[pacman-dev] Orphaning files in the filesystem after unsuccessful pacman -R

[smiszym]

Hello,

It seems I found a bug in pacman. Some information first:
  version: pacman 4.1.2-5 prebuilt from official repo
   system: Linux 3.12.7-2-ARCH i686

So it happened when I tried to remove alex package.

$ sudo pacman -R alex
    [sudo] password for michael:
    checking dependencies...

    Packages (1): alex-3.1.3-1

    Total Removed Size:   1.18 MiB

    :: Do you want to remove these packages? [Y/n] y
    error: cannot remove file '/usr/': Read-only file system
    ldconfig: Can't create temporary cache file /etc/ld.so.cache~:
Read-only file system
    error: command failed to execute correctly

Uhm... I forgot I have root filesystem mounted read-only. No problem.

$ sudo mount / -o remount,rw
$ sudo pacman -R alex
    error: target not found: alex

What? How could pacman remove the package from a read-only filesystem?
Or maybe...

$ sudo pacman -S alex
    resolving dependencies...
    looking for inter-conflicts...

    Packages (1): alex-3.1.3-1

    Total Installed Size:   1.18 MiB

    :: Proceed with installation? [Y/n] y
    (1/1) checking keys in keyring     [###] 100%
    (1/1) checking package integrity   [###] 100%
    (1/1) loading package files        [###] 100%
    (1/1) checking for file conflicts  [###] 100%
    error: failed to commit transaction (conflicting files)
    alex: /usr/bin/alex exists in filesystem
    alex: /usr/share/alex/AlexTemplate exists in filesystem
    alex: /usr/share/alex/AlexTemplate-debug exists in filesystem
    alex: /usr/share/alex/AlexTemplate-ghc exists in filesystem
    alex: /usr/share/alex/AlexTemplate-ghc-debug exists in filesystem
    alex: /usr/share/alex/AlexTemplate-ghc-nopred exists in filesystem
    alex: /usr/share/alex/AlexWrapper-basic exists in filesystem
    alex: /usr/share/alex/AlexWrapper-basic-bytestring exists in filesystem
    alex: /usr/share/alex/AlexWrapper-gscan exists in filesystem
    alex: /usr/share/alex/AlexWrapper-monad exists in filesystem
    alex: /usr/share/alex/AlexWrapper-monad-bytestring exists in filesystem
    alex: /usr/share/alex/AlexWrapper-monadUserState exists in filesystem
    alex: /usr/share/alex/AlexWrapper-monadUserState-bytestring exists
in filesystem
    alex: /usr/share/alex/AlexWrapper-posn exists in filesystem
    alex: /usr/share/alex/AlexWrapper-posn-bytestring exists in filesystem
    alex: /usr/share/alex/AlexWrapper-strict-bytestring exists in filesystem
    alex: /usr/share/licenses/alex/BSD3 exists in filesystem
    Errors occurred, no packages were upgraded.

...it didn't remove anything of course, but broke the database. Here
is the point of the bug report. I repaired things like this:

$ sudo pacman -S --force alex
    resolving dependencies...
    looking for inter-conflicts...

    Packages (1): alex-3.1.3-1

    Total Installed Size:   1.18 MiB

    :: Proceed with installation? [Y/n] y
    (1/1) checking keys in keyring     [###] 100%
    (1/1) checking package integrity   [###] 100%
    (1/1) loading package files        [###] 100%
    (1/1) checking for file conflicts  [###] 100%
    (1/1) checking available disk space[###] 100%
    (1/1) installing alex              [###] 100%
$ sudo pacman -R alex
    checking dependencies...

    Packages (1): alex-3.1.3-1

    Total Removed Size:   1.18 MiB

    :: Do you want to remove these packages? [Y/n] y
    (1/1) removing alex                [###] 100%

but this is all but elegant. The same problem occurred for several
other packages, in identical way.

I'm very surpised to find bug like that in pacman and still not sure
that it isn't just my mistake somewhere. Anyway, please test it. I
hope this report will help you. What do you think?

Best regards
Michał Szymański