html-erb: Implement context-aware comment toggling

[vitallium]

Problem

Comment toggling in .html.erb files is naive. The current config sets:

block_comment = ["<%#", "%>"]

This always wraps selections with ERB comment syntax regardless of context. In practice, .html.erb files mix two distinct comment styles:

• ERB tags → <%# code %> (insert # after <%)
• HTML content → <!-- content -->

Toggling a comment on an HTML line like <div class="foo"> produces <%#<div class="foo">%> — invalid ERB. The correct output would be <!-- <div class="foo"> -->.

There is also no line comment support, so ⌘/ does nothing useful. yaml-erb has no comment support whatsoever.

Prior Art

Herb's language server shipped exactly this logic in marcoroth/herb#1308. The CommentService classifies each line as erb-tag, erb-comment, html-comment, or html-content by walking the AST, applies the appropriate comment style per line, and handles mixed selections intelligently.

Discussed as a candidate for the Zed Ruby Extension.

[marcoroth]

I think this is mostly blocked by this issue in Zed: zed-industries/zed#20042

I have been prototyping to add arbitrary LSP requests to Zed itself, and it does seem to work. I wonder if it's worth a PR to zed-industries/zed 🤔

[vitallium]

I think this is mostly blocked by this issue in Zed: zed-industries/zed#20042

I have been prototyping to add arbitrary LSP requests to Zed itself, and it does seem to work. I wonder if it's worth a PR to zed-industries/zed 🤔

Yeah, I have been playint with a similar concept. I think the idea makes sense in general, but on the LSP level: special requests/responses for delegating comment handling to language servers, e.g. experimental/toggleComment (or something similar). Right now, herb uses the herb prefix, so adding a special LSP command just for it would probably be rejected by the Zed team, but asking to land something more general, I think, has more chances.

[marcoroth]

Yeah that makes sense! My prototype just has a general send_language_server_request on the Zed/Editor level, that the Zed Ruby Extension then can use to send the specific toggleComment request to the language server.