Opam install ocsigen-start failed

New in Ocaml world, the installation of ocsigen-start package failed; I believe that something is wrong about dependencies but I don’t have any clues :thinking:.

~$ opam config report
# opam config report
# opam-version      2.0.8 
# self-upgrade      no
# system            arch=x86_64 os=linux os-distribution=debian os-version=11
# solver            builtin-mccs+glpk
# install-criteria  -removed,-count[version-lag,request],-count[version-lag,changed],-changed
# upgrade-criteria  -removed,-count[version-lag,solution],-new
# jobs              3
# repositories      1 (http) (default repo at 256625cb)
# pinned            0
# current-switch    5.0.0

Debug log:

~$ opam  install --debug ocsigen-start
00:00.001  GSTATE                 LOAD-GLOBAL-STATE @ /home/gub/.opam
00:00.001  RSTATE                 LOAD-REPOSITORY-STATE @ /home/gub/.opam
00:00.299  RSTATE                 Loaded /home/gub/.opam/repo/state.cache in 0.267s
00:00.530  RSTATE                 Cache found
00:00.530  STATE                  LOAD-SWITCH-STATE @ 5.0.0
00:03.717  STATE                  Detected changed packages (marked for reinstall): {}
00:03.744  STATE                  Switch state loaded in 3.213s
00:03.758  FILE(switch-state)     Wrote /home/gub/.opam/5.0.0/.opam-switch/backup/state-20230404075519.export in 0.015s
00:03.906  CLIENT                 INSTALL ocsigen-start
00:04.241  SYSTEM                 [log-2660-4bcc67] (in 0.023s) lsb_release -s -r
00:04.396  SYSTEM                 [log-2660-ccabea] (in 0.146s) ocamlc -vnum
00:04.632  CLIENT                 Orphans: (changes: { ocsigen-start.1.0.0, ocsigen-start.1.1.0, ocsigen-start.1.2.0, ocsigen-start.1.3.0, ocsigen-start.1.4.0, ocsigen-start.1.5.0, ocsigen-start.1.6.0, ocsigen-start.1.7.0, ocsigen-start.1.8.0, ocsigen-start.2.0.0, ocsigen-start.2.0.1, ocsigen-start.2.2.2, ocsigen-start.2.3.0, ocsigen-start.2.4.0, ocsigen-start.2.7.0, ocsigen-start.2.9.1, ocsigen-start.2.9.2, ocsigen-start.2.11.0, ocsigen-start.2.12.0, ocsigen-start.2.13.0, ocsigen-start.2.15.0, ocsigen-start.2.15.1, ocsigen-start.2.15.2, ocsigen-start.2.16.0, ocsigen-start.2.16.1, ocsigen-start.2.18.0, ocsigen-start.2.19.2, ocsigen-start.2.19.3, ocsigen-start.2.21.1, ocsigen-start.4.0.0, ocsigen-start.4.0.1, ocsigen-start.4.1.0, ocsigen-start.4.3.0, ocsigen-start.4.4.0, ocsigen-start.4.5.0, ocsigen-start.4.6.0, ocsigen-start.4.7.0, ocsigen-start.5.0.0, ocsigen-start.6.0.1, ocsigen-start.6.1.0 }, transitive: false) -> full {}, versions {}
00:05.023  SOLVER                 resolve request=install:(ocsigen-start) remove:() upgrade:()
00:06.625  SOLVER                 Load cudf universe (depopts:false, build:true, post:true)
00:06.806  CUDF                   resolve request=install:(ocsigen-start) remove:() upgrade:()
00:06.806  SOLVER                 Calling solver builtin-mccs+glpk with criteria -removed,-count[version-lag,request],-count[version-lag,changed],-changed
00:08.437  CUDF                   Solver call done in 1.630
00:09.598  CLIENT                 conflict!
Sorry, no solution found: there seems to be a problem with your request.

No solution found, exiting
00:09.599  SYSTEM                 rm /home/gub/.opam/5.0.0/.opam-switch/backup/state-20230404075519.export

Ty for help

Hello @Gub,

Currently, ocsigen-start is not compatible with OCaml 5 because one of its dependencies (namely pgocaml) is not compatible with OCaml 5.

According to your output of the command opam config report, your active opam switch probably uses the version 5 of OCaml, hence the problem.

Prior to opam 2.1, to force the installation when there is a conflict on the OCaml version, one needs to use the flag --unlock-base. So, in your case, the following command should do the job:

opam install --unlock-base ocsigen-start

What I have done:
Install ocsigen-start with ocaml 4.11.1.

I will learn with these versions and upgrade later…

Ty for your answer.