From 893cbf04a6b1ca410d230e03e8882de72460d978 Mon Sep 17 00:00:00 2001
From: Dan Abramov <dan.abramov@gmail.com>
Date: Mon, 9 May 2016 20:23:52 +0100
Subject: [PATCH] Preserve the identity of this.router to avoid setting
 this.context directly

---
 modules/ContextUtils.js | 10 +++-------
 modules/Router.js       |  5 ++++-
 package.json            |  1 +
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/modules/ContextUtils.js b/modules/ContextUtils.js
index 0d9f9c7e1f..53fd494f0e 100644
--- a/modules/ContextUtils.js
+++ b/modules/ContextUtils.js
@@ -1,6 +1,7 @@
 import { PropTypes } from 'react'
 
 // Works around issues with context updates failing to propagate.
+// Caveat: the context value is expected to never change its identity.
 // https://github.com/facebook/react/issues/2517
 // https://github.com/reactjs/react-router/issues/470
 
@@ -43,9 +44,8 @@ export function ContextProvider(name) {
     },
 
     componentDidUpdate() {
-      const nextValue = this.getChildContext()[name]
       this[listenersKey].forEach(listener =>
-        listener(this[eventIndexKey], nextValue)
+        listener(this[eventIndexKey])
       )
     },
 
@@ -112,12 +112,8 @@ export function ContextSubscriber(name) {
       this[unsubscribeKey] = null
     },
 
-    [handleContextUpdateKey](eventIndex, nextValue) {
+    [handleContextUpdateKey](eventIndex) {
       if (eventIndex !== this.state[lastRenderedEventIndexKey]) {
-        if (this.context[name] !== nextValue) {
-          // React uses a stale value so we update it manually.
-          this.context[name] = nextValue
-        }
         this.setState({ [lastRenderedEventIndexKey]: eventIndex })
       }
     }
diff --git a/modules/Router.js b/modules/Router.js
index 3a9f57c419..eeefdbc1dc 100644
--- a/modules/Router.js
+++ b/modules/Router.js
@@ -6,6 +6,7 @@ import RouterContext from './RouterContext'
 import { createRoutes } from './RouteUtils'
 import { createRouterObject } from './RouterUtils'
 import warning from './routerWarning'
+import assign from 'object-assign'
 
 const { func, object } = React.PropTypes
 
@@ -88,7 +89,9 @@ const Router = React.createClass({
       if (error) {
         this.handleError(error)
       } else {
-        this.router = this.createRouterObject(state)
+        // Keep the identity of this.router because of a caveat in ContextUtils:
+        // they only work if the object identity is preserved.
+        assign(this.router, this.createRouterObject(state))
         this.setState(state, this.props.onUpdate)
       }
     })
diff --git a/package.json b/package.json
index 40bc492a1d..82a8a3fe69 100644
--- a/package.json
+++ b/package.json
@@ -35,6 +35,7 @@
     "history": "^2.0.1",
     "hoist-non-react-statics": "^1.0.5",
     "invariant": "^2.2.1",
+    "object-assign": "^4.1.0",
     "warning": "^2.1.0"
   },
   "peerDependencies": {