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Nox is a lightweight, high-performance LSP client for Emacs

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Nox is a LSP client for Emacs, code fork from eglot.

The project has three goals: 1. Function: only provide core functions, include code completion, jump definition, code references and rename 2. Design: Keep UX simple and clean, does not interfere user 3. Performance: cutting useless functions, optimizing code efficiency, ensure coding fluency

Why named Nox?

The Nox are considered to be a member of the Alliance of Four Great Races", along with the Alterans, Asgard, and Furlings.

My favorite a word from Nox:

Maybe one day you will learn, that your way is not the only way -- Anteaus

Install dependences

Nox depend on company-mode and posframe

Install Nox

  1. Clone this repository and put nox.el in your load-path

  2. Add below configure in your ~/.emacs

(require 'nox)

(dolist (hook (list 'js-mode-hook 'rust-mode-hook 'python-mode-hook 'ruby-mode-hook 'java-mode-hook 'sh-mode-hook 'php-mode-hook 'c-mode-common-hook 'c-mode-hook 'csharp-mode-hook 'c++-mode-hook 'haskell-mode-hook )) (add-hook hook '(lambda () (nox-ensure))))

  1. Open file, that's all.

Note: suggestion upgrade emacs to 27.x or 28.x, JSON parser much faster, and Nox completion will much smooth.

Connecting to a server

M-x nox
can guess and work out-of-the-box with these servers:

I'll add to this list as I test more servers. In the meantime you can customize

(add-to-list 'nox-server-programs '(foo-mode . ("foo-language-server" "--args")))

Let me know how well it works and we can add it to the list.

To skip the guess and always be prompted use

C-u M-x nox

Connecting via TCP

The examples above use a "pipe" to talk to the server, which works fine on Linux and OSX but in some cases may not work on Windows.

To circumvent this limitation, or if the server doesn't like pipes, you can use

C-u M-x nox
and give it
pattern to connect to a previously started TCP server serving LSP information.

If you don't want to start it manually every time, you can configure Nox to start it and immediately connect to it. Ruby's solargraph server already works this way out-of-the-box.

For another example, suppose you also wanted start Python's

this way:
(add-to-list 'nox-server-programs
             `(python-mode . ("pyls" "-v" "--tcp" "--host"
                              "localhost" "--port" :autoport)))

You can see that the element associated with

is now a more complicated invocation of the
program, which requests that it be started as a server. Notice the
symbol in there: it is replaced dynamically by a local port believed to be vacant, so that the ensuing TCP connection finds a listening server.

Per-project server configuration

Most servers can guess good defaults and will operate nicely out-of-the-box, but some need to be configured specially via LSP interfaces. Additionally, in some situations, you may also want a particular server to operate differently across different projects.

Per-project settings are realized with Emacs's directory variables and the Elisp variable

. To make a particular Python project always enable Pyls's snippet support, put a file named
in the project's root:
  . ((nox-workspace-configuration
      . ((:pyls . (:plugins (:jedi_completion (:include_params t)))))))))

This tells Emacs that any

buffers in that directory should have a particular buffer-local value of
. That variable's value should be association list of parameter sections which are presumably understood by the server. In this example, we associate section
with the parameters object
(:plugins (:jedi_completion
(:include_params t)))

Now, supposing that you also had some Go code in the very same project, you can configure the Gopls server in the same file. Adding a section for

, the file's contents become:
  . ((nox-workspace-configuration
      . ((:pyls . (:plugins (:jedi_completion (:include_params t))))))))
  . ((nox-workspace-configuration
      . ((:gopls . (:usePlaceholders t)))))))

If you can't afford an actual

file, or if managing these files becomes cumbersome, the Emacs manual teaches you programmatic ways to leverage per-directory local variables.

Handling quirky servers

Some servers need even more special hand-holding to operate correctly. If your server has some quirk or non-conformity, it's possible to extend Nox via Elisp to adapt to it. Here's an example on how to get cquery working:

(add-to-list 'nox-server-programs '((c++ mode c-mode) . (nox-cquery "cquery")))

(defclass nox-cquery (nox-lsp-server) () :documentation "A custom class for cquery's C/C++ langserver.")

(cl-defmethod nox-initialization-options ((server nox-cquery)) "Passes through required cquery initialization options" (let* ((root (car (project-roots (nox--project server)))) (cache (expand-file-name ".cquery_cached_index/" root))) (list :cacheDirectory (file-name-as-directory cache) :progressReportFrequencyMs -1)))


's section on Java's JDT server for an even more sophisticated example.

Reporting bugs

Having trouble connecting to a server? Expected to have a certain capability supported by it (e.g. completion) but nothing happens? Or do you get spurious and annoying errors in an otherwise smooth operation? We may have help, so open a new issue and try to be as precise and objective about the problem as you can:

  1. Try to replicate the problem with as clean an Emacs run as possible. This means an empty

    init file or close to it (just loading
    for example, and you don't even need
    to do that).
  2. Include the log of LSP events and the stderr output of the server (if any). You can find the former with

    and the latter with
    M-x nox-stderr-buffer
    . You run these commands in the buffer where you enabled Nox, but if you didn't manage to enable Nox at all (because of some bootstrapping problem), you can still find these buffers in your buffer list: they're named like
    *NOX /
    *NOX / stderr*
  3. If Emacs errored (you saw -- and possibly heard -- an error message), make sure you repeat the process using

    so you get a backtrace of the error that you should also attach to the bug report.

Some more notes: it's understandable that you report it to Nox first, because that's the user-facing side of the LSP experience in Emacs, but the outcome may well be that you will have to report the problem to the server's developers, as is often the case. But the problem can very well be on Nox's side, of course, and in that case we want to fix it! Also bear in mind that Nox's developers have limited resources and no way to test all the possible server combinations, so you'll have to do most of the testing.

Commands and keybindings

Here's a summary of available commands:

  • M-x nox
    , as described above;
  • M-x nox-reconnect
    reconnects to the server;
  • M-x nox-shutdown
    says bye-bye to the server;
  • M-x nox-rename
    ask the server to rename the symbol at point, if rename work, please use command
    , must something rename tool not install, sch as python need
    for rename operation;
  • M-x nox-format
    asks the server to format buffer or the active region;
  • M-x nox-show-doc
    show documentation for symbol at point.
  • M-x nox-events-buffer
    jumps to the events buffer for debugging communication with the server.
  • M-x nox-stderr-buffer
    if the LSP server is printing useful debug information in stderr, jumps to a buffer with these contents.
  • M-x nox-signal-didChangeConfiguration
    updates the LSP server configuration according to the value of the variable
    , which you may be set in a
    file, for example.
  • M-x xref-find-definitions
    find the definition of the identifier at point.
  • M-x xref-find-definitions-other-window
    find the definition of the identifier at point in other window.
  • M-x xref-pop-marker-stack
    pop bck to where xref-find-definitions last invoked.
  • M-x xref-find-references
    find references to the identifier at point.


Here's a quick summary of the customization options. In Nox's customization group (

M-x customize-group
) there is more documentation on what these do.
  • nox-doc-tooltip-font
    : The font for documentation tooltip, font format follow rule
  • nox-doc-tooltip-border-width
    : The border width of documentation tooltip.
  • nox-doc-tooltip-timeout
    : The timeout of documentation tooltip show time, default is 30 seconds, tooltip will hide after you change cursor point.
  • nox-doc-name
    : The name of documentation tooltip.
  • nox-candidate-annotation-limit
    : The width limit of candidate annotation.
  • nox-autoreconnect
    : Control ability to reconnect automatically to the LSP server;
  • nox-connect-timeout
    : Number of seconds before timing out LSP connection attempts;
  • nox-sync-connect
    : Control blocking of LSP connection attempts;
  • nox-events-buffer-size
    : Control the size of the Nox events buffer;
  • nox-ignored-server-capabilites
    : LSP server capabilities that Nox could use, but won't;
  • nox-confirm-server-initiated-edits
    : If non-nil, ask for confirmation before allowing server to edit the source buffer's text;

There are a couple more variables that you can customize via Emacs lisp:

  • nox-server-programs
    : as described above;
  • nox-strict-mode
    : Set to
    by default, meaning Nox is generally lenient about non-conforming servers. Set this to
    (disallow-non-standard-keys enforce-required-keys)
    when debugging servers.
  • nox-server-initialized-hook
    : Hook run after server is successfully initialized;
  • nox-managed-mode-hook
    : Hook run after Nox started or stopped managing a buffer. Use
    to tell if current buffer is still being managed.
  • nox-php-server
    : Language server for PHP, default is
    , you can set with other value:
  • nox-omni-sharp-path
    : Language server path for OmniSharp, default is
    , you can set with other value.
  • nox-python-server
    : Language server for Python, default is
    , you can set with other value:

If you choose

: 1. Execute command
get download url of mspyls. 2. Then extract to the directory ~/.emacs.d/nox/mspyls/ 3. Permission: ```sudo chmod -R +x ~/.emacs.d/nox/mspyls/

Note mspyls need index file before respond completion request, so please don't test single file under HOME directory, that will cost few minutes to index file, and

haven't this problem.
  • nox-optimization-p
    : Improve performance by adjust GC limit and disable
    . If you don't need Nox set this, change this option to nil.

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