NEML2 Language Support

VS Code extension providing language support for NEML2 input files.

Features

• Completion — type names for type = assignments, and option names with inline type hints inside typed blocks
• Hover documentation — docstrings for types and options shown on hover
• Format on save — re-indents the document consistently via the nmhit formatter
• Inspect model — a 🔬 CodeLens above every [model] block under [Models] (and a matching NEML2: Inspect Model palette command) runs neml2-inspect on the current buffer and renders the model's inputs, outputs, parameters, and buffers in a side-panel webview. Requires neml2 ≥ 2.1.5; on older builds the lens is silently hidden and the rest of the extension keeps working.

Requirements

A Python environment with the neml2-langserv package installed:

pip install neml2-langserv

That single install pulls in everything the language server needs — neml2 (≥ 2.1.4 for core features, ≥ 2.1.5 to enable the Inspect model lens) for the type/option metadata, nmhit (≥ 0.1.2) for the formatter, and pygls for the LSP transport.

The extension runs the server with whichever Python interpreter is selected in the Python extension. If neml2-langserv is not installed in that interpreter on first activation, the extension prompts you to install it.

Setup

NEML2 input files share the .i extension with MOOSE input files. To tell the extension that a file is a NEML2 input, add the following as the first line:

# neml2

Files without this marker are treated as MOOSE input (or plain text) and the NEML2 language server will not activate for them.

Format on save

Enable the built-in VS Code setting to auto-format on save:

// .vscode/settings.json
{
  "[neml2]": {
    "editor.formatOnSave": true
  }
}

Inspect a model

With neml2 ≥ 2.1.5 installed, a 🔬 Inspect model CodeLens appears above each [name] sub-block under [Models]. Click it to open a side-panel webview listing the model's inputs, outputs, parameters, and buffers (with their tensor types, dtypes, and device tags) for the current buffer — unsaved edits are picked up automatically.

The same action is available from the command palette as NEML2: Inspect Model, which prompts you to pick a model.

To hide the lenses (the palette command stays available), set:

// settings.json
{
  "neml2.inspect.codeLens.enabled": false
}

MOOSE compatibility

This extension does not claim the .i extension globally, so existing MOOSE workflows are unaffected. Only files whose first line matches # neml2 (optionally followed by other text) are switched to the neml2 language mode.