--- /dev/null
+/**
+ * @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
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const lodash = require("lodash");
+
+const astUtils = require("./utils/ast-utils");
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+ meta: {
+ type: "suggestion",
+
+ docs: {
+ description: "enforce a maximum cyclomatic complexity allowed in a program",
+ category: "Best Practices",
+ recommended: false,
+ url: "https://eslint.org/docs/rules/complexity"
+ },
+
+ schema: [
+ {
+ oneOf: [
+ {
+ type: "integer",
+ minimum: 0
+ },
+ {
+ type: "object",
+ properties: {
+ maximum: {
+ type: "integer",
+ minimum: 0
+ },
+ max: {
+ type: "integer",
+ minimum: 0
+ }
+ },
+ additionalProperties: false
+ }
+ ]
+ }
+ ],
+
+ messages: {
+ complex: "{{name}} has a complexity of {{complexity}}. Maximum allowed is {{max}}."
+ }
+ },
+
+ create(context) {
+ const option = context.options[0];
+ let THRESHOLD = 20;
+
+ if (
+ typeof option === "object" &&
+ (Object.prototype.hasOwnProperty.call(option, "maximum") || Object.prototype.hasOwnProperty.call(option, "max"))
+ ) {
+ THRESHOLD = option.maximum || option.max;
+ } else if (typeof option === "number") {
+ THRESHOLD = option;
+ }
+
+ //--------------------------------------------------------------------------
+ // Helpers
+ //--------------------------------------------------------------------------
+
+ // Using a stack to store complexity (handling nested functions)
+ const fns = [];
+
+ /**
+ * When parsing a new function, store it in our function stack
+ * @returns {void}
+ * @private
+ */
+ function startFunction() {
+ fns.push(1);
+ }
+
+ /**
+ * Evaluate the node at the end of function
+ * @param {ASTNode} node node to evaluate
+ * @returns {void}
+ * @private
+ */
+ function endFunction(node) {
+ const name = lodash.upperFirst(astUtils.getFunctionNameWithKind(node));
+ const complexity = fns.pop();
+
+ if (complexity > THRESHOLD) {
+ context.report({
+ node,
+ messageId: "complex",
+ data: { name, complexity, max: THRESHOLD }
+ });
+ }
+ }
+
+ /**
+ * Increase the complexity of the function in context
+ * @returns {void}
+ * @private
+ */
+ function increaseComplexity() {
+ if (fns.length) {
+ fns[fns.length - 1]++;
+ }
+ }
+
+ /**
+ * Increase the switch complexity in context
+ * @param {ASTNode} node node to evaluate
+ * @returns {void}
+ * @private
+ */
+ function increaseSwitchComplexity(node) {
+
+ // Avoiding `default`
+ if (node.test) {
+ increaseComplexity();
+ }
+ }
+
+ //--------------------------------------------------------------------------
+ // Public API
+ //--------------------------------------------------------------------------
+
+ return {
+ FunctionDeclaration: startFunction,
+ FunctionExpression: startFunction,
+ ArrowFunctionExpression: startFunction,
+ "FunctionDeclaration:exit": endFunction,
+ "FunctionExpression:exit": endFunction,
+ "ArrowFunctionExpression:exit": endFunction,
+
+ CatchClause: increaseComplexity,
+ ConditionalExpression: increaseComplexity,
+ LogicalExpression: increaseComplexity,
+ ForStatement: increaseComplexity,
+ ForInStatement: increaseComplexity,
+ ForOfStatement: increaseComplexity,
+ IfStatement: increaseComplexity,
+ SwitchCase: increaseSwitchComplexity,
+ WhileStatement: increaseComplexity,
+ DoWhileStatement: increaseComplexity
+ };
+
+ }
+};