Re: unexpected _child(lose) for a detached session from _start

Agreed, a _child(lose) before the _child(create) is bad.

It should either be a _child(create)/_child(lose) pair, or nothing in  
this case.  I'm tempted to go with "nothing" since it would be hard to  
fix the create/lose timing.  Also the new(detached => 1) seems good,  
but I admit I haven't given it much though yet.  Sometimes I change my  
mind after thinking about things too hard.

If you haven't already, please submit this to [email protected].   
I'm liable to forget about POE bugs, patches, tests, etc. if they're  
not in POE's bug tracker.

Thank you again for all your help.

-- 
Rocco Caputo - [email protected]


On Nov 19, 2009, at 14:00, Olivier Mengué wrote:

> Hi POE fellows,
>
> I'm in the process of rewriting the backend of my  
> POE::Component::Schedule
> to make the backend session independent of others session in the  
> system. The
> point is that session is just backend stuff, so it should not fire  
> _child
> events to the session from which the API may have been called. Also,  
> the
> schedule session is a singleton that may be used by multiple  
> session, so it
> has no reason for being attached to a particular session.
> To achieve that, I'm calling POE::Kernel->detach_myself in the _start
> handler of the session. POE does'nt fire _child(create) as I expected.
> However I also found out that POE still fires _child(lose).
>
> My opinion is that POE should not fire a _child(lose) event if the  
> session
> is detached from its parent in the _start handler as a 'lose' without
> 'create'/'gain' is inconsistent.
> Also it would be better if 'detach => 1' was an argument to
> POE::Session->create(): it would make the 'not attached'  
> particularity of
> this session more explicit for people reading the code.
>
> Here is a test case that shows the current flawed behavior (tested  
> with POE
> 1.006, POE 1.280):
>
> use strict;
> use warnings;
>
> use Test::More tests => 7;
> use POE;
>
> my $_child_fired = 0;
>
> POE::Session->create(
>    inline_states => {
>        _start => sub {
>            $_[KERNEL]->alias_set('First');
>            pass "_start First";
>            POE::Session->create(
>                inline_states => {
>                    _start => sub {
>                        $_[KERNEL]->alias_set('Second');
>                        pass "_start Second";
>                    },
>                },
>            );
>            POE::Session->create(
>                inline_states => {
>                    _start => sub {
>                        $_[KERNEL]->alias_set('Detached');
>                        pass "_start Detached";
>                        diag "Detaching session 'Detached' from its  
> parent";
>                        $_[KERNEL]->detach_myself;
>                    },
>                },
>            );
>        },
>        _child => sub {
>            $_child_fired++;
>            ok($_[KERNEL]->alias_list($_[ARG1]) ne 'Detached',
>                "$_[STATE]($_[ARG0]) fired for "
>                  .$_[KERNEL]->alias_list($_[ARG1]->ID));
>        },
>    },
> );
>
> POE::Kernel->run();
>
> pass "_child not fired for session detached in _start" unless  
> $_child_fired
> != 2;
> pass "Stopped";
>
>
> Olivier Mengué
> http://o.mengue.free.fr/