Add ~H support

[chrismccord]

The next Phoenix LiveView release supports a new ~H template engine, which deprecates ~L. I've updated the rules to support the new sigil. Thanks!

[chrismccord]

This only gets us partially there since some of the new ~H syntax engine won't properly syntax highlight the HTML. @msaraiva might have some insights on what it would take to properly highlight and whether it would make sense to add here or as a separate plugin ala Surface

[msaraiva]

It's probably a good idea to add a separate entry for ~H instead of using the same one as ~L.

Since they have different grammars, it might be harder to provide unified rules for both of them, especially in the tag attributes area. Depending on how the existing grammar for EEx code is defined, it might be easier to just copy the rules from Surface, starting from the tag rule.

The dependent nodes like node-attributes should be copied too but removing #tagged-expression and replacing #interpolation with EEx own syntax rules.

[msaraiva]

@chrismccord I can take a stab at it after finishing let + form_for for HEEx, unless of course, someone wants to address it before :)

[msaraiva]

@axelson we're considering having a separate package for the HEEx syntax highlighting feature. We'll still need some small configurations in vscode-elixir-ls but they will be minimal and probably only required to make the extension watch .heex files and maybe some other minor stuff that will be unlikely to change in the near future.

Having the highlighter in a separate project makes it easier for us to maintain syntax changes and release them much faster, as well as avoiding adding more stuff to vscode-elixir-ls that does not belong to elixir core. Since the highlighter does not depend on any feature of the language server, it seems like a reasonable approach.

Do you think this is the way to go? Any downsides you can see besides forcing the user to install an extra package?

[axelson]

I think that sounds good and I don't see any other downsides besides the extra package 👍

[cvkmohan]

Sorry, for posting the question on a closed issue.

1. Where does formatting heex files belong? Is it in vscode-phoenix package or this package? Or configuring prettier or beautify with file association of html? I personally liked the surface-formatter. Any chance of bringing it in for heex?

[manicat0]

@axelson @msaraiva checking in on this -- is the plugin discussed here already out? formatting + highlighting inside ~H would be a huge boost!

[lukaszsamson]

@xnkm8h a PR would be welcome

[axelson]

@xnkm8h the plugin mentioned is: https://github.com/phoenixframework/vscode-phoenix

And it does support ~H although I haven't personally tried it.

Also I'm hoping that elixir-lang/tree-sitter-elixir#2 will make it easier to integrate ~H support more widely in the elixir editor ecosystem.