Bug#681419: Proposed ballot for free/non-free dependencies question

[Colin Watson <cjwatson@debian.org>]

Here's a draft of a ballot for #681419.  Despite the form, I think this
is probably still more of a discussion document; Ian indicated that he'd
like the opportunity to discuss this by e-mail before voting, and I
don't know if I've fully captured all the positions and arguments.

Ian, I've taken the liberty of drafting option B in an attempt to
describe what I understand as your position, but I'm sure you can do a
better job of it.

I've committed this to our git repository as
681419_free_non_free_dependencies/cjwatson_draft.txt.


  Whereas:

  1. The Debian Policy Manual states (§2.2.1) that packages in main
     "must not require or recommend a package outside of main for
     compilation or execution".  Both "Depends: package-in-non-free" and
     "Recommends: package-in-non-free" clearly violate this requirement.
     The Technical Committee has been asked to determine whether a
     dependency of the form "package-in-main | package-in-non-free"
     complies with this policy requirement, or whether virtual packages
     must instead be used to avoid mentioning the non-free alternative.

  2. Both options have the following effects in common, meeting the
     standard that main should be functional and useful while being
     self-contained:

    (a) Package managers configured to consider only main will install
        package-in-main.

    (b) Package managers configured to consider both main and non-free
        will prefer to install package-in-main, but may install
        package-in-non-free instead if so instructed, or if
        package-in-main is uninstallable.

    (c) If package-in-non-free is already installed, package managers
        will proceed without installing package-in-main.

  3. The significant difference between these two options is that the
     former makes the non-free alternative visible to everyone who
     examines the dependency relationship, while the latter does not.

A 4. Merely mentioning that a non-free alternative exists does not
A    constitute a recommendation of that alternative.  For example, many
A    free software packages state quite reasonably that they can be
A    compiled and executed on non-free platforms.
A
A 5. Furthermore, virtual packages are often a clumsy way to express
A    these kinds of alternatives.  If a package happens to require any
A    of several implementations of a facility that have a certain
A    option, then it can either depend on suitable alternatives
A    directly, or its maintainer can first attempt to have fine-grained
A    virtual packages added to each of the packages they wish to permit.
A    In some cases this may be appropriate, but it can easily turn into
A    quite a heavyweight approach.
A
A Therefore:
A
A 6. The Technical Committee resolves that alternative dependencies of
A    the form "Depends: package-in-main | package-in-non-free" are
A    permissible in main, and do not constitute a violation of the
A    policy clause cited in point 1.
A
A 7. We nevertheless recommend that packages in main consider carefully
A    whether this might cause the inadvertent installation of non-free
A    packages due to conflicts, especially those with usage
A    restrictions.

B 4. Listing a package explicitly in a dependency relationship implies
B    to users that the maintainer has taken steps to confirm its
B    suitability, and thus amounts to a recommendation, even if only as
B    one of several possibilities.
B
B 5. There is a substantial risk that a secondary dependency on a
B    package in non-free will cause that package to be installed by
B    default when the primary dependency is uninstallable.
B
B 6. Virtual packages are a suitable existing mechanism for packages to
B    declare the set of abstract features they provide, and allow
B    packages in main to depend on such abstract features without
B    needing to name every (free or non-free) alternative.
B
B Therefore:
B
B 7. The Technical Committee resolves that alternative dependencies of
B    the form "Depends: package-in-main | package-in-non-free"
B    constitute a violation of the policy clause cited in point 1.
B
B 8. We recommend that affected packages consider the use of virtual
B    packages instead.

-- 
Colin Watson                                       [cjwatson@debian.org]