Tracer.CaptureState(pcCopy, op, gasCopy, cost, callContext, in.returnData, in.evm.depth, err)
 				} else {
-					in.cfg.Tracer.CaptureFault(in.evm, pcCopy, op, gasCopy, cost, callContext, in.evm.depth, err)
+					in.cfg.Tracer.CaptureFault(pcCopy, op, gasCopy, cost, callContext, in.evm.depth, err)
 				}
 			}
 		}()
@@ -253,7 +253,7 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
 		}
 
 		if in.cfg.Debug {
-			in.cfg.Tracer.CaptureState(in.evm, pc, op, gasCopy, cost, callContext, in.returnData, in.evm.depth, err)
+			in.cfg.Tracer.CaptureState(pc, op, gasCopy, cost, callContext, in.returnData, in.evm.depth, err)
 			logged = true
 		}
 

core/vm/logger.go

@@ -105,10 +105,10 @@ func (s *StructLog) ErrorString() string {
 // if you need to retain them beyond the current call.
 type EVMLogger interface {
 	CaptureStart(env *EVM, from common.Address, to common.Address, create bool, input []byte, gas uint64, value *big.Int)
-	CaptureState(env *EVM, pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, rData []byte, depth int, err error)
+	CaptureState(pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, rData []byte, depth int, err error)
 	CaptureEnter(typ OpCode, from common.Address, to common.Address, input []byte, gas uint64, value *big.Int)
 	CaptureExit(output []byte, gasUsed uint64, err error)
-	CaptureFault(env *EVM, pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, depth int, err error)
+	CaptureFault(pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, depth int, err error)
 	CaptureEnd(output []byte, gasUsed uint64, t time.Duration, err error)
 }
 
@@ -119,6 +119,7 @@ type EVMLogger interface {
 // contract their storage.
 type StructLogger struct {
 	cfg LogConfig
+	env *EVM
 
 	storage map[common.Address]Storage
 	logs    []StructLog
@@ -147,12 +148,13 @@ func (l *StructLogger) Reset() {
 
 // CaptureStart implements the EVMLogger interface to initialize the tracing operation.
 func (l *StructLogger) CaptureStart(env *EVM, from common.Address, to common.Address, create bool, input []byte, gas uint64, value *big.Int) {
+	l.env = env
 }
 
 // CaptureState logs a new structured log message and pushes it out to the environment
 //
 // CaptureState also tracks SLOAD/SSTORE ops to track storage change.
-func (l *StructLogger) CaptureState(env *EVM, pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, rData []byte, depth int, err error) {
+func (l *StructLogger) CaptureState(pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, rData []byte, depth int, err error) {
 	memory := scope.Memory
 	stack := scope.Stack
 	contract := scope.Contract
@@ -186,7 +188,7 @@ func (l *StructLogger) CaptureState(env *EVM, pc uint64, op OpCode, gas, cost ui
 		if op == SLOAD && stack.len() >= 1 {
 			var (
 				address = common.Hash(stack.data[stack.len()-1].Bytes32())
-				value   = env.StateDB.GetState(contract.Address(), address)
+				value   = l.env.StateDB.GetState(contract.Address(), address)
 			)
 			l.storage[contract.Address()][address] = value
 			storage = l.storage[contract.Address()].Copy()
@@ -206,13 +208,13 @@ func (l *StructLogger) CaptureState(env *EVM, pc uint64, op OpCode, gas, cost ui
 		copy(rdata, rData)
 	}
 	// create a new snapshot of the EVM.
-	log := StructLog{pc, op, gas, cost, mem, memory.Len(), stck, rdata, storage, depth, env.StateDB.GetRefund(), err}
+	log := StructLog{pc, op, gas, cost, mem, memory.Len(), stck, rdata, storage, depth, l.env.StateDB.GetRefund(), err}
 	l.logs = append(l.logs, log)
 }
 
 // CaptureFault implements the EVMLogger interface to trace an execution fault
 // while running an opcode.
-func (l *StructLogger) CaptureFault(env *EVM, pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, depth int, err error) {
+func (l *StructLogger) CaptureFault(pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, depth int, err error) {
 }
 
 // CaptureEnd is called after the call finishes to finalize the tracing.
@@ -291,12 +293,13 @@ func WriteLogs(writer io.Writer, logs []*types.Log) {
 type mdLogger struct {
 	out io.Writer
 	cfg *LogConfig
+	env *EVM
 }
 
 // NewMarkdownLogger creates a logger which outputs information in a format adapted
 // for human readability, and is also a valid markdown table
 func NewMarkdownLogger(cfg *LogConfig, writer io.Writer) *mdLogger {
-	l := &mdLogger{writer, cfg}
+	l := &mdLogger{out: writer, cfg: cfg}
 	if l.cfg == nil {
 		l.cfg = &LogConfig{}
 	}
@@ -304,6 +307,7 @@ func NewMarkdownLogger(cfg *LogConfig, writer io.Writer) *mdLogger {
 }
 
 func (t *mdLogger) CaptureStart(env *EVM, from common.Address, to common.Address, create bool, input []byte, gas uint64, value *big.Int) {
+	t.env = env
 	if !create {
 		fmt.Fprintf(t.out, "From: `%v`\nTo: `%v`\nData: `0x%x`\nGas: `%d`\nValue `%v` wei\n",
 			from.String(), to.String(),
@@ -321,7 +325,7 @@ func (t *mdLogger) CaptureStart(env *EVM, from common.Address, to common.Address
 }
 
 // CaptureState also tracks SLOAD/SSTORE ops to track storage change.
-func (t *mdLogger) CaptureState(env *EVM, pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, rData []byte, depth int, err error) {
+func (t *mdLogger) CaptureState(pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, rData []byte, depth int, err error) {
 	stack := scope.Stack
 	fmt.Fprintf(t.out, "| %4d  | %10v  |  %3d |", pc, op, cost)
 
@@ -334,14 +338,14 @@ func (t *mdLogger) CaptureState(env *EVM, pc uint64, op OpCode, gas, cost uint64
 		b := fmt.Sprintf("[%v]", strings.Join(a, ","))
 		fmt.Fprintf(t.out, "%10v |", b)
 	}
-	fmt.Fprintf(t.out, "%10v |", env.StateDB.GetRefund())
+	fmt.Fprintf(t.out, "%10v |", t.env.StateDB.GetRefund())
 	fmt.Fprintln(t.out, "")
 	if err != nil {
 		fmt.Fprintf(t.out, "Error: %v\n", err)
 	}
 }
 
-func (t *mdLogger) CaptureFault(env *EVM, pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, depth int, err error) {
+func (t *mdLogger) CaptureFault(pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, depth int, err error) {
 	fmt.Fprintf(t.out, "\nError: at pc=%d, op=%v: %v\n", pc, op, err)
 }
 

core/vm/logger_json.go

@@ -29,12 +29,13 @@ import (
 type JSONLogger struct {
 	encoder *json.Encoder
 	cfg     *LogConfig
+	env     *EVM
 }
 
 // NewJSONLogger creates a new EVM tracer that prints execution steps as JSON objects
 // into the provided stream.
 func NewJSONLogger(cfg *LogConfig, writer io.Writer) *JSONLogger {
-	l := &JSONLogger{json.NewEncoder(writer), cfg}
+	l := &JSONLogger{encoder: json.NewEncoder(writer), cfg: cfg}
 	if l.cfg == nil {
 		l.cfg = &LogConfig{}
 	}
@@ -42,12 +43,13 @@ func NewJSONLogger(cfg *LogConfig, writer io.Writer) *JSONLogger {
 }
 
 func (l *JSONLogger) CaptureStart(env *EVM, from, to common.Address, create bool, input []byte, gas uint64, value *big.Int) {
+	l.env = env
 }
 
-func (l *JSONLogger) CaptureFault(*EVM, uint64, OpCode, uint64, uint64, *ScopeContext, int, error) {}
+func (l *JSONLogger) CaptureFault(uint64, OpCode, uint64, uint64, *ScopeContext, int, error) {}
 
 // CaptureState outputs state information on the logger.
-func (l *JSONLogger) CaptureState(env *EVM, pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, rData []byte, depth int, err error) {
+func (l *JSONLogger) CaptureState(pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, rData []byte, depth int, err error) {
 	memory := scope.Memory
 	stack := scope.Stack
 
@@ -58,7 +60,7 @@ func (l *JSONLogger) CaptureState(env *EVM, pc uint64, op OpCode, gas, cost uint
 		GasCost:       cost,
 		MemorySize:    memory.Len(),
 		Depth:         depth,
-		RefundCounter: env.StateDB.GetRefund(),
+		RefundCounter: l.env.StateDB.GetRefund(),
 		Err:           err,
 	}
 	if l.cfg.EnableMemory {

core/vm/logger_test.go

@@ -62,7 +62,8 @@ func TestStoreCapture(t *testing.T) {
 	scope.Stack.push(uint256.NewInt(1))
 	scope.Stack.push(new(uint256.Int))
 	var index common.Hash
-	logger.CaptureState(env, 0, SSTORE, 0, 0, scope, nil, 0, nil)
+	logger.CaptureStart(env, common.Address{}, contract.Address(), false, nil, 0, nil)
+	logger.CaptureState(0, SSTORE, 0, 0, scope, nil, 0, nil)
 	if len(logger.storage[contract.Address()]) == 0 {
 		t.Fatalf("expected exactly 1 changed value on address %x, got %d", contract.Address(),
 			len(logger.storage[contract.Address()]))

core/vm/runtime/runtime_test.go

@@ -35,6 +35,9 @@ import (
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/eth/tracers"
 	"github.com/ethereum/go-ethereum/params"
+
+	// force-load js tracers to trigger registration
+	_ "github.com/ethereum/go-ethereum/eth/tracers/js"
 )
 
 func TestDefaults(t *testing.T) {
@@ -330,12 +333,12 @@ type stepCounter struct {
 func (s *stepCounter) CaptureStart(env *vm.EVM, from common.Address, to common.Address, create bool, input []byte, gas uint64, value *big.Int) {
 }
 
-func (s *stepCounter) CaptureFault(env *vm.EVM, pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, depth int, err error) {
+func (s *stepCounter) CaptureFault(pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, depth int, err error) {
 }
 
 func (s *stepCounter) CaptureEnd(output []byte, gasUsed uint64, t time.Duration, err error) {}
 
-func (s *stepCounter) CaptureState(env *vm.EVM, pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, rData []byte, depth int, err error) {
+func (s *stepCounter) CaptureState(pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, rData []byte, depth int, err error) {
 	s.steps++
 	// Enable this for more output
 	//s.inner.CaptureState(env, pc, op, gas, cost, memory, stack, rStack, contract, depth, err)
@@ -511,7 +514,7 @@ func BenchmarkSimpleLoop(b *testing.B) {
 // TestEip2929Cases contains various testcases that are used for
 // EIP-2929 about gas repricings
 func TestEip2929Cases(t *testing.T) {
-
+	t.Skip("Test only useful for generating documentation")
 	id := 1
 	prettyPrint := func(comment string, code []byte) {
 

eth/tracers/api_test.go

@@ -306,147 +306,6 @@ func TestTraceCall(t *testing.T) {
 	}
 }
 
-func TestOverriddenTraceCall(t *testing.T) {
-	t.Parallel()
-
-	// Initialize test accounts
-	accounts := newAccounts(3)
-	genesis := &core.Genesis{Alloc: core.GenesisAlloc{
-		accounts[0].addr: {Balance: big.NewInt(params.Ether)},
-		accounts[1].addr: {Balance: big.NewInt(params.Ether)},
-		accounts[2].addr: {Balance: big.NewInt(params.Ether)},
-	}}
-	genBlocks := 10
-	signer := types.HomesteadSigner{}
-	api := NewAPI(newTestBackend(t, genBlocks, genesis, func(i int, b *core.BlockGen) {
-		// Transfer from account[0] to account[1]
-		//    value: 1000 wei
-		//    fee:   0 wei
-		tx, _ := types.SignTx(types.NewTransaction(uint64(i), accounts[1].addr, big.NewInt(1000), params.TxGas, b.BaseFee(), nil), signer, accounts[0].key)
-		b.AddTx(tx)
-	}))
-	randomAccounts, tracer := newAccounts(3), "callTracerJs"
-
-	var testSuite = []struct {
-		blockNumber rpc.BlockNumber
-		call        ethapi.TransactionArgs
-		config      *TraceCallConfig
-		expectErr   error
-		expect      *callTrace
-	}{
-		// Succcessful call with state overriding
-		{
-			blockNumber: rpc.PendingBlockNumber,
-			call: ethapi.TransactionArgs{
-				From:  &randomAccounts[0].addr,
-				To:    &randomAccounts[1].addr,
-				Value: (*hexutil.Big)(big.NewInt(1000)),
-			},
-			config: &TraceCallConfig{
-				Tracer: &tracer,
-				StateOverrides: &ethapi.StateOverride{
-					randomAccounts[0].addr: ethapi.OverrideAccount{Balance: newRPCBalance(new(big.Int).Mul(big.NewInt(1), big.NewInt(params.Ether)))},
-				},
-			},
-			expectErr: nil,
-			expect: &callTrace{
-				Type:    "CALL",
-				From:    randomAccounts[0].addr,
-				To:      randomAccounts[1].addr,
-				Gas:     newRPCUint64(24979000),
-				GasUsed: newRPCUint64(0),
-				Value:   (*hexutil.Big)(big.NewInt(1000)),
-			},
-		},
-		// Invalid call without state overriding
-		{
-			blockNumber: rpc.PendingBlockNumber,
-			call: ethapi.TransactionArgs{
-				From:  &randomAccounts[0].addr,
-				To:    &randomAccounts[1].addr,
-				Value: (*hexutil.Big)(big.NewInt(1000)),
-			},
-			config: &TraceCallConfig{
-				Tracer: &tracer,
-			},
-			expectErr: core.ErrInsufficientFunds,
-			expect:    nil,
-		},
-		// Successful simple contract call
-		//
-		// // SPDX-License-Identifier: GPL-3.0
-		//
-		//  pragma solidity >=0.7.0 <0.8.0;
-		//
-		//  /**
-		//   * @title Storage
-		//   * @dev Store & retrieve value in a variable
-		//   */
-		//  contract Storage {
-		//      uint256 public number;
-		//      constructor() {
-		//          number = block.number;
-		//      }
-		//  }
-		{
-			blockNumber: rpc.PendingBlockNumber,
-			call: ethapi.TransactionArgs{
-				From: &randomAccounts[0].addr,
-				To:   &randomAccounts[2].addr,
-				Data: newRPCBytes(common.Hex2Bytes("8381f58a")), // call number()
-			},
-			config: &TraceCallConfig{
-				Tracer: &tracer,
-				StateOverrides: &ethapi.StateOverride{
-					randomAccounts[2].addr: ethapi.OverrideAccount{
-						Code:      newRPCBytes(common.Hex2Bytes("6080604052348015600f57600080fd5b506004361060285760003560e01c80638381f58a14602d575b600080fd5b60336049565b6040518082815260200191505060405180910390f35b6000548156fea2646970667358221220eab35ffa6ab2adfe380772a48b8ba78e82a1b820a18fcb6f59aa4efb20a5f60064736f6c63430007040033")),
-						StateDiff: newStates([]common.Hash{{}}, []common.Hash{common.BigToHash(big.NewInt(123))}),
-					},
-				},
-			},
-			expectErr: nil,
-			expect: &callTrace{
-				Type:    "CALL",
-				From:    randomAccounts[0].addr,
-				To:      randomAccounts[2].addr,
-				Input:   hexutil.Bytes(common.Hex2Bytes("8381f58a")),
-				Output:  hexutil.Bytes(common.BigToHash(big.NewInt(123)).Bytes()),
-				Gas:     newRPCUint64(24978936),
-				GasUsed: newRPCUint64(2283),
-				Value:   (*hexutil.Big)(big.NewInt(0)),
-			},
-		},
-	}
-	for i, testspec := range testSuite {
-		result, err := api.TraceCall(context.Background(), testspec.call, rpc.BlockNumberOrHash{BlockNumber: &testspec.blockNumber}, testspec.config)
-		if testspec.expectErr != nil {
-			if err == nil {
-				t.Errorf("test %d: want error %v, have nothing", i, testspec.expectErr)
-				continue
-			}
-			if !errors.Is(err, testspec.expectErr) {
-				t.Errorf("test %d: error mismatch, want %v, have %v", i, testspec.expectErr, err)
-			}
-		} else {
-			if err != nil {
-				t.Errorf("test %d: want no error, have %v", i, err)
-				continue
-			}
-			ret := new(callTrace)
-			if err := json.Unmarshal(result.(json.RawMessage), ret); err != nil {
-				t.Fatalf("test %d: failed to unmarshal trace result: %v", i, err)
-			}
-			if !jsonEqual(ret, testspec.expect) {
-				// uncomment this for easier debugging
-				//have, _ := json.MarshalIndent(ret, "", " ")
-				//want, _ := json.MarshalIndent(testspec.expect, "", " ")
-				//t.Fatalf("trace mismatch: \nhave %+v\nwant %+v", string(have), string(want))
-				t.Fatalf("trace mismatch: \nhave %+v\nwant %+v", ret, testspec.expect)
-			}
-		}
-	}
-}
-
 func TestTraceTransaction(t *testing.T) {
 	t.Parallel()
 
@@ -503,91 +362,178 @@ func TestTraceBlock(t *testing.T) {
 	var testSuite = []struct {
 		blockNumber rpc.BlockNumber
 		config      *TraceConfig
-		expect      interface{}
+		want        string
 		expectErr   error
 	}{
 		// Trace genesis block, expect error
 		{
 			blockNumber: rpc.BlockNumber(0),
-			config:      nil,
-			expect:      nil,
 			expectErr:   errors.New("genesis is not traceable"),
 		},
 		// Trace head block
 		{
 			blockNumber: rpc.BlockNumber(genBlocks),
-			config:      nil,
+			want:        `[{"result":{"gas":21000,"failed":false,"returnValue":"","structLogs":[]}}]`,
-			expectErr:   nil,
-			expect: []*txTraceResult{
-				{
-					Result: &ethapi.ExecutionResult{
-						Gas:         params.TxGas,
-						Failed:      false,
-						ReturnValue: "",
-						StructLogs:  []ethapi.StructLogRes{},
-					},
-				},
-			},
 		},
 		// Trace non-existent block
 		{
 			blockNumber: rpc.BlockNumber(genBlocks + 1),
-			config:      nil,
 			expectErr:   fmt.Errorf("block #%d not found", genBlocks+1),
-			expect:      nil,
 		},
 		// Trace latest block
 		{
 			blockNumber: rpc.LatestBlockNumber,
-			config:      nil,
+			want:        `[{"result":{"gas":21000,"failed":false,"returnValue":"","structLogs":[]}}]`,
-			expectErr:   nil,
-			expect: []*txTraceResult{
-				{
-					Result: &ethapi.ExecutionResult{
-						Gas:         params.TxGas,
-						Failed:      false,
-						ReturnValue: "",
-						StructLogs:  []ethapi.StructLogRes{},
-					},
-				},
-			},
 		},
 		// Trace pending block
 		{
 			blockNumber: rpc.PendingBlockNumber,
-			config:      nil,
+			want:        `[{"result":{"gas":21000,"failed":false,"returnValue":"","structLogs":[]}}]`,
-			expectErr:   nil,
-			expect: []*txTraceResult{
-				{
-					Result: &ethapi.ExecutionResult{
-						Gas:         params.TxGas,
-						Failed:      false,
-						ReturnValue: "",
-						StructLogs:  []ethapi.StructLogRes{},
-					},
-				},
-			},
 		},
 	}
-	for _, testspec := range testSuite {
+	for i, tc := range testSuite {
-		result, err := api.TraceBlockByNumber(context.Background(), testspec.blockNumber, testspec.config)
+		result, err := api.TraceBlockByNumber(context.Background(), tc.blockNumber, tc.config)
-		if testspec.expectErr != nil {
+		if tc.expectErr != nil {
 			if err == nil {
-				t.Errorf("Expect error %v, get nothing", testspec.expectErr)
+				t.Errorf("test %d, want error %v", i, tc.expectErr)
 				continue
 			}
-			if !reflect.DeepEqual(err, testspec.expectErr) {
+			if !reflect.DeepEqual(err, tc.expectErr) {
-				t.Errorf("Error mismatch, want %v, get %v", testspec.expectErr, err)
+				t.Errorf("test %d: error mismatch, want %v, get %v", i, tc.expectErr, err)
+			}
+			continue
 		}
-		} else {
 		if err != nil {
-				t.Errorf("Expect no error, get %v", err)
+			t.Errorf("test %d, want no error, have %v", i, err)
 			continue
 		}
-			if !reflect.DeepEqual(result, testspec.expect) {
+		have, _ := json.Marshal(result)
-				t.Errorf("Result mismatch, want %v, get %v", testspec.expect, result)
+		want := tc.want
+		if string(have) != want {
+			t.Errorf("test %d, result mismatch, have\n%v\n, want\n%v\n", i, string(have), want)
 		}
 	}
+}
+
+func TestTracingWithOverrides(t *testing.T) {
+	t.Parallel()
+	// Initialize test accounts
+	accounts := newAccounts(3)
+	genesis := &core.Genesis{Alloc: core.GenesisAlloc{
+		accounts[0].addr: {Balance: big.NewInt(params.Ether)},
+		accounts[1].addr: {Balance: big.NewInt(params.Ether)},
+		accounts[2].addr: {Balance: big.NewInt(params.Ether)},
+	}}
+	genBlocks := 10
+	signer := types.HomesteadSigner{}
+	api := NewAPI(newTestBackend(t, genBlocks, genesis, func(i int, b *core.BlockGen) {
+		// Transfer from account[0] to account[1]
+		//    value: 1000 wei
+		//    fee:   0 wei
+		tx, _ := types.SignTx(types.NewTransaction(uint64(i), accounts[1].addr, big.NewInt(1000), params.TxGas, b.BaseFee(), nil), signer, accounts[0].key)
+		b.AddTx(tx)
+	}))
+	randomAccounts := newAccounts(3)
+	type res struct {
+		Gas         int
+		Failed      bool
+		returnValue string
+	}
+	var testSuite = []struct {
+		blockNumber rpc.BlockNumber
+		call        ethapi.TransactionArgs
+		config      *TraceCallConfig
+		expectErr   error
+		want        string
+	}{
+		// Call which can only succeed if state is state overridden
+		{
+			blockNumber: rpc.PendingBlockNumber,
+			call: ethapi.TransactionArgs{
+				From:  &randomAccounts[0].addr,
+				To:    &randomAccounts[1].addr,
+				Value: (*hexutil.Big)(big.NewInt(1000)),
+			},
+			config: &TraceCallConfig{
+				StateOverrides: &ethapi.StateOverride{
+					randomAccounts[0].addr: ethapi.OverrideAccount{Balance: newRPCBalance(new(big.Int).Mul(big.NewInt(1), big.NewInt(params.Ether)))},
+				},
+			},
+			want: `{"gas":21000,"failed":false,"returnValue":""}`,
+		},
+		// Invalid call without state overriding
+		{
+			blockNumber: rpc.PendingBlockNumber,
+			call: ethapi.TransactionArgs{
+				From:  &randomAccounts[0].addr,
+				To:    &randomAccounts[1].addr,
+				Value: (*hexutil.Big)(big.NewInt(1000)),
+			},
+			config:    &TraceCallConfig{},
+			expectErr: core.ErrInsufficientFunds,
+		},
+		// Successful simple contract call
+		//
+		// // SPDX-License-Identifier: GPL-3.0
+		//
+		//  pragma solidity >=0.7.0 <0.8.0;
+		//
+		//  /**
+		//   * @title Storage
+		//   * @dev Store & retrieve value in a variable
+		//   */
+		//  contract Storage {
+		//      uint256 public number;
+		//      constructor() {
+		//          number = block.number;
+		//      }
+		//  }
+		{
+			blockNumber: rpc.PendingBlockNumber,
+			call: ethapi.TransactionArgs{
+				From: &randomAccounts[0].addr,
+				To:   &randomAccounts[2].addr,
+				Data: newRPCBytes(common.Hex2Bytes("8381f58a")), // call number()
+			},
+			config: &TraceCallConfig{
+				//Tracer: &tracer,
+				StateOverrides: &ethapi.StateOverride{
+					randomAccounts[2].addr: ethapi.OverrideAccount{
+						Code:      newRPCBytes(common.Hex2Bytes("6080604052348015600f57600080fd5b506004361060285760003560e01c80638381f58a14602d575b600080fd5b60336049565b6040518082815260200191505060405180910390f35b6000548156fea2646970667358221220eab35ffa6ab2adfe380772a48b8ba78e82a1b820a18fcb6f59aa4efb20a5f60064736f6c63430007040033")),
+						StateDiff: newStates([]common.Hash{{}}, []common.Hash{common.BigToHash(big.NewInt(123))}),
+					},
+				},
+			},
+			want: `{"gas":23347,"failed":false,"returnValue":"000000000000000000000000000000000000000000000000000000000000007b"}`,
+		},
+	}
+	for i, tc := range testSuite {
+		result, err := api.TraceCall(context.Background(), tc.call, rpc.BlockNumberOrHash{BlockNumber: &tc.blockNumber}, tc.config)
+		if tc.expectErr != nil {
+			if err == nil {
+				t.Errorf("test %d: want error %v, have nothing", i, tc.expectErr)
+				continue
+			}
+			if !errors.Is(err, tc.expectErr) {
+				t.Errorf("test %d: error mismatch, want %v, have %v", i, tc.expectErr, err)
+			}
+			continue
+		}
+		if err != nil {
+			t.Errorf("test %d: want no error, have %v", i, err)
+			continue
+		}
+		// Turn result into res-struct
+		var (
+			have res
+			want res
+		)
+		resBytes, _ := json.Marshal(result)
+		json.Unmarshal(resBytes, &have)
+		json.Unmarshal([]byte(tc.want), &want)
+		if !reflect.DeepEqual(have, want) {
+			t.Errorf("test %d, result mismatch, have\n%v\n, want\n%v\n", i, string(resBytes), want)
+		}
 	}
 }
 
@@ -617,11 +563,6 @@ func newRPCBalance(balance *big.Int) **hexutil.Big {
 	return &rpcBalance
 }
 
-func newRPCUint64(number uint64) *hexutil.Uint64 {
-	rpcUint64 := hexutil.Uint64(number)
-	return &rpcUint64
-}
-
 func newRPCBytes(bytes []byte) *hexutil.Bytes {
 	rpcBytes := hexutil.Bytes(bytes)
 	return &rpcBytes

eth/tracers/internal/tracetest/calltrace_test.go

@@ -1,4 +1,20 @@
-package testing
+// Copyright 2021 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package tracetest
 
 import (
 	"encoding/json"
@@ -17,14 +33,67 @@ import (
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/eth/tracers"
+	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/tests"
 
-	// Force-load the native, to trigger registration
+	// Force-load native and js pacakges, to trigger registration
+	_ "github.com/ethereum/go-ethereum/eth/tracers/js"
 	_ "github.com/ethereum/go-ethereum/eth/tracers/native"
 )
 
+// To generate a new callTracer test, copy paste the makeTest method below into
+// a Geth console and call it with a transaction hash you which to export.
+
+/*
+// makeTest generates a callTracer test by running a prestate reassembled and a
+// call trace run, assembling all the gathered information into a test case.
+var makeTest = function(tx, rewind) {
+  // Generate the genesis block from the block, transaction and prestate data
+  var block   = eth.getBlock(eth.getTransaction(tx).blockHash);
+  var genesis = eth.getBlock(block.parentHash);
+
+  delete genesis.gasUsed;
+  delete genesis.logsBloom;
+  delete genesis.parentHash;
+  delete genesis.receiptsRoot;
+  delete genesis.sha3Uncles;
+  delete genesis.size;
+  delete genesis.transactions;
+  delete genesis.transactionsRoot;
+  delete genesis.uncles;
+
+  genesis.gasLimit  = genesis.gasLimit.toString();
+  genesis.number    = genesis.number.toString();
+  genesis.timestamp = genesis.timestamp.toString();
+
+  genesis.alloc = debug.traceTransaction(tx, {tracer: "prestateTracer", rewind: rewind});
+  for (var key in genesis.alloc) {
+    genesis.alloc[key].nonce = genesis.alloc[key].nonce.toString();
+  }
+  genesis.config = admin.nodeInfo.protocols.eth.config;
+
+  // Generate the call trace and produce the test input
+  var result = debug.traceTransaction(tx, {tracer: "callTracer", rewind: rewind});
+  delete result.time;
+
+  console.log(JSON.stringify({
+    genesis: genesis,
+    context: {
+      number:     block.number.toString(),
+      difficulty: block.difficulty,
+      timestamp:  block.timestamp.toString(),
+      gasLimit:   block.gasLimit.toString(),
+      miner:      block.miner,
+    },
+    input:  eth.getRawTransaction(tx),
+    result: result,
+  }, null, 2));
+}
+*/
+
 type callContext struct {
 	Number     math.HexOrDecimal64   `json:"number"`
 	Difficulty *math.HexOrDecimal256 `json:"difficulty"`
@@ -70,7 +139,7 @@ func TestCallTracerNative(t *testing.T) {
 }
 
 func testCallTracer(tracerName string, dirPath string, t *testing.T) {
-	files, err := ioutil.ReadDir(filepath.Join("..", "testdata", dirPath))
+	files, err := ioutil.ReadDir(filepath.Join("testdata", dirPath))
 	if err != nil {
 		t.Fatalf("failed to retrieve tracer test suite: %v", err)
 	}
@@ -87,7 +156,7 @@ func testCallTracer(tracerName string, dirPath string, t *testing.T) {
 				tx   = new(types.Transaction)
 			)
 			// Call tracer test found, read if from disk
-			if blob, err := ioutil.ReadFile(filepath.Join("..", "testdata", dirPath, file.Name())); err != nil {
+			if blob, err := ioutil.ReadFile(filepath.Join("testdata", dirPath, file.Name())); err != nil {
 				t.Fatalf("failed to read testcase: %v", err)
 			} else if err := json.Unmarshal(blob, test); err != nil {
 				t.Fatalf("failed to parse testcase: %v", err)
@@ -175,7 +244,7 @@ func camel(str string) string {
 	return strings.Join(pieces, "")
 }
 func BenchmarkTracers(b *testing.B) {
-	files, err := ioutil.ReadDir(filepath.Join("..", "testdata", "call_tracer"))
+	files, err := ioutil.ReadDir(filepath.Join("testdata", "call_tracer"))
 	if err != nil {
 		b.Fatalf("failed to retrieve tracer test suite: %v", err)
 	}
@@ -185,7 +254,7 @@ func BenchmarkTracers(b *testing.B) {
 		}
 		file := file // capture range variable
 		b.Run(camel(strings.TrimSuffix(file.Name(), ".json")), func(b *testing.B) {
-			blob, err := ioutil.ReadFile(filepath.Join("..", "testdata", "call_tracer", file.Name()))
+			blob, err := ioutil.ReadFile(filepath.Join("testdata", "call_tracer", file.Name()))
 			if err != nil {
 				b.Fatalf("failed to read testcase: %v", err)
 			}
@@ -244,3 +313,82 @@ func benchTracer(tracerName string, test *callTracerTest, b *testing.B) {
 		statedb.RevertToSnapshot(snap)
 	}
 }
+
+// TestZeroValueToNotExitCall tests the calltracer(s) on the following:
+// Tx to A, A calls B with zero value. B does not already exist.
+// Expected: that enter/exit is invoked and the inner call is shown in the result
+func TestZeroValueToNotExitCall(t *testing.T) {
+	var to = common.HexToAddress("0x00000000000000000000000000000000deadbeef")
+	privkey, err := crypto.HexToECDSA("0000000000000000deadbeef00000000000000000000000000000000deadbeef")
+	if err != nil {
+		t.Fatalf("err %v", err)
+	}
+	signer := types.NewEIP155Signer(big.NewInt(1))
+	tx, err := types.SignNewTx(privkey, signer, &types.LegacyTx{
+		GasPrice: big.NewInt(0),
+		Gas:      50000,
+		To:       &to,
+	})
+	if err != nil {
+		t.Fatalf("err %v", err)
+	}
+	origin, _ := signer.Sender(tx)
+	txContext := vm.TxContext{
+		Origin:   origin,
+		GasPrice: big.NewInt(1),
+	}
+	context := vm.BlockContext{
+		CanTransfer: core.CanTransfer,
+		Transfer:    core.Transfer,
+		Coinbase:    common.Address{},
+		BlockNumber: new(big.Int).SetUint64(8000000),
+		Time:        new(big.Int).SetUint64(5),
+		Difficulty:  big.NewInt(0x30000),
+		GasLimit:    uint64(6000000),
+	}
+	var code = []byte{
+		byte(vm.PUSH1), 0x0, byte(vm.DUP1), byte(vm.DUP1), byte(vm.DUP1), // in and outs zero
+		byte(vm.DUP1), byte(vm.PUSH1), 0xff, byte(vm.GAS), // value=0,address=0xff, gas=GAS
+		byte(vm.CALL),
+	}
+	var alloc = core.GenesisAlloc{
+		to: core.GenesisAccount{
+			Nonce: 1,
+			Code:  code,
+		},
+		origin: core.GenesisAccount{
+			Nonce:   0,
+			Balance: big.NewInt(500000000000000),
+		},
+	}
+	_, statedb := tests.MakePreState(rawdb.NewMemoryDatabase(), alloc, false)
+	// Create the tracer, the EVM environment and run it
+	tracer, err := tracers.New("callTracer", nil)
+	if err != nil {
+		t.Fatalf("failed to create call tracer: %v", err)
+	}
+	evm := vm.NewEVM(context, txContext, statedb, params.MainnetChainConfig, vm.Config{Debug: true, Tracer: tracer})
+	msg, err := tx.AsMessage(signer, nil)
+	if err != nil {
+		t.Fatalf("failed to prepare transaction for tracing: %v", err)
+	}
+	st := core.NewStateTransition(evm, msg, new(core.GasPool).AddGas(tx.Gas()))
+	if _, err = st.TransitionDb(); err != nil {
+		t.Fatalf("failed to execute transaction: %v", err)
+	}
+	// Retrieve the trace result and compare against the etalon
+	res, err := tracer.GetResult()
+	if err != nil {
+		t.Fatalf("failed to retrieve trace result: %v", err)
+	}
+	have := new(callTrace)
+	if err := json.Unmarshal(res, have); err != nil {
+		t.Fatalf("failed to unmarshal trace result: %v", err)
+	}
+	wantStr := `{"type":"CALL","from":"0x682a80a6f560eec50d54e63cbeda1c324c5f8d1b","to":"0x00000000000000000000000000000000deadbeef","value":"0x0","gas":"0x7148","gasUsed":"0x2d0","input":"0x","output":"0x","calls":[{"type":"CALL","from":"0x00000000000000000000000000000000deadbeef","to":"0x00000000000000000000000000000000000000ff","value":"0x0","gas":"0x6cbf","gasUsed":"0x0","input":"0x","output":"0x"}]}`
+	want := new(callTrace)
+	json.Unmarshal([]byte(wantStr), want)
+	if !jsonEqual(have, want) {
+		t.Error("have != want")
+	}
+}

eth/tracers/js/tracer.go

@@ -0,0 +1,880 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// package js is a collection of tracers written in javascript.
+package js
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"math/big"
+	"strings"
+	"sync/atomic"
+	"time"
+	"unicode"
+	"unsafe"
+
+	"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"
+	tracers2 "github.com/ethereum/go-ethereum/eth/tracers"
+	"github.com/ethereum/go-ethereum/eth/tracers/js/internal/tracers"
+	"github.com/ethereum/go-ethereum/log"
+	"gopkg.in/olebedev/go-duktape.v3"
+)
+
+// camel converts a snake cased input string into a camel cased output.
+func camel(str string) string {
+	pieces := strings.Split(str, "_")
+	for i := 1; i < len(pieces); i++ {
+		pieces[i] = string(unicode.ToUpper(rune(pieces[i][0]))) + pieces[i][1:]
+	}
+	return strings.Join(pieces, "")
+}
+
+var assetTracers = make(map[string]string)
+
+// init retrieves the JavaScript transaction tracers included in go-ethereum.
+func init() {
+	for _, file := range tracers.AssetNames() {
+		name := camel(strings.TrimSuffix(file, ".js"))
+		assetTracers[name] = string(tracers.MustAsset(file))
+	}
+	tracers2.RegisterLookup(true, newJsTracer)
+}
+
+// makeSlice convert an unsafe memory pointer with the given type into a Go byte
+// slice.
+//
+// Note, the returned slice uses the same memory area as the input arguments.
+// If those are duktape stack items, popping them off **will** make the slice
+// contents change.
+func makeSlice(ptr unsafe.Pointer, size uint) []byte {
+	var sl = struct {
+		addr uintptr
+		len  int
+		cap  int
+	}{uintptr(ptr), int(size), int(size)}
+
+	return *(*[]byte)(unsafe.Pointer(&sl))
+}
+
+// popSlice pops a buffer off the JavaScript stack and returns it as a slice.
+func popSlice(ctx *duktape.Context) []byte {
+	blob := common.CopyBytes(makeSlice(ctx.GetBuffer(-1)))
+	ctx.Pop()
+	return blob
+}
+
+// pushBigInt create a JavaScript BigInteger in the VM.
+func pushBigInt(n *big.Int, ctx *duktape.Context) {
+	ctx.GetGlobalString("bigInt")
+	ctx.PushString(n.String())
+	ctx.Call(1)
+}
+
+// opWrapper provides a JavaScript wrapper around OpCode.
+type opWrapper struct {
+	op vm.OpCode
+}
+
+// pushObject assembles a JSVM object wrapping a swappable opcode and pushes it
+// onto the VM stack.
+func (ow *opWrapper) pushObject(vm *duktape.Context) {
+	obj := vm.PushObject()
+
+	vm.PushGoFunction(func(ctx *duktape.Context) int { ctx.PushInt(int(ow.op)); return 1 })
+	vm.PutPropString(obj, "toNumber")
+
+	vm.PushGoFunction(func(ctx *duktape.Context) int { ctx.PushString(ow.op.String()); return 1 })
+	vm.PutPropString(obj, "toString")
+
+	vm.PushGoFunction(func(ctx *duktape.Context) int { ctx.PushBoolean(ow.op.IsPush()); return 1 })
+	vm.PutPropString(obj, "isPush")
+}
+
+// memoryWrapper provides a JavaScript wrapper around vm.Memory.
+type memoryWrapper struct {
+	memory *vm.Memory
+}
+
+// slice returns the requested range of memory as a byte slice.
+func (mw *memoryWrapper) slice(begin, end int64) []byte {
+	if end == begin {
+		return []byte{}
+	}
+	if end < begin || begin < 0 {
+		// TODO(karalabe): We can't js-throw from Go inside duktape inside Go. The Go
+		// runtime goes belly up https://github.com/golang/go/issues/15639.
+		log.Warn("Tracer accessed out of bound memory", "offset", begin, "end", end)
+		return nil
+	}
+	if mw.memory.Len() < int(end) {
+		// TODO(karalabe): We can't js-throw from Go inside duktape inside Go. The Go
+		// runtime goes belly up https://github.com/golang/go/issues/15639.
+		log.Warn("Tracer accessed out of bound memory", "available", mw.memory.Len(), "offset", begin, "size", end-begin)
+		return nil
+	}
+	return mw.memory.GetCopy(begin, end-begin)
+}
+
+// getUint returns the 32 bytes at the specified address interpreted as a uint.
+func (mw *memoryWrapper) getUint(addr int64) *big.Int {
+	if mw.memory.Len() < int(addr)+32 || addr < 0 {
+		// TODO(karalabe): We can't js-throw from Go inside duktape inside Go. The Go
+		// runtime goes belly up https://github.com/golang/go/issues/15639.
+		log.Warn("Tracer accessed out of bound memory", "available", mw.memory.Len(), "offset", addr, "size", 32)
+		return new(big.Int)
+	}
+	return new(big.Int).SetBytes(mw.memory.GetPtr(addr, 32))
+}
+
+// pushObject assembles a JSVM object wrapping a swappable memory and pushes it
+// onto the VM stack.
+func (mw *memoryWrapper) pushObject(vm *duktape.Context) {
+	obj := vm.PushObject()
+
+	// Generate the `slice` method which takes two ints and returns a buffer
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		blob := mw.slice(int64(ctx.GetInt(-2)), int64(ctx.GetInt(-1)))
+		ctx.Pop2()
+
+		ptr := ctx.PushFixedBuffer(len(blob))
+		copy(makeSlice(ptr, uint(len(blob))), blob)
+		return 1
+	})
+	vm.PutPropString(obj, "slice")
+
+	// Generate the `getUint` method which takes an int and returns a bigint
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		offset := int64(ctx.GetInt(-1))
+		ctx.Pop()
+
+		pushBigInt(mw.getUint(offset), ctx)
+		return 1
+	})
+	vm.PutPropString(obj, "getUint")
+}
+
+// stackWrapper provides a JavaScript wrapper around vm.Stack.
+type stackWrapper struct {
+	stack *vm.Stack
+}
+
+// peek returns the nth-from-the-top element of the stack.
+func (sw *stackWrapper) peek(idx int) *big.Int {
+	if len(sw.stack.Data()) <= idx || idx < 0 {
+		// TODO(karalabe): We can't js-throw from Go inside duktape inside Go. The Go
+		// runtime goes belly up https://github.com/golang/go/issues/15639.
+		log.Warn("Tracer accessed out of bound stack", "size", len(sw.stack.Data()), "index", idx)
+		return new(big.Int)
+	}
+	return sw.stack.Back(idx).ToBig()
+}
+
+// pushObject assembles a JSVM object wrapping a swappable stack and pushes it
+// onto the VM stack.
+func (sw *stackWrapper) pushObject(vm *duktape.Context) {
+	obj := vm.PushObject()
+
+	vm.PushGoFunction(func(ctx *duktape.Context) int { ctx.PushInt(len(sw.stack.Data())); return 1 })
+	vm.PutPropString(obj, "length")
+
+	// Generate the `peek` method which takes an int and returns a bigint
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		offset := ctx.GetInt(-1)
+		ctx.Pop()
+
+		pushBigInt(sw.peek(offset), ctx)
+		return 1
+	})
+	vm.PutPropString(obj, "peek")
+}
+
+// dbWrapper provides a JavaScript wrapper around vm.Database.
+type dbWrapper struct {
+	db vm.StateDB
+}
+
+// pushObject assembles a JSVM object wrapping a swappable database and pushes it
+// onto the VM stack.
+func (dw *dbWrapper) pushObject(vm *duktape.Context) {
+	obj := vm.PushObject()
+
+	// Push the wrapper for statedb.GetBalance
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		pushBigInt(dw.db.GetBalance(common.BytesToAddress(popSlice(ctx))), ctx)
+		return 1
+	})
+	vm.PutPropString(obj, "getBalance")
+
+	// Push the wrapper for statedb.GetNonce
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		ctx.PushInt(int(dw.db.GetNonce(common.BytesToAddress(popSlice(ctx)))))
+		return 1
+	})
+	vm.PutPropString(obj, "getNonce")
+
+	// Push the wrapper for statedb.GetCode
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		code := dw.db.GetCode(common.BytesToAddress(popSlice(ctx)))
+
+		ptr := ctx.PushFixedBuffer(len(code))
+		copy(makeSlice(ptr, uint(len(code))), code)
+		return 1
+	})
+	vm.PutPropString(obj, "getCode")
+
+	// Push the wrapper for statedb.GetState
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		hash := popSlice(ctx)
+		addr := popSlice(ctx)
+
+		state := dw.db.GetState(common.BytesToAddress(addr), common.BytesToHash(hash))
+
+		ptr := ctx.PushFixedBuffer(len(state))
+		copy(makeSlice(ptr, uint(len(state))), state[:])
+		return 1
+	})
+	vm.PutPropString(obj, "getState")
+
+	// Push the wrapper for statedb.Exists
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		ctx.PushBoolean(dw.db.Exist(common.BytesToAddress(popSlice(ctx))))
+		return 1
+	})
+	vm.PutPropString(obj, "exists")
+}
+
+// contractWrapper provides a JavaScript wrapper around vm.Contract
+type contractWrapper struct {
+	contract *vm.Contract
+}
+
+// pushObject assembles a JSVM object wrapping a swappable contract and pushes it
+// onto the VM stack.
+func (cw *contractWrapper) pushObject(vm *duktape.Context) {
+	obj := vm.PushObject()
+
+	// Push the wrapper for contract.Caller
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		ptr := ctx.PushFixedBuffer(20)
+		copy(makeSlice(ptr, 20), cw.contract.Caller().Bytes())
+		return 1
+	})
+	vm.PutPropString(obj, "getCaller")
+
+	// Push the wrapper for contract.Address
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		ptr := ctx.PushFixedBuffer(20)
+		copy(makeSlice(ptr, 20), cw.contract.Address().Bytes())
+		return 1
+	})
+	vm.PutPropString(obj, "getAddress")
+
+	// Push the wrapper for contract.Value
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		pushBigInt(cw.contract.Value(), ctx)
+		return 1
+	})
+	vm.PutPropString(obj, "getValue")
+
+	// Push the wrapper for contract.Input
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		blob := cw.contract.Input
+
+		ptr := ctx.PushFixedBuffer(len(blob))
+		copy(makeSlice(ptr, uint(len(blob))), blob)
+		return 1
+	})
+	vm.PutPropString(obj, "getInput")
+}
+
+type frame struct {
+	typ   *string
+	from  *common.Address
+	to    *common.Address
+	input []byte
+	gas   *uint
+	value *big.Int
+}
+
+func newFrame() *frame {
+	return &frame{
+		typ:  new(string),
+		from: new(common.Address),
+		to:   new(common.Address),
+		gas:  new(uint),
+	}
+}
+
+func (f *frame) pushObject(vm *duktape.Context) {
+	obj := vm.PushObject()
+
+	vm.PushGoFunction(func(ctx *duktape.Context) int { pushValue(ctx, *f.typ); return 1 })
+	vm.PutPropString(obj, "getType")
+
+	vm.PushGoFunction(func(ctx *duktape.Context) int { pushValue(ctx, *f.from); return 1 })
+	vm.PutPropString(obj, "getFrom")
+
+	vm.PushGoFunction(func(ctx *duktape.Context) int { pushValue(ctx, *f.to); return 1 })
+	vm.PutPropString(obj, "getTo")
+
+	vm.PushGoFunction(func(ctx *duktape.Context) int { pushValue(ctx, f.input); return 1 })
+	vm.PutPropString(obj, "getInput")
+
+	vm.PushGoFunction(func(ctx *duktape.Context) int { pushValue(ctx, *f.gas); return 1 })
+	vm.PutPropString(obj, "getGas")
+
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		if f.value != nil {
+			pushValue(ctx, f.value)
+		} else {
+			ctx.PushUndefined()
+		}
+		return 1
+	})
+	vm.PutPropString(obj, "getValue")
+}
+
+type frameResult struct {
+	gasUsed    *uint
+	output     []byte
+	errorValue *string
+}
+
+func newFrameResult() *frameResult {
+	return &frameResult{
+		gasUsed: new(uint),
+	}
+}
+
+func (r *frameResult) pushObject(vm *duktape.Context) {
+	obj := vm.PushObject()
+
+	vm.PushGoFunction(func(ctx *duktape.Context) int { pushValue(ctx, *r.gasUsed); return 1 })
+	vm.PutPropString(obj, "getGasUsed")
+
+	vm.PushGoFunction(func(ctx *duktape.Context) int { pushValue(ctx, r.output); return 1 })
+	vm.PutPropString(obj, "getOutput")
+
+	vm.PushGoFunction(func(ctx *duktape.Context) int {
+		if r.errorValue != nil {
+			pushValue(ctx, *r.errorValue)
+		} else {
+			ctx.PushUndefined()
+		}
+		return 1
+	})
+	vm.PutPropString(obj, "getError")
+}
+
+// jsTracer provides an implementation of Tracer that evaluates a Javascript
+// function for each VM execution step.
+type jsTracer struct {
+	vm  *duktape.Context // Javascript VM instance
+	env *vm.EVM          // EVM instance executing the code being traced
+
+	tracerObject int // Stack index of the tracer JavaScript object
+	stateObject  int // Stack index of the global state to pull arguments from
+
+	opWrapper       *opWrapper       // Wrapper around the VM opcode
+	stackWrapper    *stackWrapper    // Wrapper around the VM stack
+	memoryWrapper   *memoryWrapper   // Wrapper around the VM memory
+	contractWrapper *contractWrapper // Wrapper around the contract object
+	dbWrapper       *dbWrapper       // Wrapper around the VM environment
+
+	pcValue     *uint   // Swappable pc value wrapped by a log accessor
+	gasValue    *uint   // Swappable gas value wrapped by a log accessor
+	costValue   *uint   // Swappable cost value wrapped by a log accessor
+	depthValue  *uint   // Swappable depth value wrapped by a log accessor
+	errorValue  *string // Swappable error value wrapped by a log accessor
+	refundValue *uint   // Swappable refund value wrapped by a log accessor
+
+	frame       *frame       // Represents entry into call frame. Fields are swappable
+	frameResult *frameResult // Represents exit from a call frame. Fields are swappable
+
+	ctx map[string]interface{} // Transaction context gathered throughout execution
+	err error                  // Error, if one has occurred
+
+	interrupt uint32 // Atomic flag to signal execution interruption
+	reason    error  // Textual reason for the interruption
+
+	activePrecompiles []common.Address // Updated on CaptureStart based on given rules
+	traceSteps        bool             // When true, will invoke step() on each opcode
+	traceCallFrames   bool             // When true, will invoke enter() and exit() js funcs
+}
+
+// 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 newJsTracer(code string, ctx *tracers2.Context) (tracers2.Tracer, error) {
+	if c, ok := assetTracers[code]; ok {
+		code = c
+	}
+	if ctx == nil {
+		ctx = new(tracers2.Context)
+	}
+	tracer := &jsTracer{
+		vm:              duktape.New(),
+		ctx:             make(map[string]interface{}),
+		opWrapper:       new(opWrapper),
+		stackWrapper:    new(stackWrapper),
+		memoryWrapper:   new(memoryWrapper),
+		contractWrapper: new(contractWrapper),
+		dbWrapper:       new(dbWrapper),
+		pcValue:         new(uint),
+		gasValue:        new(uint),
+		costValue:       new(uint),
+		depthValue:      new(uint),
+		refundValue:     new(uint),
+		frame:           newFrame(),
+		frameResult:     newFrameResult(),
+	}
+	if ctx.BlockHash != (common.Hash{}) {
+		tracer.ctx["blockHash"] = ctx.BlockHash
+
+		if ctx.TxHash != (common.Hash{}) {
+			tracer.ctx["txIndex"] = ctx.TxIndex
+			tracer.ctx["txHash"] = ctx.TxHash
+		}
+	}
+	// Set up builtins for this environment
+	tracer.vm.PushGlobalGoFunction("toHex", func(ctx *duktape.Context) int {
+		ctx.PushString(hexutil.Encode(popSlice(ctx)))
+		return 1
+	})
+	tracer.vm.PushGlobalGoFunction("toWord", func(ctx *duktape.Context) int {
+		var word common.Hash
+		if ptr, size := ctx.GetBuffer(-1); ptr != nil {
+			word = common.BytesToHash(makeSlice(ptr, size))
+		} else {
+			word = common.HexToHash(ctx.GetString(-1))
+		}
+		ctx.Pop()
+		copy(makeSlice(ctx.PushFixedBuffer(32), 32), word[:])
+		return 1
+	})
+	tracer.vm.PushGlobalGoFunction("toAddress", func(ctx *duktape.Context) int {
+		var addr common.Address
+		if ptr, size := ctx.GetBuffer(-1); ptr != nil {
+			addr = common.BytesToAddress(makeSlice(ptr, size))
+		} else {
+			addr = common.HexToAddress(ctx.GetString(-1))
+		}
+		ctx.Pop()
+		copy(makeSlice(ctx.PushFixedBuffer(20), 20), addr[:])
+		return 1
+	})
+	tracer.vm.PushGlobalGoFunction("toContract", func(ctx *duktape.Context) int {
+		var from common.Address
+		if ptr, size := ctx.GetBuffer(-2); ptr != nil {
+			from = common.BytesToAddress(makeSlice(ptr, size))
+		} else {
+			from = common.HexToAddress(ctx.GetString(-2))
+		}
+		nonce := uint64(ctx.GetInt(-1))
+		ctx.Pop2()
+
+		contract := crypto.CreateAddress(from, nonce)
+		copy(makeSlice(ctx.PushFixedBuffer(20), 20), contract[:])
+		return 1
+	})
+	tracer.vm.PushGlobalGoFunction("toContract2", func(ctx *duktape.Context) int {
+		var from common.Address
+		if ptr, size := ctx.GetBuffer(-3); ptr != nil {
+			from = common.BytesToAddress(makeSlice(ptr, size))
+		} else {
+			from = common.HexToAddress(ctx.GetString(-3))
+		}
+		// Retrieve salt hex string from js stack
+		salt := common.HexToHash(ctx.GetString(-2))
+		// Retrieve code slice from js stack
+		var code []byte
+		if ptr, size := ctx.GetBuffer(-1); ptr != nil {
+			code = common.CopyBytes(makeSlice(ptr, size))
+		} else {
+			code = common.FromHex(ctx.GetString(-1))
+		}
+		codeHash := crypto.Keccak256(code)
+		ctx.Pop3()
+		contract := crypto.CreateAddress2(from, salt, codeHash)
+		copy(makeSlice(ctx.PushFixedBuffer(20), 20), contract[:])
+		return 1
+	})
+	tracer.vm.PushGlobalGoFunction("isPrecompiled", func(ctx *duktape.Context) int {
+		addr := common.BytesToAddress(popSlice(ctx))
+		for _, p := range tracer.activePrecompiles {
+			if p == addr {
+				ctx.PushBoolean(true)
+				return 1
+			}
+		}
+		ctx.PushBoolean(false)
+		return 1
+	})
+	tracer.vm.PushGlobalGoFunction("slice", func(ctx *duktape.Context) int {
+		start, end := ctx.GetInt(-2), ctx.GetInt(-1)
+		ctx.Pop2()
+
+		blob := popSlice(ctx)
+		size := end - start
+
+		if start < 0 || start > end || end > len(blob) {
+			// TODO(karalabe): We can't js-throw from Go inside duktape inside Go. The Go
+			// runtime goes belly up https://github.com/golang/go/issues/15639.
+			log.Warn("Tracer accessed out of bound memory", "available", len(blob), "offset", start, "size", size)
+			ctx.PushFixedBuffer(0)
+			return 1
+		}
+		copy(makeSlice(ctx.PushFixedBuffer(size), uint(size)), blob[start:end])
+		return 1
+	})
+	// Push the JavaScript tracer as object #0 onto the JSVM stack and validate it
+	if err := tracer.vm.PevalString("(" + code + ")"); err != nil {
+		log.Warn("Failed to compile tracer", "err", err)
+		return nil, err
+	}
+	tracer.tracerObject = 0 // yeah, nice, eval can't return the index itself
+
+	hasStep := tracer.vm.GetPropString(tracer.tracerObject, "step")
+	tracer.vm.Pop()
+
+	if !tracer.vm.GetPropString(tracer.tracerObject, "fault") {
+		return nil, fmt.Errorf("trace object must expose a function fault()")
+	}
+	tracer.vm.Pop()
+
+	if !tracer.vm.GetPropString(tracer.tracerObject, "result") {
+		return nil, fmt.Errorf("trace object must expose a function result()")
+	}
+	tracer.vm.Pop()
+
+	hasEnter := tracer.vm.GetPropString(tracer.tracerObject, "enter")
+	tracer.vm.Pop()
+	hasExit := tracer.vm.GetPropString(tracer.tracerObject, "exit")
+	tracer.vm.Pop()
+	if hasEnter != hasExit {
+		return nil, fmt.Errorf("trace object must expose either both or none of enter() and exit()")
+	}
+	tracer.traceCallFrames = hasEnter && hasExit
+	tracer.traceSteps = hasStep
+
+	// Tracer is valid, inject the big int library to access large numbers
+	tracer.vm.EvalString(bigIntegerJS)
+	tracer.vm.PutGlobalString("bigInt")
+
+	// Push the global environment state as object #1 into the JSVM stack
+	tracer.stateObject = tracer.vm.PushObject()
+
+	logObject := tracer.vm.PushObject()
+
+	tracer.opWrapper.pushObject(tracer.vm)
+	tracer.vm.PutPropString(logObject, "op")
+
+	tracer.stackWrapper.pushObject(tracer.vm)
+	tracer.vm.PutPropString(logObject, "stack")
+
+	tracer.memoryWrapper.pushObject(tracer.vm)
+	tracer.vm.PutPropString(logObject, "memory")
+
+	tracer.contractWrapper.pushObject(tracer.vm)
+	tracer.vm.PutPropString(logObject, "contract")
+
+	tracer.vm.PushGoFunction(func(ctx *duktape.Context) int { ctx.PushUint(*tracer.pcValue); return 1 })
+	tracer.vm.PutPropString(logObject, "getPC")
+
+	tracer.vm.PushGoFunction(func(ctx *duktape.Context) int { ctx.PushUint(*tracer.gasValue); return 1 })
+	tracer.vm.PutPropString(logObject, "getGas")
+
+	tracer.vm.PushGoFunction(func(ctx *duktape.Context) int { ctx.PushUint(*tracer.costValue); return 1 })
+	tracer.vm.PutPropString(logObject, "getCost")
+
+	tracer.vm.PushGoFunction(func(ctx *duktape.Context) int { ctx.PushUint(*tracer.depthValue); return 1 })
+	tracer.vm.PutPropString(logObject, "getDepth")
+
+	tracer.vm.PushGoFunction(func(ctx *duktape.Context) int { ctx.PushUint(*tracer.refundValue); return 1 })
+	tracer.vm.PutPropString(logObject, "getRefund")
+
+	tracer.vm.PushGoFunction(func(ctx *duktape.Context) int {
+		if tracer.errorValue != nil {
+			ctx.PushString(*tracer.errorValue)
+		} else {
+			ctx.PushUndefined()
+		}
+		return 1
+	})
+	tracer.vm.PutPropString(logObject, "getError")
+
+	tracer.vm.PutPropString(tracer.stateObject, "log")
+
+	tracer.frame.pushObject(tracer.vm)
+	tracer.vm.PutPropString(tracer.stateObject, "frame")
+
+	tracer.frameResult.pushObject(tracer.vm)
+	tracer.vm.PutPropString(tracer.stateObject, "frameResult")
+
+	tracer.dbWrapper.pushObject(tracer.vm)
+	tracer.vm.PutPropString(tracer.stateObject, "db")
+
+	return tracer, nil
+}
+
+// Stop terminates execution of the tracer at the first opportune moment.
+func (jst *jsTracer) Stop(err error) {
+	jst.reason = err
+	atomic.StoreUint32(&jst.interrupt, 1)
+}
+
+// call executes a method on a JS object, catching any errors, formatting and
+// returning them as error objects.
+func (jst *jsTracer) call(noret bool, method string, args ...string) (json.RawMessage, error) {
+	// Execute the JavaScript call and return any error
+	jst.vm.PushString(method)
+	for _, arg := range args {
+		jst.vm.GetPropString(jst.stateObject, arg)
+	}
+	code := jst.vm.PcallProp(jst.tracerObject, len(args))
+	defer jst.vm.Pop()
+
+	if code != 0 {
+		err := jst.vm.SafeToString(-1)
+		return nil, errors.New(err)
+	}
+	// No error occurred, extract return value and return
+	if noret {
+		return nil, nil
+	}
+	// Push a JSON marshaller onto the stack. We can't marshal from the out-
+	// side because duktape can crash on large nestings and we can't catch
+	// C++ exceptions ourselves from Go. TODO(karalabe): Yuck, why wrap?!
+	jst.vm.PushString("(JSON.stringify)")
+	jst.vm.Eval()
+
+	jst.vm.Swap(-1, -2)
+	if code = jst.vm.Pcall(1); code != 0 {
+		err := jst.vm.SafeToString(-1)
+		return nil, errors.New(err)
+	}
+	return json.RawMessage(jst.vm.SafeToString(-1)), nil
+}
+
+func wrapError(context string, err error) error {
+	return fmt.Errorf("%v    in server-side tracer function '%v'", err, context)
+}
+
+// CaptureStart implements the Tracer interface to initialize the tracing operation.
+func (jst *jsTracer) CaptureStart(env *vm.EVM, from common.Address, to common.Address, create bool, input []byte, gas uint64, value *big.Int) {
+	jst.env = env
+	jst.ctx["type"] = "CALL"
+	if create {
+		jst.ctx["type"] = "CREATE"
+	}
+	jst.ctx["from"] = from
+	jst.ctx["to"] = to
+	jst.ctx["input"] = input
+	jst.ctx["gas"] = gas
+	jst.ctx["gasPrice"] = env.TxContext.GasPrice
+	jst.ctx["value"] = value
+
+	// Initialize the context
+	jst.ctx["block"] = env.Context.BlockNumber.Uint64()
+	jst.dbWrapper.db = env.StateDB
+	// Update list of precompiles based on current block
+	rules := env.ChainConfig().Rules(env.Context.BlockNumber)
+	jst.activePrecompiles = vm.ActivePrecompiles(rules)
+
+	// Compute intrinsic gas
+	isHomestead := env.ChainConfig().IsHomestead(env.Context.BlockNumber)
+	isIstanbul := env.ChainConfig().IsIstanbul(env.Context.BlockNumber)
+	intrinsicGas, err := core.IntrinsicGas(input, nil, jst.ctx["type"] == "CREATE", isHomestead, isIstanbul)
+	if err != nil {
+		return
+	}
+	jst.ctx["intrinsicGas"] = intrinsicGas
+}
+
+// CaptureState implements the Tracer interface to trace a single step of VM execution.
+func (jst *jsTracer) CaptureState(pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, rData []byte, depth int, err error) {
+	if !jst.traceSteps {
+		return
+	}
+	if jst.err != nil {
+		return
+	}
+	// If tracing was interrupted, set the error and stop
+	if atomic.LoadUint32(&jst.interrupt) > 0 {
+		jst.err = jst.reason
+		jst.env.Cancel()
+		return
+	}
+	jst.opWrapper.op = op
+	jst.stackWrapper.stack = scope.Stack
+	jst.memoryWrapper.memory = scope.Memory
+	jst.contractWrapper.contract = scope.Contract
+
+	*jst.pcValue = uint(pc)
+	*jst.gasValue = uint(gas)
+	*jst.costValue = uint(cost)
+	*jst.depthValue = uint(depth)
+	*jst.refundValue = uint(jst.env.StateDB.GetRefund())
+
+	jst.errorValue = nil
+	if err != nil {
+		jst.errorValue = new(string)
+		*jst.errorValue = err.Error()
+	}
+
+	if _, err := jst.call(true, "step", "log", "db"); err != nil {
+		jst.err = wrapError("step", err)
+	}
+}
+
+// CaptureFault implements the Tracer interface to trace an execution fault
+func (jst *jsTracer) CaptureFault(pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, depth int, err error) {
+	if jst.err != nil {
+		return
+	}
+	// Apart from the error, everything matches the previous invocation
+	jst.errorValue = new(string)
+	*jst.errorValue = err.Error()
+
+	if _, err := jst.call(true, "fault", "log", "db"); err != nil {
+		jst.err = wrapError("fault", err)
+	}
+}
+
+// CaptureEnd is called after the call finishes to finalize the tracing.
+func (jst *jsTracer) CaptureEnd(output []byte, gasUsed uint64, t time.Duration, err error) {
+	jst.ctx["output"] = output
+	jst.ctx["time"] = t.String()
+	jst.ctx["gasUsed"] = gasUsed
+
+	if err != nil {
+		jst.ctx["error"] = err.Error()
+	}
+}
+
+// CaptureEnter is called when EVM enters a new scope (via call, create or selfdestruct).
+func (jst *jsTracer) CaptureEnter(typ vm.OpCode, from common.Address, to common.Address, input []byte, gas uint64, value *big.Int) {
+	if !jst.traceCallFrames {
+		return
+	}
+	if jst.err != nil {
+		return
+	}
+	// If tracing was interrupted, set the error and stop
+	if atomic.LoadUint32(&jst.interrupt) > 0 {
+		jst.err = jst.reason
+		return
+	}
+
+	*jst.frame.typ = typ.String()
+	*jst.frame.from = from
+	*jst.frame.to = to
+	jst.frame.input = common.CopyBytes(input)
+	*jst.frame.gas = uint(gas)
+	jst.frame.value = nil
+	if value != nil {
+		jst.frame.value = new(big.Int).SetBytes(value.Bytes())
+	}
+
+	if _, err := jst.call(true, "enter", "frame"); err != nil {
+		jst.err = wrapError("enter", err)
+	}
+}
+
+// CaptureExit is called when EVM exits a scope, even if the scope didn't
+// execute any code.
+func (jst *jsTracer) CaptureExit(output []byte, gasUsed uint64, err error) {
+	if !jst.traceCallFrames {
+		return
+	}
+	// If tracing was interrupted, set the error and stop
+	if atomic.LoadUint32(&jst.interrupt) > 0 {
+		jst.err = jst.reason
+		return
+	}
+
+	jst.frameResult.output = common.CopyBytes(output)
+	*jst.frameResult.gasUsed = uint(gasUsed)
+	jst.frameResult.errorValue = nil
+	if err != nil {
+		jst.frameResult.errorValue = new(string)
+		*jst.frameResult.errorValue = err.Error()
+	}
+
+	if _, err := jst.call(true, "exit", "frameResult"); err != nil {
+		jst.err = wrapError("exit", err)
+	}
+}
+
+// GetResult calls the Javascript 'result' function and returns its value, or any accumulated error
+func (jst *jsTracer) GetResult() (json.RawMessage, error) {
+	// Transform the context into a JavaScript object and inject into the state
+	obj := jst.vm.PushObject()
+
+	for key, val := range jst.ctx {
+		jst.addToObj(obj, key, val)
+	}
+	jst.vm.PutPropString(jst.stateObject, "ctx")
+
+	// Finalize the trace and return the results
+	result, err := jst.call(false, "result", "ctx", "db")
+	if err != nil {
+		jst.err = wrapError("result", err)
+	}
+	// Clean up the JavaScript environment
+	jst.vm.DestroyHeap()
+	jst.vm.Destroy()
+
+	return result, jst.err
+}
+
+// addToObj pushes a field to a JS object.
+func (jst *jsTracer) addToObj(obj int, key string, val interface{}) {
+	pushValue(jst.vm, val)
+	jst.vm.PutPropString(obj, key)
+}
+
+func pushValue(ctx *duktape.Context, val interface{}) {
+	switch val := val.(type) {
+	case uint64:
+		ctx.PushUint(uint(val))
+	case string:
+		ctx.PushString(val)
+	case []byte:
+		ptr := ctx.PushFixedBuffer(len(val))
+		copy(makeSlice(ptr, uint(len(val))), val)
+	case common.Address:
+		ptr := ctx.PushFixedBuffer(20)
+		copy(makeSlice(ptr, 20), val[:])
+	case *big.Int:
+		pushBigInt(val, ctx)
+	case int:
+		ctx.PushInt(val)
+	case uint:
+		ctx.PushUint(val)
+	case common.Hash:
+		ptr := ctx.PushFixedBuffer(32)
+		copy(makeSlice(ptr, 32), val[:])
+	default:
+		panic(fmt.Sprintf("unsupported type: %T", val))
+	}
+}

eth/tracers/js/tracer_test.go

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package tracers
+package js
 
 import (
 	"encoding/json"
@@ -26,6 +26,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/eth/tracers"
 	"github.com/ethereum/go-ethereum/params"
 )
 
@@ -58,13 +59,13 @@ func testCtx() *vmContext {
 	return &vmContext{blockCtx: vm.BlockContext{BlockNumber: big.NewInt(1)}, txCtx: vm.TxContext{GasPrice: big.NewInt(100000)}}
 }
 
-func runTrace(tracer Tracer, vmctx *vmContext, chaincfg *params.ChainConfig) (json.RawMessage, error) {
+func runTrace(tracer tracers.Tracer, vmctx *vmContext, chaincfg *params.ChainConfig) (json.RawMessage, error) {
-	env := vm.NewEVM(vmctx.blockCtx, vmctx.txCtx, &dummyStatedb{}, chaincfg, vm.Config{Debug: true, Tracer: tracer})
 	var (
+		env             = vm.NewEVM(vmctx.blockCtx, vmctx.txCtx, &dummyStatedb{}, chaincfg, vm.Config{Debug: true, Tracer: tracer})
 		startGas uint64 = 10000
 		value           = big.NewInt(0)
+		contract        = vm.NewContract(account{}, account{}, value, startGas)
 	)
-	contract := vm.NewContract(account{}, account{}, value, startGas)
 	contract.Code = []byte{byte(vm.PUSH1), 0x1, byte(vm.PUSH1), 0x1, 0x0}
 
 	tracer.CaptureStart(env, contract.Caller(), contract.Address(), false, []byte{}, startGas, value)
@@ -79,14 +80,11 @@ func runTrace(tracer Tracer, vmctx *vmContext, chaincfg *params.ChainConfig) (js
 func TestTracer(t *testing.T) {
 	execTracer := func(code string) ([]byte, string) {
 		t.Helper()
-		tracer, err := New(code, new(Context))
+		tracer, err := newJsTracer(code, nil)
 		if err != nil {
 			t.Fatal(err)
 		}
-		ret, err := runTrace(tracer, &vmContext{
+		ret, err := runTrace(tracer, testCtx(), params.TestChainConfig)
-			blockCtx: vm.BlockContext{BlockNumber: big.NewInt(1)},
-			txCtx:    vm.TxContext{GasPrice: big.NewInt(100000)},
-		}, params.TestChainConfig)
 		if err != nil {
 			return nil, err.Error() // Stringify to allow comparison without nil checks
 		}
@@ -131,9 +129,8 @@ func TestTracer(t *testing.T) {
 
 func TestHalt(t *testing.T) {
 	t.Skip("duktape doesn't support abortion")
-
 	timeout := errors.New("stahp")
-	tracer, err := New("{step: function() { while(1); }, result: function() { return null; }}", new(Context))
+	tracer, err := newJsTracer("{step: function() { while(1); }, result: function() { return null; }, fault: function(){}}", nil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -147,18 +144,19 @@ func TestHalt(t *testing.T) {
 }
 
 func TestHaltBetweenSteps(t *testing.T) {
-	tracer, err := New("{step: function() {}, fault: function() {}, result: function() { return null; }}", new(Context))
+	tracer, err := newJsTracer("{step: function() {}, fault: function() {}, result: function() { return null; }}", nil)
 	if err != nil {
 		t.Fatal(err)
 	}
-	env := vm.NewEVM(vm.BlockContext{BlockNumber: big.NewInt(1)}, vm.TxContext{}, &dummyStatedb{}, params.TestChainConfig, vm.Config{Debug: true, Tracer: tracer})
+	env := vm.NewEVM(vm.BlockContext{BlockNumber: big.NewInt(1)}, vm.TxContext{GasPrice: big.NewInt(1)}, &dummyStatedb{}, params.TestChainConfig, vm.Config{Debug: true, Tracer: tracer})
 	scope := &vm.ScopeContext{
 		Contract: vm.NewContract(&account{}, &account{}, big.NewInt(0), 0),
 	}
-	tracer.CaptureState(env, 0, 0, 0, 0, scope, nil, 0, nil)
+	tracer.CaptureStart(env, common.Address{}, common.Address{}, false, []byte{}, 0, big.NewInt(0))
+	tracer.CaptureState(0, 0, 0, 0, scope, nil, 0, nil)
 	timeout := errors.New("stahp")
 	tracer.Stop(timeout)
-	tracer.CaptureState(env, 0, 0, 0, 0, scope, nil, 0, nil)
+	tracer.CaptureState(0, 0, 0, 0, scope, nil, 0, nil)
 
 	if _, err := tracer.GetResult(); err.Error() != timeout.Error() {
 		t.Errorf("Expected timeout error, got %v", err)
@@ -168,24 +166,16 @@ func TestHaltBetweenSteps(t *testing.T) {
 // TestNoStepExec tests a regular value transfer (no exec), and accessing the statedb
 // in 'result'
 func TestNoStepExec(t *testing.T) {
-	runEmptyTrace := func(tracer Tracer, vmctx *vmContext) (json.RawMessage, error) {
-		env := vm.NewEVM(vmctx.blockCtx, vmctx.txCtx, &dummyStatedb{}, params.TestChainConfig, vm.Config{Debug: true, Tracer: tracer})
-		startGas := uint64(10000)
-		contract := vm.NewContract(account{}, account{}, big.NewInt(0), startGas)
-		tracer.CaptureStart(env, contract.Caller(), contract.Address(), false, []byte{}, startGas, big.NewInt(0))
-		tracer.CaptureEnd(nil, startGas-contract.Gas, 1, nil)
-		return tracer.GetResult()
-	}
 	execTracer := func(code string) []byte {
 		t.Helper()
-		tracer, err := New(code, new(Context))
+		tracer, err := newJsTracer(code, nil)
 		if err != nil {
 			t.Fatal(err)
 		}
-		ret, err := runEmptyTrace(tracer, &vmContext{
+		env := vm.NewEVM(vm.BlockContext{BlockNumber: big.NewInt(1)}, vm.TxContext{GasPrice: big.NewInt(100)}, &dummyStatedb{}, params.TestChainConfig, vm.Config{Debug: true, Tracer: tracer})
-			blockCtx: vm.BlockContext{BlockNumber: big.NewInt(1)},
+		tracer.CaptureStart(env, common.Address{}, common.Address{}, false, []byte{}, 1000, big.NewInt(0))
-			txCtx:    vm.TxContext{GasPrice: big.NewInt(100000)},
+		tracer.CaptureEnd(nil, 0, 1, nil)
-		})
+		ret, err := tracer.GetResult()
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -212,7 +202,7 @@ func TestIsPrecompile(t *testing.T) {
 	chaincfg.IstanbulBlock = big.NewInt(200)
 	chaincfg.BerlinBlock = big.NewInt(300)
 	txCtx := vm.TxContext{GasPrice: big.NewInt(100000)}
-	tracer, err := New("{addr: toAddress('0000000000000000000000000000000000000009'), res: null, step: function() { this.res = isPrecompiled(this.addr); }, fault: function() {}, result: function() { return this.res; }}", new(Context))
+	tracer, err := newJsTracer("{addr: toAddress('0000000000000000000000000000000000000009'), res: null, step: function() { this.res = isPrecompiled(this.addr); }, fault: function() {}, result: function() { return this.res; }}", nil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -226,7 +216,7 @@ func TestIsPrecompile(t *testing.T) {
 		t.Errorf("Tracer should not consider blake2f as precompile in byzantium")
 	}
 
-	tracer, _ = New("{addr: toAddress('0000000000000000000000000000000000000009'), res: null, step: function() { this.res = isPrecompiled(this.addr); }, fault: function() {}, result: function() { return this.res; }}", new(Context))
+	tracer, _ = newJsTracer("{addr: toAddress('0000000000000000000000000000000000000009'), res: null, step: function() { this.res = isPrecompiled(this.addr); }, fault: function() {}, result: function() { return this.res; }}", nil)
 	blockCtx = vm.BlockContext{BlockNumber: big.NewInt(250)}
 	res, err = runTrace(tracer, &vmContext{blockCtx, txCtx}, chaincfg)
 	if err != nil {
@@ -239,23 +229,20 @@ func TestIsPrecompile(t *testing.T) {
 
 func TestEnterExit(t *testing.T) {
 	// test that either both or none of enter() and exit() are defined
-	if _, err := New("{step: function() {}, fault: function() {}, result: function() { return null; }, enter: function() {}}", new(Context)); err == nil {
+	if _, err := newJsTracer("{step: function() {}, fault: function() {}, result: function() { return null; }, enter: function() {}}", new(tracers.Context)); err == nil {
 		t.Fatal("tracer creation should've failed without exit() definition")
 	}
-	if _, err := New("{step: function() {}, fault: function() {}, result: function() { return null; }, enter: function() {}, exit: function() {}}", new(Context)); err != nil {
+	if _, err := newJsTracer("{step: function() {}, fault: function() {}, result: function() { return null; }, enter: function() {}, exit: function() {}}", new(tracers.Context)); err != nil {
 		t.Fatal(err)
 	}
-
 	// test that the enter and exit method are correctly invoked and the values passed
-	tracer, err := New("{enters: 0, exits: 0, enterGas: 0, gasUsed: 0, step: function() {}, fault: function() {}, result: function() { return {enters: this.enters, exits: this.exits, enterGas: this.enterGas, gasUsed: this.gasUsed} }, enter: function(frame) { this.enters++; this.enterGas = frame.getGas(); }, exit: function(res) { this.exits++; this.gasUsed = res.getGasUsed(); }}", new(Context))
+	tracer, err := newJsTracer("{enters: 0, exits: 0, enterGas: 0, gasUsed: 0, step: function() {}, fault: function() {}, result: function() { return {enters: this.enters, exits: this.exits, enterGas: this.enterGas, gasUsed: this.gasUsed} }, enter: function(frame) { this.enters++; this.enterGas = frame.getGas(); }, exit: function(res) { this.exits++; this.gasUsed = res.getGasUsed(); }}", new(tracers.Context))
 	if err != nil {
 		t.Fatal(err)
 	}
-
 	scope := &vm.ScopeContext{
 		Contract: vm.NewContract(&account{}, &account{}, big.NewInt(0), 0),
 	}
-
 	tracer.CaptureEnter(vm.CALL, scope.Contract.Caller(), scope.Contract.Address(), []byte{}, 1000, new(big.Int))
 	tracer.CaptureExit([]byte{}, 400, nil)
 

eth/tracers/native/call.go

@@ -31,7 +31,7 @@ import (
 )
 
 func init() {
-	tracers.RegisterNativeTracer("callTracer", NewCallTracer)
+	register("callTracer", newCallTracer)
 }
 
 type callFrame struct {
@@ -48,21 +48,24 @@ type callFrame struct {
 }
 
 type callTracer struct {
+	env       *vm.EVM
 	callstack []callFrame
 	interrupt uint32 // Atomic flag to signal execution interruption
 	reason    error  // Textual reason for the interruption
 }
 
-// NewCallTracer returns a native go tracer which tracks
+// newCallTracer returns a native go tracer which tracks
 // call frames of a tx, and implements vm.EVMLogger.
-func NewCallTracer() tracers.Tracer {
+func newCallTracer() tracers.Tracer {
 	// First callframe contains tx context info
 	// and is populated on start and end.
 	t := &callTracer{callstack: make([]callFrame, 1)}
 	return t
 }
 
+// CaptureStart implements the EVMLogger interface to initialize the tracing operation.
 func (t *callTracer) CaptureStart(env *vm.EVM, from common.Address, to common.Address, create bool, input []byte, gas uint64, value *big.Int) {
+	t.env = env
 	t.callstack[0] = callFrame{
 		Type:  "CALL",
 		From:  addrToHex(from),
@@ -76,6 +79,7 @@ func (t *callTracer) CaptureStart(env *vm.EVM, from common.Address, to common.Ad
 	}
 }
 
+// CaptureEnd is called after the call finishes to finalize the tracing.
 func (t *callTracer) CaptureEnd(output []byte, gasUsed uint64, _ time.Duration, err error) {
 	t.callstack[0].GasUsed = uintToHex(gasUsed)
 	if err != nil {
@@ -88,16 +92,19 @@ func (t *callTracer) CaptureEnd(output []byte, gasUsed uint64, _ time.Duration,
 	}
 }
 
-func (t *callTracer) CaptureState(env *vm.EVM, pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, rData []byte, depth int, err error) {
+// CaptureState implements the EVMLogger interface to trace a single step of VM execution.
+func (t *callTracer) CaptureState(pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, rData []byte, depth int, err error) {
 }
 
-func (t *callTracer) CaptureFault(env *vm.EVM, pc uint64, op vm.OpCode, gas, cost uint64, _ *vm.ScopeContext, depth int, err error) {
+// CaptureFault implements the EVMLogger interface to trace an execution fault.
+func (t *callTracer) CaptureFault(pc uint64, op vm.OpCode, gas, cost uint64, _ *vm.ScopeContext, depth int, err error) {
 }
 
+// CaptureEnter is called when EVM enters a new scope (via call, create or selfdestruct).
 func (t *callTracer) CaptureEnter(typ vm.OpCode, from common.Address, to common.Address, input []byte, gas uint64, value *big.Int) {
 	// Skip if tracing was interrupted
 	if atomic.LoadUint32(&t.interrupt) > 0 {
-		// TODO: env.Cancel()
+		t.env.Cancel()
 		return
 	}
 
@@ -112,6 +119,8 @@ func (t *callTracer) CaptureEnter(typ vm.OpCode, from common.Address, to common.
 	t.callstack = append(t.callstack, call)
 }
 
+// CaptureExit is called when EVM exits a scope, even if the scope didn't
+// execute any code.
 func (t *callTracer) CaptureExit(output []byte, gasUsed uint64, err error) {
 	size := len(t.callstack)
 	if size <= 1 {
@@ -134,6 +143,8 @@ func (t *callTracer) CaptureExit(output []byte, gasUsed uint64, err error) {
 	t.callstack[size-1].Calls = append(t.callstack[size-1].Calls, call)
 }
 
+// GetResult returns the json-encoded nested list of call traces, and any
+// error arising from the encoding or forceful termination (via `Stop`).
 func (t *callTracer) GetResult() (json.RawMessage, error) {
 	if len(t.callstack) != 1 {
 		return nil, errors.New("incorrect number of top-level calls")
@@ -145,6 +156,7 @@ func (t *callTracer) GetResult() (json.RawMessage, error) {
 	return json.RawMessage(res), t.reason
 }
 
+// Stop terminates execution of the tracer at the first opportune moment.
 func (t *callTracer) Stop(err error) {
 	t.reason = err
 	atomic.StoreUint32(&t.interrupt, 1)

eth/tracers/native/noop.go

@@ -1,3 +1,19 @@
+// Copyright 2021 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
 package native
 
 import (
@@ -11,36 +27,48 @@ import (
 )
 
 func init() {
-	tracers.RegisterNativeTracer("noopTracerNative", NewNoopTracer)
+	register("noopTracerNative", newNoopTracer)
 }
 
+// noopTracer is a go implementation of the Tracer interface which
+// performs no action. It's mostly useful for testing purposes.
 type noopTracer struct{}
 
-func NewNoopTracer() tracers.Tracer {
+// newNoopTracer returns a new noop tracer.
+func newNoopTracer() tracers.Tracer {
 	return &noopTracer{}
 }
 
+// CaptureStart implements the EVMLogger interface to initialize the tracing operation.
 func (t *noopTracer) CaptureStart(env *vm.EVM, from common.Address, to common.Address, create bool, input []byte, gas uint64, value *big.Int) {
 }
 
+// CaptureEnd is called after the call finishes to finalize the tracing.
 func (t *noopTracer) CaptureEnd(output []byte, gasUsed uint64, _ time.Duration, err error) {
 }
 
-func (t *noopTracer) CaptureState(env *vm.EVM, pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, rData []byte, depth int, err error) {
+// CaptureState implements the EVMLogger interface to trace a single step of VM execution.
+func (t *noopTracer) CaptureState(pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, rData []byte, depth int, err error) {
 }
 
-func (t *noopTracer) CaptureFault(env *vm.EVM, pc uint64, op vm.OpCode, gas, cost uint64, _ *vm.ScopeContext, depth int, err error) {
+// CaptureFault implements the EVMLogger interface to trace an execution fault.
+func (t *noopTracer) CaptureFault(pc uint64, op vm.OpCode, gas, cost uint64, _ *vm.ScopeContext, depth int, err error) {
 }
 
+// CaptureEnter is called when EVM enters a new scope (via call, create or selfdestruct).
 func (t *noopTracer) CaptureEnter(typ vm.OpCode, from common.Address, to common.Address, input []byte, gas uint64, value *big.Int) {
 }
 
+// CaptureExit is called when EVM exits a scope, even if the scope didn't
+// execute any code.
 func (t *noopTracer) CaptureExit(output []byte, gasUsed uint64, err error) {
 }
 
+// GetResult returns an empty json object.
 func (t *noopTracer) GetResult() (json.RawMessage, error) {
 	return json.RawMessage(`{}`), nil
 }
 
+// Stop terminates execution of the tracer at the first opportune moment.
 func (t *noopTracer) Stop(err error) {
 }

eth/tracers/native/tracer.go

@@ -0,0 +1,79 @@
+// Copyright 2021 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+/*
+Package native is a collection of tracers written in go.
+
+In order to add a native tracer and have it compiled into the binary, a new
+file needs to be added to this folder, containing an implementation of the
+`eth.tracers.Tracer` interface.
+
+Aside from implementing the tracer, it also needs to register itself, using the
+`register` method -- and this needs to be done in the package initialization.
+
+Example:
+
+```golang
+func init() {
+	register("noopTracerNative", newNoopTracer)
+}
+```
+*/
+package native
+
+import (
+	"errors"
+
+	"github.com/ethereum/go-ethereum/eth/tracers"
+)
+
+// init registers itself this packages as a lookup for tracers.
+func init() {
+	tracers.RegisterLookup(false, lookup)
+}
+
+/*
+ctors is a map of package-local tracer constructors.
+
+We cannot be certain about the order of init-functions within a package,
+The go spec (https://golang.org/ref/spec#Package_initialization) says
+
+> To ensure reproducible initialization behavior, build systems
+> are encouraged to present multiple files belonging to the same
+> package in lexical file name order to a compiler.
+
+Hence, we cannot make the map in init, but must make it upon first use.
+*/
+var ctors map[string]func() tracers.Tracer
+
+// register is used by native tracers to register their presence.
+func register(name string, ctor func() tracers.Tracer) {
+	if ctors == nil {
+		ctors = make(map[string]func() tracers.Tracer)
+	}
+	ctors[name] = ctor
+}
+
+// lookup returns a tracer, if one can be matched to the given name.
+func lookup(name string, ctx *tracers.Context) (tracers.Tracer, error) {
+	if ctors == nil {
+		ctors = make(map[string]func() tracers.Tracer)
+	}
+	if ctor, ok := ctors[name]; ok {
+		return ctor(), nil
+	}
+	return nil, errors.New("no tracer found")
+}

eth/tracers/tracers.go

@@ -14,18 +14,25 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-// Package tracers is a collection of JavaScript transaction tracers.
+// Package tracers is a manager for transaction tracing engines.
 package tracers
 
 import (
 	"encoding/json"
-	"strings"
+	"errors"
-	"unicode"
 
+	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/vm"
-	"github.com/ethereum/go-ethereum/eth/tracers/internal/tracers"
 )
 
+// Context contains some contextual infos for a transaction execution that is not
+// available from within the EVM object.
+type Context struct {
+	BlockHash common.Hash // Hash of the block the tx is contained within (zero if dangling tx or call)
+	TxIndex   int         // Index of the transaction within a block (zero if dangling tx or call)
+	TxHash    common.Hash // Hash of the transaction being traced (zero if dangling call)
+}
+
 // Tracer interface extends vm.EVMLogger and additionally
 // allows collecting the tracing result.
 type Tracer interface {
@@ -35,50 +42,31 @@ type Tracer interface {
 	Stop(err error)
 }
 
+type lookupFunc func(string, *Context) (Tracer, error)
+
 var (
-	nativeTracers map[string]func() Tracer = make(map[string]func() Tracer)
+	lookups []lookupFunc
-	jsTracers                              = make(map[string]string)
 )
 
-// RegisterNativeTracer makes native tracers which adhere
+// RegisterLookup registers a method as a lookup for tracers, meaning that
-// to the `Tracer` interface available to the rest of the codebase.
+// users can invoke a named tracer through that lookup. If 'wildcard' is true,
-// It is typically invoked in the `init()` function, e.g. see the `native/call.go`.
+// then the lookup will be placed last. This is typically meant for interpreted
-func RegisterNativeTracer(name string, ctor func() Tracer) {
+// engines (js) which can evaluate dynamic user-supplied code.
-	nativeTracers[name] = ctor
+func RegisterLookup(wildcard bool, lookup lookupFunc) {
+	if wildcard {
+		lookups = append(lookups, lookup)
+	} else {
+		lookups = append([]lookupFunc{lookup}, lookups...)
+	}
 }
 
-// New returns a new instance of a tracer,
+// New returns a new instance of a tracer, by iterating through the
-// 1. If 'code' is the name of a registered native tracer, then that tracer
+// registered lookups.
-//   is instantiated and returned
-// 2. If 'code' is the name of a registered js-tracer, then that tracer is
-//   instantiated and returned
-// 3. Otherwise, the code is interpreted as the js code of a js-tracer, and
-//   is evaluated and returned.
 func New(code string, ctx *Context) (Tracer, error) {
-	// Resolve native tracer
+	for _, lookup := range lookups {
-	if fn, ok := nativeTracers[code]; ok {
+		if tracer, err := lookup(code, ctx); err == nil {
-		return fn(), nil
+			return tracer, nil
 		}
-	// Resolve js-tracers by name and assemble the tracer object
-	if tracer, ok := jsTracers[code]; ok {
-		code = tracer
-	}
-	return newJsTracer(code, ctx)
-}
-
-// camel converts a snake cased input string into a camel cased output.
-func camel(str string) string {
-	pieces := strings.Split(str, "_")
-	for i := 1; i < len(pieces); i++ {
-		pieces[i] = string(unicode.ToUpper(rune(pieces[i][0]))) + pieces[i][1:]
-	}
-	return strings.Join(pieces, "")
-}
-
-// init retrieves the JavaScript transaction tracers included in go-ethereum.
-func init() {
-	for _, file := range tracers.AssetNames() {
-		name := camel(strings.TrimSuffix(file, ".js"))
-		jsTracers[name] = string(tracers.MustAsset(file))
 	}
+	return nil, errors.New("tracer not found")
 }

eth/tracers/tracers_test.go

@@ -17,11 +17,7 @@
 package tracers
 
 import (
-	"crypto/ecdsa"
-	"crypto/rand"
-	"encoding/json"
 	"math/big"
-	"reflect"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -35,56 +31,6 @@ import (
 	"github.com/ethereum/go-ethereum/tests"
 )
 
-// To generate a new callTracer test, copy paste the makeTest method below into
-// a Geth console and call it with a transaction hash you which to export.
-
-/*
-// makeTest generates a callTracer test by running a prestate reassembled and a
-// call trace run, assembling all the gathered information into a test case.
-var makeTest = function(tx, rewind) {
-  // Generate the genesis block from the block, transaction and prestate data
-  var block   = eth.getBlock(eth.getTransaction(tx).blockHash);
-  var genesis = eth.getBlock(block.parentHash);
-
-  delete genesis.gasUsed;
-  delete genesis.logsBloom;
-  delete genesis.parentHash;
-  delete genesis.receiptsRoot;
-  delete genesis.sha3Uncles;
-  delete genesis.size;
-  delete genesis.transactions;
-  delete genesis.transactionsRoot;
-  delete genesis.uncles;
-
-  genesis.gasLimit  = genesis.gasLimit.toString();
-  genesis.number    = genesis.number.toString();
-  genesis.timestamp = genesis.timestamp.toString();
-
-  genesis.alloc = debug.traceTransaction(tx, {tracer: "prestateTracer", rewind: rewind});
-  for (var key in genesis.alloc) {
-    genesis.alloc[key].nonce = genesis.alloc[key].nonce.toString();
-  }
-  genesis.config = admin.nodeInfo.protocols.eth.config;
-
-  // Generate the call trace and produce the test input
-  var result = debug.traceTransaction(tx, {tracer: "callTracer", rewind: rewind});
-  delete result.time;
-
-  console.log(JSON.stringify({
-    genesis: genesis,
-    context: {
-      number:     block.number.toString(),
-      difficulty: block.difficulty,
-      timestamp:  block.timestamp.toString(),
-      gasLimit:   block.gasLimit.toString(),
-      miner:      block.miner,
-    },
-    input:  eth.getRawTransaction(tx),
-    result: result,
-  }, null, 2));
-}
-*/
-
 // callTrace is the result of a callTracer run.
 type callTrace struct {
 	Type    string          `json:"type"`
@@ -99,184 +45,6 @@ type callTrace struct {
 	Calls   []callTrace     `json:"calls,omitempty"`
 }
 
-// TestZeroValueToNotExitCall tests the calltracer(s) on the following:
-// Tx to A, A calls B with zero value. B does not already exist.
-// Expected: that enter/exit is invoked and the inner call is shown in the result
-func TestZeroValueToNotExitCall(t *testing.T) {
-	var to = common.HexToAddress("0x00000000000000000000000000000000deadbeef")
-	privkey, err := crypto.HexToECDSA("0000000000000000deadbeef00000000000000000000000000000000deadbeef")
-	if err != nil {
-		t.Fatalf("err %v", err)
-	}
-	signer := types.NewEIP155Signer(big.NewInt(1))
-	tx, err := types.SignNewTx(privkey, signer, &types.LegacyTx{
-		GasPrice: big.NewInt(0),
-		Gas:      50000,
-		To:       &to,
-	})
-	if err != nil {
-		t.Fatalf("err %v", err)
-	}
-	origin, _ := signer.Sender(tx)
-	txContext := vm.TxContext{
-		Origin:   origin,
-		GasPrice: big.NewInt(1),
-	}
-	context := vm.BlockContext{
-		CanTransfer: core.CanTransfer,
-		Transfer:    core.Transfer,
-		Coinbase:    common.Address{},
-		BlockNumber: new(big.Int).SetUint64(8000000),
-		Time:        new(big.Int).SetUint64(5),
-		Difficulty:  big.NewInt(0x30000),
-		GasLimit:    uint64(6000000),
-	}
-	var code = []byte{
-		byte(vm.PUSH1), 0x0, byte(vm.DUP1), byte(vm.DUP1), byte(vm.DUP1), // in and outs zero
-		byte(vm.DUP1), byte(vm.PUSH1), 0xff, byte(vm.GAS), // value=0,address=0xff, gas=GAS
-		byte(vm.CALL),
-	}
-	var alloc = core.GenesisAlloc{
-		to: core.GenesisAccount{
-			Nonce: 1,
-			Code:  code,
-		},
-		origin: core.GenesisAccount{
-			Nonce:   0,
-			Balance: big.NewInt(500000000000000),
-		},
-	}
-	_, statedb := tests.MakePreState(rawdb.NewMemoryDatabase(), alloc, false)
-	// Create the tracer, the EVM environment and run it
-	tracer, err := New("callTracerJs", new(Context))
-	if err != nil {
-		t.Fatalf("failed to create call tracer: %v", err)
-	}
-	evm := vm.NewEVM(context, txContext, statedb, params.MainnetChainConfig, vm.Config{Debug: true, Tracer: tracer})
-	msg, err := tx.AsMessage(signer, nil)
-	if err != nil {
-		t.Fatalf("failed to prepare transaction for tracing: %v", err)
-	}
-	st := core.NewStateTransition(evm, msg, new(core.GasPool).AddGas(tx.Gas()))
-	if _, err = st.TransitionDb(); err != nil {
-		t.Fatalf("failed to execute transaction: %v", err)
-	}
-	// Retrieve the trace result and compare against the etalon
-	res, err := tracer.GetResult()
-	if err != nil {
-		t.Fatalf("failed to retrieve trace result: %v", err)
-	}
-	have := new(callTrace)
-	if err := json.Unmarshal(res, have); err != nil {
-		t.Fatalf("failed to unmarshal trace result: %v", err)
-	}
-	wantStr := `{"type":"CALL","from":"0x682a80a6f560eec50d54e63cbeda1c324c5f8d1b","to":"0x00000000000000000000000000000000deadbeef","value":"0x0","gas":"0x7148","gasUsed":"0x2d0","input":"0x","output":"0x","calls":[{"type":"CALL","from":"0x00000000000000000000000000000000deadbeef","to":"0x00000000000000000000000000000000000000ff","value":"0x0","gas":"0x6cbf","gasUsed":"0x0","input":"0x","output":"0x"}]}`
-	want := new(callTrace)
-	json.Unmarshal([]byte(wantStr), want)
-	if !jsonEqual(have, want) {
-		t.Error("have != want")
-	}
-}
-
-func TestPrestateTracerCreate2(t *testing.T) {
-	unsignedTx := types.NewTransaction(1, common.HexToAddress("0x00000000000000000000000000000000deadbeef"),
-		new(big.Int), 5000000, big.NewInt(1), []byte{})
-
-	privateKeyECDSA, err := ecdsa.GenerateKey(crypto.S256(), rand.Reader)
-	if err != nil {
-		t.Fatalf("err %v", err)
-	}
-	signer := types.NewEIP155Signer(big.NewInt(1))
-	tx, err := types.SignTx(unsignedTx, signer, privateKeyECDSA)
-	if err != nil {
-		t.Fatalf("err %v", err)
-	}
-	/**
-		This comes from one of the test-vectors on the Skinny Create2 - EIP
-
-	    address 0x00000000000000000000000000000000deadbeef
-	    salt 0x00000000000000000000000000000000000000000000000000000000cafebabe
-	    init_code 0xdeadbeef
-	    gas (assuming no mem expansion): 32006
-	    result: 0x60f3f640a8508fC6a86d45DF051962668E1e8AC7
-	*/
-	origin, _ := signer.Sender(tx)
-	txContext := vm.TxContext{
-		Origin:   origin,
-		GasPrice: big.NewInt(1),
-	}
-	context := vm.BlockContext{
-		CanTransfer: core.CanTransfer,
-		Transfer:    core.Transfer,
-		Coinbase:    common.Address{},
-		BlockNumber: new(big.Int).SetUint64(8000000),
-		Time:        new(big.Int).SetUint64(5),
-		Difficulty:  big.NewInt(0x30000),
-		GasLimit:    uint64(6000000),
-	}
-	alloc := core.GenesisAlloc{}
-
-	// The code pushes 'deadbeef' into memory, then the other params, and calls CREATE2, then returns
-	// the address
-	alloc[common.HexToAddress("0x00000000000000000000000000000000deadbeef")] = core.GenesisAccount{
-		Nonce:   1,
-		Code:    hexutil.MustDecode("0x63deadbeef60005263cafebabe6004601c6000F560005260206000F3"),
-		Balance: big.NewInt(1),
-	}
-	alloc[origin] = core.GenesisAccount{
-		Nonce:   1,
-		Code:    []byte{},
-		Balance: big.NewInt(500000000000000),
-	}
-	_, statedb := tests.MakePreState(rawdb.NewMemoryDatabase(), alloc, false)
-
-	// Create the tracer, the EVM environment and run it
-	tracer, err := New("prestateTracer", new(Context))
-	if err != nil {
-		t.Fatalf("failed to create call tracer: %v", err)
-	}
-	evm := vm.NewEVM(context, txContext, statedb, params.MainnetChainConfig, vm.Config{Debug: true, Tracer: tracer})
-
-	msg, err := tx.AsMessage(signer, nil)
-	if err != nil {
-		t.Fatalf("failed to prepare transaction for tracing: %v", err)
-	}
-	st := core.NewStateTransition(evm, msg, new(core.GasPool).AddGas(tx.Gas()))
-	if _, err = st.TransitionDb(); err != nil {
-		t.Fatalf("failed to execute transaction: %v", err)
-	}
-	// Retrieve the trace result and compare against the etalon
-	res, err := tracer.GetResult()
-	if err != nil {
-		t.Fatalf("failed to retrieve trace result: %v", err)
-	}
-	ret := make(map[string]interface{})
-	if err := json.Unmarshal(res, &ret); err != nil {
-		t.Fatalf("failed to unmarshal trace result: %v", err)
-	}
-	if _, has := ret["0x60f3f640a8508fc6a86d45df051962668e1e8ac7"]; !has {
-		t.Fatalf("Expected 0x60f3f640a8508fc6a86d45df051962668e1e8ac7 in result")
-	}
-}
-
-// jsonEqual is similar to reflect.DeepEqual, but does a 'bounce' via json prior to
-// comparison
-func jsonEqual(x, y interface{}) bool {
-	xTrace := new(callTrace)
-	yTrace := new(callTrace)
-	if xj, err := json.Marshal(x); err == nil {
-		json.Unmarshal(xj, xTrace)
-	} else {
-		return false
-	}
-	if yj, err := json.Marshal(y); err == nil {
-		json.Unmarshal(yj, yTrace)
-	} else {
-		return false
-	}
-	return reflect.DeepEqual(xTrace, yTrace)
-}
-
 func BenchmarkTransactionTrace(b *testing.B) {
 	key, _ := crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 	from := crypto.PubkeyToAddress(key.PublicKey)