every route has to be redeclared with the options method to pass the CORS

[arnaudelub]

Hey, first of all thanks for this plugin
Is this behavior expected?
Is there anyway to add this feature like for python's Flask CORS:

In the simplest case, initialize the Flask-Cors extension with default arguments in order to allow CORS for all domains on all routes.

for instance?

[lenniezelk]

Kindly provide more info on what you are trying to achieve

[arnaudelub]

sure, for instance, if you run this code:

import 'dart:io';

import 'package:shelf/shelf.dart';
import 'package:shelf/shelf_io.dart';
import 'package:shelf_router/shelf_router.dart';
import 'package:shelf_cors_headers/shelf_cors_headers.dart';

// Configure routes.
final _router = Router()
  ..get('/', _rootHandler)
  ..get('/echo/<message>', _echoHandler);

Response _rootHandler(Request req) {
  return Response.ok('Hello, World!\n');
}

Response _echoHandler(Request request) {
  final message = request.params['message'];
  return Response.ok('$message\n');
}

void main(List<String> args) async {
  // Use any available host or container IP (usually `0.0.0.0`).
  final ip = InternetAddress.anyIPv4;

  // Configure a pipeline that logs requests.
  final handler = Pipeline()
      .addMiddleware(corsHeaders())
      .addMiddleware(logRequests())
      .addHandler(_router);

  // For running in containers, we respect the PORT environment variable.
  final port = int.parse(Platform.environment['PORT'] ?? '8080');
  final server = await serve(handler, ip, port);
  print('Server listening on port ${server.port}');
}

Then when the browser is trying to call the OPTIONS on the given route, a route not found will be returned.
The be able to make the CORS pass, you have to add into your router:

  ..options('/', _rootHandler)
  ..options('/echo/<message>', _echoHandler);

So that can each routes in your router pass the CORS.

It's not an issue, i was just wondering if it's possible for this middleware to behave like CORS in python's FLASK

[lenniezelk]

I think raise this with the shelf router team, this seems like a routing issue

[SittiphanSittisak]

Any update?
How do I solve the preflight at this moment?
@arnaudelub I follow you with

  ..options('/echo/<message>', _echoHandler);

But it doesn't work the post request doesn't happen.

[arnaudelub]

If you want any help, you will probably have to give more info, code sample, logs, d'art and plugin version, etc....

[SittiphanSittisak]

When the Flutter app tried to connect the dart server with the POST method, it will send a request with the OPTIONS method to the dart server and I need a solution to handle this request.
I fix it by using

final _router = shelf_router.Router()
  //other route
  ..all('/<ignored|.*>', (Request request) {
    if (request.method == 'OPTIONS') return Response.ok(null, headers: myHeader);
    return Response.internalServerError();
  });