Need a way to interrupt pipeline when raising error

[chbk]

The goal is to test the contents of a channel, and only move on if the test succeeds.

In the current implementation, this is how I achieve it:

1. Gather the channel items into a list with collect
2. Run some tests while mapping the channel to itself with map
3. Undo gathering of channel items by spreading them with flatten

ch = Channel.of(1, 2, 3)

ch = ch.collect().map({ list ->
  // Run a test that fails
  if (list.sum() > 5) exit(1, 'ABORT')
  // Return if test succeeds
  return list
}).flatten()

// This is printed only if test succeeds
ch.view()

The issue is that I have to transform the channel and then un-transform it just for a test, and the test can't be run on the channel itself, just a list representation of that channel.

Suggested implementation

Ideally a way to formally interrupt a pipeline at a given point:

ch = Channel.of(1, 2, 3)

ch = ch.try({ it ->
  it.sum().subscribe({ sum ->
    // Run a test that fails
    if (sum > 5) throw new Exception('ABORT')
  })
}).catch({ error ->
  exit(1, error)
})

// Error was raised so nothing afterwards gets executed
ch.view()