fix: Avoid crash when exec() is passed no arguments

Closes #82
Refs #23

Author: nzakas

rules/detect-child-process.js

@@ -9,6 +9,9 @@
 // Rule Definition
 //------------------------------------------------------------------------------
 
+/*
+ * Stores variable names pointing to child_process to check (child_process).exec()
+ */
 const names = [];
 
 module.exports = {
@@ -38,7 +41,7 @@ module.exports = {
       },
       MemberExpression: function (node) {
         if (node.property.name === 'exec' && names.indexOf(node.object.name) > -1) {
-          if (node.parent && node.parent.arguments && node.parent.arguments[0].type !== 'Literal') {
+          if (node.parent && node.parent.arguments.length && node.parent.arguments[0].type !== 'Literal') {
             return context.report(node, 'Found child_process.exec() with non Literal first argument');
           }
         }

test/detect-child-process.js

@@ -4,28 +4,22 @@ const RuleTester = require('eslint').RuleTester;
 const tester = new RuleTester();
 
 const ruleName = 'detect-child-process';
-const Rule = require(`../rules/${ruleName}`);
+const rule = require(`../rules/${ruleName}`);
 
-const valid = 'child_process.exec(\'ls\')';
-const invalidRequire = 'require(\'child_process\')';
-const invalidExec = 'var child = require(\'child_process\'); child.exec(com)';
-
-tester.run(`${ruleName} (require("child_process"))`, Rule, {
-  valid: [{ code: valid }],
+tester.run(ruleName, rule, {
+  valid: ["child_process.exec('ls')"],
   invalid: [
     {
-      code: invalidRequire,
-      errors: [{ message: 'Found require("child_process")' }]
-    }
-  ]
-});
-
-tester.run(`${ruleName} (child_process.exec() wih non literal 1st arg.)`, Rule, {
-  valid: [{ code: valid }],
-  invalid: [
+      code: "require('child_process')",
+      errors: [{ message: 'Found require("child_process")' }],
+    },
+    {
+      code: "var child = require('child_process'); child.exec(com)",
+      errors: [{ message: 'Found require("child_process")' }, { message: 'Found child_process.exec() with non Literal first argument' }],
+    },
     {
-      code: invalidExec,
-      errors: [{ message: 'Found require("child_process")' }, { message: 'Found child_process.exec() with non Literal first argument' }]
-    }
-  ]
+      code: "var child = require('child_process'); child.exec()",
+      errors: [{ message: 'Found require("child_process")' }],
+    },
+  ],
 });