Language Server Protocol

A client for Textadept that communicates over the Language Server Protocol (LSP) with language servers in order to provide autocompletion, calltips, go to definition, and more. It implements version 3.17.0 of the protocol, but does not support all protocol features. The Server.new() function contains the client's current set of capabilities.

Install this module by copying it into your ~/.textadept/modules/ directory or Textadept's modules/ directory, and then putting the following in your ~/.textadept/init.lua:

local lsp = require('lsp')

You can then set up some language server commands. For example:

lsp.server_commands.cpp = 'clangd'
lsp.server_commands.go = 'gopls'

(For more example configurations, see the wiki.)

When either C++ or Go files are opened, their associated language servers are automatically started (one per project). Note that language servers typically require a root URI, so this module uses io.get_project_root() for this. If the file being opened is not part of a project recognized by Textadept, the language server will not be started.

Language Server features are available from the Tools > Language Server menu. Note that not all language servers may support the menu options.

Note: If you want to inspect the LSP messages sent back and forth, you can use the Lua command entry to set require('lsp').log_rpc = true. It doesn't matter if any LSPs are already active -- from this point forward all messages will be logged. View the log via the "Tools > Language Server > View Log" menu item.

Warning: Buggy language servers that do not respect the protocol may cause this module and Textadept to hang, waiting for a response. There is no recourse other than to force-quit Textadept and restart.

Lua Language Server

This module comes with a simple Lua language server that starts up when Textadept opens a Lua file, or whenever you request documentation for a symbol in the Lua command entry. The server looks in the project root for a .lua-lsp configuration file. That file can have the following fields:

• ignore: List of globs that match directories and files to ignore. Globs are relative to the project root. The default directories ignored are .bzr, .git, .hg, .svn, FOSSIL, and node_modules. Setting this field overrides the default.
• max_scan: Maximum number of files to scan before giving up. This is not the number of Lua files scanned, but the number of files encountered in non-ignored directories. The primary purpose of this field is to avoid hammering the disk when accidentally opening a large project or root. The default value is 10,000.

For example:

ignore = {'.git', 'build', 'test'}
max_scan = 20000

Key Bindings

Windows and Linux	macOS	Terminal	Command
Tools
Ctrl+Space	⌘Space ^Space	^Space	Complete symbol
Ctrl+?	⌘? ^?	M-? Ctrl+?‡	Show documentation
F12	F12	F12	Go To Definition

‡: Windows terminal version only.

Fields defined by lsp

events.LSP_INITIALIZED

Emitted when an LSP connection has been initialized. This is useful for sending server-specific notifications to the server upon init via Server:notify(). Emitted by lsp.start(). Arguments:

• lang: The lexer name of the LSP language.
• server: The LSP server.

events.LSP_NOTIFICATION

Emitted when an LSP server emits an unhandled notification. This is useful for handling server-specific notifications. An event handler should return true. Arguments:

• lang: The lexer name of the LSP language.
• server: The LSP server.
• method: The string LSP notification method name.
• params: The table of LSP notification params. Contents may be server-specific.

events.LSP_REQUEST

Emitted when an LSP server emits an unhandled request. This is useful for handling server-specific requests. Responses are sent using Server:respond(). An event handler should return true. Arguments:

• lang: The lexer name of the LSP language.
• server: The LSP server.
• id: The integer LSP request ID.
• method: The string LSP request method name.
• params: The table of LSP request params.

lsp.autocomplete_num_chars

The number of characters typed after which autocomplete is automatically triggered. The default value is nil, which disables this feature. A value greater than or equal to 3 is recommended to enable this feature.

lsp.log_rpc

Log RPC correspondence to the LSP message buffer. The default value is false.

lsp.server_commands <table>

Map of lexer names to LSP language server commands or configurations, or functions that return either a server command or a configuration. Commands are simple string shell commands. Configurations are tables with the following keys:

• command: String shell command used to run the LSP language server.
• init_options: Table of initialization options to pass to the language server in the "initialize" request.

lsp.show_all_diagnostics

Whether or not to show all diagnostics if show_diagnostics is true. The default value is false, and assumes any diagnostics on the current line or next line are due to an incomplete statement during something like an autocompletion, signature help, etc. request.

lsp.show_completions

Whether or not to automatically show completions when a trigger character is typed (e.g. '.'). The default value is true.

lsp.show_diagnostics

Whether or not to show diagnostics. The default value is true, and shows them as annotations.

lsp.show_hover

Whether or not to automatically show symbol information via mouse hovering. The default value is true.

lsp.show_signature_help

Whether or not to automatically show signature help when a trigger character is typed (e.g. '('). The default value is true.

lsp.snippet_completions

Whether or not to allow completions to insert snippets instead of plain text, for language servers that support it. The default value is true.

Functions defined by lsp

_G.textadept.editing.autocompleters.lsp()

Autocompleter function for a language server.

lsp.autocomplete()

Requests autocompletion at the current position, returning true on success.

lsp.find_references()

Searches for project references to the current symbol and prints them like "Find in Files".

lsp.goto_declaration()

Jumps to the declaration of the current symbol, returning whether or not a declaration was found.

Return:

• true if a declaration was found; false otherwise.

lsp.goto_definition()

Jumps to the definition of the current symbol, returning whether or not a definition was found.

Return:

• true if a definition was found; false otherwise.

lsp.goto_implementation()

Jumps to the implementation of the current symbol, returning whether or not an implementation was found.

Return:

• true if an implementation was found; false otherwise.

lsp.goto_symbol(symbol)

Jumps to a symbol selected from a list based on project symbols that match the given symbol, or based on buffer symbols.

Parameters:

• symbol: Optional string symbol to query for in the current project. If nil, symbols are presented from the current buffer.

lsp.goto_type_definition()

Jumps to the definition of the current type, returning whether or not a definition was found.

Return:

• true if a definition was found; false otherwise.

lsp.hover(position)

Shows a calltip with information about the identifier at the given or current position.

Parameters:

• position: Optional buffer position of the identifier to show information for. If nil, uses the current buffer position.

lsp.select()

Selects or expands the selection around the current position.

lsp.select_all_symbol()

Selects all instances of the symbol at the current position as multiple selections.

lsp.signature_help(no_cycle)

Shows a calltip for the current function. If a call tip is already shown, cycles to the next one if it exists unless specified otherwise.

Parameters:

• no_cycle: Flag that indicates to not cycle to the next call tip. This is used to update the current highlighted parameter.

lsp.start(cmd)

Starts a language server based on the current language and project.

Parameters:

• cmd: Optional language server command to run. The default is read from server_commands.

lsp.stop()

Stops a running language server based on the current language.

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