Doc page about using opam by default with dune pkg

[gridbugs]

No description provided.

[Alizter]

Instead of setting contexts, wouldn't it be more useful to advertise (pkg disabled) for people looking to opt out of package management given a lock directory.

[Leonidas-from-XIV]

I would also rather advertise (pkg enabled)/(pkg disabled) over dune pkg lock. I think autolocking is probably what most people who just want a tool to install their dependencies want. dune pkg lock is more for those that want to lock their package versions, which I assume is a much smaller subset of the former.

[Alizter]

It is however possible if a person wishes to contribute to a repo that has a checked in lock file but they may wish to continue to use opam.

[gridbugs]

Ok updated to use autolocking instead of lockdirs.

[Alizter]

It is also possible to do this using the --workspace cli option. But I'm not sure if its worth going into all this detail about it.

[shonfeder]

Add a line about the CLI flag is probably good, because users of either strategy are likely to want to test or try the other in one-off commands.

[Alizter]

Do we have any genuine reasons other than not wanting to change for using opam? The existence of this tutorial might be confusing without the proper motivation.

[Sudha247]

Do we have any genuine reasons other than not wanting to change for using opam? The existence of this tutorial might be confusing without the proper motivation.

This is a good question. I think this tutorial is useful because a large chunk of users of dune pkg are coming from opam. Having an incremental path makes it easier to try out Dune package management without the doubt that something might break and go into an irrecoverable state. Furthermore, for large projects with a sizeable number of contributors, (e.g. ocaml.org as observed in ocaml/ocaml.org#3280), it might be required to still have a workflow for opam even if the project decides to use dune pkg by default. Changes tend to take time, and it makes sense to try and make it as smooth as possible for the users.

[Alizter]

OK what about this. We should add a paragraph stating that we are interested in knowing what can be done with opam that can't with dune pkg for local development. If there is something we are not aware of, we should definitely ask about it. Opening an issue etc.

[shonfeder]

This is a lovely solution!

[shonfeder]

@Alizter see quantifyearth/container-image#7 (review) and the following discussion for context.

We should add a paragraph stating that we are interested in knowing what can be done with opam that can't with dune pkg for local development

IMO, this needlessly complicates the documentation here. AFAIU, we all agree dune must continue to support non dune-pkg development workflows (at least in the near to midterm future), and so we should make it easy for people who want to manage dependencies with opam to do so. I don't think we need to situate it as a resource contention or complicate the docs on how to do that easily with nudges to use dunt pkg instead.

[avsm]

This doesn't seem to actually work though...

> cat dune-project
(lang dune 3.20)
(pkg enabled)
> dune build
File "dune-project", line 2, characters 1-4:
2 | (pkg enabled)
     ^^^
Error: Unknown field "pkg"
Hint: did you mean pin?

I assume this needs lang dune 3.21 ?

[Alizter]

This doesn't seem to actually work though...

> cat dune-project
(lang dune 3.20)
(pkg enabled)
> dune build
File "dune-project", line 2, characters 1-4:
2 | (pkg enabled)
     ^^^
Error: Unknown field "pkg"
Hint: did you mean pin?

I assume this needs lang dune 3.21 ?

(pkg enabled) needs to be in the dune-workspace file and not the dune-project file. The reason is that it is workspace level configuration rather than project level.

Would be nice to have an informative error message here about that.

[avsm]

Thanks @Alizter! However, it doesn't work in the dune-workspace file either; the presence of a dune.lock seems to always activate dune package management for me.

> cat dune-workspace
(lang dune 3.20)

(pkg disabled)

(lock_dir
 (repositories upstream overlay oxcaml))

(repository
 (name oxcaml)
 (url "git+https://github.com/avsm/oxcaml-opam-repository.git#ocamlbuild.0.16"))
> dune build --verbose
Shared cache: enabled-except-user-rules
Shared cache location: /Users/avsm/.cache/dune/db
Workspace root: /Users/avsm/scratch/bushel-viewer
Auto-detected concurrency: 16
Dune context:
 { name = "default"
 ; kind = lock { default = true }
 ; profile = Dev
 ; merlin = true
 ; fdo_target_exe = None
 ; build_dir = In_build_dir "default"
 ; instrument_with = []
 }
Actual targets:
- alias @@default
Running[4]: (cd _build/.sandbox/199d1cb959c09d62ea0b0fe791cda853/_private/default/.pkg/conf-autoconf/source && /opt/homebrew/bin/autoconf -V) 2> /var/folders/sg/gylc81bj6s54lsgs0zwh3qxc0000gn/T/dune-pkg_7d8574_stderr
Running[5]: (cd _build/.sandbox/ecc939f651c744d8510fd55913c6fe44/_private/default/.pkg/conf-which/source && /usr/bin/which which) 2> /var/folders/sg/gylc81bj6s54lsgs0zwh3qxc0000gn/T/dune-pkg_e9ba03_stderr
Output[5]:
/usr/bin/which
Output[4]:
autoconf (GNU Autoconf) 2.72
Copyright (C) 2023 Free Software Foundation, Inc.
License GPLv3+/Autoconf: GNU GPL version 3 or later
<https://gnu.org/licenses/gpl.html>, <https://gnu.org/licenses/exceptions.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by David J. MacKenzie and Akim Demaille.
Got signal INT, exiting.           ^C
> dune --version
3.20.2

[Alizter]

@avsm Yes, unfortunately this is a bug with 3.20. This is fixed in the soon-to-be-released 3.21.