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LPC development environment

FluffOS ships its own language tooling. The grammar is generated from the driver compiler (tools/lpc-syntax/), so highlighting, format, and lint cannot drift from what the VM actually accepts.

Use this page when you are writing LPC — in an editor, on this docs site, or in another Docusaurus site.

1. Editor: LPC (FluffOS)​

The fluffos/fluffos-vscode extension is the supported editor plugin. It works in VS Code, Cursor, VSCodium, and other Code OSS forks.

It packages the grammar, highlighter, formatter, and linter from tools/lpc-syntax/ at a pinned fluffos commit. Language-engine changes go in this repo; extension UI and packaging go in fluffos-vscode.

Install from the latest GitHub release (.vsix):

code --install-extension fluffos-lpc-<version>.vsix
# Cursor:
cursor --install-extension fluffos-lpc-<version>.vsix

Marketplace / Open VSX: install LPC (FluffOS) when the publish job has run (same extension id).

What you get:

FeatureNotes
Syntax highlightingTextMate grammar generated from lpc-grammar.json
Format Document / format-on-saveSame engine as testsuite/format.sh
As-you-type diagnosticsStructural lint (unbalanced brackets, unterminated literals, …)
Compiler errors on saveOptional: point at lpcc + a mudlib config
Compiler ExplorerSource / tokens / AST / bytecode views
Language serverOther editors can run the same LSP over stdio

Useful settings (workspace or user):

{
  "lpc.format.printWidth": 100,
  "lpc.format.indentSize": 2,
  "lpc.lpcc.path": "/path/to/fluffos/build/bin/lpcc",
  "lpc.lpcc.configFile": "/path/to/mudlib/config.cfg"
}

In a mudlib workspace, run LPC: Initialize compiler config once so save-time diagnostics and the Explorer can find master file and include dirs. Do not point that config at fluffos/testsuite/ unless you are changing the driver.

Standalone LSP (Neovim, Helix, …), after cloning fluffos-vscode and npm install in extension/:

node extension/server/main.js --stdio

2. This documentation site​

The docs site uses the same grammar via a first-party Prism plugin (tools/lpc-syntax/prism-lpc.cjs). Fence LPC as lpc:

foreach (string name, int weight in ([ "sword": 4, "lamp": 1 ])) {
    write(`${name} weighs ${weight}\n`);
}

string *lines = @@HELP
A shop. Dust. A counter.
Type "list" to see wares.
HELP;

Existing ```c fences on language, efun, apply, stdlib, and concept pages are treated as LPC at build time. The remark plugin leaves docs/driver/ and build-wasm alone, so LPC samples there must use ```lpc. Real C stays ```c / ```cpp.

Prefer ```lpc on new pages.

3. Use the highlighter on another Docusaurus 3 site​

The plugin lives in the driver repo (not a separate npm package yet). From a fluffos checkout:

  1. Register the language (swizzle prism-include-languages and require the file while globalThis.Prism is the Prism instance):
require('/path/to/fluffos/tools/lpc-syntax/prism-lpc.cjs');
  1. Optional — remap leftover ```c fences to LPC, except paths you pass in keepCAsC (this site keeps docs/driver/ and build-wasm). Use ```lpc for LPC on those pages, and ```cpp for C samples elsewhere.
// docusaurus.config.js
presets: [
  ['classic', {
    docs: {
      remarkPlugins: [
        require('/path/to/fluffos/tools/lpc-syntax/docusaurus-plugin.cjs'),
      ],
    },
  }],
];

The remark plugin does not rewrite docs/driver/** or build-wasm.

HTML highlighter (no Prism) for static pages or a mudlib help site:

import { highlightLPC, defaultCss } from './tools/lpc-syntax/highlight.mjs';

const html = highlightLPC('int f() { return `v=${x}`; }');

4. Formatter without an editor​

Same engine as the extension. Node ≥ 18; no npm install.

testsuite/format.sh            # format testsuite/**/*.lpc,*.c
testsuite/format.sh --check    # CI
find lib -name '*.lpc' | node tools/lpc-syntax/bin/format-corpus.mjs

Details: LPC formatter and the style guide.

5. Efun metadata for your own tools​

After a driver build:

cd build && ./generate_keywords   # writes keywords.json

That file is the efun list for the compiled binary (packages you actually enabled). See generate_keywords.

6. Suggested mudlib workspace​

your-mudlib/
  AGENTS.md          # copy from /mudlib-agents
  config.cfg         # or whatever that lib already ships
  .vscode/settings.json

.vscode/settings.json (optional):

{
  "files.associations": {
    "*.c": "lpc",
    "*.h": "lpc",
    "*.lpc": "lpc"
  },
  "[lpc]": {
    "editor.formatOnSave": true
  }
}

Many mudlibs still use .c for LPC. Associating those files with the LPC language is how the highlighter actually runs.

Do not put this files.associations block in the fluffos/fluffos driver repo — that tree’s .c / .h files are C++. Only use it in a mudlib workspace.

Then fill Mudlib AGENTS.md so the next session knows ports and the master path.