racket-langserver

racket-langserver is a Language Server Protocol implementation for Racket. This project seeks to use DrRacket's public APIs to provide functionality that mimics DrRacket's code tools as closely as possible.

Installation and usage

A Racket runtime is a prerequisite, so before using racket-langserver, ensure that a Racket runtime is installed. You can install an from the official download page or install one from your package manager. Currently racket-langserver is compatible with Racket version 7.6 to 9.2.

VSCode

Use the Magic Racket extension.

Other editors and IDEs

First, install an LSP runtime for your editor.

Next, install the package via raco:

raco pkg install racket-langserver

Once it is installed, you can configure your editor to use a custom LSP client for Racket (and all installed module, e.g. Rhombus) files (usually .rkt), and set the command for the custom client to

racket -l racket-langserver

You may need to restart your LSP runtime or your editor for racket-langserver to start.

Language Support

The server recognizes language families and provides different levels of support depending on whether the language uses s-expression syntax.

• Racket - The standard Racket language (#lang racket, #lang racket/*, etc.).
• Typed Racket - (#lang typed/racket, #lang typed/racket/*, etc.).
• Other sexp - Predefined s-expression language families beyond Racket and Typed Racket.
• Scribble - (#lang scribble, #lang scribble/*, etc.).
• Rhombus - (#lang rhombus, #lang rhombus/*, etc.).
• Unknown - Language declaration found and parsed, but not in the predefined list.
• Unrecognized - No language declaration found (missing #lang, #reader, or (module ...) form).

Legend

Mark	Meaning
✅	Feature works well and produces useful results.
⚠️	Partial support - the feature runs but may produce incomplete or imprecise results.
❌	Not implemented or intentionally filtered out for this language family.

The matrix rates expected usefulness for each language family. Expansion-based features are marked supported when they only depend on successful expansion and check-syntax data. Features are marked partial when they have additional syntax-family limits, lexer limits, or intentionally noisy results.

Support Matrix

Feature	Racket	Typed Racket	Other sexp	Scribble	Rhombus	Unknown	Unrecognized
Completion	✅	✅	✅	⚠️	⚠️	⚠️	⚠️
Definition	✅	✅	✅	✅	✅	✅	❌
Hover	✅	✅	✅	✅	✅	✅	❌
Signature Help	✅	✅	✅	❌	❌	⚠️	❌
References	✅	✅	✅	✅	✅	✅	❌
Document Highlight	✅	✅	✅	✅	✅	✅	❌
Rename	✅	✅	✅	✅	✅	✅	❌
Prepare Rename	✅	✅	✅	✅	✅	✅	❌
Code Action	✅	✅	✅	✅	✅	✅	❌
Diagnostics	✅	✅	✅	✅	✅	⚠️	✅
Document Symbols	⚠️	⚠️	⚠️	⚠️	⚠️	⚠️	⚠️
Semantic Tokens, Delta	❌	❌	❌	❌	❌	❌	❌
Semantic Tokens, Full	✅	✅	✅	⚠️	⚠️	⚠️	⚠️
Semantic Tokens, Range	✅	✅	✅	⚠️	⚠️	⚠️	⚠️
Formatting	✅	✅	✅	❌	❌	❌	❌
Range Formatting	✅	✅	✅	❌	❌	❌	❌
On-Type Formatting	✅	✅	✅	❌	❌	❌	❌
Inlay Hints	❌	❌	❌	❌	❌	❌	❌

Features

See features.md for a detailed breakdown of each feature.

Development

See CONTRIBUTING.md.