Fix wrapper extension JSON serialization (#821)

packages/protobuf-test/extra/extensions-proto2.proto

@@ -62,6 +62,7 @@ extend Proto2Extendee {
   repeated string repeated_string_ext = 7002;
   repeated uint32 packed_uint32_ext = 7003 [packed = true];
   repeated uint32 unpacked_uint32_ext = 7004; // unpacked by default in proto2
+  repeated uint64 repeated_uint64_ext_js_string = 7006 [jstype = JS_STRING];
 
   optional google.protobuf.UInt32Value wrapper_ext = 8001;
 

packages/protobuf-test/extra/extensions-proto3.proto

@@ -23,4 +23,10 @@ extend google.protobuf.FileOptions {
   optional uint32 optional_uint32_ext = 1002;
   repeated uint32 packed_uint32_ext = 7003;
   repeated uint32 unpacked_uint32_ext = 7004 [packed = false];
+  Proto3ExtMessage message_ext = 7005;
+}
+
+// A message used in extensions
+message Proto3ExtMessage {
+  string string_field = 1;
 }

packages/protobuf-test/src/extension-accessor.test.ts

@@ -44,6 +44,7 @@ import {
   repeated_enum_ext,
   repeated_message_ext,
   repeated_string_ext,
+  repeated_uint64_ext_js_string,
   repeatedgroupext,
   string_ext,
   string_ext_with_default,
@@ -99,6 +100,7 @@ const goldenValues: extensionWithValueCollection = [
   { ext: repeated_string_ext, val: ["a", "b", "c"] },
   { ext: packed_uint32_ext, val: [1, 2, 3] },
   { ext: unpacked_uint32_ext, val: [4, 5, 6] },
+  { ext: repeated_uint64_ext_js_string, val: ["1", "2", "3"] },
   { ext: wrapper_ext, val: 123 },
   { ext: groupext, val: create(GroupExtDesc, { a: 123 }) },
   {
@@ -130,6 +132,7 @@ const goldenValuesZero: extensionWithValueCollection = [
   { ext: repeated_string_ext, val: [] },
   { ext: packed_uint32_ext, val: [] },
   { ext: unpacked_uint32_ext, val: [] },
+  { ext: repeated_uint64_ext_js_string, val: [] },
   { ext: wrapper_ext, val: 0 },
   { ext: groupext, val: create(GroupExtDesc) },
   { ext: repeatedgroupext, val: [] },