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) {
    // takes some ideas from http://tools.ietf.org/html/rfc3986#appendix-B, however:
    // - They're matching an entire string that we know is a URI
    // - We're matching part of a string where we think there *might* be a URL
    // - We're only concerned about URLs, as picking out any URI would cause too many false positives
    // - We don't care about matching the entire URL, any small segment is fine
    var URL_REGEXP = /[^:/?#]:\/\/[^?#]/;

    /**
     * Computes the length of a line that may contain tabs. The width of each
     * tab will be the number of spaces to the next tab stop.
     * @param {string} line The line.
     * @param {int} tabWidth The width of each tab stop in spaces.
     * @returns {int} The computed line length.
     * @private
     */
    function computeLineLength(line, tabWidth) {
        var extraCharacterCount = 0;
        line.replace(/\t/g, function(match, offset) {
            var totalOffset = offset + extraCharacterCount,
                previousTabStopOffset = tabWidth ? totalOffset % tabWidth : 0,
                spaceCount = tabWidth - previousTabStopOffset;
            extraCharacterCount += spaceCount - 1;  // -1 for the replaced tab
        });
        return line.length + extraCharacterCount;
    }

    // The options object must be the last option specified…
    var lastOption = context.options[context.options.length - 1];
    var options = typeof lastOption === "object" ? Object.create(lastOption) : {};
    // …but max code length…
    if (typeof context.options[0] === "number") {
        options.code = context.options[0];
    }
    // …and tabWidth can be optionally specified directly as integers.
    if (typeof context.options[1] === "number") {
        options.tabWidth = context.options[1];
    }

    var maxLength = options.code || 80,
        tabWidth = options.tabWidth || 4,
        ignorePattern = options.ignorePattern || null,
        ignoreComments = options.ignoreComments || false,
        ignoreTrailingComments = options.ignoreTrailingComments || options.ignoreComments || false,
        ignoreUrls = options.ignoreUrls || false,
        maxCommentLength = options.comments;

    if (ignorePattern) {
        ignorePattern = new RegExp(ignorePattern);
    }

    //--------------------------------------------------------------------------
    // Helpers
    //--------------------------------------------------------------------------

    /**
     * Tells if a given comment is trailing: it starts on the current line and
     * extends to or past the end of the current line.
     * @param {string} line The source line we want to check for a trailing comment on
     * @param {number} lineNumber The one-indexed line number for line
     * @param {ASTNode} comment The comment to inspect
     * @returns {boolean} If the comment is trailing on the given line
     */
    function isTrailingComment(line, lineNumber, comment) {
        return comment &&
            (comment.loc.start.line === lineNumber && lineNumber <= comment.loc.end.line) &&
            (comment.loc.end.line > lineNumber || comment.loc.end.column === line.length);
    }

    /**
     * Tells if a comment encompasses the entire line.
     * @param {string} line The source line with a trailing comment
     * @param {number} lineNumber The one-indexed line number this is on
     * @param {ASTNode} comment The comment to remove
     * @returns {boolean} If the comment covers the entire line
     */
    function isFullLineComment(line, lineNumber, comment) {
        var start = comment.loc.start,
            end = comment.loc.end;

        return comment &&
            (start.line < lineNumber || (start.line === lineNumber && start.column === 0)) &&
            (end.line > lineNumber || end.column === line.length);
    }

    /**
     * Gets the line after the comment and any remaining trailing whitespace is
     * stripped.
     * @param {string} line The source line with a trailing comment
     * @param {number} lineNumber The one-indexed line number this is on
     * @param {ASTNode} comment The comment to remove
     * @returns {string} Line without comment and trailing whitepace
     */
    function stripTrailingComment(line, lineNumber, comment) {
        // loc.column is zero-indexed
        return line.slice(0, comment.loc.start.column).replace(/\s+$/, "");
    }

    /**
     * Check the program for max length
     * @param {ASTNode} node Node to examine
     * @returns {void}
     * @private
     */
    function checkProgramForMaxLength(node) {
        // split (honors line-ending)
        var lines = context.getSourceLines(),
            // list of comments to ignore
            comments = ignoreComments || maxCommentLength ? context.getAllComments() : [],
            // we iterate over comments in parallel with the lines
            commentsIndex = 0;

        lines.forEach(function(line, i) {
            // i is zero-indexed, line numbers are one-indexed
            var lineNumber = i + 1;
            // if we're checking comment length; we need to know whether this
            // line is a comment
            var lineIsComment = false;

            // we can short-circuit the comment checks if we're already out of comments to check
            if (commentsIndex < comments.length) {
                // iterate over comments until we find one past the current line
                do {
                    var comment = comments[++commentsIndex];
                } while (comment && comment.loc.start.line <= lineNumber);
                // and step back by one
                comment = comments[--commentsIndex];

                if (isFullLineComment(line, lineNumber, comment)) {
                    lineIsComment = true;
                } else if (ignoreTrailingComments && isTrailingComment(line, lineNumber, comment)) {
                    line = stripTrailingComment(line, lineNumber, comment);
                }
            }
            if (ignorePattern && ignorePattern.test(line) ||
                ignoreUrls && URL_REGEXP.test(line)) {
                // ignore this line
                return;
            }

            var lineLength = computeLineLength(line, tabWidth);

            if (lineIsComment && ignoreComments) {
                return;
            }

            if (lineIsComment && lineLength > maxCommentLength) {
                context.report(node, { line: lineNumber, column: 0 }, "Line " + (i + 1) + " exceeds the maximum comment line length of " + maxCommentLength + ".");
            } else if (lineLength > maxLength) {
                context.report(node, { line: lineNumber, column: 0 }, "Line " + (i + 1) + " exceeds the maximum line length of " + maxLength + ".");
            }
        });
    }


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

    return {
        "Program": checkProgramForMaxLength
    };

};

var OPTIONS_SCHEMA = {
    "type": "object",
    "properties": {
        "code": {
            "type": "integer",
            "minimum": 0
        },
        "comments": {
            "type": "integer",
            "minimum": 0
        },
        "tabWidth": {
            "type": "integer",
            "minimum": 0
        },
        "ignorePattern": {
            "type": "string"
        },
        "ignoreComments": {
            "type": "boolean"
        },
        "ignoreUrls": {
            "type": "boolean"
        },
        "ignoreTrailingComments": {
            "type": "boolean"
        }
    },
    "additionalProperties": false
};

var OPTIONS_OR_INTEGER_SCHEMA = {
    "anyOf": [
        OPTIONS_SCHEMA,
        {
            "type": "integer",
            "minimum": 0
        }
    ]
};

module.exports.schema = [
    OPTIONS_OR_INTEGER_SCHEMA,
    OPTIONS_OR_INTEGER_SCHEMA,
    OPTIONS_SCHEMA
];