[wpkg-users] [Bug 117] Dependencies ignore priority

[bugzilla-daemon at bugzilla.wpkg.org]

http://bugzilla.wpkg.org/show_bug.cgi?id=117





--- Comment #7 from Rainer Meier <r.meier at wpkg.org>  2008-05-09 16:46:00 ---
I clearly have to state here that a dependency clearly means to me that a
package really does not work at all if the package it depends upon is not
installed.

For example I use dependencies on a package called "shortcut" which itself has
very low priority as it is not a user program important to be on the system for
users. However the applications which depend on it will fail to install (or at
least to create the shortcuts) if this program is not installed. So for me this
is a dependency.

Each time an application which depends on "shortcut" is installed it makes sure
"shortcut" is actually installed properly (before).

If it wouldn't do that then I could also simply omit the dependency. However I
would have to add both packages to the profile then.
In my eyes you're not talking about real dependencies. You're talking about
includes! So you say that if a package is installed another one is
automatically pulled to the profile (regarding its priority).

There is anyway an ongoing discussion for "chained installations" (see Bug
111).
To me it looks like your goal would simply be to "pull" some packages to the
profile which are not actually add to the profile. Each package should be able
to pull some other packages while the install order completely depends on the
package priorities.

To allow this I would clearly add a new XML node like <include... />.
I am absolutely against re-defining the meaning of dependencies as I totally
disagree that dependencies should be related in any way to priorities.

In general I don't like priorities at all (almost all my packages have priority
50). Why? It's quite simple - if one uses a proper dependency management it
would even be possible to install all packages in parallel. But this only works
if you know all the dependencies between them because some of them have to wait
until others are finished (no matter what their priority is).

Hava a look at Unix init scripts. Older systems are based on priorities which
are controlled by the file name. This does not allow to start multiple scripts
in paralle. All newer systems (look at Gentoo or BSD) define dependencies
between modules and allow to run them independently. This works perfectly if
dependencies are inserted properly. OK, I have to admit that parallel package
installation is not so easy (Windows installer does not work in parallel) but
you get the idea.


Bug 111 goes into a slightly different directory. It asks for chained
installation. Therefore the algorithm using dependencies, includes and chained
installations would be as follows (simplified):

- add included packages of all applying packages to the profile
- sort packages
- start installation
- check for dependencies, install them if required
- install actual package
- run chained packages in order

Again, cheined packages will not regard priorities as a package with very high
priority will also install a chained package even with lowest priority before
proceeding to the next package.


Again, dependencies are called dependencies since the package specifying the
dependency really needs the specified package to run or even to install. So I
will not change that as it will potentially break a lot of systems.

However as I wrote I could probably offer a kind of <include /> syntax to add a
specified package to the profile on run-time while taking care of the
priorities.


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