From 2f3df5f0b3dea452cd64508f760ff8684f7ce971 Mon Sep 17 00:00:00 2001
From: Andrew Clark <acdlite@fb.com>
Date: Tue, 7 Feb 2017 13:49:55 -0800
Subject: [PATCH] Warn about setState in render

---
 scripts/fiber/tests-passing-except-dev.txt      |  1 -
 scripts/fiber/tests-passing.txt                 |  1 +
 .../shared/fiber/ReactFiberScheduler.js         | 17 +++++++++++++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/scripts/fiber/tests-passing-except-dev.txt b/scripts/fiber/tests-passing-except-dev.txt
index e5eb1addef..525db56f42 100644
--- a/scripts/fiber/tests-passing-except-dev.txt
+++ b/scripts/fiber/tests-passing-except-dev.txt
@@ -106,7 +106,6 @@ src/renderers/__tests__/ReactComponentTreeHook-test.native.js
 * does not report top-level wrapper as a root
 
 src/renderers/__tests__/ReactCompositeComponent-test.js
-* should warn about `setState` in render
 * should warn about `setState` in getChildContext
 * should disallow nested render calls
 
diff --git a/scripts/fiber/tests-passing.txt b/scripts/fiber/tests-passing.txt
index 525a558660..70888b0002 100644
--- a/scripts/fiber/tests-passing.txt
+++ b/scripts/fiber/tests-passing.txt
@@ -577,6 +577,7 @@ src/renderers/__tests__/ReactCompositeComponent-test.js
 * should warn about `forceUpdate` on unmounted components
 * should warn about `setState` on unmounted components
 * should silently allow `setState`, not call cb on unmounting components
+* should warn about `setState` in render
 * should cleanup even if render() fatals
 * should call componentWillUnmount before unmounting
 * should warn when shouldComponentUpdate() returns undefined
diff --git a/src/renderers/shared/fiber/ReactFiberScheduler.js b/src/renderers/shared/fiber/ReactFiberScheduler.js
index 258a254fab..9d4e3f36f2 100644
--- a/src/renderers/shared/fiber/ReactFiberScheduler.js
+++ b/src/renderers/shared/fiber/ReactFiberScheduler.js
@@ -102,6 +102,16 @@ if (__DEV__) {
       ctor && (ctor.displayName || ctor.name) || 'ReactClass'
     );
   };
+
+  var warnAboutUpdateInRender = function(instance : ReactClass<any>) {
+    warning(
+      ReactCurrentOwner.current == null,
+      'Cannot update during an existing state transition (such as within ' +
+      '`render` or another component\'s constructor). Render methods should ' +
+      'be a pure function of props and state; constructor side-effects are ' +
+      'an anti-pattern, but can be moved to `componentWillMount`.'
+    );
+  };
 }
 
 var timeHeuristicForUnitOfWork = 1;
@@ -1102,6 +1112,13 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(config : HostConfig<T, P,
       nextUnitOfWork = null;
     }
 
+    if (__DEV__) {
+      if (fiber.tag === ClassComponent) {
+        const instance = fiber.stateNode;
+        warnAboutUpdateInRender(instance);
+      }
+    }
+
     let node = fiber;
     let shouldContinue = true;
     while (node !== null && shouldContinue) {