Bend 2 language server

bend2-lsp provides formatting, live compiler diagnostics, Markdown hover, and import go-to-definition for Bend 2 over LSP stdio. Node.js 26.9 or newer is required.

npm install -g bend2-lsp
bend2-lsp --stdio

To build from source, run npm ci && npm test.

The server accepts the bend and bend2 language IDs. It uses full-document sync, publishes diagnostics on open and 250 ms after edits, and rechecks open documents that import a changed buffer. Open buffers override files on disk. Go-to-definition resolves relative import paths, aliases, and imported top-level declarations. Compiler analysis is limited to file: documents; untitled documents still receive formatting, lexical diagnostics, and syntax hover.

Analysis uses the bundled Bend compiler and Base library in a worker thread. Relative imports resolve from the document, then from open overlays. Hash package imports use BEND_LIB; missing packages may be downloaded from BEND_HUB, checked by the compiler, and cached in the normal package layout. Downloads time out after 10 seconds.

The formatter preserves line breaks, blank lines, comments, literal spelling, line endings, and final-newline state. It normalizes indentation and safe token spacing without wrapping code.

Editor setup

VS Code:

Install the Bend 2 extension (kbrianps.bend2, also on Open VSX), which bundles bend2-lsp and provides syntax highlighting, live diagnostics, hover, and formatting out of the box.

To point the extension at a custom or local server build, set bend.server.path in settings.json:

{
  "bend.server.path": "bend2-lsp"
}

Neovim with nvim-lspconfig:

vim.api.nvim_create_autocmd("FileType", {
  pattern = "bend",
  callback = function()
    vim.lsp.start({
      name = "bend2-lsp",
      cmd = { "bend2-lsp", "--stdio" },
      root_dir = vim.fs.root(0, { ".git" }),
    })
  end,
})

Helix (languages.toml):

[language-server.bend2-lsp]
command = "bend2-lsp"
args = ["--stdio"]

[[language]]
name = "bend"
scope = "source.bend"
file-types = ["bend"]
language-servers = ["bend2-lsp"]
auto-format = true

Emacs with Eglot:

(add-to-list 'eglot-server-programs
             '(bend-mode . ("bend2-lsp" "--stdio")))

Local-variable type hover is intentionally out of scope because it would require instrumentation in the trusted checker. Unknown names and inferred locals therefore return no hover.

Compiler source

vendor/bend2/bend.ts and vendor/bend2/base.bend are unmodified copies from don2e4/bend commit bacc663. They are bundled into the npm package so installation does not require a Bend checkout. The compiler and this language server are licensed under Apache 2.0; see LICENSE. Update both vendored files together from a pinned Bend commit, then run npm test and inspect npm pack --dry-run before releasing.