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Merged
merged 2 commits into from
Dec 10, 2019
Merged

Add reflection encoder for lists #67

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b1f97d8
Add reflection encoder for lists
nhooyr Dec 10, 2019
1dec25a
Document encoding
nhooyr Dec 10, 2019
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43 changes: 35 additions & 8 deletions map.go
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Original file line number Diff line number Diff line change
Expand Up @@ -13,13 +13,29 @@ import (
// Map represents an ordered map of fields.
type Map []Field

// SlogValue implements Value.
func (m Map) SlogValue() interface{} {
return ForceJSON(m)
}

var _ json.Marshaler = Map(nil)

// MarshalJSON implements json.Marshaler.
//
// It is guaranteed to return a nil error.
// Any error marshalling a field will
// become the field's value.
// Any error marshalling a field will become the field's value.
//
// Every field value is encoded with the following process:
//
// 1. slog.Value is handled to allow any type to replace its representation for logging.
//
// 2. xerrors.Formatter is handled.
//
// 3. error and fmt.Stringer are handled.
//
// 4. slices and arrays are handled to go through the encode function for every value.
//
// 5. json.Marshal is invoked as the default case.
func (m Map) MarshalJSON() ([]byte, error) {
b := &bytes.Buffer{}
b.WriteByte('{')
Expand Down Expand Up @@ -55,14 +71,14 @@ func (v jsonVal) MarshalJSON() ([]byte, error) {
return json.Marshal(v.v)
}

func marshalArray(a []interface{}) []byte {
func marshalList(rv reflect.Value) []byte {
b := &bytes.Buffer{}
b.WriteByte('[')
for i, v := range a {
for i := 0; i < rv.Len(); i++ {
b.WriteByte('\n')
b.Write(encode(v))
b.Write(encode(rv.Index(i).Interface()))

if i < len(a)-1 {
if i < rv.Len()-1 {
b.WriteByte(',')
}
}
Expand All @@ -75,13 +91,24 @@ func encode(v interface{}) []byte {
switch v := v.(type) {
case Value:
return encode(v.SlogValue())
case []interface{}:
return marshalArray(v)
case xerrors.Formatter:
return encode(errorChain(v))
case error, fmt.Stringer:
return encode(fmt.Sprint(v))
default:
rv := reflect.Indirect(reflect.ValueOf(v))
if rv.IsValid() {
switch rv.Type().Kind() {
case reflect.Slice:
if rv.IsNil() {
break
}
fallthrough
case reflect.Array:
return marshalList(rv)
}
}

b, err := json.Marshal(v)
if err != nil {
return encode(M(
Expand Down
12 changes: 11 additions & 1 deletion map_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -93,7 +93,7 @@ func TestMap(t *testing.T) {
{
"msg": "failed to marshal to JSON",
"fun": "cdr.dev/slog.encode",
"loc": "`+mapTestFile+`:88"
"loc": "`+mapTestFile+`:115"
},
"json: unsupported type: func(*testing.T, string) string"
],
Expand Down Expand Up @@ -164,6 +164,16 @@ func TestMap(t *testing.T) {
"error": "xdxd"
}`)
})

t.Run("nilSlice", func(t *testing.T) {
t.Parallel()

test(t, slog.M(
slog.F("slice", []string(nil)),
), `{
"slice": null
}`)
})
}

type meow struct {
Expand Down