Bug#1055760: debian-policy,dpkg: Please document maintscript flow with `prerm deconfigure`

Package: debian-policy,dpkg
Severity: wishlist
X-Debbugs-Cc: [email protected],[email protected]

Hi

The flow charts at 
https://www.debian.org/doc/debian-policy/ap-flowcharts.html 
unfortunately does not cover the `prerm deconfigure [...]`

This makes it hard to figure whether a package needs to consider 
`deconfigure` when it needs to have `prerm` code.

Like if a `prerm deconfigure` will be followed by a `prerm remove` then 
doing anything in `prerm deconfigure` is basically redundant (?) as you 
can just do it in `prerm remove` instead. Or does `deconfigure` imply a 
`remove` (despite the name suggesting it would only move the package to 
"configured -> unpacked")

This would also be relevant to understand whether postinst need to react 
to `abort-deconfigure` or can one assume that a `configure` will always 
(timely) follow an `abort-deconfigure`?

I had a look at `deb-prerm` and `deb-postinst`. Sadly, these does not 
answer my questions (they say when the action occurs). However, I am 
missing an overview and the terse descriptions do not give me that (nor 
tell me what state the package is in after success/failure, which could 
have helped in some cases).

Best regards,
Niels

PS: In debhelper, I have liberally sprinkled in `abort-*` cases in to 
the postinst and avoided any conditions in the prerm scripts. But it is 
not out of understanding but out of assumptions.