ERB injection for other source languages

[joeldrapper]

ERB can be used to template any kind of source file — not just HTML. However, it’s most commonly used for generating HTML, YAML and Ruby source.

This PR updates the ERB language to be more generic, treating .erb files as plain text with Ruby injections within the ERB template tags.

It then introduces two new languages: HTML/ERB and YAML/ERB, which handle switching between HTML and Ruby and YAML and Ruby respectively.

I attempted to make a specialised language for Ruby/ERB, but couldn’t get past some basic syntax highlighting issues. I think it’s quite reasonable to highlight .rb.erb files as plain text with Ruby inside the ERB tags since it would be very difficult to guess at how the generated Ruby will look structurally. It’s certainly an improvement on treating it like HTML.

I’ve configured mappings from ERB, HTML/ERB and YAML/ERB for Ruby LSP, which will handle them all as erb. I’ve also updated the Herb LSP to handle HTML/ERB files specifically.

Next steps

I would be nice if the YAML language server was configured to run on YAML/ERB files. I believe this can be done by updating this file.

However, I don’t think this is a blocker as most YAML/ERB files are actually named .yml not .yml.erb and so will be treated as regular old YAML files.

[kaspth]

I wonder if @marcoroth has thoughts on this given his HERB work.

[joeldrapper]

I wonder if unmatched .erb files should just be plain text outside of the ERB tags. I would much rather my .rb.erb file was like that than treated as an HTML/ERB file.

[joeldrapper]

Here’s what that looks like.

I think this is a good solution for Ruby and other files, but I still haven't figured out how to enable the YAML language server.

[joeldrapper]

I think because YAML is a built-in language server, it will actually need to be associated in this file. https://github.com/zed-industries/zed/blob/a067c16c823354da63966273ac15d1aa93c0e922/crates/languages/src/lib.rs#L98

[joeldrapper]

There’s one more problem that’s come up. The language ID is being passed through to Ruby LSP as HTML/ERB or YAML/ERB and RubyLSP doesn’t support those languages. It only supports Ruby or ERB.

We will need a way to map YAML/ERB and HTML/ERB to ERB because as that’s all the language server cares about.

I think this will require upstream changes in the zed_extension_api crate.

Here is an example of the RPS message with the wrong languageId.

{"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"file:///Users/joeldrapper/src/zed-ruby/example.html.erb","languageId":"html/erb","version":0,"text":""}}}

[joeldrapper]

Looks like this was already supported, I just need to add the mappings.

So the final issue is that the YAML language server isn’t being enabled, but that has to be fixed in the main Zed repo.

[vitallium]

@joeldrapper Thanks! This awesome improvement works like a charm!