Don't allow to call connect* methods on the composite component elements

src/bindConnectorMethod.js

@@ -1,7 +1,7 @@
 import shallowEqual from './utils/shallowEqual';
 import cloneWithRef from './utils/cloneWithRef';
 import { Disposable, SerialDisposable } from 'disposables';
-import { findDOMNode, isValidElement } from 'react';
+import { isValidElement } from 'react';
 
 export default function bindConnectorMethod(handlerId, connect) {
   const disposable = new SerialDisposable();
@@ -14,12 +14,25 @@ export default function bindConnectorMethod(handlerId, connect) {
     // This helps us achieve a neat API where user doesn't even know that refs
     // are being used under the hood.
     if (isValidElement(nextWhatever)) {
+      // Custom components can no longer be wrapped directly in React DnD 2.0
+      // so that we don't need to depend on findDOMNode() from react-dom.
+      if (typeof nextWhatever.type !== 'string') {
+        const displayName = nextWhatever.type.displayName ||
+          nextWhatever.type.name ||
+          'the component';
+        throw new Error(
+          `Only native element nodes can now be passed to ${connect.name}(). ` +
+          `You can either wrap ${displayName} into a <div>, or turn it into a ` +
+          `drag source or a drop target itself.`
+        );
+      }
+
       const nextElement = nextWhatever;
       return cloneWithRef(nextElement, inst => ref(inst, nextOptions));
     }
 
-    // At this point we can only receive components or DOM nodes.
-    const nextNode = findDOMNode(nextWhatever);
+    // At this point we can only receive DOM nodes.
+    const nextNode = nextWhatever;
 
     // If nothing changed, bail out of re-connecting the node to the backend.
     if (nextNode === currentNode && shallowEqual(currentOptions, nextOptions)) {

src/createSourceConnector.js

@@ -1,6 +1,10 @@
 export default function createSourceConnector(backend) {
   return {
-    dragSource: backend.connectDragSource.bind(backend),
-    dragPreview: backend.connectDragPreview.bind(backend)
+    dragSource: function connectDragSource(...args) {
+      return backend.connectDragSource(...args);
+    },
+    dragPreview: function connectDragPreview(...args) {
+      return backend.connectDragPreview(...args);
+    }
   };
 }

src/createTargetConnector.js

@@ -1,5 +1,7 @@
 export default function createTargetConnector(backend) {
   return {
-    dropTarget: backend.connectDropTarget.bind(backend)
+    dropTarget: function connectDropTarget(...args) {
+      return backend.connectDropTarget(...args);
+    }
   };
 }