Add reason language to ast_editor

[pedrobslisboa]

Description

This PR adds reasonml to ast_editor to be able to see AST and Pp

Screenshots

Working with both ocaml and reason

How to test

• Follow this steps:

  vscode-ocaml-platform/CONTRIBUTING.md

  Line 27 in 88cbda6

  ### Running the extension

• On the debug view, create a .re file
• To see the pp you need to build it to have the .pp.ml file

[rgrinberg]

Can we think of a way of having this feature without making the plugin on reason? In the past, I've found the the dependency on reason to be rather disruptive to development. I would much prefer if we had a way to extend this plugin so that you could reason support externally.

[davesnx]

Do you have any idea of how "extending the plugin" would work in terms of VSCode packaging, APIs, etc.? Or are you talking about like an ocamlmerlin-reason integration, or to have "reason" installed in the host?

The OCaml platform already supports syntax highlight for Reason files, and I personally find it useful to have a better integration with Reason, such as converting between syntaxes built-in visiting the AST or ppx output.

What are the problems of reason as a dependency on development? Maybe we can fix those?

[rgrinberg]

The problem is that the reason package is not actively maintained, and the version in opam has historically lagged behind. This is particularly painful for a package that depends on the internals of the compiler.

I don't really have a concrete idea on how to work around this. I was hoping that you would think of something. One simple approach is to call out to a reason binary to dump the parsetree

[davesnx]

Oh, reason has been very maintained this past years (since 2022), and we plan to keep it that way: https://github.com/reasonml/reason/releases releases are pushed to opam only.

Sure, there might be other options, but it faces problems with compatibility (that a package manager like opam fixes for us) and other issues.

Happy to commit to keep ocaml-platform up-to-date as dependency of Reason.

[rgrinberg]

Happy to hear reason is being maintained again. While that certainly makes this more risky, the fact that reason is barely used, makes the reward for taking such a risk less enticing.

Merlin and lsp both support reason without a hard dependency. I'd hate to improvish the vscode extension with such a dependency.

[pedrobslisboa]

@rgrinberg, it turned out that I was overcomplicating it; Ast can handle .re
Just changed it.

[smorimoto]

@pedrobslisboa You have to add a change log entry as well.

[pedrobslisboa]

@pedrobslisboa You have to add a change log entry as well.

True, thank you. I'm going to fix it as well

[pedrobslisboa]

@smorimoto Done, ready for review

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[pedrobslisboa]

@rgrinberg @smorimoto 🏓