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Detect unhandled promise rejections

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  • ¿Algo no está bien?
#82 3 comentarios 0 reacciones 0 asignados Ver en GitHub

Nadie ha tomado este issue todavía.

Evaluación

Dificultad
5/5
Tiempo estimado
Más de una semana
Aptitud para principiantes
25/100
Tipo de issue
Nueva funcionalidad
Claridad
Bastante claro
Estado de actividad
Estancado
Stack tecnológico
javascript, ruby
Área
api, backend

Línea de trabajo

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.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

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>
Lenguaje dominante
JavaScript
Estrellas
628
Forks
100
Merge medio
1 d 20 h
PR fusionados (30 d)
2

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