[gentoo-dev] ebuild optional dependencies question

[Jason Rhinelander]

I've recently created a MySQL-4.1.x ebuild (bug 62582), but, as reported 
in the bug, it breaks a couple modules (notably, Perl's DBD-mysql and 
ruby's mysql module).  Realistically, the pseudo-dependency for this 
package needs to be something like:

if DBD-mysql is installed:
     post-depend on DBD-mysql >= 2.9004
if ruby's mysql module is installed
     post-depend on mysql-ruby >= 2.5

Putting both in PDEPEND would seem wrong as it forces both on people who 
might use only one or neither.  The following ought to more-or-less 
accomplish it:

PDEPEND="perl? ( >=dev-perl/DBD-mysql )
	ruby? ( >=dev-ruby/mysql-ruby-2.5 )"

The current mysql ebuild does this for "perl" (it also includes an 
unnecessary dev-perl/DBI dependency).  However, I've seen comments in 
the past that give me the impression that using USE flags ONLY for 
dependencies, such as the 'ruby' flag above, is discouraged (the 'perl' 
USE flag is also used elsewhere in the ebuild).

Is there an alternative, established way of dealing with a situation 
like this, or is the PDEPEND USE-flags above the best way?

-- 
-- Jason Rhinelander
-- Gossamer Threads, Inc.

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