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The Gleam Language Server reference |
Gleam IDE features for all editors |
The Gleam Language Server is a program that can provide IDE features to text editors that implement the language server protocol, such as VS Code and Neovim. This document details the current state of the language server and its features.
The Gleam Language Server is an official Gleam project and the newest part of the Gleam toolchain. It is actively being developed and is rapidly improving, but it does not have all the features you might find in more mature language servers for older languages.
If you wish to to see what is currently being worked on you can view the project roadmap on GitHub.
The Gleam Language Server is included in the regular gleam binary, so if you
have Gleam installed then you have the Gleam language server installed. You may
need to configure your editor to use the language server for Gleam code.
Helix supports the language server out-of-the-box. No additional configuration is required and Helix will automatically start the language server when a Gleam file is opened.
Neovim's nvim-lspconfig includes
configuration for Gleam. Install nvim-lspconfig with your preferred plugin
manager and then add the language server to your init.lua.
require('lspconfig').gleam.setup({})The language server will then be automatically started when you open a Gleam file.
If you are using nvim-treesitter
you can run :TSInstall gleam to get syntax highlighting and other tree-sitter
features.
Install the VS Code Gleam plugin.
The language server will then automatically started when you open a Gleam
file. If VS Code is unable to run the language server ensure that the gleam
binary is included on VS Code's PATH, and consider restarting VS Code.
Zed supports the language server out-of-the-box. No additional configuration is required and Zed will automatically start the language server when a Gleam file is opened.
Any other editor that supports the Language Server Protocol can use the Gleam
Language Server. Configure your editor to run gleam lsp from the root of your
workspace.
You can open Gleam files from multiple projects in one editor session and the Gleam language server will understand which projects they each belong to, and how to work with each of them.
The language server will automatically compile code in Gleam projects opened in the editor. Code generation and Erlang compilation are not performed.
If any files are edited in the editor but not yet saved then these edited versions will be used when compiling in the language server.
The target specified in gleam.toml is used by the language server. If no
target is specified then it defaults to Erlang.
Any errors and warnings found when compiling Gleam code are surfaced in the editor as language server diagnostics.
The language server can format Gleam code using the Gleam formatter. You may want to configure your code to run this automatically when you save a file.
The language server will show documentation, types, and other information when hovering on:
- Constants.
- Import statements, including unqualified values and types.
- Module functions.
- Patterns.
- Record fields.
- The
..used to ignore additional fields in record pattern. - Type annotations.
- Values.
The language server supports go-to definition for:
- Constants.
- Functions.
- Import statements, including unqualified values and types.
- Type annotations.
- Variables.
The language server support completion of:
- Modules in import statements.
- Unqualified types and values in import statements.
- Type constructors in type annotations.
- Record fields.
- Functions and constants defined in the same module.
- Functions and constants defined in other modules, automatically adding import statements if the module has not yet been imported.
The language server supports listing document symbols, such as functions and constants, for the current Gleam file.
The language server can show the type of each argument when calling a function, along with the labels of the arguments that have them.
This code action can correct names written with the wrong case.
pub main() {
let myNumber = 100
}If your cursor is within the name written with the wrong case then code action will be suggested, and if run the code will be updated to this:
pub main() {
let my_number = 100
}This code action can add any expected labels to a call.
pub fn main() {
Date()
}If your cursor is within the Date() import the code action will be suggested,
and if run the code will be updated to this:
pub fn main() {
Date(year: todo, month: todo, day: todo)
}This code action can be used to delete unused import statements from a module.
import gleam/io
import gleam/list
pub fn main() {
io.println("Hello, Joe!")
}If your cursor is within the unused import gleam/list import the code action
will be suggested, and if run the module will be updated to this:
import gleam/io
pub fn main() {
io.println("Hello, Joe!")
}This code action removes redundant tuples from case expression subjects and patterns.
case #(a, b) {
#(1, 2) -> todo
_ -> todo
}If your cursor is within the case expression the code action will be suggested, and if run the module will be updated to this:
case a, b {
1, 2 -> todo
_, _ -> todo
}This code action updates calls and patterns to use the label shorthand syntax.
case date {
Day(day: day, month: month, year: year) -> todo
}If your cursor is within the call that could use the shorthand syntax the code action will be suggested, and if run the module will be updated to this:
case date {
Day(day:, month:, year:) -> todo
}The language server does not perform code generation or compile Erlang or Elixir code, so there is no chance of any code execution occurring due to opening a file in an editor using the Gleam language server.
The language server is unable to build Gleam code that are not in Gleam projects. When one of these files is opened the language server will provide code formatting but other features are not available.