Re: [gentoo-dev] ebuild optional dependencies question

[Jason Rhinelander]

Ciaran McCreesh wrote:

 > Can't you solve this with blocking versions?

I don't see how - I made a (fictitious) DBD-mysql-2.9005 ebuild (I 
currently have 2.9004), and tried changing my mysql ebuild to:

PDEPEND="!<dev-perl/DBD-mysql-2.9005"

But that neither pulled in 2.9005 nor blocked the emerge.  I tried 
throwing it into RDEPEND, which (expectedly) blocks the emerge entirely 
- but emerging DBD-mysql /before/ mysql won't work, and the whole thing 
is wrong anyway because DBD-mysql is in no way a run-time dependency or 
blocker of mysql.

I suppose a specific version requirement could be added to DBD-mysql, 
but this wouldn't be "correct" either as the newer DBD-mysql does *not* 
require a newer mysql.  Alternatively, every ebuild <2.9004 could block 
 >=mysql-4.1 - but that is quite a bit more maintenance to solve this 
problem.

I did notice after I sent earlier e-mail that the mysql-4.0.21 ebuild 
uses the selinux USE flag only in RDEPEND, so I concluded that USE-flags 
that exist only in DEPEND's are a somewhat necessary evil and added a 
"ruby? (...)" to PDEPEND.

That said, USE=ruby has *no* impact on how MySQL is built, and as such 
also seems "wrong" - and I wonder how many other, similar cases exist. 
However, having portage upgrade my DBD-mysql when I emerge mysql would 
be a very nice feature, and keep a blocker from happening - which is 
never a nice thing.

To that end, I wonder if it might be useful to expand the var?, !var?, 
etc. syntax in DEPEND's to allow not just use-flags for 'var', but also 
package atoms, allowing for syntax such as:

cat-a/package? ( >=cat-a/package-1.2 )
=cat-b/packb-1*? ( >=cat-b/packb-1.2 )
 >=cat-b/packb-2? ( >=cat-b/packb-2.4 )

Currently this is invalid, but it would appear to be an elegant solution 
to this problem, and wouldn't appear to break anything (aside from old 
portage versions).

-- Jason Rhinelander
-- Gossamer Threads, Inc.

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