Fix wrong name printed in custom elements (when passed as props) (#46)

* Fix wrong name printed in custom elements

* Update Node versions for Travis

* Use plain old function declaration for ReactElement test

* Fix test

* Update test.js

.travis.yml

@@ -1,4 +1,4 @@
 language: node_js
 node_js:
   - "4"
-  - "5"
+  - "6"

__tests__/test.js

@@ -514,6 +514,18 @@ describe('prettyFormat()', () => {
       );
     });
 
+    it('supports a single element with custom React elements with props', () => {
+      function Cat() {
+        return React.createElement('div');
+      };
+      assertPrintedJSX(
+        React.createElement('Mouse', {
+          prop: React.createElement(Cat, {foo: 'bar'})
+        }),
+        '<Mouse\n  prop={\n    <Cat\n      foo="bar" />\n  } />'
+      );
+    });
+
     it('supports a single element with React elements with a child', () => {
       assertPrintedJSX(
         React.createElement('Mouse', {

plugins/ReactElement.js

@@ -46,7 +46,14 @@ function printProps(props, print, indent, opts) {
 }
 
 function printElement(element, print, indent, opts) {
-  let result = '<' + element.type;
+  let result = '<';
+  if (typeof element.type === 'string') {
+    result += element.type;
+  } else if (typeof element.type === 'function') {
+    result += element.type.displayName || element.type.name || 'Unknown';
+  } else {
+    result += 'Unknown';
+  }
   result += printProps(element.props, print, indent, opts);
 
   const opaqueChildren = element.props.children;