在fetch api的catch块中重新引发错误时，未触发Web Worker onError事件处理程序 [英] web worker onerror event handler not triggered when rethrowing an error in the catch block of fetch api

问题描述

TL; DR; 是否存在在Promise(即fetch-api)和Webworker全局错误事件处理程序中重新抛出错误的问题?

我很难将网络工作者中的获取api引发的错误鼓吹到启动网络工作者的客户端上.我看到" 未捕获(承诺)错误 "，而不是Webworkers self.onerror 事件中的代码经理...当我在同一Web Worker中的同步函数中引发错误时，它的确会出现在self.onerror事件处理程序中...

要进一步解释，在我的Webworker内部:

• onerror事件处理程序
• 使用获取api调用webapi的功能

我想传递调用Web api到客户端时遇到的某些错误...因此，我在获取的末尾(在catch块中)抛出了错误.这就是我当前的测试结果:

  fetch('https://< server>/api/token?key = version'，{方法:'GET'，凭据:'include'}).then((response)=> {抛出新的错误(哦，不-出了点问题")；返回response.json();}).then((data)=> {/*对正常流中的数据执行某些操作*/}).catch((错误)=> {/*我们要传递某些类型的错误*/投掷(错误);/*< ----这是我在F12调试窗口中看到的最后一个错误->}) 

但是我从不看到错误到达onerror事件处理程序，看起来像这样(只是一些测试输出):

  self.onerror =函数(事件){console.trace(event);} 

我看到(使用F12调试)在获取api捕获的行上记录了 未捕获(承诺)错误

我忽略了什么?重新抛出错误和全局onerror事件处理程序是否存在问题?

解决方案

事实证明，有两种方法可以确保promise(fetch-api基于promise)中的重新抛出错误:

1)如何在Promise中捕获未捕获的异常

->为您的网络工作人员添加 unhandledrejection 的事件处理程序:

  self.addEventListener('unhandledrejection'，function(event){//事件对象具有两个特殊属性://event.promise-产生错误的承诺//event.reason-未处理的错误对象抛出event.reason;}); 

TL;DR; Is there an issue with rethrowing errors in promises (i.e. the fetch-api) and the webworker global onerror event handler ?

I'm having a hard time bubbling up an error thrown by the fetch api in a web worker to the client that started the web worker. I see an "Uncaught (in promise) Error" instead of the code in the webworkers self.onerror event handler.... When I throw an error in a synchronous function in that same web worker it does end up in the self.onerror event handler...

To explain in further detail, inside my webworker I'm having :

• an onerror event handler
• functions that call a webapi with the fetch api

I want to pass along certain errors encountered when calling the web api to my client... Thus I rethrow the error at the end of the fetch (in the catch block). This is how my current test looks like :

fetch('https://<server>/api/token?key=version', { method: 'GET', credentials: 'include'})
.then((response) => {
  throw new Error("Oh no - something went wrong");
  return response.json();
})
.then((data) => {
  /* do something with the data in normal flow */
})
.catch((error) => { 
  /* we want to pass along certain types of errors */
  throw(error); /* <---- this is the last error I see logged in F12 debug windows -->
})

However i never see the error reaching the onerror event handler, which looks like this (just some test output) :

self.onerror = function (event) {
    console.trace(event);
}

I see (using F12 debug) that an Uncaught (in promise) Error is logged at the line that the fetch api catch

Anything I'm overlooking ? Is there an issue with rethrowing errors and the global onerror event handler ?

解决方案

It turns out there are two ways that I can make sure a rethrown error in a promise (fetch-api is promise-based) get's bubbled up :

1 ) The trick mentioned in How to bubble a web worker error in a promise via worker.onerror?

-- > just wrap the throw (inside the fetch catch block) in a setTimeout :

 fetch
 .then()
 .catch((error) => { 
    setTimeout(function() { throw error; });
 })

2) The new way mentioned in How to catch uncaught exception in Promise

-- > add an eventhandler for unhandledrejection to your webworker :

self.addEventListener('unhandledrejection', function (event) {
    // the event object has two special properties:
    // event.promise - the promise that generated the error
    // event.reason  - the unhandled error object
    throw event.reason;
});

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