Specifying multiple binary package dependencies

[Sam Varshavchik]

I am building multiple binary packages, and testing them: a main package,  
and additional sub-packages that depend on the main package. For this test I  
am using a main package and two additional sub-packages.

So, I built them and installed them.

I then increment the release number, and try to install only the main  
package and one of the two sub-packages. I expected one of two things to  
happen: either the old version of the missing additional package is going to  
get uninstalled because it depends on the removed old version of the main  
package, or dpkg will refuse to install anything.

To my surprise, dpkg installed the two packages and broke the third  
package's dependencies.

Before, I had three packages installed, version 0.71.4-147

Then I did "sudo dpkg -i [ first two packages, version 0.71.4-148 ]"

End result:

ii  libcourier-auth              0.71.4-148   amd64        Courier authenticati>
ii  libcourier-auth-dev          0.71.4-148   amd64        Courier authenticati>
ii  libcourier-auth-userdb       0.71.4-147   amd64        Userdb support for t>

A dpkg --status on the last one shows:

Depends: libcourier-auth (= 0.71.4-147), libc6 (>= 2.14), libcrypt1 (>= 1:4.1.0), libgdbm6 (>= 1.16)

This dependency is now broken. Am I missing something about how dependencies  
are supposed to work? I tried adding a Replaces: header, based on Debian's  
packaging documentation. It made no difference. After installing the first  
two updated packages with "dpkg -i" I ended up with:

ii  libcourier-auth                            0.71.4-152                      >
ii  libcourier-auth-dev                        0.71.4-152                      >
ii  libcourier-auth-userdb                     0.71.4-150

(I had some additional test builds and installs done which incremented the  
release numbers).

The first one's explicit dependencies, from dpkg:

Version: 0.71.4-152
Replaces: libcourier-auth-dev (<< 0.71.4-152), libcourier-auth-ldap (<<
0.71.4-152), libcourier-auth-mysql (<< 0.71.4-152), libcourier-auth-pgsql
(<< 0.71.4-152), libcourier-auth-pipe (<< 0.71.4-152), libcourier-auth-
sqlite (<< 0.71.4-152), libcourier-auth-userdb (<< 0.71.4-152)

I then tried using Conflicts instead of Replaces. I installed three -153  
versions, then attempted to install two -154 versions. I did get an error,  
but one of the packages got installed:

ii  libcourier-auth                            0.71.4-153                      >
iU  libcourier-auth-dev                        0.71.4-154                      >
iU  libcourier-auth-userdb                     0.71.4-153

I'm very confused. I do see this sentence in the Debian packaging guide:

"A Depends field takes effect only when a package is to be configured. It  
does not prevent a package being on the system" etc…

Which explains why the packages still wind up getting extracted, even though  
they break dependencies. But extracting the package overwrites the previous  
version's files. To me, this seems like the cat is out of the bag.

I also tried specifying "Breaks" in addition to "Replaces", that didn't get  
the desired results, producing more errors during installation and partially  
installing stuff.

So: is it possible to specify package dependencies that will prevent the  
packages from even be extracted unless everything is the same exact version- 
release; and otherwise abort the extraction? One of the two possible results  
will work for me:

A) completely prevent any attempt to install new versions if doing so will  
end up with broken dependencies

B) uninstall the missing subpackage automatically, as part of upgrading the  
remaining packages.

This is basically equivalent to rpm packages' "Requires" dependency. When  
I'm building the equivalemt rpm packages all I need is to have each sub- 
package specify:

Requires: $package = $version-$release

and that's it. depending on the packaging tool I use nothing is going to get  
extracted or overwritten, or the missing subpackage gets automatically  
removed. How can I do the same with deb packages?

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