Example fails to build with up-to-date opam-repository

[LogicalOverflow]

Updating the flake inputs of the example repo causes it to fail to build
since the release of ptime.1.1.0, even when ensuring ocaml 4 is used.

This invocation fails to build (my fork just updates the flake.lock and adds package "ocaml" ~max:"5.0.0" to the packages in the config.ml):

nix build "github:LogicalOverflow/mirage-hello-hillingar" --override-input opam-repository \
    "github:ocaml/opam-repository?rev=49c3ad31df3f2f60c2006211900b6553c097277c"

With the following error:

File "duniverse/mirage-logs/src/dune", line 4, characters 50-55:
4 |   (libraries logs mirage-clock lwt mirage-profile ptime))
                                                      ^^^^^
Error: Library "ptime" not found.
-> required by library "mirage-logs" in
   _build/default/duniverse/mirage-logs/src
-> required by executable main in dune.build:12
-> required by _build/default/main.exe
-> required by _build/default/hello
-> required by _build/default/dist/hello
-> required by alias dist/all
-> required by alias dist/default

The previous commit of opam-repository still works:

nix build "github:LogicalOverflow/mirage-hello-hillingar" --override-input opam-repository \
    "github:ocaml/opam-repository?rev=29869b0a1ad4fb7fc4a08d8a888a7abb6d0fa5cc"

The first bad commit is ocaml/opam-repository@49c3ad3, which adds ptime.1.1.0

I am not sure yet, where the issue lies (here, with opam-nix or somewhere else), but I am still able to build the example unikernel without nix. (mirage configure -t unix followed by make)

As a work-around, adding package "ptime" ~max:"1.1.0" to the packages in the config.ml allows the build with nix to work again.

[RyanGibb]

The reason dune isn't picking up ptime.1.1.0 from the monorepo is because it isn't built with dune. We use the overlay for v1.0.0 here: https://github.com/dune-universe/opam-overlays/blob/master/packages/ptime/ptime.1.0.0%2Bdune/opam, but no such overlay has been created for v1.1.0 (yet). (More info on these overlays here: https://github.com/dune-universe/opam-overlays.)

Building outside the nix derivation with make uses the opam monorepo solver which filters out non-dune dependent packages so that only those with overlays are returned. We're using opam's default solver which doesn't filter out non-dune dependent packages, hence this problem. This issue is tracked here: #3

I also tried to build a repository for using the solver on that had the non-dune dependent packages filtered out, but that was ridiculously slow: tweag/opam-nix#18 (comment).

Until #3 is resolved, manually specifying the dependency version seems like a reasonable workaround.

[LogicalOverflow]

Thanks for the insight. I'll close this issue then, as it's a duplicate of #3.