WCL — Wil's Configuration Language

WCL is a typed configuration language with schemas, expressions, functions, and imports. A document declares its schema alongside its data, so wcl check can validate it before another program reads it.

The same language powers wdoc, which renders documentation to HTML websites, Markdown, and PDF. The wcl binary also provides formatting, field editing, evaluated diffs, a REPL, and an LSP server for editor support.

WCL is pre-release software. The language and APIs may change while they stabilise.

Install

From a checkout with Rust and Cargo installed:

cargo install --path crates/wcl --locked
wcl --version

For prebuilt binaries, see the releases and the installer. The installer requires --pre for pre-releases. The reference manual covers the language, CLI, and wdoc.

Quickstart

This config.wcl declares a server schema and one server:

@block("server") type Server {
  @inline(0) id: identifier
  host: utf8
  @default(8080) port: u16
}

@document type Config {
  @children("server") servers: list<Server>
}

server web {
  host = "localhost"
}

Validate it, then read the port supplied by the schema default:

wcl check config.wcl                  # prints OK
wcl get config.wcl servers.web.port   # prints 8080

Change host to a number and wcl check reports a schema violation.

Scaffolding a project

wcl init generates a new project folder from a template. A template is a WCL document declaring property questions plus the file / folder blocks to create; WCL ships a few built-ins.

wcl init --list                      # list built-in templates
wcl init minimal ./my-project        # prompts for each property
wcl init minimal ./app -D name=app --defaults   # non-interactive

Built-in templates include minimal (a single commented main.wcl), website (custom HTML layout), and three multi-folder wdoc projects: page, book (sidebar TOC), and presentation (slide deck). The page, book, and presentation templates lay out main.wcl with schema/, data/, and wdoc/ folders, and project custom data into one generated page per entry:

wcl init page ./my-site -D name="My Site" --defaults
wcl wdoc build ./my-site/main.wcl --out ./my-site/_site

<template> may also be a path to your own template .wcl file, or the name of a user template installed under $XDG_DATA_HOME/wcl/templates/<name>/ (default ~/.local/share/wcl/templates/<name>/) as a folder containing a template.wcl — these show up in wcl init --list too. Inside a template, a file's contents pull in answers with the answer("name") builtin (in an interpolating heredoc):

import <scaffold.wcl>

property "name" {
  prompt  = "Project name"
  default = "my-project"
}

file "main.wcl" {
  content = $<<WCL
// ${answer("name")}
WCL
}

Layout

• crates/wcl_lang — parser, evaluator, schema validation, formatting, and document APIs
• crates/wcl — wcl CLI binary
• crates/wcl_lsp — language server behind wcl lsp
• crates/wcl_wdoc — documentation schemas and HTML, Markdown, and PDF rendering
• editors/ — VS Code extension and tree-sitter grammar
• examples/ — sample configurations and wdoc documents
• docs/reference/ — reference manual source, written in WCL

Development

just workspace-build      # cargo build --workspace
just workspace-test       # cargo test --workspace
just workspace-lint       # clippy with -D warnings
just workspace-bench      # criterion benchmarks
just cli-run -- check examples/basic.wcl

Install + editor integrations:

just cli-install          # release build installed to ~/.local/bin or WCL_INSTALL_DIR
just vscode-build         # npm install + tsc compile (editors/vscode)
just vscode-package       # produce a .vsix via @vscode/vsce
just vscode-install       # install the .vsix into VS Code via `code --install-extension`

Run just --list to see every recipe grouped by purpose.

License

WCL is licensed under the MIT License. Copyright (c) 2026 Wil Taylor.