[3.0 opam failures] This is not a regular file (S_DIR)

[voodoos]

Error log from posix-socket.2.0.0:

#=== ERROR while compiling posix-socket.2.0.0 =================================#
# context              2.1.1 | linux/x86_64 | ocaml-base-compiler.4.12.1 | file:///home/opam/opam-repository
# path                 ~/.opam/4.12+dune3/.opam-switch/build/posix-socket.2.0.0
# command              ~/.opam/opam-init/hooks/sandbox.sh build dune build -p posix-socket -j 71 @install
# exit-code            1
# env-file             ~/.opam/log/posix-socket-19-dacd78.env
# output-file          ~/.opam/log/posix-socket-19-dacd78.out
### output ###
# File "posix-socket/src/generator/dune", line 16, characters 0-190:
# 16 | (rule
# 17 |  (targets gen_types_c)
# 18 |  (deps
# 19 |   (:c_code ./gen_types.c))
# 20 |  (action
# 21 |   (run %{ocaml-config:c_compiler} -I %{lib:ctypes:} -I
# 22 |     %{ocaml-config:standard_library} -o %{targets} %{c_code})))
# Error: File unavailable: /home/opam/.opam/4.12+dune3/lib/ctypes
# This is not a regular file (S_DIR)

Impacted packages:

• posix-socket.2.0.0 (log)
• posix-types.2.0.0 (log)
• sys-socket.1.0.0 (log)
• posix-uname.2.0.0 (log)
• ctypes-zarith.0.2.0 (log)
• luv.0.5.10 (log)
• posix-getopt.2.0.0 (log)
• lp-glpk (log)
• mpg123.0.3 (log)
• portmidi.0.1 (log)
• posix-signal.2.0.0 (log)

Full report.

Parent issue: #5257

[ghost]

There are quite a few failures here and they all follow the same pattern: %{lib:ctypes:}. So let's (re-)add support for %{lib:<name>:} in lang dune < 2.0. No need to do it for all %{lib:<name>:<dir>} in general as that's more complicated and there doesn't seem to be any use case for it.

In lang dune >= 3.0, the recommendation is to switch to the ctypes support.