Implement the optional output field on ots_traceTransaction (#10014)

This is for E2.

It implements the backward compatible output field for traces on
ots_traceTransaction: otterscan/execution-apis#1

It'll be consumed by Otterscan in an upcoming release of this feature:
otterscan/otterscan#1530

turbo/jsonrpc/otterscan_trace_transaction.go

@@ -2,9 +2,10 @@ package jsonrpc
 
 import (
 	"context"
-	"github.com/ledgerwatch/erigon-lib/common/hexutil"
 	"math/big"
 
+	"github.com/ledgerwatch/erigon-lib/common/hexutil"
+
 	"github.com/holiman/uint256"
 
 	"github.com/ledgerwatch/erigon-lib/common"
@@ -29,68 +30,68 @@ func (api *OtterscanAPIImpl) TraceTransaction(ctx context.Context, hash common.H
 }
 
 type TraceEntry struct {
-	Type  string           `json:"type"`
-	Depth int              `json:"depth"`
-	From  common.Address   `json:"from"`
-	To    common.Address   `json:"to"`
-	Value *hexutil.Big     `json:"value"`
-	Input hexutility.Bytes `json:"input"`
+	Type   string           `json:"type"`
+	Depth  int              `json:"depth"`
+	From   common.Address   `json:"from"`
+	To     common.Address   `json:"to"`
+	Value  *hexutil.Big     `json:"value"`
+	Input  hexutility.Bytes `json:"input"`
+	Output hexutility.Bytes `json:"output"`
 }
 
 type TransactionTracer struct {
 	DefaultTracer
 	ctx     context.Context
 	Results []*TraceEntry
 	depth   int // computed from CaptureStart, CaptureEnter, and CaptureExit calls
+	stack   []*TraceEntry
 }
 
 func NewTransactionTracer(ctx context.Context) *TransactionTracer {
 	return &TransactionTracer{
 		ctx:     ctx,
 		Results: make([]*TraceEntry, 0),
+		stack:   make([]*TraceEntry, 0),
 	}
 }
 
 func (t *TransactionTracer) captureStartOrEnter(typ vm.OpCode, from, to common.Address, precompile bool, input []byte, value *uint256.Int) {
-	if precompile {
-		return
-	}
-
 	inputCopy := make([]byte, len(input))
 	copy(inputCopy, input)
 	_value := new(big.Int)
 	if value != nil {
 		_value.Set(value.ToBig())
 	}
+
+	var entry *TraceEntry
 	if typ == vm.CALL {
-		t.Results = append(t.Results, &TraceEntry{"CALL", t.depth, from, to, (*hexutil.Big)(_value), inputCopy})
-		return
-	}
-	if typ == vm.STATICCALL {
-		t.Results = append(t.Results, &TraceEntry{"STATICCALL", t.depth, from, to, nil, inputCopy})
-		return
-	}
-	if typ == vm.DELEGATECALL {
-		t.Results = append(t.Results, &TraceEntry{"DELEGATECALL", t.depth, from, to, nil, inputCopy})
-		return
-	}
-	if typ == vm.CALLCODE {
-		t.Results = append(t.Results, &TraceEntry{"CALLCODE", t.depth, from, to, (*hexutil.Big)(_value), inputCopy})
-		return
-	}
-	if typ == vm.CREATE {
-		t.Results = append(t.Results, &TraceEntry{"CREATE", t.depth, from, to, (*hexutil.Big)(value.ToBig()), inputCopy})
-		return
-	}
-	if typ == vm.CREATE2 {
-		t.Results = append(t.Results, &TraceEntry{"CREATE2", t.depth, from, to, (*hexutil.Big)(value.ToBig()), inputCopy})
-		return
+		entry = &TraceEntry{"CALL", t.depth, from, to, (*hexutil.Big)(_value), inputCopy, nil}
+	} else if typ == vm.STATICCALL {
+		entry = &TraceEntry{"STATICCALL", t.depth, from, to, nil, inputCopy, nil}
+	} else if typ == vm.DELEGATECALL {
+		entry = &TraceEntry{"DELEGATECALL", t.depth, from, to, nil, inputCopy, nil}
+	} else if typ == vm.CALLCODE {
+		entry = &TraceEntry{"CALLCODE", t.depth, from, to, (*hexutil.Big)(_value), inputCopy, nil}
+	} else if typ == vm.CREATE {
+		entry = &TraceEntry{"CREATE", t.depth, from, to, (*hexutil.Big)(value.ToBig()), inputCopy, nil}
+	} else if typ == vm.CREATE2 {
+		entry = &TraceEntry{"CREATE2", t.depth, from, to, (*hexutil.Big)(value.ToBig()), inputCopy, nil}
+	} else if typ == vm.SELFDESTRUCT {
+		last := t.Results[len(t.Results)-1]
+		entry = &TraceEntry{"SELFDESTRUCT", last.Depth + 1, from, to, (*hexutil.Big)(value.ToBig()), nil, nil}
+	} else {
+		// safeguard in case new CALL-like opcodes are introduced but not handled,
+		// otherwise CaptureExit/stack will get out of sync
+		entry = &TraceEntry{"UNKNOWN", t.depth, from, to, (*hexutil.Big)(value.ToBig()), inputCopy, nil}
 	}
 
-	if typ == vm.SELFDESTRUCT {
-		last := t.Results[len(t.Results)-1]
-		t.Results = append(t.Results, &TraceEntry{"SELFDESTRUCT", last.Depth + 1, from, to, (*hexutil.Big)(value.ToBig()), nil})
+	// Ignore precompiles in the returned trace (maybe we shouldn't?)
+	if !precompile {
+		t.Results = append(t.Results, entry)
 	}
+
+	// stack precompiles in order to match captureEndOrExit
+	t.stack = append(t.stack, entry)
 }
 
 func (t *TransactionTracer) CaptureStart(env *vm.EVM, from common.Address, to common.Address, precompile bool, create bool, input []byte, gas uint64, value *uint256.Int, code []byte) {
@@ -103,6 +104,22 @@ func (t *TransactionTracer) CaptureEnter(typ vm.OpCode, from common.Address, to
 	t.captureStartOrEnter(typ, from, to, precompile, input, value)
 }
 
-func (t *TransactionTracer) CaptureExit(output []byte, usedGas uint64, err error) {
+func (t *TransactionTracer) captureEndOrExit(output []byte, usedGas uint64, err error) {
 	t.depth--
+
+	lastIdx := len(t.stack) - 1
+	pop := t.stack[lastIdx]
+	t.stack = t.stack[:lastIdx]
+
+	outputCopy := make([]byte, len(output))
+	copy(outputCopy, output)
+	pop.Output = outputCopy
+}
+
+func (t *TransactionTracer) CaptureExit(output []byte, usedGas uint64, err error) {
+	t.captureEndOrExit(output, usedGas, err)
+}
+
+func (t *TransactionTracer) CaptureEnd(output []byte, usedGas uint64, err error) {
+	t.captureEndOrExit(output, usedGas, err)
 }