Example of writing a CSSLint extension using the new Brackets linting API (https://github.com/adobe/brackets/pull/4588)

gistfile1.js

/*jslint vars: true, plusplus: true, devel: true, nomen: true, indent: 4, maxerr: 50 */
/*global define, brackets, $, CSSLint */

define(function (require, exports, module) {
    "use strict";
    
    // Brackets modules
    var Linting = brackets.getModule("language/Linting");
    
    // Load CSSLint library
    require("csslint/csslint");
    
    function cssLinter(text, fullPath) {
        var results = CSSLint.verify(text);
        if (!results.messages.length) {
            return null;  // no warnings - passing 100%
        }
        
        // Convert list of warnings to the API's required format
        var errors = results.messages.map(function (csslintError) {
            return {
                pos: { line: csslintError.line - 1, ch: csslintError.col - 1 },
                message: csslintError.message,
                type: csslintError.type === "error" ? Linting.Type.ERROR : Linting.Type.WARNING
            };
        });
        return { errors: errors };
    }
    
    Linting.registerLinter("css", {
        name: "CSSLint",
        scanFile: cssLinter
    });
});