YMMSL Language Support

Download the latest VS Code extension (.vsix)

VS Code installation tutorial

YMMSL Language Support provides a Language Server Protocol (LSP) server built on top of the validation and consistency checks provided by ymmsl-python.

The server enables IDEs and editors such as VS Code, Emacs, and Neovim to provide inline diagnostics and highlight validation errors directly in YMMSL files.

Installation

Linux executable

On Linux, you can download the latest prebuilt executable:

https://github.com/multiscale/ymmsl-lsp/releases?q=server-

Place the executable under bin/ in the repository root.

Requirements

• glibc >= 2.34

If you use the VS Code extension, the executable is already bundled and ready to use.

Installing with pip, pipx, or uv

You can directly install from this repository, or from PyPi.

As this is a tool it is recommended to use either ´uv tool´ or ´pipx´, after which you will find the executable ymmsl-language-server in /path/to/venv/bin and or have it exposed in your shell.

For example, you could use ´´´ uv tool install ymmsl-lsp ´´´

Usage

The LSP server must be connected to an editor or IDE to be useful.

You can either:

• Install the VS Code extension, or
• Generate configuration files for Emacs and Neovim

Generate editor configurations with:

python scripts/generate_editor_configs.py

Generated files are written to:

editors/generated/

Visual Studio Code

Download the extension from the latest GitHub release.

The VS Code extension and the Python language server are released separately. Extension releases are tagged extension-vX.Y.Z; server releases are tagged server-vX.Y.Z. Every server release also publishes a new extension release containing that server version.

Installation tutorial:

https://www.youtube.com/watch?v=nlHnlmtvjF4

The extension bundles the LSP server and should work out of the box.

If not, you need to install it yourself and set the environment variable ´YMMSL_LSP_PATH´

export YMMSL_LSP_PATH=/path/to/venv/bin/ymmsl-language-server

Emacs

The generated file ymmsl-mode_emacs.el provides YMMSL language support for Emacs.

Quick test

Load the generated mode directly:

emacs -l editors/generated/ymmsl-mode_emacs.el

Alternatively, start Emacs and load the file manually:

M-x load-file

Select:

editors/generated/ymmsl-mode_emacs.el

Permanent installation

Copy or symlink the file into your Emacs configuration and load it from init.el:

(add-to-list 'load-path "/path/to/editors/generated")
(load "ymmsl-mode_emacs")

Emacs package installation tutorial:

https://www.youtube.com/watch?v=at_fACZ_o9Q

Neovim

The generated file ymmsl-nvim.lua provides YMMSL language support for Neovim.

Quick test

nvim -c "source editors/generated/ymmsl-nvim.lua"

Permanent installation

Copy the plugin into Neovim's plugin directory:

mkdir -p ~/.config/nvim/plugin
cp editors/generated/ymmsl-nvim.lua ~/.config/nvim/plugin/

Or create a symbolic link:

mkdir -p ~/.config/nvim/plugin
ln -s $(pwd)/editors/generated/ymmsl-nvim.lua \
      ~/.config/nvim/plugin/ymmsl-nvim.lua

Neovim will automatically load the plugin on startup.

What is YMMSL_PATH?

The Python validator resolves imported YMMSL modules using the YMMSL_PATH environment variable.

When a YMMSL file imports another module, the validator searches the directories listed in YMMSL_PATH. If an import cannot be resolved, ensure that YMMSL_PATH points to the directory or directories containing the required YMMSL modules.

Example:

export YMMSL_PATH=/path/to/ymmsl/modules

Multiple directories can be specified using a colon-separated list:

export YMMSL_PATH=/path/one:/path/two:/path/three

This works similarly to PATH and PYTHONPATH.

License

Copyright © 2026 Kristoffer Gustafsson

This repository, including its complete commit history, is licensed under the European Union Public Licence (EUPL) v1.2.

See the LICENSE file for the full license text.