From d0e3cdd37c00675d77d461bd48e64117b10bd244 Mon Sep 17 00:00:00 2001
From: Dan Abramov <dan.abramov@gmail.com>
Date: Wed, 9 Aug 2017 01:37:51 +0100
Subject: [PATCH] Find callsites that would call toString() if we pass
 attributes through

---
 .../shared/hooks/ReactDOMUnknownPropertyHook.js | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/renderers/dom/shared/hooks/ReactDOMUnknownPropertyHook.js b/src/renderers/dom/shared/hooks/ReactDOMUnknownPropertyHook.js
index e68bf66d913fe..a24005bf74c66 100644
--- a/src/renderers/dom/shared/hooks/ReactDOMUnknownPropertyHook.js
+++ b/src/renderers/dom/shared/hooks/ReactDOMUnknownPropertyHook.js
@@ -126,6 +126,23 @@ var warnUnknownProperties = function(type, props, debugID) {
     var isValid = validateProperty(type, key, debugID);
     if (!isValid) {
       unknownProps.push(key);
+      var value = props[key];
+      if (
+        typeof value === 'object' &&
+        value !== null &&
+        !Array.isArray(value) &&
+        value.toString !== Object.prototype.toString
+      ) {
+        warning(
+          false,
+          'The %s prop on <%s> is not a known property, and was given an object ' +
+            'with a custom toString() method. Remove it, or it will appear in the ' +
+            'DOM after a future React update.%s',
+          key,
+          type,
+          getStackAddendum(debugID),
+        );
+      }
     }
   }