As a clarification, the foo example above should wait for all connected inputs only it it is an addressable param port. Input ports should cause processing on any packet, but pass the index to the processing function

In some cases you'd want input ports to wait for all sockets too. We might want a config option for this.

See implementation details below:

If a param port is addressable, the component waits for data on all its attached indexes to arrive before proceeding. In proc function such a parameter is accessible as an object with keys matching port indexes, e.g.:

component.params.arr = {
  0: 'foo',
  1: 'bar',
  2: 'baz'
}

If an in port is addressable, the component activates the proc function whenever data arrives, given that data on other ports has also been received. The data on an addressable port is an object with keys matching port indexes. E.g. if just one packet was received while data on other ports arrived, it will contain just one element, e.g.:

data.arr = {
  1: 'bar'
}

But if several indexes were triggered while waiting for other ports, it may contain several elements:

data.arr = {
  0: 'foo',
  1: 'bar'
}

Therefore for components with just one in port, it is always passed one array object per invocation.

There are cases when a component should act the opposite way: wait for just any param index or wait for in on all indexes at once. That's why there are several "waiting" policies for array ports available, with the above example used by default:

noflo.helpers.WirePattern component,
  in: [ 'd1', 'd2' ]
  params: 'p'
  out: 'out'
  arrayPolicy: # these are defaults
    in: 'any' # trigger on any index
    params: 'all' # wait for all indexes

Other combinations are also possible, e.g.:

noflo.helpers.WirePattern component,
  in: [ 'd1', 'd2' ]
  params: 'p'
  out: 'out'
  arrayPolicy:
    in: 'all' # wait for all indexes
    params: 'all' # wait for all indexes