Effortless Language Servers

The goal of the Effortless Language Servers project is to enable the creation of language servers for dynamic languages based on a share language-agnostic infrastructure.

Building a language server with standard features should not take more than a few hundred lines of code.

Currently, we support the following features:

• semantic highlighting (Som, Newspeak, Simple Language)
• file and workspace symbols
• goto definition
• code completion
• references and highlights
• signature help
• hover information
• parse errors
• basic linting
• CodeLens for running unit tests

Supported Languages and IDEs

We are building on top of the Language Server Protocol, but provide currently only a VS code extension.

The following languages are supported:

• SOM, the Simple Object Machine, a language for research and teaching
• SOMns, a Newspeak for concurrency research language
• SimpleLanguage, a language to document Oracle's Truffle framework

Additionally, we also provide support for the Debug Adapter Protocol for SOMns programs.

Screenshot of SOMns Semantic Highlighting

Screenshot of SOMns Syntax Highlighting

Screencast of debugging a SOMns Program

Development Setup

To work on the extension, you can build it with the following commands:

npm install .
npm run compile

When working on the extension, it is better to not install it via the Marketplace, but link the code repo directly into the VS Code extension directory. Please replace $pathToCheckout in the following example with the actual path to your checkout:

cd ~/.vscode/extensions
ln -s /$pathToCheckout/effortless-language-servers effortless-language-servers

To debug the extension, open the main folder in VS code and select "Launch Extension" in the debug menu.

Because of current restrictions in VS Code, the same project cannot be opened twice, and it is not possible to debug the debugger and the language server at the same time. As a work around, one can use a separate folder with symlinks:

.
..
.vscode -> ../SOMns-vscode/.vscode
out -> ../SOMns-vscode/out
package.json -> ../SOMns-vscode/package.json
src -> ../SOMns-vscode/src
syntaxes -> ../SOMns-vscode/syntaxes
tsconfig.json -> ../SOMns-vscode/tsconfig.json
typings -> ../SOMns-vscode/typings
typings.json -> ../SOMns-vscode/typings.json

Debugging the Language Server in Java

When working on the Language Server, which provides the IDE services, it is best to start it for instance from Eclipse.

To instruct VS code to use an already running instance of the language server, add the following to your VS Code User Settings:

"els.debugMode" : true

The server can also be started from the command line:

npm run create-server-shell-script
out/server/start.sh

This will run the server exactly as VScode would run it. In this mode it will accept communication from stdin. To configure it for use with TCP, see the create-server-shell-script script in package.json. It currently configure the generated script to disable the debugging mode and TCP, which can be enable individually by changing the corresponding false in the script.

Debugging the Debugger Adapter

To debug the Debugger Adapter, load the code in VS code, and select "Run Debugger as server" in the debugger menu.

In the configuration of the VS Code instance with the SOM code, add a configuration that executes a SOM program, and add the debugServer port as part of the configuration. This needs to be inside the config, i.e., for instance next to the "program" setting.

  "debugServer": 4711,