Eval does not stop on the first assertion failure it encouters.
Instead, it tries to evaluate all assertions and returns with a list of
those that failed.
This means our very top `config.mailserver.stateVersion != null`
assertion does not gate against any other assertions trying to compare
null against an integer.
The error prior to this commit can be reproduced by removing
`mailserver.stateVersion = 999;` in tests/lib/config.nix and then trying
to evaluate any of the tests:
~~~bash
# nix eval --raw .#checks.x86_64-linux.internal-unstable
error:
… while evaluating the attribute 'outPath'
at /nix/store/syvnmj3hhckkbncm94kfkbl76qsdqqj3-source/lib/customisation.nix:421:7:
420| drv.drvPath;
421| outPath =
| ^
422| assert condition;
… while calling the 'getAttr' builtin
at «internal»:1:500:
(stack trace truncated; use '--show-trace' to show the full trace)
error: cannot compare null with an integer
~~~
With upcoming changes to the dovecot home and maildirectories we need to
introduce a way to nudge users to inform themselves about manual
migration steps they might need to carry out.
The idea here is to allow us to safely make breaking changes and notify
the user of required migration steps at eval time, so they can make the
necessary changes in time.
To generate the list of options, we need to generate and commit a rst
file to make all files available for ReadTheDoc.
An Hydra test ensures this generated file is up-to-date. If it is not
up-to-date, the error message explains the user how to generate it:
the user just needs to run `nix-shell --run generate-rst-options`.
