GitHub - joaotavora/eglot: A client for Language Server Protocol servers
source link: https://github.com/joaotavora/eglot
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README.md
Eglot
Emacs Polyglot. An Emacs client to Language Server Protocol servers.
Eglot is in ELPA. Installation is straightforward:
(package-install 'eglot) ; Requires Emacs 26!
;; Now find some source file, any source file
M-x eglot
That's it. If you're lucky, this guesses the LSP executable to start for the language of your choice. Otherwise, it prompts you to enter one:
M-x eglot
can guess and work out-of-the-box with these servers:
- Javascript's javascript-typescript-stdio
- Rust's rls
- Python's pyls
- Bash's bash-language-server
- PHP's php-language-server
I'll add to this list as I test more servers. In the meantime you can
customize eglot-server-programs
:
(add-to-list 'eglot-server-programs '(fancy-mode . ("fancy-language-server" "--args"")))
Let me know how well it works and we can add it to the list. You can
also enter a server:port
pattern to connect to an LSP server. To
skip the guess and always be prompted use C-u M-x eglot
.
Commands and keybindings
Here's a summary of available commands:
-
M-x eglot
, as described above; -
M-x eglot-reconnect
reconnects to the server; -
M-x eglot-shutdown
says bye-bye to the server; -
M-x eglot-rename
asks the server to rename the symbol at point; -
M-x eglot-help-at-point
asks the server for help for symbol at point. Currently this is whateldoc-mode
displays in the echo area; -
M-x eglot-events-buffer
jumps to the events buffer for debugging communication with the server.
There are no keybindings specific to Eglot, but you can bind stuff
in eglot-mode-map
, which is active as long as Eglot is managing a
file in your project. The commands don't need to be Eglot-specific,
either:
(define-key eglot-mode-map (kbd "C-c h") 'eglot-help-at-point)
(define-key eglot-mode-map (kbd "<f6>") 'xref-find-definitions)
How does this work exactly?
M-x eglot
starts a server via a shell-command guessed from
eglot-server-programs
, using the current major-mode (for whatever
language you're programming in) as a hint.
If the connection is successful, you see an [eglot:<server>]
indicator pop up in your mode-line. More importantly, this means
current and future file buffers of that major mode inside your
current project automatically become "managed" by the LSP server,
i.e. information about their contents is exchanged periodically to
provide enhanced code analysis via xref-find-definitions
,
flymake-mode
, eldoc-mode
, completion-at-point
, among others.
To "unmanage" these buffers, shutdown the server with M-x eglot-shutdown
.
Supported Protocol features (3.6)
General
- initialize
- initalized
- shutdown
- exit
- $/cancelRequest
Window
- window/showMessage
- window/showMessageRequest
- window/logMessage
- telemetry/event
Client
- client/registerCapability (but only
workspace/didChangeWatchedFiles
, like RLS asks) - client/unregisterCapability (ditto)
Workspace
- workspace/workspaceFolders (3.6.0)
- workspace/didChangeWorkspaceFolders (3.6.0)
- workspace/didChangeConfiguration
- workspace/configuration (3.6.0)
- workspace/didChangeWatchedFiles
- workspace/symbol is
- workspace/applyEdit
Text Synchronization
- textDocument/didOpen
- textDocument/didChange (incremental or full)
- textDocument/willSave
- textDocument/willSaveWaitUntil
- textDocument/didSave
- textDocument/didClose
Diagnostics
- textDocument/publishDiagnostics
Language features
- textDocument/completion
- completionItem/resolve (works quite well with company-mode)
- textDocument/hover
- textDocument/signatureHelp (fancy stuff with Python's pyls)
- textDocument/definition
- textDocument/typeDefinition (3.6.0)
- textDocument/implementation (3.6.0)
- textDocument/references
- textDocument/documentHighlight
- textDocument/documentSymbol
- textDocument/codeAction
- textDocument/codeLens
- codeLens/resolve
- textDocument/documentLink
- documentLink/resolve
- textDocument/documentColor
- textDocument/colorPresentation (3.6.0)
- textDocument/formatting
- textDocument/rangeFormatting
- textDocument/onTypeFormatting
- textDocument/rename
Differences to lsp-mode.el
Eglot is beta. It may currently underperform
lsp-mode.el, both in functionality and correctness. That
other extension is much more mature and has a host of
plugins for bells and whistles. If you don't
like the minimalist approach of eglot.el
, you could be better served
with lsp-mode.el
for now.
User-visible differences:
- Single and friendly entry point
M-x eglot
, notM-x eglot-<language>
. Also noeglot-<language>
extra packages. - No "whitelisting" or "blacklisting" directories to languages.
M-x eglot
starts servers to handle major modes inside a specific project. Uses Emacs's built-inproject.el
library to discover projects. Automatically detects current and future opened files under that project and syncs with server. - Easy way to quit/restart a server, just middle/right click on the connection name.
- Pretty interactive mode-line section for live tracking of server communication.
- Automatically restarts frequently crashing servers (like RLS).
- Server-initiated edits are confirmed with the user.
- Diagnostics work out-of-the-box (no
flycheck.el
needed). - Smoother/more responsive (read below).
Under the hood:
- Message parser is much simpler.
- Defers signature requests like
textDocument/hover
until server is ready. Also sendstextDocument/didChange
for groups of edits, not one per each tiny change. - Easier to read and maintain elisp. Yeah I know, very subjective, so judge for yourself.
- About 1k LOC lighter.
- Development doesn't require Cask, just Emacs.
- Project support doesn't need
projectile.el
, uses Emacs'sproject.el
- Requires the upcoming Emacs 26
- Contained in one file
- Has automated tests that check against actual LSP servers
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