node/tools/eslint/lib/rules/comma-spacing.js

/**
 * @fileoverview Comma spacing - validates spacing before and after comma
 * @author Vignesh Anand aka vegetableman.
 * @copyright 2014 Vignesh Anand. All rights reserved.
 */
"use strict";

var astUtils = require("../ast-utils");

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

module.exports = function(context) {

    var sourceCode = context.getSourceCode();
    var tokensAndComments = sourceCode.tokensAndComments;

    var options = {
        before: context.options[0] ? !!context.options[0].before : false,
        after: context.options[0] ? !!context.options[0].after : true
    };

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

    // list of comma tokens to ignore for the check of leading whitespace
    var commaTokensToIgnore = [];

    /**
     * Determines if a given token is a comma operator.
     * @param {ASTNode} token The token to check.
     * @returns {boolean} True if the token is a comma, false if not.
     * @private
     */
    function isComma(token) {
        return !!token && (token.type === "Punctuator") && (token.value === ",");
    }

    /**
     * Reports a spacing error with an appropriate message.
     * @param {ASTNode} node The binary expression node to report.
     * @param {string} dir Is the error "before" or "after" the comma?
     * @param {ASTNode} otherNode The node at the left or right of `node`
     * @returns {void}
     * @private
     */
    function report(node, dir, otherNode) {
        context.report({
            node: node,
            fix: function(fixer) {
                if (options[dir]) {
                    if (dir === "before") {
                        return fixer.insertTextBefore(node, " ");
                    } else {
                        return fixer.insertTextAfter(node, " ");
                    }
                } else {
                    var start, end;
                    var newText = "";

                    if (dir === "before") {
                        start = otherNode.range[1];
                        end = node.range[0];
                    } else {
                        start = node.range[1];
                        end = otherNode.range[0];
                    }

                    return fixer.replaceTextRange([start, end], newText);
                }
            },
            message: options[dir] ?
              "A space is required " + dir + " ','." :
              "There should be no space " + dir + " ','."
        });
    }

    /**
     * Validates the spacing around a comma token.
     * @param {Object} tokens - The tokens to be validated.
     * @param {Token} tokens.comma The token representing the comma.
     * @param {Token} [tokens.left] The last token before the comma.
     * @param {Token} [tokens.right] The first token after the comma.
     * @param {Token|ASTNode} reportItem The item to use when reporting an error.
     * @returns {void}
     * @private
     */
    function validateCommaItemSpacing(tokens, reportItem) {
        if (tokens.left && astUtils.isTokenOnSameLine(tokens.left, tokens.comma) &&
                (options.before !== sourceCode.isSpaceBetweenTokens(tokens.left, tokens.comma))
        ) {
            report(reportItem, "before", tokens.left);
        }

        if (tokens.right && !options.after && tokens.right.type === "Line") {
            return;
        }

        if (tokens.right && astUtils.isTokenOnSameLine(tokens.comma, tokens.right) &&
                (options.after !== sourceCode.isSpaceBetweenTokens(tokens.comma, tokens.right))
        ) {
            report(reportItem, "after", tokens.right);
        }
    }

    /**
     * Adds null elements of the given ArrayExpression or ArrayPattern node to the ignore list.
     * @param {ASTNode} node An ArrayExpression or ArrayPattern node.
     * @returns {void}
     */
    function addNullElementsToIgnoreList(node) {
        var previousToken = context.getFirstToken(node);

        node.elements.forEach(function(element) {
            var token;

            if (element === null) {
                token = context.getTokenAfter(previousToken);

                if (isComma(token)) {
                    commaTokensToIgnore.push(token);
                }
            } else {
                token = context.getTokenAfter(element);
            }

            previousToken = token;
        });
    }

    //--------------------------------------------------------------------------
    // Public
    //--------------------------------------------------------------------------

    return {
        "Program:exit": function() {

            var previousToken,
                nextToken;

            tokensAndComments.forEach(function(token, i) {

                if (!isComma(token)) {
                    return;
                }

                if (token && token.type === "JSXText") {
                    return;
                }

                previousToken = tokensAndComments[i - 1];
                nextToken = tokensAndComments[i + 1];

                validateCommaItemSpacing({
                    comma: token,
                    left: isComma(previousToken) || commaTokensToIgnore.indexOf(token) > -1 ? null : previousToken,
                    right: isComma(nextToken) ? null : nextToken
                }, token);
            });
        },
        "ArrayExpression": addNullElementsToIgnoreList,
        "ArrayPattern": addNullElementsToIgnoreList

    };

};

module.exports.schema = [
    {
        "type": "object",
        "properties": {
            "before": {
                "type": "boolean"
            },
            "after": {
                "type": "boolean"
            }
        },
        "additionalProperties": false
    }
];