Fix json serialization of wrapper types

src/ocaml_protoc_plugin/serialize_json.ml

@@ -140,16 +140,16 @@ let%expect_test "timestamp_to_json" =
 let wrapper_to_json json = get_key ~f:(fun id -> id) ~default:`Null "value" json
 
 (* Convert already emitted json based on json mappings *)
-let map_json: type a. (module Message with type t = a) -> Yojson.Basic.t -> Yojson.Basic.t = fun (module Message) ->
+let map_json: type a. (module Message with type t = a) -> (Yojson.Basic.t -> Yojson.Basic.t) option = fun (module Message) ->
   match Message.name' () |> String.split_on_char ~sep:'.' with
   | [_; "google"; "protobuf"; "Empty"]  ->
-    fun json -> json
+    Some (fun json -> json)
   (* Duration - google/protobuf/timestamp.proto *)
   | [_; "google"; "protobuf"; "Duration"] ->
-    duration_to_json
+    Some (duration_to_json)
   (* Timestamp - google/protobuf/timestamp.proto *)
   | [_; "google"; "protobuf"; "Timestamp"] ->
-    timestamp_to_json
+    Some (timestamp_to_json)
   (* Wrapper types - google/protobuf/wrappers.proto *)
   | [_; "google"; "protobuf"; "DoubleValue"]
   | [_; "google"; "protobuf"; "FloatValue"]
@@ -160,17 +160,17 @@ let map_json: type a. (module Message with type t = a) -> Yojson.Basic.t -> Yojs
   | [_; "google"; "protobuf"; "BoolValue"]
   | [_; "google"; "protobuf"; "StringValue"]
   | [_; "google"; "protobuf"; "BytesValue"] ->
-    wrapper_to_json
+    Some (wrapper_to_json)
   | [_; "google"; "protobuf"; "Value"] ->
     let map = function
       | `Assoc [_, json] -> json
       | json -> value_error "google.protobuf.Value" json
     in
-    map
+    Some map
   (* FieldMask - /usr/include/google/protobuf/field_mask.proto *)
   | [_; "google"; "protobuf"; "FieldMask"] ->
     let open StdLabels in
-    let convert = function
+    let map = function
       | `Assoc ["masks", `List masks] ->
         List.map ~f:(function
           | `String mask -> (to_camel_case mask)
@@ -180,8 +180,8 @@ let map_json: type a. (module Message with type t = a) -> Yojson.Basic.t -> Yojs
         |> fun mask -> `String mask
       | json -> value_error "google.protobuf.FieldMask" json
     in
-    convert
-  | _ -> fun json -> json
+    Some map
+  | _ -> None
 
 let rec json_of_spec: type a b. enum_names:bool -> json_names:bool -> omit_default_values:bool -> (a, b) spec -> a -> Yojson.Basic.t =
   fun ~enum_names ~json_names ~omit_default_values -> function
@@ -221,7 +221,12 @@ let rec json_of_spec: type a b. enum_names:bool -> json_names:bool -> omit_defau
       | false -> enum_value ~f:Enum.to_int
     end
   | Message (module Message) ->
-    fun v -> Message.to_json ~enum_names ~json_names ~omit_default_values v |> map_json (module Message)
+    let omit_default_values, map =
+      match map_json (module Message) with
+      | Some map -> false, map
+      | None -> omit_default_values, (fun json -> json)
+    in
+    fun v -> Message.to_json ~enum_names ~json_names ~omit_default_values v |> map
 
 and write: type a b. enum_names:bool -> json_names:bool -> omit_default_values:bool -> (a, b) compound -> a -> field list =
   fun ~enum_names ~json_names ~omit_default_values -> function

test/json_encoding.proto

@@ -2,11 +2,41 @@ syntax = "proto3";
 
 import "google/protobuf/duration.proto";
 import "google/protobuf/timestamp.proto";
+import "google/protobuf/empty.proto";
+import "google/protobuf/struct.proto";
+import "google/protobuf/any.proto";
+import "google/protobuf/wrappers.proto";
 
+package Json_test;
 message Duration {
   google.protobuf.Duration duration = 1;
 }
 
 message Timestamp {
   google.protobuf.Timestamp timestamp = 1;
 }
+
+message Empty {
+  google.protobuf.Empty empty = 1;
+}
+
+message Value {
+  google.protobuf.Struct struct = 1;
+}
+
+message Any {
+  google.protobuf.Any any = 1;
+}
+
+// Wrappers
+message Wrappers {
+  google.protobuf.DoubleValue double = 1;
+  google.protobuf.FloatValue float = 2;
+  google.protobuf.Int64Value s64 = 3;
+  google.protobuf.UInt64Value u64 = 4;
+  google.protobuf.Int32Value s32 = 5;
+  google.protobuf.UInt32Value u32 = 6;
+  google.protobuf.BoolValue bool = 7;
+  google.protobuf.StringValue string = 8;
+  google.protobuf.BytesValue bytes = 9;
+}

test/json_encoding_test.ml

@@ -1,4 +1,4 @@
-open Json_encoding
+open Json_encoding.Json_test
 module G = Google_types_pp
 
 let%expect_test _ =
@@ -60,3 +60,117 @@ let%expect_test _ =
     }
     Json: { "timestamp": "1970-01-01T00:00:00.000000005Z" }
     Ref:  { "timestamp": "1970-01-01T00:00:00.000000005Z" } |}]
+
+let%expect_test _ =
+  let module T = Empty in
+  let module I = G.Empty.Google.Protobuf.Empty in
+  Some (I.make ()) |> Test_lib.test_encode ~debug_json:true (module T);
+  ();
+  [%expect {|
+    empty {
+    }
+    Json: { "empty": {} }
+    Ref:  { "empty": {} } |}]
+
+
+let%expect_test _ =
+  let module T = Wrappers in
+  T.make () |> Test_lib.test_encode ~debug_json:true (module T);
+  let bytes = Bytes.of_string "bytes" in
+  T.make ~double:0.0 ~float:0.0 ~s64:0 ~u64:0 ~s32:0 ~u32:0 ~string:"" ~bytes:Bytes.empty ~bool:false ()
+  |> Test_lib.test_encode ~debug_json:true (module T);
+  T.make ~double:5.5 ~float:5.5 ~s64:5 ~u64:5 ~s32:5 ~u32:5 ~string:"str" ~bytes ~bool:true ()
+  |> Test_lib.test_encode ~debug_json:true (module T);
+  ();
+  [%expect {|
+    Json: {}
+    Ref:  {}
+    double {
+    }
+    float {
+    }
+    s64 {
+    }
+    u64 {
+    }
+    s32 {
+    }
+    u32 {
+    }
+    bool {
+    }
+    string {
+    }
+    bytes {
+    }
+    Json: {
+      "double": 0,
+      "float": 0,
+      "s64": "0",
+      "u64": "0",
+      "s32": 0,
+      "u32": 0,
+      "bool": false,
+      "string": "",
+      "bytes": ""
+    }
+    Ref:  {
+      "double": 0,
+      "float": 0,
+      "s64": "0",
+      "u64": "0",
+      "s32": 0,
+      "u32": 0,
+      "bool": false,
+      "string": "",
+      "bytes": ""
+    }
+    double {
+      value: 5.5
+    }
+    float {
+      value: 5.5
+    }
+    s64 {
+      value: 5
+    }
+    u64 {
+      value: 5
+    }
+    s32 {
+      value: 5
+    }
+    u32 {
+      value: 5
+    }
+    bool {
+      value: true
+    }
+    string {
+      value: "str"
+    }
+    bytes {
+      value: "bytes"
+    }
+    Json: {
+      "double": 5.5,
+      "float": 5.5,
+      "s64": "5",
+      "u64": "5",
+      "s32": 5,
+      "u32": 5,
+      "bool": true,
+      "string": "str",
+      "bytes": "Ynl0ZXM="
+    }
+    Ref:  {
+      "double": 5.5,
+      "float": 5.5,
+      "s64": "5",
+      "u64": "5",
+      "s32": 5,
+      "u32": 5,
+      "bool": true,
+      "string": "str",
+      "bytes": "Ynl0ZXM="
+    } |}]