eslint/lib/rules/space-before-blocks.js

/**
 * @fileoverview A rule to ensure whitespace before blocks.
 * @author Mathias Schreck <https://github.com/lo1tuma>
 * @copyright 2014 Mathias Schreck. All rights reserved.
 */

"use strict";

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

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

module.exports = function(context) {
    var config = context.options[0],
        sourceCode = context.getSourceCode(),
        checkFunctions = true,
        checkKeywords = true,
        checkClasses = true;

    if (typeof config === "object") {
        checkFunctions = config.functions !== "never";
        checkKeywords = config.keywords !== "never";
        checkClasses = config.classes !== "never";
    } else if (config === "never") {
        checkFunctions = false;
        checkKeywords = false;
        checkClasses = false;
    }

    /**
     * Checks whether or not a given token is an arrow operator (=>) or a keyword
     * in order to avoid to conflict with `arrow-spacing` and `keyword-spacing`.
     *
     * @param {Token} token - A token to check.
     * @returns {boolean} `true` if the token is an arrow operator.
     */
    function isConflicted(token) {
        return (token.type === "Punctuator" && token.value === "=>") || token.type === "Keyword";
    }

    /**
     * Checks the given BlockStatement node has a preceding space if it doesn’t start on a new line.
     * @param {ASTNode|Token} node The AST node of a BlockStatement.
     * @returns {void} undefined.
     */
    function checkPrecedingSpace(node) {
        var precedingToken = context.getTokenBefore(node),
            hasSpace,
            parent,
            requireSpace;

        if (precedingToken && !isConflicted(precedingToken) && astUtils.isTokenOnSameLine(precedingToken, node)) {
            hasSpace = sourceCode.isSpaceBetweenTokens(precedingToken, node);
            parent = context.getAncestors().pop();
            if (parent.type === "FunctionExpression" || parent.type === "FunctionDeclaration") {
                requireSpace = checkFunctions;
            } else if (node.type === "ClassBody") {
                requireSpace = checkClasses;
            } else {
                requireSpace = checkKeywords;
            }

            if (requireSpace) {
                if (!hasSpace) {
                    context.report({
                        node: node,
                        message: "Missing space before opening brace.",
                        fix: function(fixer) {
                            return fixer.insertTextBefore(node, " ");
                        }
                    });
                }
            } else {
                if (hasSpace) {
                    context.report({
                        node: node,
                        message: "Unexpected space before opening brace.",
                        fix: function(fixer) {
                            return fixer.removeRange([precedingToken.range[1], node.range[0]]);
                        }
                    });
                }
            }
        }
    }

    /**
     * Checks if the CaseBlock of an given SwitchStatement node has a preceding space.
     * @param {ASTNode} node The node of a SwitchStatement.
     * @returns {void} undefined.
     */
    function checkSpaceBeforeCaseBlock(node) {
        var cases = node.cases,
            firstCase,
            openingBrace;

        if (cases.length > 0) {
            firstCase = cases[0];
            openingBrace = context.getTokenBefore(firstCase);
        } else {
            openingBrace = context.getLastToken(node, 1);
        }

        checkPrecedingSpace(openingBrace);
    }

    return {
        "BlockStatement": checkPrecedingSpace,
        "ClassBody": checkPrecedingSpace,
        "SwitchStatement": checkSpaceBeforeCaseBlock
    };

};

module.exports.schema = [
    {
        "oneOf": [
            {
                "enum": ["always", "never"]
            },
            {
                "type": "object",
                "properties": {
                    "keywords": {
                        "enum": ["always", "never"]
                    },
                    "functions": {
                        "enum": ["always", "never"]
                    },
                    "classes": {
                        "enum": ["always", "never"]
                    }
                },
                "additionalProperties": false
            }
        ]
    }
];