node/tools/eslint/lib/rules/block-scoped-var.js

/**
 * @fileoverview Rule to check for "block scoped" variables by binding context
 * @author Matt DuVall <http://www.mattduvall.com>
 * @copyright 2015 Toru Nagashima. All rights reserved.
 * @copyright 2015 Mathieu M-Gosselin. All rights reserved.
 */
"use strict";

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

module.exports = function(context) {
    var stack = [];

    /**
     * Makes a block scope.
     * @param {ASTNode} node - A node of a scope.
     * @returns {void}
     */
    function enterScope(node) {
        stack.push(node.range);
    }

    /**
     * Pops the last block scope.
     * @returns {void}
     */
    function exitScope() {
        stack.pop();
    }

    /**
     * Reports a given reference.
     * @param {escope.Reference} reference - A reference to report.
     * @returns {void}
     */
    function report(reference) {
        var identifier = reference.identifier;
        context.report(
            identifier,
            "'{{name}}' used outside of binding context.",
            {name: identifier.name});
    }

    /**
     * Finds and reports references which are outside of valid scopes.
     * @param {ASTNode} node - A node to get variables.
     * @returns {void}
     */
    function checkForVariables(node) {
        if (node.kind !== "var") {
            return;
        }

        // Defines a predicate to check whether or not a given reference is outside of valid scope.
        var scopeRange = stack[stack.length - 1];

        /**
         * Check if a reference is out of scope
         * @param {ASTNode} reference node to examine
         * @returns {boolean} True is its outside the scope
         * @private
         */
        function isOutsideOfScope(reference) {
            var idRange = reference.identifier.range;
            return idRange[0] < scopeRange[0] || idRange[1] > scopeRange[1];
        }

        // Gets declared variables, and checks its references.
        var variables = context.getDeclaredVariables(node);
        for (var i = 0; i < variables.length; ++i) {
            // Reports.
            variables[i]
                .references
                .filter(isOutsideOfScope)
                .forEach(report);
        }
    }

    return {
        "Program": function(node) {
            stack = [node.range];
        },

        // Manages scopes.
        "BlockStatement": enterScope,
        "BlockStatement:exit": exitScope,
        "ForStatement": enterScope,
        "ForStatement:exit": exitScope,
        "ForInStatement": enterScope,
        "ForInStatement:exit": exitScope,
        "ForOfStatement": enterScope,
        "ForOfStatement:exit": exitScope,
        "SwitchStatement": enterScope,
        "SwitchStatement:exit": exitScope,
        "CatchClause": enterScope,
        "CatchClause:exit": exitScope,

        // Finds and reports references which are outside of valid scope.
        "VariableDeclaration": checkForVariables
    };

};

module.exports.schema = [];