"private method `raise' called for nil (NoMethodError)" error if stop Async HTTP server

[Watson1978]

I'm trying to launch an Async HTTP server like following:

  Async do |task|
    @server_task = task.async do
      @server.run
    end
  end

Then, I called stop method on a task created with task.async to stop the http server, like:

  def stop
    @server_task&.stop
  end

and, I got a NoMethodError error.
Is there something wrong with my code?
Please see Reproduction code and Result sections in below.

Environment

• Ruby 3.3.4
• async 2.16.1
• async-http 0.71.0

Reproduction code

require 'bundler/inline'
gemfile do
  source 'https://rubygems.org'
  gem 'async-http'
end

require 'net/http'
require 'async/http/protocol'
require 'timeout'

module HttpServer
  class Router
    def initialize
      @router = { get: {} }
    end

    def mount(method, path, app)
      @router[method][path] = app
    end

    def route!(method, path, request)
      @router.fetch(method).fetch(path).call(request)
    end
  end

  class Server
    class App
      def initialize(router)
        @router = router
      end

      def call(request)
        method = request.method
        resp = get(request)

        Protocol::HTTP::Response[*resp]
      rescue => e
        Protocol::HTTP::Response[500, { 'Content-Type' => 'text/plain' }, 'Internal Server Error']
      end

      def get(request)
        @router.route!(:get, request.path, request)
      end
    end

    def initialize(addr:, port:, tls_context: nil)
      @uri = URI("http://#{addr}:#{port}").to_s
      @router = Router.new
      @server_task = nil

      @server = Async::HTTP::Server.new(App.new(@router), Async::HTTP::Endpoint.parse(@uri))
    end

    def start
      Async do |task|
        @server_task = task.async do
          @server.run
        end
      end
    end

    def stop
      @server_task&.stop
    end

    def get(path, app = nil, &block)
      @router.mount(:get, path, app || block)
    end
  end
end


def http_server_start(addr:, port:)
  server = HttpServer::Server.new(addr: addr, port: port)
  server.get('/api/plugins.json') { |req| [200, { 'Content-Type' => 'text/html' }, "Hello"] }

  Thread.new do
    server.start
  end

  sleep 1 # Wait until the server starts up.

  server
end

#################################################

puts "[http server start]"
server = http_server_start(addr: "127.0.0.1", port: "8080")

server.stop

Result

$ ruby async-http.rb
[http server start]
/home/watson/.rbenv/versions/3.3.4/lib/ruby/gems/3.3.0/gems/async-2.16.1/lib/async/task.rb:288:in `stop': private method `raise' called for nil (NoMethodError)

                                                Fiber.scheduler.raise(@fiber, Stop)
                                                               ^^^^^^
        from /home/watson/.rbenv/versions/3.3.4/lib/ruby/gems/3.3.0/gems/async-2.16.1/lib/async/node.rb:291:in `block in stop_children'
        from /home/watson/.rbenv/versions/3.3.4/lib/ruby/gems/3.3.0/gems/async-2.16.1/lib/async/list.rb:290:in `each'
        from /home/watson/.rbenv/versions/3.3.4/lib/ruby/gems/3.3.0/gems/async-2.16.1/lib/async/list.rb:303:in `each'
        from /home/watson/.rbenv/versions/3.3.4/lib/ruby/gems/3.3.0/gems/async-2.16.1/lib/async/list.rb:178:in `each'
        from /home/watson/.rbenv/versions/3.3.4/lib/ruby/gems/3.3.0/gems/async-2.16.1/lib/async/node.rb:290:in `stop_children'
        from /home/watson/.rbenv/versions/3.3.4/lib/ruby/gems/3.3.0/gems/async-2.16.1/lib/async/task.rb:401:in `stopped!'
        from /home/watson/.rbenv/versions/3.3.4/lib/ruby/gems/3.3.0/gems/async-2.16.1/lib/async/task.rb:414:in `stop!'
        from /home/watson/.rbenv/versions/3.3.4/lib/ruby/gems/3.3.0/gems/async-2.16.1/lib/async/task.rb:296:in `stop'
        from t.rb:63:in `stop'
        from t.rb:91:in `<main>'

[ioquatix]

I will check it.

[ioquatix]

If you want to invoke stop across threads, you wil need to use an appropriate mechanism, e.g.

    def start
      @stop = Thread::Queue.new
      
      Async do |task|
        @server_task = task.async do
          @server.run
        end
        
        @stop.pop
        @server_task.stop
      end
    end

    def stop
      @stop.push(true)
    end

I didn't test this, but something like this will probably work.

[Watson1978]

Thanks!!
I was able to stop the server that way without error.