SuperHTML

HTML Language Server and Templating Language Library

HTML Language Server

The SuperHTML CLI Tool offers validation and autoformatting features for HTML files.

The tool can be used either directly (for example by running it on save), or through a LSP client implementation.

$ superhtml
Usage: superhtml COMMAND [OPTIONS]

Commands:
  check         Check documents for errors.
  fmt           Format documents.
  lsp           Start the Language Server.
  help          Show this menu and exit.
  version       Print the version and exit.

General Options:
  --help, -h        Print command specific usage.
  --syntax-only     Disable HTML element and attribute validation.

WARNING SuperHTML only supports HTML5 (the WHATWG living spec) regardless of what you put in your doctype (a warning will be generated for unsupported doctypes).

Diagnostics

SuperHTML validates not only syntax but also element nesting and attribute values. No other language server implements the full HTML spec in its validation code.

Autoformatting

The autoformatter has two main ways of interacting with it in order to request for horizontal / vertical alignment.

1. Adding / removing whitespace between the start tag of an element and its content.
2. Adding / removing whitespace between the last attribute of a start tag and the closing >.

Example of rule #1

Before:

<div> <p>Foo</p></div>

After:

<div>
    <p>Foo</p>
</div>

Reverse

Before:

<div><p>Foo</p>
</div>

After:

<div><p>Foo</p></div>

Example of rule #2

Before:

<div foo="bar" style="verylongstring" hidden>
    Foo
</div>

After:

<div foo="bar" 
     style="verylongstring" 
     hidden
>
    Foo
</div>

Reverse

Before:

<div foo="bar" 
     style="verylongstring"
     hidden>
    Foo
</div>

After:

<div foo="bar" style="verylongstring" hidden>
    Foo
</div>

Download

See the Releases section here on GitHub.

Editor support

VSCode

Install the Super HTML VSCode extension (doesn't require the CLI tool as it bundles a WASM build of the language server).

Neovim

1. Download a prebuilt version of superhtml from the Releases section (or build it yourself).

2. Put superhtml in your PATH.

3. Configure superhtml for your chosen lsp

   • Neovim Built-In

     vim.api.nvim_create_autocmd("Filetype", {
         pattern = { "html", "shtml", "htm" },
         callback = function()
             vim.lsp.start({
                 name = "superhtml",
                 cmd = { "superhtml", "lsp" },
                 root_dir = vim.fs.dirname(vim.fs.find({".git"}, { upward = true })[1])
             })
         end
     })
     

   • LspZero

     local lsp = require("lsp-zero")
     
     require('lspconfig.configs').superhtml = {
             default_config = {
                     name = 'superhtml',
                     cmd = {'superhtml', 'lsp'},
                     filetypes = {'html', 'shtml', 'htm'},
                     root_dir = require('lspconfig.util').root_pattern('.git')
             }
     }
     
     lsp.configure('superhtml', {force_setup = true})
     

Helix

In versions later than 24.07 superhtml is supported out of the box, simply add executable to your PATH.

Flow Control

Already defaults to using SuperHTML, just add the executable to your PATH.

Vim

Vim should be able to parse the errors that superhtml check [PATH] generates. This means that you can use :make and the quickfix window to check for syntax errors.

Set the makeprg to the following in your .vimrc:

" for any html file, a :make<cr> action will populate the quickfix menu
autocmd filetype html setlocal makeprg=superhtml\ check\ %
" if you want to use gq{motion} to format sections or the whole buffer (with gggqG)
autocmd filetype html setlocal formatprg=superhtml\ fmt\ --stdin

Zed

See WeetHet/superhtml-zed.

Other editors

Follow your editor specific instructions on how to define a new Language Server for a given language / file format.

(Also feel free to contribute more specific instructions to this readme / add files under the editors/ subdirectory).

Templating Language Library

SuperHTML is also a HTML templating language. More on that soon.

Contributing

SuperHTML tracks the latest Zig release (0.15.1 at the moment of writing).

Contributing to the HTML parser & LSP

Contributing to the HTML parser and LSP doesn't require you to be familiar with the templating language, basically limiting the scope of what you have to worry about to:

• src/cli.zig
• src/cli/
• src/html/

In particular, you will care about the source files under src/html.

You can invoke zig build test to run all unit tests.

Running zig build will compile the SuperHTML CLI tool, allowing you to also then test the LSP behavior directly from your favorite editor.

For testing within VSCode:

1. Run zig build wasm -p src/editors/vscode/wasm
2. Open src/editors/vscode in VSCode
3. Start debugging.

Debug builds will produce logs in your cache directory so you can tail -f ~/.cache/superhtml.log.