From 012e80c42199d642c492a271b6bc75f581df8661 Mon Sep 17 00:00:00 2001
From: marusama <maru.sama@gmail.com>
Date: Wed, 4 Apr 2018 17:57:46 +0300
Subject: [PATCH 1/2] emit null value for oneof field with 'nil-interface'
 value.

example proto:
message test {
    oneof roadIdNil {
        int32 roadId = 12;
    }
}

go code:
```
var roadId *proto.Test_RoadIdNil
test.RoadIdNil = roadId
```
will produce json:
{
    "roadId": null
}
instead of panic
---
 jsonpb/jsonpb.go | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/jsonpb/jsonpb.go b/jsonpb/jsonpb.go
index ff368f33c5..32d363aa31 100644
--- a/jsonpb/jsonpb.go
+++ b/jsonpb/jsonpb.go
@@ -316,9 +316,15 @@ func (m *Marshaler) marshalObject(out *errWriter, v proto.Message, indent, typeU
 		// Oneof fields need special handling.
 		if valueField.Tag.Get("protobuf_oneof") != "" {
 			// value is an interface containing &T{real_value}.
-			sv := value.Elem().Elem() // interface -> *T -> T
-			value = sv.Field(0)
-			valueField = sv.Type().Field(0)
+			svPtr := value.Elem() // interface -> *T
+			if !svPtr.IsNil() {
+				sv := svPtr.Elem() // *T -> T
+				value = sv.Field(0)
+				valueField = sv.Type().Field(0)
+			} else {
+				value = reflect.ValueOf(nil)
+				valueField = svPtr.Type().Elem().Field(0)
+			}
 		}
 		prop := jsonProperties(valueField, m.OrigName)
 		if !firstField {

From 04e8c554184b10aa819c107eeb26b48cd76f5ad2 Mon Sep 17 00:00:00 2001
From: marusama <maru.sama@gmail.com>
Date: Thu, 5 Apr 2018 19:30:21 +0300
Subject: [PATCH 2/2] make nil-interface value for field: null

---
 jsonpb/jsonpb.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/jsonpb/jsonpb.go b/jsonpb/jsonpb.go
index 32d363aa31..5df6db1fc8 100644
--- a/jsonpb/jsonpb.go
+++ b/jsonpb/jsonpb.go
@@ -940,6 +940,13 @@ func (u *Unmarshaler) unmarshalValue(target reflect.Value, inputValue json.RawMe
 				if !ok {
 					continue
 				}
+
+				if string(raw) == "null" {
+					nv := reflect.New(reflect.PtrTo(oop.Type.Elem()))
+					target.Field(oop.Field).Set(nv.Elem())
+					continue
+				}
+
 				nv := reflect.New(oop.Type.Elem())
 				target.Field(oop.Field).Set(nv)
 				if err := u.unmarshalValue(nv.Elem().Field(0), raw, oop.Prop); err != nil {