Dune generated opam files are not correct when the version is = version

[FardaleM]

Expected Behavior

When generate_opam_files is enabled and a dependency has the constraint (= version), the opam file should contain the constraint {= version}

Actual Behavior

The constraint is currently {= "version"}.

Reproduction

By using the following dune-project file:

(lang dune 3.13)

(generate_opam_files true)

(package
  (name bug)
  (depends (bug-lib (= version)))
)

and the following dune file:

(executable
 (name bug))

with an empty bug.ml file, the command dune build will generate the bug.opam file.

Specifications

• Version of dune (output of dune --version): 3.16.0
• Version of ocaml (output of ocamlc --version): 5.2.0
• Operating system (distribution and version): Debian Unstable

[emillon]

Hi,
This is the intended behavior, there's no difference between "version" and version in dune files. To generate version variable in opam files, use :version in the dune file:

(depends (bug-lib (= :version)))

I'll add that as an example in the docs.