The current "pipable" variant of this operator is called finalize() (since RxJS 6). The older and now deprecated "patch" operator was called finally() (until RxJS 5.5).
I think finalize() operator is actually correct. You say:
do that logic only when I subscribe, and after the stream has ended
which is not a problem I think. You can have a single source and use finalize() before subscribing to it if you want. This way you're not required to always use finalize():
let source = new Observable(observer => {
observer.next(1);
observer.error('error message');
observer.next(3);
observer.complete();
}).pipe(
publish(),
);
source.pipe(
finalize(() => console.log('Finally callback')),
).subscribe(
value => console.log('#1 Next:', value),
error => console.log('#1 Error:', error),
() => console.log('#1 Complete')
);
source.subscribe(
value => console.log('#2 Next:', value),
error => console.log('#2 Error:', error),
() => console.log('#2 Complete')
);
source.connect();
This prints to console:
#1 Next: 1
#2 Next: 1
#1 Error: error message
Finally callback
#2 Error: error message
Jan 2019: Updated for RxJS 6