打字稿异步等待调试

Question

I have a strange issue in my code and I'm unable to root cause it.

try {
    const result = await somePromise.catch((err) => {
        console.log(new Date()); // this prints time, t0
        console.log('Stats', eventLoopStats.sense());
        throw err;
    });
} catch (e) {
    console.log(new Date()); // this prints time, t0 + 15 seconds
    console.log('Stats', eventLoopStats.sense()); // this prints {0, 0, 0, 0}, meaning, event loop hasn't been involved since last call to sense
}

My question is, why is there a huge lag between the promise rejecting and it actually being caught in the outer catch block?

I'm in my dev environment, which is fairly idle. Also, it is consistently has around 15 second delay.

Are there any other debugging approaches?

Notes:

1. I'm using node version 12.11.1
2. Also using bluebird for promises
3. somePromise is obtained from a library which was transpiled into Javascript from Typescript.

Answer 1

The root cause was that my code had monkey patched promise binding which caused code to be injected between the promise rejection and continuation of the event loop. If you have a similar issue, check if your code has patched Promise.bind .