Debian dpkg behavior for all cases

opendj.log

# Deps available; regular install, remove, and purge
dpkg -i opendj-deb-standard-repack.deb
Selecting previously unselected package opendj.
(Reading database ... 128058 files and directories currently installed.)
Unpacking opendj (from opendj-deb-standard-repack.deb) ...
/var/lib/dpkg/tmp.ci/preinst Arguments: install
Setting up opendj (3.0.0) ...
/var/lib/dpkg/info/opendj.postinst Arguments: configure
Processing triggers for ureadahead ...

dpkg -i opendj-deb-standard-repack.deb
(Reading database ... 128438 files and directories currently installed.)
Preparing to replace opendj 3.0.0 (using opendj-deb-standard-repack.deb) ...
/var/lib/dpkg/info/opendj.prerm Arguments: upgrade 3.0.0
/var/lib/dpkg/tmp.ci/preinst Arguments: upgrade 3.0.0
Unpacking replacement opendj ...
/var/lib/dpkg/info/opendj.postrm Arguments: upgrade 3.0.0
Setting up opendj (3.0.0) ...
/var/lib/dpkg/info/opendj.postinst Arguments: configure 3.0.0
Processing triggers for ureadahead ...

dpkg --remove opendj
(Reading database ... 128438 files and directories currently installed.)
Removing opendj ...
/var/lib/dpkg/info/opendj.prerm Arguments: remove
/var/lib/dpkg/info/opendj.postrm Arguments: remove
Processing triggers for ureadahead ...

dpkg --purge opendj
(Reading database ... 128059 files and directories currently installed.)
Removing opendj ...
Purging configuration files for opendj ...
/var/lib/dpkg/info/opendj.postrm Arguments: purge
dpkg: warning: while removing opendj, directory '/opt' not empty so not removed.


# Deps available; install then purge
dpkg -i opendj-deb-standard-repack.deb
dpkg --purge opendj
(Reading database ... 128438 files and directories currently installed.)
Removing opendj ...
/var/lib/dpkg/info/opendj.prerm Arguments: remove
/var/lib/dpkg/info/opendj.postrm Arguments: remove
Purging configuration files for opendj ...
/var/lib/dpkg/info/opendj.postrm Arguments: purge
dpkg: warning: while removing opendj, directory '/opt' not empty so not removed.
Processing triggers for ureadahead ...

# Deps not available
dpkg -i opendj-deb-standard-repack.deb
Selecting previously unselected package opendj.
(Reading database ... 128058 files and directories currently installed.)
Unpacking opendj (from opendj-deb-standard-repack.deb) ...
/var/lib/dpkg/tmp.ci/preinst Arguments: install
dpkg: dependency problems prevent configuration of opendj:
 opendj depends on fake-package; however:
  Package fake-package is not installed.
dpkg: error processing opendj (--install):
 dependency problems - leaving unconfigured
Processing triggers for ureadahead ...
Errors were encountered while processing:
 opendj

dpkg -i opendj-deb-standard-repack.deb
(Reading database ... 128438 files and directories currently installed.)
Preparing to replace opendj 3.0.0 (using opendj-deb-standard-repack.deb) ...
/var/lib/dpkg/tmp.ci/preinst Arguments: upgrade 3.0.0
Unpacking replacement opendj ...
/var/lib/dpkg/info/opendj.postrm Arguments: upgrade 3.0.0
dpkg: dependency problems prevent configuration of opendj:
 opendj depends on fake-package; however:
  Package fake-package is not installed.
dpkg: error processing opendj (--install):
 dependency problems - leaving unconfigured
Processing triggers for ureadahead ...
Errors were encountered while processing:
 opendj

Also useful:
https://wiki.debian.org/MaintainerScripts