feat: add default to deriving

derive/attributes.ml

@@ -1,3 +1,5 @@
+open Ppxlib
+
 type type_attributes = {
   rename : string;
   mode :
@@ -26,7 +28,7 @@ type variant_attributes = {
 
 type field_attributes = {
   name : string;
-  default : string option;
+  presence : [ `required | `optional | `with_default of Parsetree.expression ];
   should_skip :
     [ `skip_serializing_if of string
     | `skip_deserializing_if of string
@@ -37,8 +39,13 @@ type field_attributes = {
 let of_field_attributes lbl =
   let open Ppxlib in
   let name = ref lbl.pld_name.txt in
-  let default = ref None in
   let should_skip = ref `never in
+  let presence =
+    ref
+      (match lbl.pld_type.ptyp_desc with
+      | Ptyp_constr ({ txt = Lident "option"; _ }, _) -> `optional
+      | _ -> `required)
+  in
   let () =
     match lbl.pld_attributes with
     | [
@@ -63,9 +70,12 @@ let of_field_attributes lbl =
                 { pexp_desc = Pexp_constant (Pconst_string (s, _, _)); _ } ) ->
                 name := s;
                 ()
+            | { txt = Lident "default"; _ }, expr ->
+                presence := `with_default expr;
+                ()
             | _ -> ())
           fields
     | _ -> ()
   in
 
-  (lbl, { name = !name; default = !default; should_skip = !should_skip })
+  (lbl, { name = !name; presence = !presence; should_skip = !should_skip })

derive/de.ml

@@ -138,7 +138,6 @@ module Record_deserializer = struct
   let deserialize_with_unordered_fields ~ctxt labels final_expr =
     let loc = loc ~ctxt in
     let labels = List.rev labels in
-    (* [@serde { rename = "type" }] *)
     let labels = List.map Attributes.of_field_attributes labels in
 
     (* NOTE(@leostera): Generate the final assembling of the record value
@@ -198,11 +197,27 @@ module Record_deserializer = struct
                  Attributes.(attr.name)
                  field.pld_name.txt)
           in
-          [%expr
-            let* [%p field_pat] =
-              Option.to_result ~none:(`Msg [%e missing_msg]) ![%e field_var]
-            in
-            [%e last]])
+          match Attributes.(attr.presence) with
+          | `required ->
+              [%expr
+                let* [%p field_pat] =
+                  Option.to_result ~none:(`Msg [%e missing_msg]) ![%e field_var]
+                in
+                [%e last]]
+          | `optional ->
+              [%expr
+                let [%p field_pat] =
+                  match ![%e field_var] with Some opt -> opt | None -> None
+                in
+                [%e last]]
+          | `with_default str ->
+              [%expr
+                let [%p field_pat] =
+                  match ![%e field_var] with
+                  | Some opt -> opt
+                  | None -> [%e str]
+                in
+                [%e last]])
         body labels
     in
 

derive/ppx.t/run.t

@@ -289,11 +289,8 @@
                               "missing field \"updated_at\" (\"updated_at\")")
                      (!updated_at)
                   in
-                 let* credits =
-                   Option.to_result
-                     ~none:(`Msg "missing field \"credits\" (\"credits\")")
-                     (!credits)
-                  in
+                 let credits =
+                   match !credits with | Some opt -> opt | None -> None in
                  let* keywords =
                    Option.to_result
                      ~none:(`Msg "missing field \"keywords\" (\"keywords\")")

serde_json/serde_json_test.ml

@@ -1,5 +1,4 @@
 open Serde
-open Serde_json
 
 let keyword fmt = Spices.(default |> fg (color "#00FF00") |> build) fmt
 let error fmt = Spices.(default |> fg (color "#FF0000") |> build) fmt
@@ -488,4 +487,35 @@ let _serde_json_roundtrip_tests =
 
   test "record_with_key_rename" pp_with_type_field serialize_with_type_field
     deserialize_with_type_field { type_ = "hello" } {|{type="hello"}|};
+
+  ()
+
+type hello = { hello : string; count : int option }
+[@@deriving serialize, deserialize]
+
+let _serde_json_parse_test_no_key =
+  let str = {| {"hello":"world"} |} in
+  let parsed = Serde_json.of_string deserialize_hello str in
+  match parsed with
+  | Ok _ ->
+      Format.printf "serde_json.ser/de test %S %s\r\n%!" "parsed with no key"
+        (keyword "OK")
+  | Error _ ->
+      Format.printf "serde_json.ser/de test %S %s\r\n%!" "parsed with no key"
+        (error "Failed!");
+      assert false
+
+type with_default = {
+  greeting : string;
+  count_with_default : int; [@serde { default = 5 }]
+}
+[@@deriving serialize, deserialize]
+
+let _serde_json_parse_test_with_default =
+  let str = {| {"greeting":"yoyo"} |} in
+  let parsed = Serde_json.of_string deserialize_with_default str in
+  let parsed = Result.get_ok parsed in
+  assert (parsed.count_with_default = 5);
+  Format.printf "serde_json.ser/de test %S %s\r\n%!" "parsed with default"
+    (keyword "OK");
   ()