@lass-lang/core

Core transpiler for the Lass language. Converts .lass files to executable JavaScript modules that produce CSS.

Installation

pnpm add @lass-lang/core

Usage

import { transpile } from '@lass-lang/core';

// Transpile Lass source to a JavaScript module
const source = `
.button {
  color: blue;
  padding: 8px 16px;
}
`;

const { code } = transpile(source);
// code is a JS module string that exports the CSS

// Execute the transpiled code to get CSS
const dataUrl = `data:text/javascript;charset=utf-8,${encodeURIComponent(code)}`;
const module = await import(dataUrl);
console.log(module.default); // The CSS string

API

transpile(source, options?)

Transpiles Lass source code to a JavaScript module.

Parameters:

• source (string): The Lass source code
• options (TranspileOptions, optional):
  • filename (string): Source file path for error messages
  • sourceMap (boolean): Generate source maps (future)

Returns: TranspileResult

• code (string): The generated JavaScript module code
• map (string, optional): Source map (future)

Error Handling

import { LassTranspileError, ErrorCategory } from '@lass-lang/core';

try {
  const { code } = transpile(source, { filename: 'style.lass' });
} catch (error) {
  if (error instanceof LassTranspileError) {
    console.error(`${error.category} error at line ${error.location.line}`);
  }
}

Error Categories:

• ErrorCategory.SCAN - Scanner-level errors
• ErrorCategory.SYMBOL - Symbol detection errors
• ErrorCategory.SYNTAX - Syntax errors

Features

The Lass transpiler supports the full language feature set:

• Two-zone model - Use --- separator to define a JS preamble zone followed by a CSS zone
• Dollar substitution - $name text substitution from preamble variables
• Expression interpolation - {{ expr }} for inline JavaScript expressions
• Property lookup - @(prop) or @prop shorthand to reference previously defined CSS property values
• Style blocks - @{ } to embed CSS fragments generated from JavaScript
• Comment stripping - // single-line comments are removed from output

TypeScript Support

For TypeScript projects using .lass files, add type declarations:

// lass.d.ts
declare module '*.lass' {
  const css: string;
  export default css;
}

License

MIT