Public SourceMage Discussion List

[Juuso Alasuutari <iuso AT sourcemage.org>]

I'm still in the blue about what's the best way to handle grouped optional 
dependencies. I mean cases where one optional compile flag, if enabled, will 
require more than one dependency to be added.

Here are some ways to solve this:

1) The oft-used approach is to config_query about the option, then do 'if 
VAR; 
then depends foo && depends bar'. This has the problem 
that 'dispel --dispel-parent yes foo' will treat the parent as broken, not as 
recastable.

2) Another solution is to do 'optional_depends foo && if is_depends_enabled 
foo; then depends bar'. Although this causes the first dependency to get 
marked as optional, the rest of them still suffer from the same issue as in 
1).

3) Adding a meta spell (i.e. dedicated profile spell) is something that would 
actually seem to work. If the parent spell optionally depends on "meta", 
which only pulls in foo and bar, then all is well. In that 
case 'dispel --dispel-parent yes foo' will dispel meta, and that in turn will 
prompt to recast the parent spell without the optional dependency "meta".

But we don't seem to have any tradition of using "meta spells" like this. The 
profile spells out there are for pulling together big stuff like e.g. the 
basesystem. The idea of adding a new profile spell (of the present kind) for 
a single optional dependency is certainly a bit of a turn-off.

Yet I can't help but wonder if we could indeed use "meta spells" for handling 
grouped optional dependencies. Let's say we add a section called meta in the 
grimoire. We'll make use of the soon-to-be spell file inheritance scheme and 
put dummy PRE_BUILD, BUILD, and INSTALL files in the section directory. The 
spells could have a naming scheme that distinguishes them from the rest, for 
instance they could all begin with _. They could be more liberally disposed 
of when the occasion arises, i.e. when they're not needed by any spells 
anymore.

Although I can't completely wash away the taste of ad-hoc from my mouth when 
I 
ponder the option, I think it's at least worth a discussion, as it would fit 
in well with our present practices. I don't know if I'm alone with my 
concern, but I do feel that we should somehow address the problem I've 
outlined, be it through "meta spells" or some other means.

-- 
        Juuso Alasuutari
[[ Source Mage GNU/Linux ]]

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