alternative dependency ordering - with respect of packages in main

[Gerfried Fuchs <rhonda@deb.at>]

        Hi!

 Policy is clear on packages in main aren't allowed to depend on
packages outside of main.  Now in a fair amount of cases this has been
worked around by having the package outside of main as alternative
dependency and a package in main offer basic functionality for the
package to still be able to work.

 I know that the buildd system likes to pull in the first package in
such an alternative dependency chain.  And now I start to wonder:

 Is it allowed for a package in main to have a package _outside_ of main
as first component of an alternative dependency?  The package in
question is extremely unlikely to ever be used as Build-Depends, so this
is of a more general question.

 What also might be used as argument is the social contract, DFSG #4:
"Our priorities are our users and free software" -- it can be argued
that we don't put the priority on free software in such a case.

 tl;dr - what do you think, is a "Depends: foo-contrib | foo" acceptable
for packages in main or should it be "Depends: foo | foo-contrib"
instead?

 Thanks for answering to the short strawpoll,
Rhonda
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