[PATCH v2 1/2] schema: move space_mt and index_mt definition out of space bless

[Vladimir Davydov]

For the record, as I said before

> I don't understand why anyone would do that. If one wants to
> implement some extra methods, they can always create a wrapper
> in Lua. Overwriting a metatable for this looks like a dirty hack.

so this is a purely technical review.

On Thu, Mar 29, 2018 at 05:31:44PM +0300, Vladislav Shpilevoy wrote:

> +function space_mt:len()
> +    check_space_arg(self, 'len')
> +    local pk = self.index[0]
> +    if pk == nil then
> +        return 0 -- empty space without indexes, return 0
>      end
> +end

> -    space_mt.len = function(space)
> -        check_space_arg(space, 'len')
> -        local pk = space.index[0]
> -        if pk == nil then
> -            return 0 -- empty space without indexes, return 0
> -        end
> -        return space.index[0]:len()
> -    end

This isn't what I meant when I wrote

> move index_mt and space_mt definitions from box.schema.space.bless
> without introducing any functional changes, then export them

I meant that in the first patch you should just move these functions to
the top-level, without doing ANY changes to them, otherwise the patch
will be rather difficult to review.

Anyway, I don't think the piece of syntax sugar you're trying to push
(passing the object to a class method implicitly) is really necessary.
We never do it in schema.lua, why do it for space_mt/index_mt now?
And it's definitely doesn't belong to this patch. Please remove.

> diff --git a/test/box-tap/schema_mt.test.lua b/test/box-tap/schema_mt.test.lua

The test should go to patch 2, the one that exports the metatables.