Developers of Sympa

[Guillaume Rousse <address@concealed>]

Le 23/06/2014 18:53, IKEDA, Soji a écrit :
> Guillaume,
>
> I don't agree to this method.
You're supposed to provide technical argumentation to backup your point...

The previous code is difficult to test, without relying on non-trivial 
techniques such as preloading a mock Site class, and rewriting it on the 
fly to chain multiple tests with different parameters. The new code, 
making the method self-contained, allows to chain arbitrary tests 
without troubles.

More generally, having each part of Sympa code directly access 
configuration has multiple drawbacks:
- circular dependencies between packages
- strong components coupling
- lack of internal compartimentation

Modularity does not means moving code around in different files, it's 
also ensuring that each part if independant enough to be potentially 
replaced by something else. There is no way to replace parts of Sympa 
specific code with CPAN alternative as long as those parts have so much 
intimity with Sympa internals. And for me the target design is clear: 
only the top-level code should access the configuration directly, not 
the objects modeling the application logic.

Basically, that's about switching from this model:

package main;

my $object = Sympa::Object->new();
$object->do_something();

package Sympa::Object;

# configuration access needed
use Sympa::Site;

# no parameter, because of direct configuration access
sub do_something {
}

to this model:

package main;

# configuration access needed
use Sympa::Site;

my $object = Sympa::Object->new();
$object->do_something(foo => Sympa::Site->foo());

package Sympa::Object;

# no dependency

# parameters needed, because the method is self-contained
sub do_something {
    my (%params) = @_;

    my $foo = $params{foo};
    croak "missing parameter foo" unless $params{foo};
}

In the second model, the do_something() method needs are explicit, 
whereas they are hidden in the first. And the day where the 
configuration parameter name change, or the way to access it from the 
configuration change, there is no need to change anything in Sympa::Object.
--
Guillaume Rousse
INRIA, Direction des systèmes d'information
Domaine de Voluceau
Rocquencourt - BP 105
78153 Le Chesnay
Tel: 01 39 63 58 31

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