⚡ Config schemas with structure, readability, and tooling

LSP-first • Node/WASM • Cross-IDE

Config Schema Language

A concise, type-safe language for describing configuration schemas — with inline validation, expressive constraints, and editor-grade tooling.

Types & unions Annotations like @regex Constraint blocks Wildcard keys *: Opaque any{} / any[]

Get started Read the spec See examples

First-class IDE support

CSL ships with a language server, plus official integrations for VS Code and IntelliJ—diagnostics, completion, hover docs, rename, references, and more.

✨ Semantic highlighting 🧠 Completion 🔎 Hover docs 🧹 Diagnostics 🧭 Go to definition 🔁 Rename & references

Browse repo Report issues

Cross‑platform by design

Run CSL as a native C++ binary or via a Node wrapper backed by the WASM build. Use the LSP over stdio, sockets, or named pipes.

🧱 Native C++ CLI 🧩 Node + WASM 🔌 LSP: stdio / socket / pipe 🧪 Regression tests

Build & run See implementation

What CSL covers well

CSL combines “what shape is this config?” with “what rules must it follow?” — in one schema your tools can understand.

🔒 Type safety

Primitives, tables, arrays, and unions like "dev" | "prod".

🔍 Inline validation

Annotations such as @min(1), @regex("..."), @format(email).

⚖️ Constraints

Describe relationships with conflicts, requires, and validate ….

🧩 Flexible areas

Use wildcard keys *: and opaque types any{}/any[] to “leave room” safely.

🧠 Tooling‑ready

The language server powers completion, hover, diagnostics, rename, and navigation.

🌍 Multiple runtimes

Native CLI for speed, or Node + WASM for portability and integration.

Quick taste

A small schema showing types, annotations, defaults, and constraints.

config AppConfig {
  app_name: string;
  version: string @regex("^\\d+\\.\\d+(\\.\\d+)?$");
  environment: "dev" | "prod" = "dev";

  database: {
    host: string @format(url);
    port: number @range(1024, 65535);
    ssl?: boolean;
  };

  insecure_mode?: boolean;

  constraints {
    conflicts database.ssl with insecure_mode;
    requires database.ssl => environment == "prod";
  };
}

Tooling built on LSP

CSL’s core implementation includes parsing + validation, a language server, and a docs generator—wired into editor extensions.

🧱 Native core (C++20)

Fast CLI for parsing/validation plus an LSP server that can run over stdio, sockets, or named pipes.

🧩 Node + WASM wrapper

Portable CLI/LSP entrypoint for environments where shipping a native binary is hard.

🧠 VS Code extension

Semantic highlighting, completion, hover docs, formatting, rename, and navigation.

🧠 IntelliJ plugin

LSP-powered editing plus a built‑in “Generate CSL HTML Docs” action.

📚 Documentation

Keep a schema and human-readable docs in sync—great for teams and reviewers.

🧪 Regression tests

Run the bundled suite to validate changes and ensure consistent behavior across platforms.

Get started

Pick your path: native, Node/WASM, or an editor integration. All of them ultimately talk to the same language server.

git clone https://github.com/nullptr-0/csl.git
cd csl
cmake -B build -S impl/core -DCMAKE_BUILD_TYPE=Release
cmake --build build

Test a schema

path/to/csl --test path/to/schema.csl

Run the language server

path/to/csl --langsvr --stdio (or --socket/--pipe)

# Build the WASM module
impl/core/BuildWasm Release

# Then compile the Node wrapper
cd impl/node
npm install
npm run compile

node ./out/csl.js --test path/to/schema.csl
node ./out/csl.js --langsvr --stdio

# 1) Build the native core (Native core tab)
# 2) Copy the resulting csl binary into:
#    impl/extension/VSCode/core/

cd impl/extension/VSCode
npm install
vsce package
code --install-extension csl-0.0.1.vsix

Generate HTML docs

Right‑click a .csl file → Generate CSL HTML Docs to export a browsable site (including index.html).

Tip: If LSP features don’t start, double-check that the csl binary exists under impl/extension/VSCode/core/.

# 1) Build native csl (Native core tab)
# 2) Copy the resulting binary into resources:
#    impl/extension/IntelliJ/src/main/resources/bin/<os>/csl(.exe)

cd impl/extension/IntelliJ
./gradlew build
./gradlew runIde

Generate HTML docs

Right‑click a .csl file → Generate CSL HTML Docs to export a browsable site (including index.html).

Tip: If LSP features don’t start, double-check that the csl binary exists under impl/extension/IntelliJ/src/main/resources/bin/<os>/.

Read the full spec

Everything from lexing rules to advanced constraint semantics lives in the docs page.

Open docs

Learn by example

See how wildcard keys, unions, and constraints map to real-world formats.

Open examples