[BUG] ResponseFilter does not serialize

[ktalebian]

Describe the bug

I use Generics and CollectionOf for a pagination response type. This is working perfectly, and everything is serialized without an issue.

For a particular use case, I decided to use https://tsed.io/docs/response-filter.html - this filter is to conditionally modify certain response objects. The response type is not changing in the modification - just some of the parameters are modified:

@ResponseFilter('application/json')
export class PaginationResponseFilter implements ResponseFilterMethods {
    transform(data: unknown, $ctx: Context) {
        if (!($ctx.data instanceof Page)) {
          return data;
        }
    
        if ($ctx.event.request.url) {
            $ctx.response.status(206);
            return $ctx.data.toResponse($ctx.event.request.url);
        }
    
        return data;
    }
}

Where toResposne object would modify some fields, and ultimately return another Page:

public toResponse(url: string): Page<T> {
    // ultimately return a new version of Page
    return new Page(this.list, this.metadata);
  }

Without response filter, I get the following response:

❯ curl localhost:8083/hosts | jq .
{
  "list": [
    {
      "id": "0396b829-5414-4519-9387-c817e2915715",
      "name": "host1"
    },
    {
      "id": "deed0453-6146-4a96-a4d9-a0c468b6e005",
      "name": "host2"
    }
  ],...
}

With the response filter, I get:

❯ curl localhost:8083/hosts | jq .
{
  "list": [
    {
      "id": {
        "value": "0396b829-5414-4519-9387-c817e2915715"
      },
      "name": "host1"
    },
    {
      "id": {
        "value": "deed0453-6146-4a96-a4d9-a0c468b6e005"
      },
      "name": "host2"
    }
  ],...
}

Note how the id field is {"value": "..."} vs being the actual value.

Here is a repo you can run: https://github.com/ktalebian/tsed-bug

To Reproduce

Clone https://github.com/ktalebian/tsed-bug and run

Expected behavior

I expect both responses to be identical

Code snippets

No response

Repository URL example

https://github.com/ktalebian/tsed-bug

OS

macOs

Node version

Node v18

Library version

v7.53.0

Additional context

No response

[Romakita]

ok, the serialization is run before the response filter.

  async flush($ctx: PlatformContext) {
    const {response} = $ctx;

    if (!$ctx.isDone()) {
      let data = await this.responseFilter.serialize($ctx.data, $ctx as any);
      data = await this.responseFilter.transform(data, $ctx as any);
      response.body(data);
    }
  }

https://github.com/tsedio/tsed/blob/production/packages/platform/common/src/services/PlatformHandler.ts

your code is wrong because it work on the $ctx.data and not over the data itself. it's not a bug you choose to work on the $ctx.data.

I should even make a fix to prevent you from using $ctx.data, as the devs don't do bad implementations in the response filter ^^.

Two solution:

1. make transformation over data, just use $ctx.data to dermine if it's a Page instance, but apply url on data
2. Inject PlatformResponseFilter and call serialize method, but, it's much less efficient to do that.

I close this issue
See you

[github-actions]

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[Romakita]

I'll update the pagination to clarify this issue ;)

[Romakita]

#2556