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Add custom error serialization support and provide sane defaults (#78) 

As per https://github.com/rs/zerolog/issues/9 and to offer a different approach from  https://github.com/rs/zerolog/pull/11 and https://github.com/rs/zerolog/pull/35 this PR introduces custom error serialization with sane defaults without breaking the existing APIs.

This is just a first draft and is missing tests. Also, a bit of code duplication which I feel could be reduced but it serves to get the idea across.

It provides global error marshalling by exposing a `var ErrorMarshalFunc func(error) interface{}` in zerolog package that by default is  a function that returns the passed argument. It should be overriden if you require custom error marshalling.

Then in every function that accept error or array of errors `ErrorMarshalFunc` is called on the error and then the result of it is processed like this:
- if it implements `LogObjectMarshaler`, serialize it as an object
- if it is a string serialize as a string
- if it is an error, serialize as a string with the result of `Error()`
- else serialize it as an interface

The side effect of this change is that the encoders don't need the `AppendError/s` methods anymore, as the errors are serialized directly to other types.
This commit is contained in:
Dušan Kasan 2018-07-02 21:46:01 +02:00 committed by Olivier Poitrey
parent 1a88fbfdd0
commit 1c6d99b455
8 changed files with 186 additions and 108 deletions
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19
array.go
View File

@ -71,9 +71,24 @@ func (a *Array) Hex(val []byte) *Array {
return a
}
// Err append append the err as a string to the array.
// Err serializes and appends the err to the array.
func (a *Array) Err(err error) *Array {
a.buf = enc.AppendError(enc.AppendArrayDelim(a.buf), err)
marshaled := ErrorMarshalFunc(err)
switch m := marshaled.(type) {
case LogObjectMarshaler:
e := newEvent(nil, 0)
e.buf = e.buf[:0]
e.appendObject(m)
a.buf = append(enc.AppendArrayDelim(a.buf), e.buf...)
eventPool.Put(e)
case error:
a.buf = enc.AppendString(enc.AppendArrayDelim(a.buf), m.Error())
case string:
a.buf = enc.AppendString(enc.AppendArrayDelim(a.buf), m)
default:
a.buf = enc.AppendInterface(enc.AppendArrayDelim(a.buf), m)
}
return a
}

46
context.go
View File

@ -101,27 +101,47 @@ func (c Context) RawJSON(key string, b []byte) Context {
return c
}
// AnErr adds the field key with err as a string to the logger context.
// AnErr adds the field key with serialized err to the logger context.
func (c Context) AnErr(key string, err error) Context {
if err != nil {
c.l.context = enc.AppendError(enc.AppendKey(c.l.context, key), err)
marshaled := ErrorMarshalFunc(err)
switch m := marshaled.(type) {
case nil:
return c
case LogObjectMarshaler:
return c.Object(key,m)
case error:
return c.Str(key, m.Error())
case string:
return c.Str(key, m)
default:
return c.Interface(key, m)
}
return c
}
// Errs adds the field key with errs as an array of strings to the logger context.
// Errs adds the field key with errs as an array of serialized errors to the
// logger context.
func (c Context) Errs(key string, errs []error) Context {
c.l.context = enc.AppendErrors(enc.AppendKey(c.l.context, key), errs)
return c
arr := Arr()
for _, err := range errs {
marshaled := ErrorMarshalFunc(err)
switch m := marshaled.(type) {
case LogObjectMarshaler:
arr = arr.Object(m)
case error:
arr = arr.Str(m.Error())
case string:
arr = arr.Str(m)
default:
arr = arr.Interface(m)
}
}
return c.Array(key, arr)
}
// Err adds the field "error" with err as a string to the logger context.
// To customize the key name, change zerolog.ErrorFieldName.
// Err adds the field "error" with serialized err to the logger context.
func (c Context) Err(err error) Context {
if err != nil {
c.l.context = enc.AppendError(enc.AppendKey(c.l.context, ErrorFieldName), err)
}
return c
return c.AnErr(ErrorFieldName, err)
}
// Bool adds the field key with val as a bool to the logger context.

2
encoder.go
View File

@ -16,8 +16,6 @@ type encoder interface {
AppendDuration(dst []byte, d time.Duration, unit time.Duration, useInt bool) []byte
AppendDurations(dst []byte, vals []time.Duration, unit time.Duration, useInt bool) []byte
AppendEndMarker(dst []byte) []byte
AppendError(dst []byte, err error) []byte
AppendErrors(dst []byte, errs []error) []byte
AppendFloat32(dst []byte, val float32) []byte
AppendFloat64(dst []byte, val float64) []byte
AppendFloats32(dst []byte, vals []float32) []byte

57
event.go
View File

@ -18,6 +18,11 @@ var eventPool = &sync.Pool{
},
}
// ErrorMarshalFunc allows customization of global error marshaling
var ErrorMarshalFunc = func (err error) interface{} {
return err
}
// Event represents a log event. It is instanced by one of the level method of
// Logger and finalized by the Msg or Msgf method.
type Event struct {
@ -239,39 +244,53 @@ func (e *Event) RawJSON(key string, b []byte) *Event {
return e
}
// AnErr adds the field key with err as a string to the *Event context.
// AnErr adds the field key with serialized err to the *Event context.
// If err is nil, no field is added.
func (e *Event) AnErr(key string, err error) *Event {
if e == nil {
marshaled := ErrorMarshalFunc(err)
switch m := marshaled.(type) {
case nil:
return e
case LogObjectMarshaler:
return e.Object(key, m)
case error:
return e.Str(key, m.Error())
case string:
return e.Str(key, m)
default:
return e.Interface(key, m)
}
if err != nil {
e.buf = enc.AppendError(enc.AppendKey(e.buf, key), err)
}
return e
}
// Errs adds the field key with errs as an array of strings to the *Event context.
// If err is nil, no field is added.
// Errs adds the field key with errs as an array of serialized errors to the
// *Event context.
func (e *Event) Errs(key string, errs []error) *Event {
if e == nil {
return e
}
e.buf = enc.AppendErrors(enc.AppendKey(e.buf, key), errs)
return e
arr := Arr()
for _, err := range errs {
marshaled := ErrorMarshalFunc(err)
switch m := marshaled.(type) {
case LogObjectMarshaler:
arr = arr.Object(m)
case error:
arr = arr.Err(m)
case string:
arr = arr.Str(m)
default:
arr = arr.Interface(m)
}
}
return e.Array(key, arr)
}
// Err adds the field "error" with err as a string to the *Event context.
// Err adds the field "error" with serialized err to the *Event context.
// If err is nil, no field is added.
// To customize the key name, change zerolog.ErrorFieldName.
func (e *Event) Err(err error) *Event {
if e == nil {
return e
}
if err != nil {
e.buf = enc.AppendError(enc.AppendKey(e.buf, ErrorFieldName), err)
}
return e
return e.AnErr(ErrorFieldName, err)
}
// Bool adds the field key with val as a bool to the *Event context.

40
fields.go
View File

@ -29,9 +29,45 @@ func appendFields(dst []byte, fields map[string]interface{}) []byte {
case []byte:
dst = enc.AppendBytes(dst, val)
case error:
dst = enc.AppendError(dst, val)
marshaled := ErrorMarshalFunc(val)
switch m := marshaled.(type) {
case LogObjectMarshaler:
e := newEvent(nil, 0)
e.buf = e.buf[:0]
e.appendObject(m)
dst = append(dst, e.buf...)
eventPool.Put(e)
case error:
dst = enc.AppendString(dst, m.Error())
case string:
dst = enc.AppendString(dst, m)
default:
dst = enc.AppendInterface(dst, m)
}
case []error:
dst = enc.AppendErrors(dst, val)
dst = enc.AppendArrayStart(dst)
for i, err := range val {
marshaled := ErrorMarshalFunc(err)
switch m := marshaled.(type) {
case LogObjectMarshaler:
e := newEvent(nil, 0)
e.buf = e.buf[:0]
e.appendObject(m)
dst = append(dst, e.buf...)
eventPool.Put(e)
case error:
dst = enc.AppendString(dst, m.Error())
case string:
dst = enc.AppendString(dst, m)
default:
dst = enc.AppendInterface(dst, m)
}
if i < (len(val) - 1) {
enc.AppendArrayDelim(dst)
}
}
dst = enc.AppendArrayEnd(dst)
case bool:
dst = enc.AppendBool(dst, val)
case int:

36
internal/cbor/base.go
View File

@ -8,38 +8,4 @@ func (e Encoder) AppendKey(dst []byte, key string) []byte {
dst = e.AppendBeginMarker(dst)
}
return e.AppendString(dst, key)
}
// AppendError adds the Error to the log message if error is NOT nil
func (e Encoder) AppendError(dst []byte, err error) []byte {
if err == nil {
return append(dst, `null`...)
}
return e.AppendString(dst, err.Error())
}
// AppendErrors when given an array of errors,
// adds them to the log message if a specific error is nil, then
// Nil is added, or else the error string is added.
func (e Encoder) AppendErrors(dst []byte, errs []error) []byte {
if len(errs) == 0 {
return e.AppendArrayEnd(e.AppendArrayStart(dst))
}
dst = e.AppendArrayStart(dst)
if errs[0] != nil {
dst = e.AppendString(dst, errs[0].Error())
} else {
dst = e.AppendNil(dst)
}
if len(errs) > 1 {
for _, err := range errs[1:] {
if err == nil {
dst = e.AppendNil(dst)
continue
}
dst = e.AppendString(dst, err.Error())
}
}
dst = e.AppendArrayEnd(dst)
return dst
}
}

36
internal/json/base.go
View File

@ -9,38 +9,4 @@ func (e Encoder) AppendKey(dst []byte, key string) []byte {
}
dst = e.AppendString(dst, key)
return append(dst, ':')
}
// AppendError encodes the error string to json and appends
// the encoded string to the input byte slice.
func (e Encoder) AppendError(dst []byte, err error) []byte {
if err == nil {
return append(dst, `null`...)
}
return e.AppendString(dst, err.Error())
}
// AppendErrors encodes the error strings to json and
// appends the encoded string list to the input byte slice.
func (e Encoder) AppendErrors(dst []byte, errs []error) []byte {
if len(errs) == 0 {
return append(dst, '[', ']')
}
dst = append(dst, '[')
if errs[0] != nil {
dst = e.AppendString(dst, errs[0].Error())
} else {
dst = append(dst, "null"...)
}
if len(errs) > 1 {
for _, err := range errs[1:] {
if err == nil {
dst = append(dst, ",null"...)
continue
}
dst = e.AppendString(append(dst, ','), err.Error())
}
}
dst = append(dst, ']')
return dst
}
}

58
log_test.go
View File

@ -521,3 +521,61 @@ func TestOutputWithTimestamp(t *testing.T) {
t.Errorf("invalid log output:\ngot: %v\nwant: %v", got, want)
}
}
type loggableError struct {
error
}
func (l loggableError) MarshalZerologObject(e *Event) {
e.Str("message", l.error.Error() + ": loggableError")
}
func TestErrorMarshalFunc(t *testing.T) {
out := &bytes.Buffer{}
log := New(out)
// test default behaviour
log.Log().Err(errors.New("err")).Msg("msg")
if got, want := decodeIfBinaryToString(out.Bytes()), `{"error":"err","message":"msg"}`+"\n"; got != want {
t.Errorf("invalid log output:\ngot: %v\nwant: %v", got, want)
}
out.Reset()
log.Log().Err(loggableError{errors.New("err")}).Msg("msg")
if got, want := decodeIfBinaryToString(out.Bytes()), `{"error":{"message":"err: loggableError"},"message":"msg"}`+"\n"; got != want {
t.Errorf("invalid log output:\ngot: %v\nwant: %v", got, want)
}
out.Reset()
// test overriding the ErrorMarshalFunc
originalErrorMarshalFunc := ErrorMarshalFunc
defer func(){
ErrorMarshalFunc = originalErrorMarshalFunc
}()
ErrorMarshalFunc = func(err error) interface{} {
return err.Error() + ": marshaled string"
}
log.Log().Err(errors.New("err")).Msg("msg")
if got, want := decodeIfBinaryToString(out.Bytes()), `{"error":"err: marshaled string","message":"msg"}`+"\n"; got != want {
t.Errorf("invalid log output:\ngot: %v\nwant: %v", got, want)
}
out.Reset()
ErrorMarshalFunc = func(err error) interface{} {
return errors.New(err.Error() + ": new error")
}
log.Log().Err(errors.New("err")).Msg("msg")
if got, want := decodeIfBinaryToString(out.Bytes()), `{"error":"err: new error","message":"msg"}`+"\n"; got != want {
t.Errorf("invalid log output:\ngot: %v\nwant: %v", got, want)
}
out.Reset()
ErrorMarshalFunc = func(err error) interface{} {
return loggableError{err}
}
log.Log().Err(errors.New("err")).Msg("msg")
if got, want := decodeIfBinaryToString(out.Bytes()), `{"error":{"message":"err: loggableError"},"message":"msg"}`+"\n"; got != want {
t.Errorf("invalid log output:\ngot: %v\nwant: %v", got, want)
}
}