Bug 1221363

Description of problem:

I drew up a whole plan about how to use direct soft dependencies (Recommends, Suggests) in order to achieve the desired effect for a bunch of related packages.
But then I found out that nobody knows whether use of soft dependencies in current Fedora is forbidden or not.

Basically, I want precise information about how dnf supports soft dependencies so I can make the decision of whether to take the time to implement or improve my plan
or whether my time is better spent figuring out some way to achieve close
to what I want with hard dependencies and a bunch of meta-packages.

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1.
2.
3.

Actual results:


Expected results:


Additional info:

The plan, as far as it went:

1) For libblockdev:
  - Add Recommends: <plugin> to libblockdev package forall <plugin>s
    that have a subpackage in libblockdev.

  * The expected result is that when libblockdev is installed all these
    plugins will be available and so will be pulled in. However, it is
    possible to specifically exclude packages via command line or config
    file. If a plugin package is excluded then there will be no error
    and installation of libblockdev will still proceed but without that
    plugin and its dependencies (so long as nothing else requires them).

  * There are a few ways to do this:
    - Make plugins-all meta-package Recommend rather than require
      every plugin. Leaves Requires: libblockdev in there.
    - Get rid of plugins-all meta-package and have libblockdev package
      Recommend: all plugins.
    - Others...

  * Later maybe libblockdev plugin versions will diverge from libblockdev
    versions. This can all still be handled in libblockdev spec file.

  * Still later may be alternative plugins that are not part of standard
    libblockdev distribution. These can have reverse dependencies
    of one sort or another on libblockdev.

2) For blivet:
  - Require the libblockdev package or metapackage or whatever (see 1) that
    recommends the libblockdev plugins _and_ requires libblockdev itself.
  - Suggest a whole bunch of packages that correspond to those that
    are not currently required by blivet but have external
    resource objects listed in availability.py file (because blivet
    does need them in some situations).
  - Recommend dosfstools (it is currently required). Another option
    is Suggest, a little more dramatic but I think preferable. That
    option is discussed below.
  - Continue to require e2fstools. It supports blivet's default
    filesystem type.

  * The expected result is that when blivet is installed it will
    get libblockdev with all the plugins that were not excluded
    when libblockdev was installed. Of course, a knowledgeable user
    could do the whole install in one go, excluding plugin packages
    as necessary. The use of Suggests will simply cause the suggested
    packages to be slightly more favored when solving dependencies
    for other packages. However, it will allow to keep versioning
    information if necessary. dosfstools will generally be installed,
    but if it is absent blivet can still be installed.

3) For anaconda:
  - Do nothing at all.

4) For blivet-gui.
  - Do nothing at all.

* The expected result is that things will go on much as before _except_
that dosfstools is no longer required by blivet and therefore not
transitively required by anaconda. How does anaconda feel about the
possibility of getting a blivet without dosfstools?

An alternative is that blivet suggest dosfstools and that anaconda/blivet-gui require it.
I believe that in that case, the suggested version will be used to guide the version
required, but I have not seen anything specific about that in any documentation.
I like this approach a lot better than recommending dosfstools.