Single operator returns undefined

[DusanDjordjic]

Greetings,
I am was going through RxJS operators documentation and I noticed that it says that the single operator will throw a NotFoundError if no value matches the predicate but it sends undefined to the next function.

Here is the code that I wrote:

  const source = of(
    { name: 'Dusan' },
    { name: 'Jovana' },
    { name: 'Jovan' },
    { name: 'Aleksandar' }
  );

source.pipe(single((person) => person.name.startsWith('N'))).subscribe({
    next: (value) => {
      console.log({value});
    },
    error: (err) => {
      console.log({err});
    },
});

My question is, is it a bug or just an error in the documentation?

[josepot]

What version of rxjs are you using? 🤔

I get the NotFoundError on version 7.5.2. Could you please share a codesandbox/stackblitz that reproduces the issue?

[DusanDjordjic]

My bad. I loaded an old project with rxjs 6.6 and I didn't check the version, so it didn`t work.

Sorry for taking your time. 😅

[josepot]

Sorry for taking your time. sweat_smile

Nothing to be sorry about.

In fact, by the looks of it: this is a bug on version 6, because the docs of v6 have the same statement. I'm not sure whether v6 is still under maintenance, but if it is, then I think that this issue should be addressed.