FIREBASE WARNING: Exception was thrown by user callback. Error: test

[hiranya911]

Moved from firebase/firebase-admin-node#89

• Operating System version:
  macOS Sierra 10.12.6
  node/6.11.1

• Firebase SDK version:
  "firebase": "4.4.0",
  "firebase-admin": "5.2.1",

• Library version:

• Firebase Product: database

When an exception is thrown from a user callback (inside .once or .then)
the exception is raised as a uncaught exception event instead of
calling the .catch function.

const db = getDatabase();
const id = `/path/key`;

process.on('uncaughtException', function (err) {
  // this event is called instead of the .catch(err)
  console.error( "UNCAUGHT EXCEPTION " );
  console.error( "[Inside 'uncaughtException' event] " + err.stack || err.message );
  process.exit();
});

db.ref(id)
.once('value', snap => {
  throw new Error('test');
})
.catch(err=>{
  // This catch function is not ever called.
  console.log('caught the error', err);
});

This behavior is not consistent with the standard promise model.

const promise = new Promise(function (resolve, reject) { resolve('ok'); });

promise
.then(value=>{
  console.log(value);
  throw new Error('test');
})
.catch (err=>{
  // This catch function is called.
  console.log('catch 1');
});

[mikelehen]

cc/ @firebaseatdj

This is expected. In order to participate in the promise chain you should /not/ use the .once() callback and instead just attach your .then handler directly, i.e.:

db.ref(id)
.once('value')
.then(snap => {
  throw new Error('test');
})
.catch(err=>{
  ...
});