Alt-Ergo 2.5.2 doesn't compile with `Dune 3.13`

[Pierrot]

Last week, I noticed that Alt-Ergo 2.5.2 cannot be installed on Marvin with opam anymore.
It was a fresh installation (the switch was completely new), so I guessed the issue comes from one of the dependencies of Alt-Ergo.

I didn't find a way to produce any valuable logs with Dune but I got the same bug on my laptop this afternoon so I started a long bisection with opam and dune.

My first guess was correct: the issue comes from the last version of Dune. It seems this combination of rules produces a deadlock somewhere in Dune 3.13 but everything is fine with older versions:

(executable
  (name Main_text)
  (public_name alt-ergo)
  (package alt-ergo)
  (libraries alt_ergo_common)
  (link_flags (:include flags.dune))
  (modules Main_text)
  (promote (until-clean)))

(rule
  (target alt-ergo.1)
  (action (with-stdout-to %{target} (run alt-ergo --help=groff))))

(install
 (files alt-ergo.1)
 (section man)
 (package alt-ergo))

If I removes the rules to generate and install the manpage, Alt-Ergo compiles. I believe dune is stuck in a deadlock.

To solve this issue I have several options:

• For the release 2.5.2, we can amend the package on opam-repository to add an upper bound for the dune version.
• We can remove the rule completely. Honestly, no one cares about the man page as we get a similar result with alt-ergo --help and I'm not fond of running Alt-Ergo while installing it.

It seems the compilation works if we specify the dependency:

(rule
  (deps (:bin Main_text.exe))
  (target alt-ergo.1)
  (action (with-stdout-to %{target} (run %{bin} --help=groff))))

I don't know if it's a bug of Dune. I open an issue ocaml/dune#9944 for it.

[Basile Clément]

The rule for alt-ergo.1 indeed seems incorrect (although it is a bug in dune that it gets stuck on it) as it doesn't declare its dependencies — it should be:

(rule
  (target alt-ergo.1)
  (action (with-stdout-to %{target} (run %{bin:alt-ergo} --help=groff))))

I think that is the patch that should go on opam-repository for release 2.5.2 (we could also release a version 2.5.3 that fixes the build, which the maintainers of opam-repository may prefer, not sure).

Re: building the man pages, this is very standard for dune packages, see e.g. opam doing the same thing. Man pages are a standard way to access this information, we shouldn't remove them.

[Pierrot]

Good news, the very last release of Dune solved the issue. It means that users can run into this bug only if they have the constraint dune <= 3.13.0 in some packages of their switches.

I think we should publish a release 2.5.3 to be sure everyone can install it.

[Basile Clément]

Ah, so this comment was correct. If only dune 3.13.0 is affected, I don't think we need to do a release — the likelihood of anyone having dune <= 3.13.0 as a dependency is fairly low (and it is a bogus dependency specification anyways).

[Pierrot]

Ok :)