Disclaimer

Glas is a personal project, the official Gleam Language Server can be found here.

glas: Gleam Language Server

A language server for the Gleam programming language. Glas tries it's best to help users write Gleam, even when there are parsing and typechecking errors!

Installation

Currently MacOS (arm64, x86), Linux (x86), Windows (x86) are supported. Other targets have to be compiled from source.

VSCode

Install the extension from VisualStudio Marketplace. Binaries are included in the extension archive.

NeoVim

require'lspconfig'.gleam.setup{
  cmd = { "glas", "--stdio" }
}

Features

• Resilient Parsing and Type Checking
• Completions
• Goto Definition
• Find References
• Highlight Related
• Hover Info
• Syntax Errors
• Semantic Highlighting
• Show Syntax Tree
• Rename

Motivation?

This project was primarily motivated by my personal learning about how language servers, in general, and rust-analyzer, in particular, work. Gleam caught my interest due to it's lovely and active community and the interesting niche (functional, statically typed, simple) it's trying to fill.

Goals

• Personal Learning
• Good UX
• Provide only correct refactorings (if it compiles before it compiles after)
• Robustness

Non goals

• Aiming for 100% diagnostics (at least short / midterm)
• Code generation

Architecture

Since the code in an actual file during development is usually in a broken state, having a specialized IDE architecture helps making sense of the code on a best-effort basis.

In a broad sense, the architecture of glas can be thought of as going from chained steps of fn(IR) -> Result(IRn, Err) to fn(IR) -> (IRn, List(Err))

Where this is particularly evident is in the parser. Instead of aborting at the first error, the parser always produces a concrete syntax tree and collects errors as it goes. This blog post by matklad provides an excellent explanation of this concept, and the parser in this project is based on the ideas presented there. To visualize the syntax tree of a file, the VSCode extension implements the "show syntax tree" command, allowing you to explore the tree as you type.

Acknowledgments

This project is heavily inspired by the exellent Nix language server and rust-analyzer.