nil: Language server for Nix Expression Language

🚧 This project is under development, but be happy to try it out!

Super fast incremental analysis! Scans all-packages.nix in less than 0.1s and completes with no delay!

Features

• Goto definition. textDocument/definition
  • References to parameters, let and rec {} bindings.
  • Relative paths.
• Find references. textDocument/reference
  • Parameters, let and rec {} bindings.
  • With expression.
• Completion. textDocument/completion
  • Builtin names.
  • Local bindings and rec-attrset fields.
  • Keywords.
  • Attrset fields.
• Diagnostics. textDocument/publishDiagnostics
  • Syntax errors.
    • Incomplete syntax errors are currently suppressed to avoid noisy outputs during typing.
  • Hard semantic errors reported as parse errors by Nix, like duplicated keys in attrsets.
  • Undefiend names.
  • Warnings of legacy syntax.
  • Warnings of unnecessary syntax.
  • Warnings of unused bindings, with and rec.
  • Client pulled diagnostics.
• Expand selection. textDocument/selectionRange
• Renaming. textDocument/renamme, textDocument/prepareRename
  • Identifiers in parameters and bindings, from let, rec and non-rec attrsets.
  • Static string literal bindings.
  • Merged path-value binding names.
  • Names introduced by inherit.
  • Names used by inherit.
  • Conflict detection.
  • Rename to string literals.
• Semantic highlighting. textDocument/semanticTokens/{range,full}
  • Delta response. textDocument/semanticTokens/full/delta
  • ⚠️ Currently it has performance issue in large files with coc.nvim. vim would consume 100% CPU and is slow to respond when editing all-packages.nix. Though our LSP server's CPU usage is quite low. Other LSP clients are not tested.
• Cross-file analysis.
• Multi-threaded.

Installation

This repo is packaged via Nix flakes, the language server binary package is available through the default flake output github:oxalica/nil# with the path bin/nil.

You can enable flakes support in your nix configuration, and then run nix profile install github:oxalica/nil to get nil installed. You can also use this repository as a flake input and add its output to your own flake-managed systemwide or home configuration.

Flake output structure:

├───devShells
│   └───(...)
└───packages
    ├───x86_64-linux
    │   ├───default: package 'nil-unstable-2022-08-04'
    │   └───nil: package 'nil-unstable-2022-08-04'
    └───(...)

Editor integration

Neovim native LSP and nvim-lspconfig

We are officially supported by nvim-lspconfig, see upstream docs.

Vim/Neovim via coc.nvim

Merge this setting into your coc-settings.json, which can be opened by :CocConfig.

{
  "languageserver": {
    "nix": {
      "command": "nil",
      "filetypes": ["nix"],
      "rootPatterns":  ["flake.nix"]
    }
  }
}

Emacs eglot

Add the following elisp code to your configuration. (using use-package)

(use-package nix-mode)
(use-package eglot
  :config
  ;; Ensure `nil` is in your PATH.
  (add-to-list 'eglot-server-programs '(nix-mode . ("nil")))
  :hook
  (nix-mode . eglot-ensure))

For vscode Nix IDE user

Modify the extension's settings in your settings.json

{
  // ...
  "nix.serverPath": "nil"
}

License

"nil" is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0).

See LICENSE-APACHE and LICENSE-MIT for details.