langium

What is langium?

Langium is a tool for developing domain-specific languages (DSLs) and language servers. It provides a framework for creating custom languages with a focus on language design, parsing, and tooling support.

What are langium's main functionalities?

Language Definition

Langium allows you to define a custom language using a grammar syntax. This code sample demonstrates how to define a simple DSL with a model and elements using Langium's grammar services.

const { createLangiumGrammarServices } = require('langium');
const services = createLangiumGrammarServices();
const grammar = `grammar MyDSL
entry Model:
    'model' name=ID '{'
        (elements+=Element)*
    '}';
Element:
    'element' name=ID;`;
services.GrammarParser.parse(grammar);

Language Server

Langium can be used to create a language server that provides IDE features like auto-completion and error checking for your custom language. This code sample shows how to start a language server for a simple DSL.

const { startLanguageServer } = require('langium');
startLanguageServer({
    grammar: `grammar MyDSL
entry Model:
    'model' name=ID '{'
        (elements+=Element)*
    '}';
Element:
    'element' name=ID;`,
    port: 5000
});

Other packages similar to langium

antlr4

ANTLR (Another Tool for Language Recognition) is a powerful parser generator for reading, processing, executing, or translating structured text or binary files. It is similar to Langium in that it allows you to define grammars and generate parsers, but it is more focused on parsing and less on providing language server features.

pegjs

PEG.js is a simple parser generator for JavaScript that produces fast parsers with excellent error reporting. It is similar to Langium in terms of grammar definition and parsing capabilities, but it does not provide built-in support for language servers or IDE features.

lezer

Lezer is a parser system for JavaScript that is designed to be small and fast. It is similar to Langium in that it allows you to define grammars and create parsers, but it is more lightweight and does not include language server capabilities.

README

Langium

Langium is a language engineering tool with built-in support for the Language Server Protocol. It has a simple and direct integration with the VS Code extension API.

Getting Started

Langium offers a Yeoman generator to create a new language extension for VS Code. The only prerequisite for the following terminal commands is NodeJS version 14 or higher.

1. Install Yeoman and the Langium extension generator.

npm install -g yo generator-langium

1. Run the generator and answer a few questions.

yo langium

1. Open the new folder in VS Code (replace hello-world with the extension name you chose).

code hello-world

1. Press F5 to launch the extension in a new Extension Development Host window.

2. Open a folder, create a file with your chosen file name extension (.hello is the default), and see that validation and completion (ctrl+space) works:

Follow the instructions in langium-quickstart.md (in your extension folder) to go further.

How Does it Work?

The core of Langium is a grammar declaration language in which you describe multiple aspects of your language:

• Tokens (keywords and terminal rules)
• Syntax (parser rules)
• Abstract syntax tree (AST)

The grammar declaration language of Langium is very similar to Xtext. Please follow the Xtext documentation to learn how to use this language.

Langium features a command line interface (langium-cli) that reads a grammar declaration and generates a parser, TypeScript type declarations for the AST and more.

Integration with the Language Server Protocol (LSP) is done with vscode-languageserver. You have full access to the LSP API in Langium, so you can register additional message handlers or extend the protocol in a breeze.

The main code of Langium consists of a set of services that are connected via dependency injection (DI). You can override the default functionality and add your own service classes by specifying a DI module.

Examples

The source repository of Langium includes examples that demonstrate different use cases.