打字稿承诺拒绝和vscode调试器行为

问题描述

我正在尝试使用打字稿来学习Promise，并且在理解导致vscode调试行为的原因时遇到了一些问题。

I'm trying to learn promises, with typescript, and i have some problems, understanding what causes such vscode debugging behavior.

这里是一个示例：

// example 1
new Promise((resolve, reject) => {
    reject("test1"); // debugger stops as on uncaught exception
})
.catch(
    error => {
        console.log(error);
    }
);
// output: "test1"

，并且：

//example 2
new Promise((resolve, reject) => {
    setTimeout(() => {
        reject("test2"); // debugger never stops
    });
})
.catch(
    error => {
        console.log(error);
    }
);
// output: "test2"

如您所见，调试器在以下位置停止答应拒绝，但在其他情况下则不能。但是在所有情况下都捕获了错误，并且没有未处理的异常。

As you can see in one case debugger stops at promise reject, but in other case, not. But in all cases error is catched, and no unhandled exceptions.

是vscode特定行为还是我使用的es6-promise绑定？还是我做错了方法？有没有人遇到过同样的问题？

Is it vscode specific behavior or maybe es6-promise binding that i use? Or i'm doing it incorrect way? Has anyone faced same problem?

推荐答案

这是VSCode挂钩的Chrome调试器使用的一种启发式方法。他们认为，同步拒绝通常是您要打破的程序员错误（例如拼写错误），而异步错误则不是，因为它们通常是IO（读取文件）。

This is a heuristic that the Chrome debugger which VSCode hooks into uses. They assume that synchronous rejections are typically programmer errors you want to break on (like a typo) and asynchronous ones are not since they're typically IO (reading a file).

这是一种非常愚蠢的启发式方法，但在某些情况下通常很有意义。您可以做的一件事是包含用于调试构建的bluebird（如果不将 Promise 子类化，则100％兼容），然后添加未处理的拒绝钩子：

It's a pretty dumb heuristic but it typically makes sense for some cases. One thing you can do is include bluebird for the debug build (it's 100% compliant if you don't subclass Promise) and then add an unhandled rejection hook:

Promise.onPossiblyUnhandledRejection(function(e, promise) {
    throw e;
});

使用更好的启发式方法。您也可以使用本机的Promise（带有拒绝事件）来执行此操作，但是我不知道如何关闭同步引发的自动中断。

Which uses a much nicer heuristic. You can also do this with native promises (with rejection events) but I don't know how you can turn off the automatic breaking on synchronous throws.

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