NodeJS Q Promise捕获从未用护照JS调用

Question

I'm using the passport library for node to assist me in user signup. I'm also using the 'Q' promise library to avoid the pyramid of doom as I go through several asynchronous steps.

Everything works fine, until I throw an error from one of the promised steps. I would have assumed execution would drop into the .fail function, where I could handle the error and return out of passport with a failed signup. But for a reason that I don't understand, the .fail function never gets called. Instead, I just get a stackdump in my browser window and in my console.

The controlling code is here:

q.fcall(checkEmailIsFree({'email':email, 'username':username, 'password':password}))
.then(checkUsernameIsFree)
.then(registerUser)
.then(function (user) {
  if (user) {
    logDebug('REGISTERED: ' + email);
    return done(null, user);
  }
  else {
    logDebug('Could not register');
    return done(null, false);
  }
})
.fail(function (err) {
  logError('I never get here');
  return done(null, false);
})
.done();

And here's how I'm throwing, from within checkEmailIsFree

var error = new Error('Bad times. Email is in use: ' + email);
throw error;

Is there some overall express / node code somewhere that is set to fast dump out an exception somehow? Why isn't my catch being called? What am I missing?

Answer 1

I think done(onFulfilled, onRejected, onProgress) can help in this case. You can try:

q.fcall(checkEmailIsFree({'email':email, 'username':username, 'password':password}))
.then(checkUsernameIsFree)
.then(registerUser)
.then(function (user) {
  if (user) {
    logDebug('REGISTERED: ' + email);
    return done(null, user);
  }
  else {
    logDebug('Could not register');
    return done(null, false);
  }
})
.done(undefined, function (err) {
  logError('Error!'); // used in case of reject
  return done(null, false);
});