node/tools/eslint/lib/rules/max-len.js

/**
 * @fileoverview Rule to check for max length on a line.
 * @author Matt DuVall <http://www.mattduvall.com>
 * @copyright 2013 Matt DuVall. All rights reserved.
 */

"use strict";

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

module.exports = function(context) {

    /**
     * Creates a string that is made up of repeating a given string a certain
     * number of times. This uses exponentiation of squares to achieve significant
     * performance gains over the more traditional implementation of such
     * functionality.
     * @param {string} str The string to repeat.
     * @param {int} num The number of times to repeat the string.
     * @returns {string} The created string.
     * @private
     */
    function stringRepeat(str, num) {
        var result = "";
        for (num |= 0; num > 0; num >>>= 1, str += str) {
            if (num & 1) {
                result += str;
            }
        }
        return result;
    }

    var tabWidth = context.options[1];

    var maxLength = context.options[0],
        tabString = stringRepeat(" ", tabWidth);

    //--------------------------------------------------------------------------
    // Helpers
    //--------------------------------------------------------------------------
    function checkProgramForMaxLength(node) {
        var lines = context.getSourceLines();

        // Replace the tabs
        // Split (honors line-ending)
        // Iterate
        lines.forEach(function(line, i) {
            if (line.replace(/\t/g, tabString).length > maxLength) {
                context.report(node, { line: i + 1, col: 1 }, "Line " + (i + 1) + " exceeds the maximum line length of " + maxLength + ".");
            }
        });
    }


    //--------------------------------------------------------------------------
    // Public API
    //--------------------------------------------------------------------------

    return {
        "Program": checkProgramForMaxLength
    };

};