Fix/good error msg pkg enabled

[benodiwal]

Closes #12801

[Leonidas-from-XIV]

Thanks for the PR. I have made some comments on how to improve the code.

However I think I would ask the opinion of other Dune maintainers to ask whether adding support for pkg in dune-project only to state that you don't support is is a good idea. It feels a bit.. odd. Likewise, should we add stanzas for other error cases too (lock_dir etc)?

[benodiwal]

Thanks for the PR. I have made some comments on how to improve the code.

However I think I would ask the opinion of other Dune maintainers to ask whether adding support for pkg in dune-project only to state that you don't support is is a good idea. It feels a bit.. odd. Likewise, should we add stanzas for other error cases too (lock_dir etc)?

Thanks for the feedback @Leonidas-from-XIV ! I've implemented all your suggestions ! You raise a good point about whether this approach feels odd. I can see the concern, we're essentially adding a field just to reject it with a better error message.

Concerns addressed

[Alizter]

@Leonidas-from-XIV Given that we are/will be pushing people to use package management it would be good to handle this particular case since it does occur if users are new to the dune-workspace file. It's better than the confusing message we get otherwise. #12761 (comment)

[Leonidas-from-XIV]

Thanks for addressing the issues, quite nice.

I've been looking at this a little and if we decide that we want to support a feature like this maybe we should extend Syntax.check_supported with an additional case for something like `Unsupported_in_dune_project. That way it would be easier to add stanzas that are unsupported without having to write an ad-hoc error message for every single of them.

noticed something

[Alizter]

cc @avsm, since you encountered this situation before, could you give this a read and see if you would have found it useful with your issue before?

[Alizter]

Sorry to keep iterating on the wording but I am still not happy. Let me block this to avoid others merging.

[Alizter]

File "dune-project", line 2, characters 0-13:
2 | (pkg enabled)
    ^^^^^^^^^^^^^
Error: The (pkg ...) stanza is only valid in dune-workspace files.
Hint: Move this stanza to your dune-workspace file. If you don't have one,
create one in your workspace root.

This should be better I think.

[benodiwal]

Sorry to keep iterating on the wording but I am still not happy. Let me block this to avoid others merging.

Sure @Alizter

[benodiwal]

Hey @Alizter, is there any update on the new message text

[Alizter]

@benodiwal Did you see my proposed wording above? #12802 (comment)

[benodiwal]

@benodiwal Did you see my proposed wording above? #12802 (comment)

Ohh shoot, missed it. Making the change now

[Alizter]

You don't need to put new lines in the text. Pp will break it appropriately for you.

[benodiwal]

I have fixed it

[Alizter]

Looks great. Thanks!

[Alizter]

@shonfeder This will be in 3.21, but I don't know if you want to keep the changelog entry since it is package management related. I think its fine to keep in this case but I defer judgement to you.