From:	Alexis Sukrieh	Date:	Mon Sep 29 00:42:09 2008
Subject:	Re: Mouse and Coat

Hi,

Sartak a écrit :
> Hi Alexis,
> 
> I've been aware of Coat since you started it. (But I hadn't seen the
> value of a lite Moose until much later). I had even contributed two
> patches. :)

Indeed, and I thank you for that ;)

> I started Mouse (originally called Neutrino) a few months ago for fun,
> to better understand how Moose fits together. It wasn't going to be
> anything serious or used by anything. But then I mentioned it to a few
> people and here we are.

Ok,

> Mouse strives very hard to be a *compatible*, fast, light replacement
> for Moose. Coat is the latter two. It's marginally compatible, but
> running s/Coat/Moose/g will probably not work for a decent sized
> project. 

Maybe, but I think I should precise my baseline when I'm at working on 
Coat:

Coat should be as compatible as possible to Moose when it's not about 
meta. To be short: there's no point to rewrite Class::MOP, I don't think 
a tiny-fast-perl5-core-only code will be able to do what Class::MOP does.

After talking with Stevan on IRC a couple of months ago, we agreed on 
that: if you need strong meta information, go use Moose; otherwise, it's 
a descent target for Coat to be a light-remplacement.

Yes, I know, it's not already the case, and some parts are just not even 
started (like Roles) but this is a target for me. That's why I'm taking 
as many tests I can from Moose's test-suite and add them to Coat. I want 
Coat features to be as compatible as possible to Moose.

So, again, I fear we're starting to do duplicate work here, I would be 
so glad to welcome you to the Coat maintenance, if you'd like to ;)

> There are too many details that are different. For example,
> if you leave out the "is" option to "has" in Coat, you get a
> read-write accessor. In Moose, you get no accessor (not even
> read-only). Coat probably did this to optimize for convenience. But it
> is something you have to know about when upgrading from Coat to Moose.

Well, as I said above : this is a bug in Coat. Every Moose's feature 
implemented in Coat should behave like in Moose, as long as it doesn't 
involve meta-data exposition.

I'm going to fix that soon, hopefully I can find a test that put that 
issue into the light).


> I've tried to model even Mouse's internals on Moose as well. I have
> Mouse::Meta::Attribute, Mouse::Meta::Class->linearized_isa, etc. Mouse
> does provide a very barebones MOP, but that's often all you need.
> Almost all of the features provided by Mouse's MOP are given the same
> name and functionality as Moose. Even if you use the MOP you can
> probably safely upgrade from Mouse to Moose. Coat's MOP is quite a bit
> different (not bad, just different).

Then we have a divergence of concept there. Indeed Coat's MOP is 
different from Moose's, for the reasons I explained before.


> There are a number of Moose features (such as practically all the type
> features) that Coat has that Moose doesn't have yet. Coat::Persistent
> is also nowhere to be seen in Mouse. So I think there's plenty of room
> in this space for two (or five) lightweight Mooses. :)

I don't think Coat::Persistent as something to do with this debate ;) 
It's just an ORM that is using Coat.

Anyways, as the Perl mantra said: "there's more than one way to do 
it"[1], so I understand your path, but don't forget you're more than 
welcome if you like to contribute to Coat (event tests that shows up bug 
of Moose's compatibility).

Regards,

	Alexis

1: by the way I had to fight a little when I starting working on Coat, 
some people were angry because of the idea behind Coat; I'm happy to see 
that, at the end, I was right: there's is room and even need for 
light-weight Mooses.