qtest wrapped libraries?

[ttamttam]

Trying dune runtest in the following toy project fails because during test runner generation, qtest does not add open Mylibrary at the top of the ML test file, which would be needed because Mylibrary is wrapped.

~/projets/test_qtest$ ls -lRt .
.:
total 8
drwxr-xr-x 2 me me 4096 22 déc.  09:56 lib
-rw-r--r-- 1 me me   46 22 déc.  09:48 dune-project

./lib:
total 8
-rw-r--r-- 1 matt matt 92 22 déc.  09:56 dune
-rw-r--r-- 1 matt matt 42 22 déc.  09:55 a.ml
~/projets/test_qtest$ cat dune-project
(lang dune 2.9)

(package
 (name mylibrary)
)
~/projets/test_qtest$ cat lib/dune
(library
 (public_name mylibrary)
 ; (wrapped false)
 (inline_tests
  (backend qtest.lib)))
~/projets/test_qtest$ cat lib/a.ml
let add = (+)

(*$= add

  (add 1 2) 3
*)

I had a look at qtest.2.11.2 inline_tests backend definition:

  (inline_tests.backend
    (generate_runner (run qtest extract --quiet %{impl-files} %{intf-files}))
    (runner_libraries qcheck ounit2 bytes)))

As an experiment, I added --preamble "open %{library-name}" in the generate_runner action, and pinned this modified qtest.

Then, my test failed again:

$ dune runtest
File "/home/me/.opam/4.13.1/lib/qtest/dune-package", line 31, characters 12-25:
31 |     "open %{library-name}"
                 ^^^^^^^^^^^^^
Error: Unknown variable "library-name"

Still experimenting, I then edited /home/me/.opam/4.13.1/lib/qtest/dune-package, replacing %{library-name} with Mylibrary: now, dune runtest is working.

So… What would be the right incantation to use (if there is one?), in order to get the Capitalized library name? And to get this added only if the tested library is wrapped?

Best regards