Use (format-dune-file) instead of dune format-dune-file

[nojb]

Hello,

You are currently calling dune format-dune-file from one of your tests. This command does not honour the Dune lang version used in the project which means that your test will break whenever we change the formatting style in Dune.

In Dune 3.18 we introduced a built-in action (format-dune-file <src> <dst>) precisely for this purpose. This action honours the current Dune lang version and does not require shelling out to an external process.

Note that dune format-dune-file may evolve in ways that may not be backwards compatible in the near future (as the CLI interface does not have any backwards compatibility or versioning guarantees), so we are encouraging users of this command to switch to the action instead.

See ocaml/dune#10892 (comment) for some of the context.

[maiste]

Thanks @nojb!
I was about to do it today but you were clearly faster 😄

One question I have regarding this: shouldn't it add a dependency on dune >= 3.18 to make sure it supports the functionality?

[nojb]

Thanks @nojb! I was about to do it today but you were clearly faster 😄

One question I have regarding this: shouldn't it add a dependency on dune >= 3.18 to make sure it supports the functionality?

Yes, indeed. I pushed a fix (I think ; I am not very familiar with OPAM).