Thanks for reminding. The rebase isn't the problem, it's just that this patch is still in my backlog.

There seems to be an issue with some non-wrapped libraries without implementation for their main modules.
For instance with digestif.0.7.1: (side note: the latest version compiles fine)

#=== ERROR while compiling digestif.0.7.1 =====================================#
# context              2.1.0~beta3 | linux/x86_64 | ocaml-variants.4.12.0+trunk | file:///home/opam/opam-repository
# path                 ~/.opam/4.12.0+trunk/.opam-switch/build/digestif.0.7.1
# command              ~/.opam/4.12.0+trunk/bin/dune build -p digestif -j 47
# exit-code            1
# env-file             ~/.opam/log/digestif-7-a77a5e.env
# output-file          ~/.opam/log/digestif-7-a77a5e.out
### output ###
# File "src/dune", line 1, characters 0-206:
# 1 | (library
# 2 |  (name        digestif)
# 3 |  (public_name digestif)
# 4 |  (modules     digestif)
# 5 |  (wrapped     false)
# 6 |  (flags       (:standard -no-keep-locs))
# 7 |  (libraries   eqaf)
# 8 |  (modules_without_implementation digestif))
# Error: Rule failed to generate the following targets:
# - src/digestif.a
#       ocamlc src-c/.digestif_c.objs/byte/digestif.{cmo,cmt}

Does Modules.is_empty return false in this particular case? Or maybe this is an issue with dune master?

Does Modules.is_empty return false in this particular case? Or maybe this is an issue with dune master?

Could you try it with dune master if you don't mind?

Could you try it with dune master if you don't mind?

I just tried with dune master and this also failed

Just summarising an(other!) offline discussion on this: the (modules) trick is clearly misappropriating the feature, especially for wrapped libraries where it's not enough. Plan at the moment:

• introduce a dummy module by default, so a .a/.lib file is always created
• have an opt-in option which stdlib-shims can use to explicitly opt-out of the dummy module, and indicate to Dune that there will be no .a/.lib file. If the compiler generates one (i.e. if the user lied), Dune could choose to fail the build step (or just ignore the .a/.lib file, just like any other rule which generates files it didn't claim it was going to)
• note that Dune may need to be more liberal about external libraries for 4.12+ - a separately-compiled library providing a META could have foo.cmxa now and no foo.a/foo.lib
• in the future, as and when Dune becomes able to determine exactly when no .a/.lib will be generated, stop needing the opt-out flag

@dra27 , what is the current status of this specific plan for supporting 4.12?

@Octachron - there's a new fix in #3973

Oops, I missed this PR, thanks for the pointer!

No problem - this issue has created myriad issues and PRs!!