eth/tracers/logger: use omitempty in error JSON tag to avoid unnecessary log bloat

[odeke-em]

System information

Geth version: geth version Not Applicable
OS & Version: Windows/Linux/OSX Not Applicable
Commit hash : 687e4dc

Expected behaviour

Lack of error strings should NOT log "error":"" which bloats logs and can actually be confusing when you grep for "error" in logs when things are failing.

Actual behaviour

Looking at such logs like

{"pc":4716,"op":80,"gas":"0x688e5","gasCost":"0x2","memory":"0x","memSize":352,"stack":["0xfa31de01","0x29a","0x7d0","0xabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd","0x80","0x534","0xc0","0x5f646b5592c4159d4963fbf901f81144ef53cc51a7082435e3a6120a45002ff7","0x15dc","0x34","0x5f646b5592c4159d4963fbf901f81144ef53cc51a7082435e3a6120a45002ff7"],"returnData":"0x","depth":2,"refund":0,"opName":"POP","error":""}
{"pc":4717,"op":80,"gas":"0x688e3","gasCost":"0x2","memory":"0x","memSize":352,"stack":["0xfa31de01","0x29a","0x7d0","0xabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd","0x80","0x534","0xc0","0x5f646b5592c4159d4963fbf901f81144ef53cc51a7082435e3a6120a45002ff7","0x15dc","0x34"],"returnData":"0x","depth":2,"refund":0,"opName":"POP","error":""}
{"pc":4718,"op":86,"gas":"0x688e1","gasCost":"0x8","memory":"0x","memSize":352,"stack":["0xfa31de01","0x29a","0x7d0","0xabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd","0x80","0x534","0xc0","0x5f646b5592c4159d4963fbf901f81144ef53cc51a7082435e3a6120a45002ff7","0x15dc"],"returnData":"0x","depth":2,"refund":0,"opName":"JUMP","error":""}
{"pc":5596,"op":91,"gas":"0x688d9","gasCost":"0x1","memory":"0x","memSize":352,"stack":["0xfa31de01","0x29a","0x7d0","0xabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd","0x80","0x534","0xc0","0x5f646b5592c4159d4963fbf901f81144ef53cc51a7082435e3a6120a45002ff7"],"returnData":"0x","depth":2,"refund":0,"opName":"JUMPDEST","error":""}
{"pc":5597,"op":97,"gas":"0x688d8","gasCost":"0x3","memory":"0x","memSize":352,"stack":["0xfa31de01","0x29a","0x7d0","0xabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd","0x80","0x534","0xc0","0x5f646b5592c4159d4963fbf901f81144ef53cc51a7082435e3a6120a45002ff7"],"returnData":"0x","depth":2,"refund":0,"opName":"PUSH2","error":""}
{"pc":5600,"op":97,"gas":"0x688d5","gasCost":"0x3","memory":"0x","memSize":352,"stack":["0xfa31de01","0x29a","0x7d0","0xabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd","0x80","0x534","0xc0","0x5f646b5592c4159d4963fbf901f81144ef53cc51a7082435e3a6120a45002ff7","0x15ef"],"returnData":"0x","depth":2,"refund":0,"opName":"PUSH2","error":""}
{"pc":5603,"op":97,"gas":"0x688d2","gasCost":"0x3","memory":"0x","memSize":352,"stack":["0xfa31de01","0x29a","0x7d0","0xabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd","0x80","0x534","0xc0","0x5f646b5592c4159d4963fbf901f81144ef53cc51a7082435e3a6120a45002ff7","0x15ef","0x15e7"],"returnData":"0x","depth":2,"refund":0,"opName":"PUSH2","error":""}

Notice that each log line has "error":"" per

Steps to reproduce the behaviour

Just run the tracers

This bug was sponsored by Tharsis / evmos.org

[s1na]

I take it you're using the evm command? Because debug_traceTransaction already omits empty errors. Anyhow this patch should omit empty errors for evm too.

diff --git a/eth/tracers/logger/gen_structlog.go b/eth/tracers/logger/gen_structlog.go
index 9e71b555c..7818fbe70 100644
--- a/eth/tracers/logger/gen_structlog.go
+++ b/eth/tracers/logger/gen_structlog.go
@@ -30,7 +30,7 @@ func (s StructLog) MarshalJSON() ([]byte, error) {
                RefundCounter uint64                      `json:"refund"`
                Err           error                       `json:"-"`
                OpName        string                      `json:"opName"`
-               ErrorString   string                      `json:"error"`
+               ErrorString   string                      `json:"error,omitempty"`
        }
        var enc StructLog
        enc.Pc = s.Pc
diff --git a/eth/tracers/logger/logger.go b/eth/tracers/logger/logger.go
index 846193582..444a665d6 100644
--- a/eth/tracers/logger/logger.go
+++ b/eth/tracers/logger/logger.go
@@ -82,8 +82,8 @@ type structLogMarshaling struct {
        GasCost     math.HexOrDecimal64
        Memory      hexutil.Bytes
        ReturnData  hexutil.Bytes
-       OpName      string `json:"opName"` // adds call to OpName() in MarshalJSON
-       ErrorString string `json:"error"`  // adds call to ErrorString() in MarshalJSON
+       OpName      string `json:"opName"`          // adds call to OpName() in MarshalJSON
+       ErrorString string `json:"error,omitempty"` // adds call to ErrorString() in MarshalJSON
 }

 // OpName formats the operand name in a human-readable format.