eslint/lib/rules/complexity.js

/**
 * @fileoverview Counts the cyclomatic complexity of each function of the script. See http://en.wikipedia.org/wiki/Cyclomatic_complexity.
 * Counts the number of if, conditional, for, whilte, try, switch/case,
 * @author Patrick Brosset
 */

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

module.exports = function(context) {

    "use strict";

    var THRESHOLD = context.options[0];

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

    // Using a stack to store complexity (handling nested functions)
    var fns = [];

    // When parsing a new function, store it in our function stack
    function startFunction() {
        fns.push(1);
    }

    function endFunction(node) {
        var complexity = fns.pop(), name = "anonymous";

        if (node.id) {
            name = node.id.name;
        }
        if (complexity > THRESHOLD) {
            context.report(node, "Function '{{name}}' has a complexity of {{complexity}}.", { name: name, complexity: complexity });
        }
    }

    function increaseComplexity() {
        if (fns.length) {
            fns[fns.length - 1] ++;
        }
    }

    function increaseSwitchComplexity(node) {
        // Avoiding `default`
        if (node.test) {
            increaseComplexity(node);
        }
    }

    function increaseLogicalComplexity(node) {
        // Avoiding &&
        if (node.operator === "||") {
            increaseComplexity(node);
        }
    }

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

    return {
        "FunctionDeclaration": startFunction,
        "FunctionExpression": startFunction,
        "FunctionDeclaration:exit": endFunction,
        "FunctionExpression:exit": endFunction,

        "CatchClause": increaseComplexity,
        "ConditionalExpression": increaseComplexity,
        "LogicalExpression": increaseLogicalComplexity,
        "ForStatement": increaseComplexity,
        "ForInStatement": increaseComplexity,
        "IfStatement": increaseComplexity,
        "SwitchCase": increaseSwitchComplexity,
        "WhileStatement": increaseComplexity,
        "DoWhileStatement": increaseComplexity
    };

};