Reproduction requires a few packages:
- ocaml (4.14.2 - it's not working with 5 right now)
- dune (3.15.2 - should not matter)
- ocaml-solo5 (0.8.4 - but should not matter)
So, opam sw create 4.14.2 dune-variant-repro ; eval opam env ; opam install ocaml-solo5 dune
I suspect the ocaml-solo5 is needed for the findlib.conf.
This leads to the original issue reported in ocaml/dune#10460
$ dune bu dist
File "dune.build", line 13, characters 40-60:
13 | (libraries duration lwt mirage-bootvar mirage-bootvar.solo5
^^^^^^^^^^^^^^^^^^^^
Error: Library "mirage-bootvar.solo5" in
_build/solo5/duniverse/mirage-bootvar/solo5 is hidden (optional with
unavailable dependencies).
-> required by _build/solo5/main.exe
-> required by alias all (context solo5)
-> required by alias default (context solo5)
Change proposed by Rudi in ocaml/dune#10460 (comment) doesn't result in different behaviour.
The build results in a different error:
File "duniverse/mirage-time/unix/dune", line 5, characters 12-20:
5 | (libraries lwt.unix duration))
^^^^^^^^
Error: Library "lwt.unix" not found.
-> required by library "mirage-time.unix" in
_build/solo5/duniverse/mirage-time/unix
-> required by library "mirage-bootvar.solo5" in
_build/solo5/duniverse/mirage-bootvar/solo5
-> required by executable main in dune.build:11
-> required by _build/solo5/main.exe
-> required by _build/solo5/hello.hvt
-> required by _build/solo5/dist/hello.hvt
-> required by alias dist/all (context solo5)
-> required by alias dist/default (context solo5)
There's a different error:
Error: No implementation found for virtual library "mirage-time" in
_build/solo5/duniverse/mirage-time/src.
-> required by library "mirage-solo5" in
_build/solo5/duniverse/mirage-solo5/lib
-> required by library "mirage-bootvar.solo5" in
_build/solo5/duniverse/mirage-bootvar/solo5
-> required by executable main in dune.build:11
-> required by _build/solo5/main.exe
-> required by _build/solo5/hello.hvt
-> required by _build/solo5/dist/hello.hvt
-> required by alias dist/all (context solo5)
-> required by alias dist/default (context solo5)
Change in duniverse/mirage-time/src/dune the
(default_implementation mirage-time.unix) to
(default_implementation mirage-time.solo5).
In dune.build, the dependencies include: mirage-bootvar.solo5, mirage-time.solo5
Both are implementations of the virtual_modules (mirage-bootvar, mirage-time).
The package mirage-solo5 depends on mirage-time; the package mirage-bootvar depends on mirage-solo5.
It looks like during building mirage-bootvar.solo5 the specification of the implementation of mirage-time is not taken into consideration.