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encoding/json: allow non-string type keys for (un-)marshal

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This CL allows JSON-encoding & -decoding maps whose keys are types that
implement encoding.TextMarshaler / TextUnmarshaler.

During encode, the map keys are marshaled upfront so that they can be
sorted.

Fixes #12146

Change-Id: I43809750a7ad82a3603662f095c7baf75fd172da
Reviewed-on: https://go-review.googlesource.com/20356
Run-TryBot: Caleb Spare <cespare@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Augusto Roman 2016-03-08 12:41:35 -08:00 • committed by Brad Fitzpatrick
parent acefcb732c
commit ffbd31e9f7
4 changed files with 124 additions and 41 deletions
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55
src/encoding/json/encode.go
View file

@ -116,8 +116,8 @@ import (
// an anonymous struct field in both current and earlier versions, give the field
// a JSON tag of "-".
//
// Map values encode as JSON objects.
// The map's key type must be string; the map keys are used as JSON object
// Map values encode as JSON objects. The map's key type must either be a string
// or implement encoding.TextMarshaler. The map keys are used as JSON object
// keys, subject to the UTF-8 coercion described for string values above.
//
// Pointer values encode as the value pointed to.
@ -611,21 +611,31 @@ func (me *mapEncoder) encode(e *encodeState, v reflect.Value, _ bool) {
return
}
e.WriteByte('{')
var sv stringValues = v.MapKeys()
sort.Sort(sv)
for i, k := range sv {
// Extract and sort the keys.
keys := v.MapKeys()
sv := make([]reflectWithString, len(keys))
for i, v := range keys {
sv[i].v = v
if err := sv[i].resolve(); err != nil {
e.error(&MarshalerError{v.Type(), err})
}
}
sort.Sort(byString(sv))
for i, kv := range sv {
if i > 0 {
e.WriteByte(',')
}
e.string(k.String())
e.string(kv.s)
e.WriteByte(':')
me.elemEnc(e, v.MapIndex(k), false)
me.elemEnc(e, v.MapIndex(kv.v), false)
}
e.WriteByte('}')
}
func newMapEncoder(t reflect.Type) encoderFunc {
if t.Key().Kind() != reflect.String {
if t.Key().Kind() != reflect.String && !t.Key().Implements(textMarshalerType) {
return unsupportedTypeEncoder
}
me := &mapEncoder{typeEncoder(t.Elem())}
@ -775,14 +785,29 @@ func typeByIndex(t reflect.Type, index []int) reflect.Type {
return t
}
// stringValues is a slice of reflect.Value holding *reflect.StringValue.
// It implements the methods to sort by string.
type stringValues []reflect.Value
type reflectWithString struct {
v reflect.Value
s string
}
func (sv stringValues) Len() int { return len(sv) }
func (sv stringValues) Swap(i, j int) { sv[i], sv[j] = sv[j], sv[i] }
func (sv stringValues) Less(i, j int) bool { return sv.get(i) < sv.get(j) }
func (sv stringValues) get(i int) string { return sv[i].String() }
func (w *reflectWithString) resolve() error {
if w.v.Kind() == reflect.String {
w.s = w.v.String()
return nil
}
buf, err := w.v.Interface().(encoding.TextMarshaler).MarshalText()
w.s = string(buf)
return err
}
// byString is a slice of reflectWithString where the reflect.Value is either
// a string or an encoding.TextMarshaler.
// It implements the methods to sort by string.
type byString []reflectWithString
func (sv byString) Len() int { return len(sv) }
func (sv byString) Swap(i, j int) { sv[i], sv[j] = sv[j], sv[i] }
func (sv byString) Less(i, j int) bool { return sv[i].s < sv[j].s }
// NOTE: keep in sync with stringBytes below.
func (e *encodeState) string(s string) int {