OCaml 5.3 support

[kit-ty-kate]

Dream currently doesn't compile with OCaml 5.3 and fails with the following error:

#=== ERROR while compiling dream-httpaf.1.0.0~alpha3 ==========================#
# context     2.2.1 | linux/x86_64 | ocaml-base-compiler.5.3.0~alpha1 | file:///home/opam/opam-repository
# path        ~/.opam/5.3~alpha1/.opam-switch/build/dream-httpaf.1.0.0~alpha3
# command     ~/.opam/5.3~alpha1/bin/dune build -p dream-httpaf -j 255
# exit-code   1
# env-file    ~/.opam/log/dream-httpaf-1-ea8029.env
# output-file ~/.opam/log/dream-httpaf-1-ea8029.out
### output ###
# (cd _build/default && /home/opam/.opam/5.3~alpha1/bin/ocamlc.opt -w -40 -g -bin-annot -bin-annot-occurrences -I src/vendor/h2/hpack/util/.gen_huffman.eobjs/byte -I /home/opam/.opam/5.3~alpha1/lib/ocaml/compiler-libs -no-alias-deps -open Dune__exe -o src/vendor/h2/hpack/util/.gen_huffman.eobjs/byte/dune__exe__Gen_huffman.cmo -c -impl src/vendor/h2/hpack/util/gen_huffman.ml)
# File "src/vendor/h2/hpack/util/gen_huffman.ml", line 113, characters 28-71:
# 113 |              [ Exp.constant (Pconst_integer (string_of_int code, None))
#                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
# Error: This expression should not be a constructor, the expected type is
#        Parsetree.constant

[aantron]

This is a problem in upstream package hpack, which was vendored into Dream until #351, but that PR hasn't been released yet. Does hpack compile with 5.3?

[kit-ty-kate]

The latest release does yes. (dune build @all has some issues anmonteiro/ocaml-h2#252 but it doesn't matter for vendored libraries)

[aantron]

This should vanish completely with the next releases of hpack and Dream. I'd like to keep it open to make sure I check it. Thank you!

[alxtuz]

I've tried to install Dream from repo with OCaml 5.3.0~alpha1. It fails on opam pin.
opam pin add dream --dev-repo
ends with the following error:

[dream.1.0.0~alpha7] synchronised (git+https://github.com/aantron/dream.git)
dream is now pinned to git+https://github.com/aantron/dream.git (version 1.0.0~alpha7)

[ERROR] Package conflict!
  * No agreement on the version of ocaml:
    - (invariant) → ocaml-base-compiler >= 5.3.0~alpha1 → ocaml-compiler >= 5.3.0~alpha1 → ocaml = 5.3.0
    - dream → dream-httpaf >= 1.0.0~alpha3 → ocaml < 5.3
    You can temporarily relax the switch invariant with `--update-invariant'

[NOTE] Pinning command successful, but your installed packages may be out of sync.

The same error is returned on opam install dream

[kit-ty-kate]

@alxtuz The issue is that you're pinning only dream from its remote repository, not the rest of the dream packages. So dream is trying to install dream-httpaf from opam-repository which has been rightfully marked as not compatible with OCaml 5.3. opam install still doesn't work since you've pinned the package.

The correct command is: opam pin add https://github.com/aantron/dream.git. I haven't tried it locally as i don't want to downgrade my installation of h2 but hopefully it should work for you.

[alxtuz]

Now running opam pin add https://github.com/aantron/dream.git fails on compilation of dream-mirage.dev with the error below:

[ERROR] The compilation of dream-mirage.dev failed at "dune build -p dream-mirage -j 7".

#=== ERROR while compiling dream-mirage.dev ===================================#
# context     2.2.1 | linux/x86_64 | ocaml-base-compiler.5.3.0~alpha1 ocaml-compiler.5.3.0~alpha1 | pinned(git+https://github.com/aantron/dream.git#6c75fb9e2289bb1ac7e6f22f6712bb242e1a2f96)
# path        ~/.opam/dream-5.3.0/.opam-switch/build/dream-mirage.dev
# command     ~/.opam/opam-init/hooks/sandbox.sh build dune build -p dream-mirage -j 7
# exit-code   1
# env-file    ~/.opam/log/dream-mirage-10236-0fb5d7.env
# output-file ~/.opam/log/dream-mirage-10236-0fb5d7.out
### output ###
# File "src/mirage/dune", line 18, characters 2-31:
# 18 |   dream-mirage.dream-paf.mirage
#        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
# Error: Library "dream-mirage.dream-paf.mirage" not found.
# -> required by library "dream-mirage" in _build/default/src/mirage
# -> required by _build/default/META.dream-mirage
# -> required by _build/install/default/lib/dream-mirage/META
# -> required by _build/default/dream-mirage.install
# -> required by alias install

Whole output attached
opam_pin_add_dream_output.txt

[aantron]

Perhaps

opam pin add dream-pure --dev-repo
opam pin add dream-httpaf --dev-repo
opam pin add dream --dev-repo

[kit-ty-kate]

The inverse would be required in this case since they already pinned all the dream packages:

opam pin remove dream-mirage

[alxtuz]

Thanks!
Both ways worked in my case. To make sure that pinning packages in that specific order is working I created switch again. Finally, it installed Dream with Ocaml 5.3.0~alpha1 without any errors.

Output attached
Dream_support_ocaml-5.3_output.txt

[aantron]

Thank you for checking that @alxtuz and for reporting @kit-ty-kate! I think we can close this issue at this point, because Dream master will continue to compile on 5.3, and if not, then not due to this issue, and any issues with Dream not compiling would likely be upstream.

[kit-ty-kate]

Would it be possible to have a release so people have a way to install the latest release of dream on 5.3 ? The final release is approaching and is currently slotted for mid-december

[aantron]

The release is in ocaml/opam-repository#27005. Thanks for the ping @kit-ty-kate!