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support custom JSON (de)serialization by delegating to message if it implements json.Marshaler/json.Unmarshaler #325

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Merged
merged 4 commits into from
May 22, 2017
Merged

support custom JSON (de)serialization by delegating to message if it implements json.Marshaler/json.Unmarshaler #325

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e7d161e
support custom JSON (de)serialization by delegating to message if it …
jhump Mar 31, 2017
e8c65fd
use custom marshal/unmarshal interfaces that can preserve marshaler/u…
jhump May 22, 2017
cbc0d77
add tests; move JSONPBUnmarshaler check into unmarshalValue
jhump May 22, 2017
a26be53
address nits
jhump May 22, 2017
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28 changes: 28 additions & 0 deletions jsonpb/jsonpb.go
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Original file line number Diff line number Diff line change
Expand Up @@ -74,6 +74,22 @@ type Marshaler struct {
OrigName bool
}

// JSONPBMarshaler is implemented by protobuf messages that customize the
// way they are marshaled to JSON. Messages that implement this should
// also implement JSONPBUnmarshaler so that the custom format can be
// parsed.
type JSONPBMarshaler interface {
MarshalJSONPB(*Marshaler) ([]byte, error)
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@cybrcodr, I wasn't sure if this struct could ever become stateful, so I have it passed by ref. Should this instead be pass-by-value? I know it currently just represents marshaling options; but it seemed like, from the name, it could at some point change to such that a pointer is the correct way to pass it.

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(same goes for passing Unmarshaler by pointer in the other interface)

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Pass by ref sounds good.

}

// JSONPBUnmarshaler is implemented by protobuf messages that customize
// the way they are unmarshaled from JSON. Messages that implement this
// should also implement JSONPBMarshaler so that the custom format can be
// produced.
type JSONPBUnmarshaler interface {
UnmarshalJSONPB(*Unmarshaler, []byte) error
}

// Marshal marshals a protocol buffer into JSON.
func (m *Marshaler) Marshal(out io.Writer, pb proto.Message) error {
writer := &errWriter{writer: out}
Expand Down Expand Up @@ -102,6 +118,15 @@ type wkt interface {

// marshalObject writes a struct to the Writer.
func (m *Marshaler) marshalObject(out *errWriter, v proto.Message, indent, typeURL string) error {
if jsm, ok := v.(JSONPBMarshaler); ok {
b, err := jsm.MarshalJSONPB(m)
if err != nil {
return err
}
out.write(string(b))
return out.err
}

s := reflect.ValueOf(v).Elem()

// Handle well-known types.
Expand Down Expand Up @@ -528,6 +553,9 @@ func (u *Unmarshaler) UnmarshalNext(dec *json.Decoder, pb proto.Message) error {
if err := dec.Decode(&inputValue); err != nil {
return err
}
if jsu, ok := pb.(JSONPBUnmarshaler); ok {
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How about moving this inside unmarshalValue instead? And I think it may need to be after block that allocates memory for pointer fields, i.e. 597-600.

You can do type assertion using ...
if jsu, ok := target.Addr().Interface().(JSONPBUnmarshaler); ok { ... }

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Good catch

return jsu.UnmarshalJSONPB(u, []byte(inputValue))
}
return u.unmarshalValue(reflect.ValueOf(pb).Elem(), inputValue, nil)
}

Expand Down