enabled_if field does not support environment variables on executable stanza

[fsestini]

In the docs, it is claimed that the field enabled_if behaves for executables the same as libraries. As of dune 3.15, enabled_if should allow to enable/disable a library (and therefore executable) based on environment variables.

Expected Behavior

Given a directory with

dune-project file:

(lang dune 3.15)
(name dune-test)
(package
 (name dune-test))

dune file:

(executable
 (name main)
 (public_name dune_test)
 (modules main)
 (package dune-test)
 (modes exe))

(executable
 (name main_2)
 (public_name dune_test_2)
 (enabled_if (= %{env:MYVAR=disabled} enabled))
 (modules main_2)
 (package dune-test)
 (modes exe))

and files main.ml and main_2.ml (omitted as irrelevant), running dune build should result in producing either main.exe, or both main.exe and main_2.exe, based on the value of $MYVAR.

Actual Behavior

dune build fails with the following error:

File "dune", line 11, characters 16-37:
11 |  (enabled_if (= %{env:MYVAR=disabled} enabled))
                     ^^^^^^^^^^^^^^^^^^^^^
Error: Only architecture, system, model, os_type, ccomp_type, profile,
ocaml_version, context_name and arch_sixtyfour variables are allowed in this
'enabled_if' field. Please upgrade your dune language to at least 3.15.

Note that dune-project already states (lang dune 3.15). Setting the language version to 3.16 results in the same error.

Also note that the same enabled_if expression has the desired effect if used on library.

Specifications

• Version of dune: 3.16.0
• Version of ocaml: 4.12.1
• Operating system: macOS 13.5.1, Darwin Kernel Version 22.6.0 arm64

[rgrinberg]

Thanks for the report. @moyodiallo do you want to try fixing this one?

[moyodiallo]

Thanks for the report. @moyodiallo do you want to try fixing this one?

Yeah, I'll try.