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Detect unhandled promise rejections

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  • Algo errado?
#82 3 comentários 0 reações 0 responsáveis Ver no GitHub

Ninguém assumiu esta issue ainda.

Avaliação

Dificuldade
5/5
Tempo estimado
Mais de uma semana
Facilidade para iniciantes
25/100
Tipo de issue
Funcionalidade
Clareza
Razoavelmente clara
Status de atividade
Estagnada
Stack de tecnologia
javascript, ruby
Domínio
api, backend

Direção de pesquisa

The issue points to V8's SetPromiseRejectCallback and PromiseRejectMessage; start by reading those API definitions and locating how mini_racer connects V8 callbacks to Ruby exceptions. The example shows the missed rejection and the expected error behavior, while the issue leaves the default behavior and configurability undecided. Done means unhandled rejections are reported to Ruby, with the handling behavior defined.

Escrita pelo modelo de indexação a partir do texto da issue.

Descrição

When working with promises, one important aspect of them is that an unhandled rejected promise is an error. However, V8 will drop notifications by default.

I think that mini_racer should consider this an error and raise an exception, though possibly it should be configurable how these are handled (e.g. via a callback where the user can decide to re-raise?).

To do so, it's necessary to register for unhandled promise rejections via SetPromiseRejectCallback.

The callback will receive a PromiseRejectMessage that should probably (by default) raise a exception in ruby, although I suppose it could be configurable.

Comparisons for reference:

Running this code:

var x = async () => { throw "failure"; };
var y = async () => { x() /* ignore the rejected result */ }; 
y().then(() => console.log("done")).catch(e => console.log(e));

In node:

> var x = async () => { throw "failure"; }; var y = async () => { x() /* ignore the rejected result */ }; y().then(() => console.log("done")).catch(e => console.log(e));
Promise {
  <pending>,
  domain:
   Domain {
     domain: null,
     _events:
      { removeListener: [Function: updateExceptionCapture],
        newListener: [Function: updateExceptionCapture],
        error: [Function: debugDomainError] },
     _eventsCount: 3,
     _maxListeners: undefined,
     members: [] } }
> done
(node:83056) UnhandledPromiseRejectionWarning: failure
(node:83056) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 3)

In chrome:

var x = async () => { throw "failure"; }; var y = async () => { x() /* ignore the rejected result */ }; y().then(() => console.log("done")).catch(e => console.log(e));
VM131:1 done
Promise {<resolved>: undefined}
VM131:1 Uncaught (in promise) failure

In mini_racer:

irb(main):001:0> require 'mini_racer'
=> true
irb(main):002:0> vm = MiniRacer::Context.new
=> #<MiniRacer::Context:0x00007ff4350f1438 @functions={}, @timeout=nil, @max_memory=nil, @current_exception=nil, @isolate=#<MiniRacer::Isolate:0x00007ff4350f12f8 @lock=#<Thread::Mutex:0x00007ff4350f12a8>>, @disposed=false, @callback_mutex=#<Thread::Mutex:0x00007ff4350f1280>, @callback_running=false, @thread_raise_called=false, @eval_thread=nil>
irb(main):003:0> vm.attach('console.log', proc{ |*args| puts('LOG> ' + args.map(&:to_s).join(' ')) })
=> #<MiniRacer::Context::ExternalFunction:0x00007ff43602b1b0 @name="log", @callback=#<Proc:0x00007ff43602b200@/usr/local/lib/ruby/gems/2.5.0/gems/mini_racer-0.1.15/lib/mini_racer.rb:201 (lambda)>, @parent=#<MiniRacer::Context:0x00007ff4350f1438 @functions={"console.log"=>#<MiniRacer::Context::ExternalFunction:0x00007ff43602b1b0 ...>}, @timeout=nil, @max_memory=nil, @current_exception=nil, @isolate=#<MiniRacer::Isolate:0x00007ff4350f12f8 @lock=#<Thread::Mutex:0x00007ff4350f12a8>>, @disposed=false, @callback_mutex=#<Thread::Mutex:0x00007ff4350f1280>, @callback_running=false, @thread_raise_called=false, @eval_thread=nil>, @parent_object_eval="if (typeof console === 'undefined') { console = {} };\nconsole;", @parent_object="console">
irb(main):004:0> vm.eval('var x = async () => { throw "failure"; }; var y = async () => { x() /* ignore the rejected result */ }; y().then(() => console.log("done")).catch(e => console.log(e));')
LOG> done
=> {}
irb(main):005:0>
Linguagem predominante
JavaScript
Estrelas
628
Forks
100
Merge médio
1d 20h
PRs com merge (30d)
2

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Primeiros passos

  1. Leia a issue inteira e depois o guia de contribuição do projeto.
  2. Comente na issue dizendo que vai assumir — evita que duas pessoas façam o mesmo trabalho.
  3. Faça um fork do repositório e trabalhe em uma branch.
  4. Abra um pull request que referencie o número da issue.

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