Is it possible to support Optional<string>

[CRC32EX]

Server code

// DB Model
class User
{
  public uint Id { get; set; }
  public string? StatusMessage { get; set; } // nullable
}

// HTTP Model
[TranspilationSource]
class UpdateUserRequest 
{
  public int UserId { get; set; }
  [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
  public Optional<string?> StatusMessage { get; set; }
}

// Controller
[HttpPatch]
public IActionResult UpdateUser(UpdateUserRequest request)
{
  var user = DB.FindUserById(request.UserId);

  // if status_message is provided, update it
  if (request.StatusMessage.HasValue) {
    user.StatusMessage = request.StatusMessage;
    DB.Update(user);
  }

  // if (request.Prefecture.HasValue) { /* ... */ }
  // if (request.FirstName.HasValue) { /* ... */ }
  // if (request.LastName.HasValue) { /* ... */ }
  // if (request.BirthDay.HasValue) { /* ... */ }
  // ...
}

HTTP Request example

PATCH /api/user HTTP/1.1
Content-Type: application/json

{ "user_id": 1, "status_message": "I'm fine" }

I want to know JSON string parameter is null or undefined.
For example,

Request	Update DB?
{ "user_id": 1, "status_message": "I'm fine" }	Yes. Value is I'm fine
{ "user_id": 1, "status_message": "" }	Yes. Value is ``
{ "user_id": 1, "status_message": null }	Yes. Value is null
{ "user_id": 1 }	No.

But, Tapper is not supported it.
Could you support it?
Or, do you have some other good ideas?

Ref:

• https://stackoverflow.com/a/71074603/4771485
• https://tnakamura.hatenablog.com/entry/2020/02/03/how-to-differentiate-between-null-and-non-existing-data-in-json-in-asp-net-core-mvc

[nenoNaninu]

The class Optional<T> does not exist in the standard library. It would help if you showed an implementation of Optional<T>.
I assume that Optional<T> is a type like System.Nullable<T>, but there are two challenges.

First, Tapper needs to support user-defined generics types. This feature could be done with time.

Second, you must implement a custom JsonConverter to get the desired JSON string. And since custom JsonConverter is highly flexible, it is difficult for Tapper to support it.

[CRC32EX]

Optional<T> implementation is here.

How about implement attribute, that force emit TypeScript type.
Like TranspilationSourceForceType.

Input

// UpdateUserRequest.cs
[TranspilationSource]
class UpdateUserRequest 
{
  public int UserId { get; set; }

  // [TranspilationSourceForceType(Type = TypeScriptType.String | TypeScriptType.Null | TypeScriptType.Undefined)]
  [TranspilationSourceForceType(TypeString = "(string | undefined)", Nullable = true)]
  [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
  public Optional<string?> StatusMessage { get; set; }
}

Output

// UpdateUserRequest.ts
/** Transpiled from UpdateUserRequest */
export type ConfigInfo = {
  /** Transpiled from uint */
  userId: number;
  /** Transpiled from unknown(Defined by user) */
  statusMessage?: (string | undefined);
}

[nenoNaninu]

It seems like a good idea.

[hahn-kev]

I would also like to be able to specify the explicit output type. I've got a struct that wraps a string, when serialized it's just turned into a string so I'd like to represent that in TS