comma-spacing.js

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

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

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

/** @type {import('../shared/types').Rule} */
module.exports = {
    meta: {
        type: "layout",

        docs: {
            description: "Enforce consistent spacing before and after commas",
            recommended: false,
            url: "https://eslint.org/docs/rules/comma-spacing"
        },

        fixable: "whitespace",

        schema: [
            {
                type: "object",
                properties: {
                    before: {
                        type: "boolean",
                        default: false
                    },
                    after: {
                        type: "boolean",
                        default: true
                    }
                },
                additionalProperties: false
            }
        ],

        messages: {
            missing: "A space is required {{loc}} ','.",
            unexpected: "There should be no space {{loc}} ','."
        }
    },

    create(context) {

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

        const 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
        const commaTokensToIgnore = [];

        /**
         * Reports a spacing error with an appropriate message.
         * @param {ASTNode} node The binary expression node to report.
         * @param {string} loc 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, loc, otherNode) {
            context.report({
                node,
                fix(fixer) {
                    if (options[loc]) {
                        if (loc === "before") {
                            return fixer.insertTextBefore(node, " ");
                        }
                        return fixer.insertTextAfter(node, " ");

                    }
                    let start, end;
                    const newText = "";

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

                    return fixer.replaceTextRange([start, end], newText);

                },
                messageId: options[loc] ? "missing" : "unexpected",
                data: {
                    loc
                }
            });
        }

        /**
         * 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) {
            let previousToken = sourceCode.getFirstToken(node);

            node.elements.forEach(element => {
                let token;

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

                    if (astUtils.isCommaToken(token)) {
                        commaTokensToIgnore.push(token);
                    }
                } else {
                    token = sourceCode.getTokenAfter(element);
                }

                previousToken = token;
            });
        }

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

        return {
            "Program:exit"() {
                tokensAndComments.forEach((token, i) => {

                    if (!astUtils.isCommaToken(token)) {
                        return;
                    }

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

                    if (
                        previousToken &&
                        !astUtils.isCommaToken(previousToken) && // ignore spacing between two commas

                        /*
                         * `commaTokensToIgnore` are ending commas of `null` elements (array holes/elisions).
                         * In addition to spacing between two commas, this can also ignore:
                         *
                         *   - Spacing after `[` (controlled by array-bracket-spacing)
                         *       Example: [ , ]
                         *                 ^
                         *   - Spacing after a comment (for backwards compatibility, this was possibly unintentional)
                         *       Example: [a, /* * / ,]
                         *                          ^
                         */
                        !commaTokensToIgnore.includes(token) &&

                        astUtils.isTokenOnSameLine(previousToken, token) &&
                        options.before !== sourceCode.isSpaceBetweenTokens(previousToken, token)
                    ) {
                        report(token, "before", previousToken);
                    }

                    if (
                        nextToken &&
                        !astUtils.isCommaToken(nextToken) && // ignore spacing between two commas
                        !astUtils.isClosingParenToken(nextToken) && // controlled by space-in-parens
                        !astUtils.isClosingBracketToken(nextToken) && // controlled by array-bracket-spacing
                        !astUtils.isClosingBraceToken(nextToken) && // controlled by object-curly-spacing
                        !(!options.after && nextToken.type === "Line") && // special case, allow space before line comment
                        astUtils.isTokenOnSameLine(token, nextToken) &&
                        options.after !== sourceCode.isSpaceBetweenTokens(token, nextToken)
                    ) {
                        report(token, "after", nextToken);
                    }
                });
            },
            ArrayExpression: addNullElementsToIgnoreList,
            ArrayPattern: addNullElementsToIgnoreList

        };

    }
};