Clean up variable utils and add more tests

Author: jomasti

lib/util/Components.js

@@ -258,10 +258,9 @@ function componentRule(rule, context) {
       var destructuredReactCreateElement = function () {
         var variables = variableUtil.variablesInScope(context);
         var variable = variableUtil.getVariable(variables, 'createElement');
-        if (variable !== null) {
+        if (variable) {
           var map = variable.scope.set;
-          // eslint-disable-next-line no-undef
-          if (map instanceof Map && map.has('React')) {
+          if (map.has('React')) {
             return true;
           }
         }

lib/util/variable.js

@@ -11,16 +11,9 @@
  * @returns {Boolean} True if the variable was found, false if not.
  */
 function findVariable(variables, name) {
-  var i;
-  var len;
-
-  for (i = 0, len = variables.length; i < len; i++) {
-    if (variables[i].name === name) {
-      return true;
-    }
-  }
-
-  return false;
+  return variables.some(function (variable) {
+    return variable.name === name;
+  });
 }
 
 /**
@@ -30,16 +23,9 @@ function findVariable(variables, name) {
  * @returns {Object} Variable if the variable was found, null if not.
  */
 function getVariable(variables, name) {
-  var i;
-  var len;
-
-  for (i = 0, len = variables.length; i < len; i++) {
-    if (variables[i].name === name) {
-      return variables[i];
-    }
-  }
-
-  return null;
+  return variables.find(function (variable) {
+    return variable.name === name;
+  });
 }
 
 /**

tests/lib/rules/display-name.js

@@ -572,5 +572,29 @@ ruleTester.run('display-name', rule, {
     errors: [{
       message: 'Component definition is missing display name'
     }]
+  }, {
+    code: [
+      'import React from "react";',
+      'const { createElement } = React;',
+      'export default (props) => {',
+      '  return createElement("div", {}, "hello");',
+      '};'
+    ].join('\n'),
+    parser: 'babel-eslint',
+    errors: [{
+      message: 'Component definition is missing display name'
+    }]
+  }, {
+    code: [
+      'import React from "react";',
+      'const createElement = React.createElement;',
+      'export default (props) => {',
+      '  return createElement("div", {}, "hello");',
+      '};'
+    ].join('\n'),
+    parser: 'babel-eslint',
+    errors: [{
+      message: 'Component definition is missing display name'
+    }]
   }]
 });