An LSP implementation for tree-sitter query files

Configuration

{
  "settings": {
    // Where to look for parsers, of the form <lang>.(so|dll|dylib)
    // or tree-sitter-<lang>.wasm
    "parser_install_directories": ["a/list/of", "parser/installation/paths"],
    // A list of parser aliases (e.g. point queries/ecma/*.scm files to the
    // javascript parser)
    "parser_aliases": {
      "ecma": "javascript"
    },
    // A list of patterns to aid the LSP in finding a language, given a file
    // path. Patterns must have one capture group which represents the language
    // name. Ordered from highest to lowest precedence.
    "language_retrieval_patterns": [
      // E.g. zed support
      "languages/src/([^/]+)/[^/]+\\.scm$"
      // The following fallbacks are *always* provided:
      //
      // tree-sitter-([^/]+)/queries/[^/]+\.scm$
      // queries/([^/]+)/[^/]+\.scm$
    ]
  }
}

Example setup (for Neovim):

vim.api.nvim_create_autocmd('FileType', {
  pattern = 'query',
  callback = function(ev)
    if vim.bo[ev.buf].buftype == 'nofile' then
      return
    end
    vim.lsp.start {
      name = 'ts_query_ls',
      cmd = { '/path/to/ts_query_ls/target/release/ts_query_ls' },
      root_dir = vim.fs.root(0, { 'queries' }),
      settings = {
        parser_install_directories = {
          -- If using nvim-treesitter with lazy.nvim
          vim.fs.joinpath(
            vim.fn.stdpath('data'),
            '/lazy/nvim-treesitter/parser/'
          ),
        },
        parser_aliases = {
          ecma = 'javascript',
        },
        language_retrieval_patterns = {
          'languages/src/([^/]+)/[^/]+\\.scm$',
        },
      },
    }
  end,
})

Checklist

• References for captures
• Renaming captures
• Completions for capture names in a pattern (for predicates)
• Completions for node names
• Fix utility functions, making them robust when it comes to UTF-16 code points
• Go to definition for captures
• Recognition/completion of supertypes (requires tree-sitter 0.25)
• Completions and diagnostics for a supertype's subtypes
  • Requires https://github.com/tree-sitter/tree-sitter/pull/3938
• Completions field names
• Diagnostics for unrecognized nodes
• Diagnostics for referencing undefined capture groups in predicates
• Diagnostics for incorrect syntax
• Diagnostics for impossible patterns
  • Currently not possible without a full (sometimes expensive) run of the query file. This should either be implemented as a user command, or core methods should be exposed to gather pattern information more efficiently
• Recognize parsers built for WASM
• Document formatting compatible with the nvim-treesitter formatter
• Code cleanup
• Add tests for all* functionality

*All handlers are tested, but core functionality like language loading will be more complicated, and does not yet have test coverage.

Packaging

• homebrew (in progress, requires repo to reach 75 GitHub stars)
• nixpkgs
• mason.nvim (in progress)

And others?

References

Many thanks to @lucario387, and the asm-lsp, jinja-lsp, beancount-language-server, and helix-editor projects for the amazing code that I took inspiration from!