JSInterop: Consider JSType.Json for conveniently marshaling data

[lambdageek]

consider some code like this:

public record Todo(int id, int userId, string title, bool completed);

public class SampleApp {
  public static async Task<Todo[]> GetTodos() { ... }
}

Right now to make use of something like that from JavaScript, we have to write some boilerplate:

public class SampleApp {
  [JSExport]
  public static Task<string> GetTodosExportWrapper() => JsonSerializer.SerializeAsync (await GetTodos());
}

   // in main.js
   const exports = await getAssemblyExports(...);
   const json = JSON.parse (await exports.SampleApp.GetTodosExportWrapper());

It would be nice if we had a convenience marshaler for moving Json blobs around:

  [JSExport]
  [return:JSMarshalAs<JSType.Promise<JSType.Json>>]
  public static Task<Todo[]> GetTodos() { ... }

  // in main.js
  const exports = await getAssemblyExports(...);
  const json = await exports.SampleApp.GetTodos ();

[ghost]

Tagging subscribers to this area: @dotnet/area-system-text-json, @gregsdennis See info in area-owners.md if you want to be subscribed.

Issue Details

---

consider some code like this: ```csharp public record Todo(int id, int userId, string title, bool completed); public static async Task GetTodos() { ... } ``` Right now to make use of something like that from JavaScript, we have to write some boilerplate: ```csharp public class SampleApp { [JSExport] public static Task GetTodosExportWrapper() => JsonSerializer.SerializeAsync (await GetTodos()); } ``` ```js // in main.js const exports = await getAssemblyExports(...); const json = JSON.parse (await exports.SampleApp.GetTodosExportWrapper()); ``` It would be nice if we had a convenience marshaler for moving Json blobs around: ```csharp [JSExport] [return:JSMarshalAs>] public static Task GetTodos() { ... } ``` ```js // in main.js const exports = await getAssemblyExports(...); const json = await exports.SampleApp.GetTodos (); ```

Author:	lambdageek
Assignees:	-
Labels:	`area-System.Text.Json`
Milestone:	-

[lambdageek]

/cc @pavelsavara

[ghost]

Tagging subscribers to 'arch-wasm': @lewing See info in area-owners.md if you want to be subscribed.

Issue Details

---

consider some code like this: ```csharp public record Todo(int id, int userId, string title, bool completed); public class SampleApp { public static async Task GetTodos() { ... } } ``` Right now to make use of something like that from JavaScript, we have to write some boilerplate: ```csharp public class SampleApp { [JSExport] public static Task GetTodosExportWrapper() => JsonSerializer.SerializeAsync (await GetTodos()); } ``` ```js // in main.js const exports = await getAssemblyExports(...); const json = JSON.parse (await exports.SampleApp.GetTodosExportWrapper()); ``` It would be nice if we had a convenience marshaler for moving Json blobs around: ```csharp [JSExport] [return:JSMarshalAs>] public static Task GetTodos() { ... } ``` ```js // in main.js const exports = await getAssemblyExports(...); const json = await exports.SampleApp.GetTodos (); ```

Author:	lambdageek
Assignees:	-
Labels:	`api-suggestion`, `arch-wasm`, `area-System.Runtime.InteropServices.JavaScript`
Milestone:	Future

[gregsdennis]

Why not use STJ? Maybe I don't understand the use case.

[FranklinWhale]

Not sure how this will work with <RunAOTCompilation>true</RunAOTCompilation>. Currently, to make AOT work, I have to create a JsonSerializerContext. Otherwise, the following warning appears:

Using member System.Text.Json.JsonSerializer.Serialize<TValue>(TValue, JsonSerializerOptions) which has RequiresUnreferencedCodeAttribute can break functionality when trimming application code. JSON serialization and deserialization might require types that cannot be statically analyzed. Use the overload that takes a JsonTypeInfo or JsonSerializerContext, or make sure all of the required types are preserved.

[pavelsavara]

Yes, we already have json trimming issue on Blazor https://github.com/dotnet/aspnetcore/issues/39839

Since we have code generator here, we could generate

[JsonSerializable(typeof(List<Item>))]
private partial class ItemListSerializerContext : JsonSerializerContext { }