eslint/lib/rules/one-var.js

/**
 * @fileoverview A rule to ensure the use of a single variable declaration.
 * @author Ian Christian Myers
 */

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

module.exports = function(context) {

    "use strict";

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

    var functionStack = [];

    function startFunction() {
        functionStack.push(false);
    }

    function endFunction() {
        functionStack.pop();
    }

    function checkDeclarations(node) {
        if (functionStack[functionStack.length - 1]) {
            context.report(node, "Combine this with the previous 'var' statement.");
        } else {
            functionStack[functionStack.length - 1] = true;
        }
    }

    //--------------------------------------------------------------------------
    // Public API
    //--------------------------------------------------------------------------

    return {
        "Program": startFunction,
        "FunctionDeclaration": startFunction,
        "FunctionExpression": startFunction,

        "VariableDeclaration": checkDeclarations,

        "Program:exit": endFunction,
        "FunctionDeclaration:exit": endFunction,
        "FunctionExpression:exit": endFunction
    };

};