add tests and restructure function to reach 100% test coverage

lib/rules/prefer-arrow-callback.js

@@ -5,7 +5,7 @@
  * core eslint `prefer-arrow-callback` rule code so that future updates to that code
  * can be more easily applied here.
  */
-/* eslint "complexity": [ "error", 18 ], "max-statements": [ "error", 14 ] */
+/* eslint "complexity": [ "error", 18 ], "max-statements": [ "error", 15 ] */
 
 /**
  * @fileoverview A rule to suggest using arrow functions as callbacks.
@@ -45,21 +45,22 @@ function checkMetaProperty(node, metaName, propertyName) {
  */
 function getVariableOfArguments(scope) {
     const variables = scope.variables;
+    let variableObject = null;
 
     for (let i = 0; i < variables.length; i += 1) {
         const variable = variables[i];
 
-        if (variable.name === 'arguments') {
-            /*
-             * If there was a parameter which is named "arguments", the
-             * implicit "arguments" is not defined.
-             * So does fast return with null.
-             */
-            return variable.identifiers.length === 0 ? variable : null;
+        /*
+         * If there was a parameter which is named "arguments", the
+         * implicit "arguments" is not defined.
+         * So does fast return with null.
+         */
+        if (variable.name === 'arguments' && variable.identifiers.length === 0) {
+            variableObject = variable;
+            break;
         }
     }
-
-    return null;
+    return variableObject;
 }
 
 /**
@@ -96,10 +97,11 @@ function isBindThis(node, currentNode) {
  */
 function getCallbackInfo(node, context) {
     const retv = { isCallback: false, isLexicalThis: false };
+    let searchComplete = false;
     let currentNode = node;
     let parent = node.parent;
 
-    while (currentNode) {
+    while (currentNode && !searchComplete) {
         switch (parent.type) {
         // Checks parents recursively.
 
@@ -115,7 +117,7 @@ function getCallbackInfo(node, context) {
                         parent.parent.arguments[0].type === 'ThisExpression';
                 parent = parent.parent;
             } else {
-                return retv;
+                searchComplete = true;
             }
             break;
 
@@ -129,17 +131,19 @@ function getCallbackInfo(node, context) {
             if (retv.isCallback && astUtils.isMochaFunctionCall(parent, context.getScope())) {
                 retv.isMochaCallback = true;
             }
-            return retv;
+            searchComplete = true;
+            break;
 
         default:
-            return retv;
+            searchComplete = true;
         }
 
-        currentNode = parent;
-        parent = parent.parent;
+        if (!searchComplete) {
+            currentNode = parent;
+            parent = parent.parent;
+        }
     }
-
-    throw new Error('unreachable');
+    return retv;
 }
 
 /**
@@ -197,7 +201,7 @@ module.exports = {
          * {Array<{this: boolean, super: boolean, meta: boolean}>}
          * - this - A flag which shows there are one or more ThisExpression.
          * - super - A flag which shows there are one or more Super.
-         * - meta - A flag which shows there are one or more MethProperty.
+         * - meta - A flag which shows there are one or more MetaProperty.
          */
         let stack = [];
 

test/rules/prefer-arrow-callback.js

@@ -42,8 +42,10 @@ ruleTester.run('prefer-arrow-callback', rules['prefer-arrow-callback'], {
         'foo(function bar() { arguments; }.bind(this));',
         'foo(function bar() { super.a; });',
         'foo(function bar() { super.a; }.bind(this));',
+        '() => super()',
         'foo(function bar() { new.target; });',
         'foo(function bar() { new.target; }.bind(this));',
+        '() => new.target',
         'foo(function bar() { this; }.bind(this, somethingElse));',
         // mocha-specific valid test cases
         'before(function bar() {});',