[gentoo-alt] Detecting unsatisfied dependencies in gentoo-alt

[Peter Waller]

Dear list,

I hope this can be of use to you. I have written a few hundred lines of
python which can parse the dependency lines in the metadata cache. Now it is
possible to generate a big list of unsatisfied dependencies, to detect
packages which will not merge or run. I still haven't tuned the output so
that it is totally optimal, I don't think, but it is better than nothing.

The program can be run in several ways, and the source still needs tweaking
to make it work differently. I have attached the output for a few different
scenarios.

output-portage.txt : The run on portage. It detects 7 packages which it
thinks will not merge (under certain USE flag conditions). I did this to
show that the program produces no false-positives on a system we know should
be reasonably polished
output-prefix-nouse.txt : A run on prefix, ignoring any dependencies pulled
in by use flags. Reveals 40 missing packages which will probably prevent 32
packages from merging (including metacity and nautilus)
output-prefix-withuse.txt : A run on prefix, looking at all possible use
flag combinations (ignoring those listed in use.mask. As darkside was saying
on IRC, this could be used to detect new use flags which should obviously go
in use.mask). This finds 219 packages which will probably not merge or run,
and 347 packages missing from prefix.

I know grobian had some idea of making this run nightly (It's nice and fast
now, ~5 seconds with a warm disk cache, ~30 to run on the main portage
tree). I'm happy to help out however I can to get this happening, just let
me know what you need of it.

I have various ideas of how it might be improved.

* The only part of the dependency detection still missing is the OR-wise
dependencies. This should not affect many packages, but does mean that the
list is not quite complete.
* When a missing dependency is found, it would be pretty easy to go and look
at the graph of the required packages from portage, and generate a list of
packages which would need to be pulled in to fix it.
* Output could be prettier. I don't know exactly what is most useful yet
though.

Please, let me know what you think.

Cheers,

- Pete