bug#37388: <nginx-configuration> can lead to syntactically invalid configs

["Ludovic Courtès" <ludo@gnu.org>]

Hello Guix!

It’s nice that we have <nginx-configuration> but I noticed that, unlike
most or all other configuration records that we have, it’s possible to
create an <nginx-configuration> record that leads to a syntactically
invalid nginx config file.

For example, if you have a location block like this:

        (nginx-location-configuration
          (uri "/manual/")
          (body (list "alias /srv/guix-manual")))

Guix will silently create an invalid nginx config file, which you’ll
only notice once you’ve reconfigured and nginx fails to start.

See why?  That’s because we’re missing a semicolon in the “alias”
directive, and that directive is spit out directly as is.

To address it, we could have record types for <alias>, <root>, and all
the directives out there; it could be tedious, unless we automate it,
effectively creating a complete EDSL.

Another approach would be to have an sexp representation of the nginx
configuration language.  That’d effectively replace semicolons with
parentheses :-), but more importantly, that would allow us to not paste
strings as-is in the resulting config file.  The downside is that it’s
very much “free style” compared to records, but we could still
pattern-match the sexp to validate certain properties.

Thoughts?

Ludo’.