From 87d297210f25d8c13c13307b419840ed3e1ef9f6 Mon Sep 17 00:00:00 2001
From: Lauren Tan <poteto@users.noreply.github.com>
Date: Mon, 12 Aug 2024 11:56:21 -0400
Subject: [PATCH] [fresh] Add failing test for useMemoCache reset case

During local development it's common to add or remove code which may
change the cache size between renders. Add a failing test to show that
currently (without the compiled fast refresh check) this issues a
warning and reuses the cache which may have stale values.

ghstack-source-id: 2f1a071303983c67825a1836f0d278552b49a75d
Pull Request resolved: https://github.com/facebook/react/pull/30662
---
 .../__tests__/ReactFreshIntegration-test.js   | 55 +++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/packages/react-refresh/src/__tests__/ReactFreshIntegration-test.js b/packages/react-refresh/src/__tests__/ReactFreshIntegration-test.js
index c83e36f13a44b..2115a15f67705 100644
--- a/packages/react-refresh/src/__tests__/ReactFreshIntegration-test.js
+++ b/packages/react-refresh/src/__tests__/ReactFreshIntegration-test.js
@@ -1637,6 +1637,61 @@ describe('ReactFreshIntegration', () => {
       }
     });
 
+    // eslint-disable-next-line jest/no-disabled-tests
+    it.skip('resets useMemoCache cache slots', async () => {
+      if (__DEV__) {
+        await render(`
+          const useMemoCache = require('react/compiler-runtime').c;
+          let cacheMisses = 0;
+          const cacheMiss = (id) => {
+            cacheMisses++;
+            return id;
+          };
+          export default function App(t0) {
+            const $ = useMemoCache(1);
+            const {reset1} = t0;
+            let t1;
+            if ($[0] !== reset1) {
+              $[0] = t1 = cacheMiss({reset1});
+            } else {
+              t1 = $[1];
+            }
+            return <h1>{cacheMisses}</h1>;
+          }
+        `);
+        const el = container.firstChild;
+        expect(el.textContent).toBe('1');
+        await patch(`
+          const useMemoCache = require('react/compiler-runtime').c;
+          let cacheMisses = 0;
+          const cacheMiss = (id) => {
+            cacheMisses++;
+            return id;
+          };
+          export default function App(t0) {
+            const $ = useMemoCache(2);
+            const {reset1, reset2} = t0;
+            let t1;
+            if ($[0] !== reset1) {
+              $[0] = t1 = cacheMiss({reset1});
+            } else {
+              t1 = $[1];
+            }
+            let t2;
+            if ($[1] !== reset2) {
+              $[1] = t2 = cacheMiss({reset2});
+            } else {
+              t2 = $[1];
+            }
+            return <h1>{cacheMisses}</h1>;
+          }
+        `);
+        expect(container.firstChild).toBe(el);
+        // cache size changed between refreshes
+        expect(el.textContent).toBe('2');
+      }
+    });
+
     describe('with inline requires', () => {
       beforeEach(() => {
         global.FakeModuleSystem = {};