As of the last commit this builds and passes tests in CI. Our docker images for static binaries aren't updated, so it doesn't get all the way through, but close enough for now

What is the process of updating to be able to build stanc3 once we merge this? Is it very involved or just upgrading ocaml?

What are the next steps now?

It’s just opam switch 4.12.0 and then opam install <list of 3-4 packages> (or re-run the install_*.sh scripts).

The core_kernel PR was just approved so it’s just ppx_deriving and then updating our CI machines once that’s available. Then this should be ready

Super cool!

ppx_deriving is now cross-compiling which means I have been able to build and test a windows binary built with OCaml 4.12.0!

Once it is merged into opam-cross-windows this PR will be ready to go.

@serban-nicusor-toptal Is there a way to build docker images which feature different versions of our dependencies without messing up our existing CI? It's not ready yet but hopefully within the next week we will want to do this.

Hey @WardBrian, of course, we can do that, I think we can just create a new dir here with its Dockerfile/requirements. If you create a PR with it just tag me and I'll add it to the CI.

Thanks @serban-nicusor-toptal. After this is merged, we'd want these updated images to replace the existing stanc3:static etc, but for testing it would be great to have them separate. Building them will basically just consist of re-running the docker builds but with the scripts from this branch

@serban-nicusor-toptal I'm updating the scripts/ folder of this repository now. Would you be able to do the build or guide me through it?

The only thing that needs to change in the actual dockerfiles is any reference to js_of_ocaml* should just call scripts/install_js_deps.sh now. Besides that the same dockerfiles can be used with the new scripts

@serban-nicusor-toptal - could I actually update this PR to use those dockerfiles for the testing of this, and then after it is merged sort of redo #1020? Just trying to think of the shortest/fewest steps that doesn't require breaking the existing build pipeline while we sort it out

Just for the record I had a talk with Brian and if this can wait until tomorrow/Monday I think it's best if we can automate it. Our idea is to modify the current ci-scripts pipeline that build the Dockerfiles to receive at least 2 new arguments.
One is stanc3_branch and one is ciscripts_branch, pipeline will checkout these branches, build our Docker images using Dockerfile and scripts from those branches then push each image (here maybe I can also make it optional to build each image) to stanorg/stanc3 Dockerhub with a tag ${dockerfile_name}-${stanc3_branch}. We are also thinking about how to best do the "switch" so we avoid CI failures the best we can.
I'll get working on it.

I've switched the format from janestreet to the default. This still has most of the changes compared to compact (what we were using before), but it has a few key differences.

In particular, I didn't notice that the Jane Street format enforced every top-level expression being terminated with ;;, which I think is a really ugly thing to have in a code base

I've just collected all the non-formatting changes into a single commit here.

After trying all the options, I think the one that makes the fewest bad choices in still compact (what we've been using so far), so I've left that. My plan is to try to keep this PR at only those 2 core commits before merging to make the blame easier to navigate after the fact.

While the CI is still being worked out, this PR is ready for general review. The updates are pretty minimal besides the formatting changes.

This is passing in CI and ready to merge

Besides @rok-cesnovar 's Qs and my lil one I think this looks good!