Bug#557975: apt: Satisfy virtual dependencies in a second pass

[Michael Terry <michael.terry@canonical.com>]

Package: apt
Version: 0.7.23.1ubuntu2
Severity: normal
User: ubuntu-devel@lists.ubuntu.com
Usertags: origin-ubuntu lucid

Virtual dependency satisfaction picks the first possible provider alphabetically (bug 473247), but doesn't consider whether a package that will be installed later in this same run will satisfy the dependency.

To give a concrete example, consider xdg-utils (Depends: iceweasel | www-browser) and firefox (Depends: firefox-3.5 which provides www-browser).  Depending on how you order your apt-get line, you may end up with the arora browser.

To reproduce, in a chroot without any www-browsers installed:
$ apt-get install -s xdg-utils firefox | grep arora
$ apt-get install -s firefox xdg-utils | grep arora

The first line will install arora (i.e. give output).  The second line will not install arora and will give no output.

I claim that the set of installed packages should be the same (possibly with different install order, but the same set of packages).  Though maybe I'm misunderstanding how apt-get is designed to work when I expect that.

-- Package-specific info:

-- (no /etc/apt/preferences present) --


-- (/etc/apt/sources.list present, but not submitted) --


-- System Information:
Debian Release: squeeze/sid
  APT prefers karmic-updates
  APT policy: (500, 'karmic-updates'), (500, 'karmic-security'), (500, 'karmic')
Architecture: i386 (i686)

Kernel: Linux 2.6.31-15-generic (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages apt depends on:
ii  libc6                   2.10.1-0ubuntu15 GNU C Library: Shared libraries
ii  libgcc1                 1:4.4.1-4ubuntu8 GCC support library
ii  libstdc++6              4.4.1-4ubuntu8   The GNU Standard C++ Library v3

Versions of packages apt recommends:
ii  ubuntu-keyring                2009.08.28 GnuPG keys of the Ubuntu archive

Versions of packages apt suggests:
pn  apt-doc               <none>             (no description available)
ii  aptitude              0.4.11.11-1ubuntu6 terminal-based package manager
ii  bzip2                 1.0.5-3            high-quality block-sorting file co
ii  dpkg-dev              1.15.4ubuntu2      Debian package development tools
ii  lzma                  4.43-14ubuntu1     Compression method of 7z format in
ii  python-apt            0.7.13.2ubuntu4    Python interface to libapt-pkg
ii  synaptic              0.62.7ubuntu6      Graphical package manager

-- no debconf information