From af4855ca7dae51534cd148a139049142eeecc5de Mon Sep 17 00:00:00 2001
From: Andrew Clark <git@andrewclark.io>
Date: Thu, 7 Nov 2019 15:33:07 -0800
Subject: [PATCH] Pass Suspense config to `startTransition`

...instead of `useTransition`.

This avoids the problem of having to bind the config object to
`startTransition`, invalidating downstream memoizations.
---
 .../react-reconciler/src/ReactFiberHooks.js   | 54 +++++++------------
 ...eactHooksWithNoopRenderer-test.internal.js | 47 +++++++++-------
 2 files changed, 47 insertions(+), 54 deletions(-)

diff --git a/packages/react-reconciler/src/ReactFiberHooks.js b/packages/react-reconciler/src/ReactFiberHooks.js
index 14d70b5c5c459..cf4b5246d99a7 100644
--- a/packages/react-reconciler/src/ReactFiberHooks.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.js
@@ -1172,50 +1172,34 @@ function updateDeferredValue<T>(
   return prevValue;
 }
 
+function startTransition(setPending, callback, config) {
+  setPending(true);
+  Scheduler.unstable_next(() => {
+    const previousConfig = ReactCurrentBatchConfig.suspense;
+    ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
+    try {
+      setPending(false);
+      callback();
+    } finally {
+      ReactCurrentBatchConfig.suspense = previousConfig;
+    }
+  });
+}
+
 function mountTransition(
   config: SuspenseConfig | void | null,
 ): [(() => void) => void, boolean] {
   const [isPending, setPending] = mountState(false);
-  const startTransition = mountCallback(
-    callback => {
-      setPending(true);
-      Scheduler.unstable_next(() => {
-        const previousConfig = ReactCurrentBatchConfig.suspense;
-        ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
-        try {
-          setPending(false);
-          callback();
-        } finally {
-          ReactCurrentBatchConfig.suspense = previousConfig;
-        }
-      });
-    },
-    [config, isPending],
-  );
-  return [startTransition, isPending];
+  const startTransitionRef = mountRef(startTransition.bind(null, setPending));
+  return [startTransitionRef.current, isPending];
 }
 
 function updateTransition(
   config: SuspenseConfig | void | null,
 ): [(() => void) => void, boolean] {
-  const [isPending, setPending] = updateState(false);
-  const startTransition = updateCallback(
-    callback => {
-      setPending(true);
-      Scheduler.unstable_next(() => {
-        const previousConfig = ReactCurrentBatchConfig.suspense;
-        ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
-        try {
-          setPending(false);
-          callback();
-        } finally {
-          ReactCurrentBatchConfig.suspense = previousConfig;
-        }
-      });
-    },
-    [config, isPending],
-  );
-  return [startTransition, isPending];
+  const [isPending] = updateState(false);
+  const startTransitionRef = updateRef();
+  return [startTransitionRef.current, isPending];
 }
 
 function dispatchAction<S, A>(
diff --git a/packages/react-reconciler/src/__tests__/ReactHooksWithNoopRenderer-test.internal.js b/packages/react-reconciler/src/__tests__/ReactHooksWithNoopRenderer-test.internal.js
index c1954e36ed8c9..114bfc0971746 100644
--- a/packages/react-reconciler/src/__tests__/ReactHooksWithNoopRenderer-test.internal.js
+++ b/packages/react-reconciler/src/__tests__/ReactHooksWithNoopRenderer-test.internal.js
@@ -1977,16 +1977,18 @@ describe('ReactHooksWithNoopRenderer', () => {
     it.experimental(
       'delays showing loading state until after timeout',
       async () => {
+        const SUSPENSE_CONFIG = {
+          timeoutMs: 1000,
+        };
+
         let transition;
         function App() {
           const [show, setShow] = useState(false);
-          const [startTransition, isPending] = useTransition({
-            timeoutMs: 1000,
-          });
+          const [startTransition, isPending] = useTransition();
           transition = () => {
             startTransition(() => {
               setShow(true);
-            });
+            }, SUSPENSE_CONFIG);
           };
           return (
             <Suspense
@@ -2043,17 +2045,19 @@ describe('ReactHooksWithNoopRenderer', () => {
     it.experimental(
       'delays showing loading state until after busyDelayMs + busyMinDurationMs',
       async () => {
+        const SUSPENSE_CONFIG = {
+          busyDelayMs: 1000,
+          busyMinDurationMs: 2000,
+        };
+
         let transition;
         function App() {
           const [show, setShow] = useState(false);
-          const [startTransition, isPending] = useTransition({
-            busyDelayMs: 1000,
-            busyMinDurationMs: 2000,
-          });
+          const [startTransition, isPending] = useTransition();
           transition = () => {
             startTransition(() => {
               setShow(true);
-            });
+            }, SUSPENSE_CONFIG);
           };
           return (
             <Suspense
@@ -2113,13 +2117,15 @@ describe('ReactHooksWithNoopRenderer', () => {
     );
 
     it.experimental('always returns the same startTransition', async () => {
+      const SUSPENSE_CONFIG = {
+        busyDelayMs: 1000,
+        busyMinDurationMs: 2000,
+      };
+
       let transition;
       function App() {
         const [step, setStep] = useState(0);
-        const [startTransition, isPending] = useTransition({
-          busyDelayMs: 1000,
-          busyMinDurationMs: 2000,
-        });
+        const [startTransition, isPending] = useTransition();
         // Log whenever startTransition changes
         useEffect(
           () => {
@@ -2130,7 +2136,7 @@ describe('ReactHooksWithNoopRenderer', () => {
         transition = () => {
           startTransition(() => {
             setStep(n => n + 1);
-          });
+          }, SUSPENSE_CONFIG);
         };
         return (
           <Suspense fallback={<Text text="Loading..." />}>
@@ -2175,12 +2181,12 @@ describe('ReactHooksWithNoopRenderer', () => {
     });
 
     it.experimental(
-      'can update suspense config (without changing startTransition)',
+      'can pass different suspense configs per transition',
       async () => {
         let transition;
         function App({timeoutMs}) {
           const [step, setStep] = useState(0);
-          const [startTransition, isPending] = useTransition({timeoutMs});
+          const [startTransition, isPending] = useTransition();
           // Log whenever startTransition changes
           useEffect(
             () => {
@@ -2189,9 +2195,12 @@ describe('ReactHooksWithNoopRenderer', () => {
             [startTransition],
           );
           transition = () => {
-            startTransition(() => {
-              setStep(n => n + 1);
-            });
+            startTransition(
+              () => {
+                setStep(n => n + 1);
+              },
+              {timeoutMs},
+            );
           };
           return (
             <Suspense fallback={<Text text="Loading..." />}>