Multiple Mojo::IOLoop::Subprocess trigger the same parent code at runtime

[ggl]

• Mojolicious version: 7.25
• Perl version: 5.20.3
• Operating system: Darwin Kernel Version 14.5.0: Sun Sep 25 22:07:15 PDT 2016; root:xnu-2782.50.9~1/RELEASE_X86_64 x86_64

Steps to reproduce the behavior

If you start multiple Mojo::IOLoop::Subprocess processes from a for loop, the parent code will get triggered for every one of the created children at every iteration of the loop. What's more annoying is that this is done with undef @results, triggering a Storable error (thaw with an empty buffer).

#!/usr/bin/env perl

use feature 'say';
use Mojo::IOLoop;
use Mojo::IOLoop::Subprocess;

# Operation that would block the event loop for 5 seconds
for (0..2) {
  my $subprocess = Mojo::IOLoop::Subprocess->new;
  $subprocess->run(
    sub {
      my $subprocess = shift;
      sleep 5;
      return '♥', 'Mojolicious';
    },
    sub {
      my ($subprocess, $err, @results) = @_;
      $pid = $subprocess->pid;
      say "Subprocess $pid error: $err" and return if $err;
      say "Subprocess $pid $results[0] $results[1]!";
    }
  );
}

# Start event loop if necessary
Mojo::IOLoop->start unless Mojo::IOLoop->is_running;

Expected behavior

The parent sub should only be executed once the current child returns.

Actual behavior

The parent code gets triggered once for every child spawned with the run method.

[kraih]

Looks like a bug.