eslint/lib/rules/semi-spacing.js

/**
 * @fileoverview Validates spacing before and after semicolon
 * @author Mathias Schreck
 * @copyright 2015 Mathias Schreck
 */

"use strict";

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

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

module.exports = function(context) {

    var config = context.options[0],
        requireSpaceBefore = false,
        requireSpaceAfter = true,
        sourceCode = context.getSourceCode();

    if (typeof config === "object") {
        if (config.hasOwnProperty("before")) {
            requireSpaceBefore = config.before;
        }
        if (config.hasOwnProperty("after")) {
            requireSpaceAfter = config.after;
        }
    }

    /**
     * Checks if a given token has leading whitespace.
     * @param {Object} token The token to check.
     * @returns {boolean} True if the given token has leading space, false if not.
     */
    function hasLeadingSpace(token) {
        var tokenBefore = context.getTokenBefore(token);
        return tokenBefore && astUtils.isTokenOnSameLine(tokenBefore, token) && sourceCode.isSpaceBetweenTokens(tokenBefore, token);
    }

    /**
     * Checks if a given token has trailing whitespace.
     * @param {Object} token The token to check.
     * @returns {boolean} True if the given token has trailing space, false if not.
     */
    function hasTrailingSpace(token) {
        var tokenAfter = context.getTokenAfter(token);
        return tokenAfter && astUtils.isTokenOnSameLine(token, tokenAfter) && sourceCode.isSpaceBetweenTokens(token, tokenAfter);
    }

    /**
     * Checks if the given token is the last token in its line.
     * @param {Token} token The token to check.
     * @returns {boolean} Whether or not the token is the last in its line.
     */
    function isLastTokenInCurrentLine(token) {
        var tokenAfter = context.getTokenAfter(token);
        return !(tokenAfter && astUtils.isTokenOnSameLine(token, tokenAfter));
    }

    /**
     * Checks if the given token is the first token in its line
     * @param {Token} token The token to check.
     * @returns {boolean} Whether or not the token is the first in its line.
     */
    function isFirstTokenInCurrentLine(token) {
        var tokenBefore = context.getTokenBefore(token);
        return !(tokenBefore && astUtils.isTokenOnSameLine(token, tokenBefore));
    }

    /**
     * Checks if the next token of a given token is a closing parenthesis.
     * @param {Token} token The token to check.
     * @returns {boolean} Whether or not the next token of a given token is a closing parenthesis.
     */
    function isBeforeClosingParen(token) {
        var nextToken = context.getTokenAfter(token);
        return (
            nextToken &&
            nextToken.type === "Punctuator" &&
            (nextToken.value === "}" || nextToken.value === ")")
        );
    }

    /**
     * Checks if the given token is a semicolon.
     * @param {Token} token The token to check.
     * @returns {boolean} Whether or not the given token is a semicolon.
     */
    function isSemicolon(token) {
        return token.type === "Punctuator" && token.value === ";";
    }

    /**
     * Reports if the given token has invalid spacing.
     * @param {Token} token The semicolon token to check.
     * @param {ASTNode} node The corresponding node of the token.
     * @returns {void}
     */
    function checkSemicolonSpacing(token, node) {
        var location;

        if (isSemicolon(token)) {
            location = token.loc.start;

            if (hasLeadingSpace(token)) {
                if (!requireSpaceBefore) {
                    context.report({
                        node: node,
                        loc: location,
                        message: "Unexpected whitespace before semicolon.",
                        fix: function(fixer) {
                            var tokenBefore = context.getTokenBefore(token);
                            return fixer.removeRange([tokenBefore.range[1], token.range[0]]);
                        }
                    });
                }
            } else {
                if (requireSpaceBefore) {
                    context.report({
                        node: node,
                        loc: location,
                        message: "Missing whitespace before semicolon.",
                        fix: function(fixer) {
                            return fixer.insertTextBefore(token, " ");
                        }
                    });
                }
            }

            if (!isFirstTokenInCurrentLine(token) && !isLastTokenInCurrentLine(token) && !isBeforeClosingParen(token)) {
                if (hasTrailingSpace(token)) {
                    if (!requireSpaceAfter) {
                        context.report({
                            node: node,
                            loc: location,
                            message: "Unexpected whitespace after semicolon.",
                            fix: function(fixer) {
                                var tokenAfter = context.getTokenAfter(token);
                                return fixer.removeRange([token.range[1], tokenAfter.range[0]]);
                            }
                        });
                    }
                } else {
                    if (requireSpaceAfter) {
                        context.report({
                            node: node,
                            loc: location,
                            message: "Missing whitespace after semicolon.",
                            fix: function(fixer) {
                                return fixer.insertTextAfter(token, " ");
                            }
                        });
                    }
                }
            }
        }
    }

    /**
     * Checks the spacing of the semicolon with the assumption that the last token is the semicolon.
     * @param {ASTNode} node The node to check.
     * @returns {void}
     */
    function checkNode(node) {
        var token = context.getLastToken(node);
        checkSemicolonSpacing(token, node);
    }

    return {
        "VariableDeclaration": checkNode,
        "ExpressionStatement": checkNode,
        "BreakStatement": checkNode,
        "ContinueStatement": checkNode,
        "DebuggerStatement": checkNode,
        "ReturnStatement": checkNode,
        "ThrowStatement": checkNode,
        "ForStatement": function(node) {
            if (node.init) {
                checkSemicolonSpacing(context.getTokenAfter(node.init), node);
            }

            if (node.test) {
                checkSemicolonSpacing(context.getTokenAfter(node.test), node);
            }
        }
    };
};

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