🔧 Fix for usage of React.Children methods

Fixes the case where you are iterating over a children prop via the
React.Children API.

lib/rules/no-array-index-key.js

@@ -47,6 +47,32 @@ module.exports = {
         && indexParamNames.indexOf(node.name) !== -1;
     }
 
+    function isUsingReactChildren(node) {
+      const callee = node.callee;
+      if (
+        !callee
+        || !callee.property
+        || !callee.object
+      ) {
+        return null;
+      }
+
+      const isReactChildMethod = ['map', 'forEach'].indexOf(callee.property.name) > -1;
+      if (!isReactChildMethod) {
+        return null;
+      }
+
+      const obj = callee.object;
+      if (obj && obj.name === 'Children') {
+        return true;
+      }
+      if (obj && obj.object && obj.object.name === 'React') {
+        return true;
+      }
+
+      return false;
+    }
+
     function getMapIndexParamName(node) {
       const callee = node.callee;
       if (callee.type !== 'MemberExpression') {
@@ -59,16 +85,19 @@ module.exports = {
         return null;
       }
 
-      const firstArg = node.arguments[0];
-      if (!firstArg) {
+      const callbackArg = isUsingReactChildren(node)
+        ? node.arguments[1]
+        : node.arguments[0];
+
+      if (!callbackArg) {
         return null;
       }
 
-      if (!astUtil.isFunctionLikeExpression(firstArg)) {
+      if (!astUtil.isFunctionLikeExpression(callbackArg)) {
         return null;
       }
 
-      const params = firstArg.params;
+      const params = callbackArg.params;
 
       const indexParamPosition = iteratorFunctionsToIndexParamPosition[callee.property.name];
       if (params.length < indexParamPosition + 1) {
@@ -132,24 +161,20 @@ module.exports = {
           && ['createElement', 'cloneElement'].indexOf(node.callee.property.name) !== -1
           && node.arguments.length > 1
         ) {
-          // React.createElement
           if (!indexParamNames.length) {
             return;
           }
-
           const props = node.arguments[1];
 
           if (props.type !== 'ObjectExpression') {
             return;
           }
-
           props.properties.forEach(prop => {
             if (!prop.key || prop.key.name !== 'key') {
               // { ...foo }
               // { foo: bar }
               return;
             }
-
             checkPropValue(prop.value);
           });