FS#7524 - misleading info when a versioned dep needed by another dep
Attached to Project:
Pacman
Opened by Not Important (pholie) - Wednesday, 27 June 2007, 23:08 GMT
Last edited by Roman Kyrylych (Romashka) - Thursday, 28 June 2007, 08:33 GMT
Opened by Not Important (pholie) - Wednesday, 27 June 2007, 23:08 GMT
Last edited by Roman Kyrylych (Romashka) - Thursday, 28 June 2007, 08:33 GMT
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Details
Summary and Info:
I tried to install a compiz-git which requires cairo. I already have cairo-lcd installed which provides and conflicts with cairo. # pacman -S compiz-git resolving dependencies... done. looking for inter-conflicts... :: cairo conflicts with cairo-lcd. Remove cairo-lcd? [Y/n] n error: unresolvable package conflicts detected error: failed to prepare transaction (conflicting dependencies) :: cairo: conflicts with cairo-lcd pacman -Si compiz-git Repository : compiz-fusion Name : compiz-git Version : 20070626-1 Groups : None Provides : None Depends On : mesa cairo libxml2 libxslt startup-notification libpng libxdamage libxrandr libwnck gnome-desktop control-center librsvg libxcomposite metacity libgl Removes : None Conflicts With : compiz-core compiz compiz-decorator-gnome compiz-decorator-kde Replaces : compiz-core-git compiz compiz-decorator-gnome compiz-decorator-kde Download Size : 973.82 K Installed Size : 4010.97 K Description : Composite and window manager MD5 Sum : 231b72c7e3893444238baaf5556c1470 pacman -Qi cairo-lcd Name : cairo-lcd Version : 1.4.6-1 URL : http://cairographics.org/ License : LGPL MPL Groups : None Provides : cairo Depends On : libpng libxrender fontconfig Removes : None Required By : cairo-perl gtk-aqualooks-engine pango poppler Conflicts With : cairo Installed Size : 1342.33 K Packager : Arch Linux (http://www.archlinux.org) Architecture : i686 Build Date : Sat Jun 9 02:30:58 2007 UTC Build Type : Unknown Install Date : Wed Jun 27 22:29:39 2007 UTC Install Reason : Explicitly installed Install Script : No Description : Cairo vector graphics library (with custom LCD filter) So I couldn't figure it out why it wants to remove the cairo-lcd until I ran it with --debug. ... debug: depcmp: cairo-lcd-1.4.6-1 ~= cairo => match ... debug: missing dependency 'pycairo' for package 'pygtk' ... debug: started resolving dependencies ... debug: depcmp: cairo-lcd-1.4.6-1 >= cairo-1.4.6-2 => no match debug: depcmp: cairo-lcd-1.4.6-1 >= cairo-1.4.6-2 => no match ... debug: missing dependency 'cairo' for package 'pycairo' ... debug: pulling dependency cairo (needed by pycairo) ... debug: package 'cairo' not found in sync debug: adding package cairo-1.4.8-2 to the transaction targets ... ... debug: cannot find package installed 'cairo' ... ... debug: checkconflicts: db vs target 'cairo' debug: found conflict 'cairo' : package 'cairo' So here it is: # pacman -Si pycairo Repository : current Name : pycairo Version : 1.4.0-2 Groups : None Provides : None Depends On : python>=2.5 cairo>=1.4.6-2 python-numeric>=24.2-2 Removes : None Conflicts With : None Replaces : None Download Size : 31.32 K Installed Size : 0.00 K Description : Python bindings for the cairo graphics library MD5 Sum : 093154b9eb145b06617e94aeeb80bf1d The package that I want to install, compiz-git needs cairo (no matter what version), this condition is true but *also* its dependency, pycairo (not yet installed) needs cairo>=1.4.6-2 which is not installed. So after I let it replace the conflicting package or update manually the cairo-lcd to the newest version, it installs successfully at last. The installing process should inform which of the deps needs exactly which particular version of the package that is conflicting so one would understand better why the conflict arises. A debug log attached in case it's needed. 
cairo-conflicts.txt
(59.2 KiB)
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it would indeed be better if pacman showed that cairo-lcd doesn't provide the correct version.
The problem happens at two different steps, without any real link between them.
1) dependency resolving
Here, it realizes that cairo-lcd-1.4.6-1 doesn't match the cairo-1.4.6-2 dependency. So it pulls cairo-1.4.6-2.
2) conflicts resolving
it finds out that cairo conflicts with cairo-lcd. But we don't keep track of what pulled every package. Se we don't know that cairo was pulled because of pycairo.
Maybe we could check the dependencies again, but that would be weird. We could rather try to keep the tree of dependencies computed by checkdeps somehow, and reuse this information, as Nagy mentioned several times.
I have no idea how hard this would be however. Or maybe there is a simpler solution I don't see. So comments welcome.
The problem is, that the installed cairo-lcd is not "good enough" to satisfy the dependency of compiz-git that's why the original cairo is pulled. But this of course conflicts with cairo-lcd which thus was selected for removal; so if user wants to keep his cairo-lcd then of course he cannot install compiz-git. (Versioned provisions can help here.)
I cannot admit that the provided info is misleading, I would say, it maybe not enough.
So we can modify the unsuccessful conflict resolving error message something like this:
If pulledpkg<->localpkg conflict wasn't resolved, we could say: "A needed dependency ('pulledpkg') conflicts with a local package ('localpkg')."
Of course we could change pmconflict_t struct to store pmpkg_t...
Now our conflict_check stuff is quite sophisticated, so after outerconflict call we should know that conflict->package1 is the target package.