Catch() and its shared subscriptions

[staltz]

When writing tests for catch(), I noticed this behavior:

  it('should catch and allow the cold observable to be repeated with the third ' +
  '(caught) argument', function () {
    var e1 =  cold('--a--b--c--------|       ');
    var subs =    ['^                       !',
                   '        ^               !',
                   '                ^       !'];
    var expected = '--a--b----a--b----a--b--#';

    var retries = 0;
    var result = e1
      .map(function (n) {
        if (n === 'c') {
          throw 'bad';
        }
        return n;
      })
      .catch(function (err, caught) {
        if (retries++ === 2) {
          throw 'done';
        }
        return caught;
      });

    expectObservable(result).toBe(expected, undefined, 'done');
    expectSubscriptions(e1.subscriptions).toBe(subs);
  });

Special attention given to this part:

    var e1 =  cold('--a--b--c--------|       ');
    var subs =    ['^                       !',
                   '        ^               !',
                   '                ^       !'];

This happens because CatchSubscriber does

  _error(err) {
    const result = tryCatch(this.selector)(err, this.caught);
    if (result === errorObject) {
      this.destination.error(errorObject.e);
    } else {
      this.add(result.subscribe(this.destination)); // <====
    }
  }

As a consequence, if someone uses source.catch(e => source) as a flavor of retry(), the number of subscriptions will indefinitely grow and stay retained.

What do you think should be done about this behavior?

[kwonoj]

At immediate sight, I'd expect each subscription unsubscribed when next subscription starts, like below.

var subs =    ['^        !',
                '        ^       !',
                '                ^       !'];

[benlesh]

@staltz ... I believe this was solved with #769, no?

[kwonoj]

I believe so (though I'm not @staltz :) ) PR still need to be merged though.

[benlesh]

okay... reopening until the merge.

[kwonoj]

Now really closing issue.