From 06e410ec608820b65d81536bb4630228b4e04d48 Mon Sep 17 00:00:00 2001
From: Ricky <rickhanlonii@gmail.com>
Date: Fri, 9 Feb 2024 16:59:47 -0500
Subject: [PATCH] Move modern strict to experimental (#28152)

Turn this on

Edited: ope, nvm
<details>
Looks like there's still an outstanding issue with this. The original PR
turned off a strict effects test, which causes a stray
`componentWillUnmount` to fire.


https://github.com/facebook/react/commit/5d1ce651393524639a3b4b1e861a0413a4d25629#diff-19df471970763c4790c2cc0811fd2726cc6a891b0e1d5dedbf6d0599240c127aR70


Before:
```js
expect(log).toEqual([
      'constructor',
      'constructor',
      'getDerivedStateFromProps',
      'getDerivedStateFromProps',
      'render',
      'render',
      'componentDidMount',
    ]);
```

After:

```js
expect(log).toEqual([
      'constructor',
      'constructor',
      'getDerivedStateFromProps',
      'getDerivedStateFromProps',
      'render',
      'render',
      'componentDidMount',
      'componentWillUnmount',
      'componentDidMount',
    ]);
```

So there's a bug somewhere
</details>
---
 packages/react-reconciler/src/ReactFiberWorkLoop.js | 5 +----
 packages/shared/ReactFeatureFlags.js                | 2 +-
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.js b/packages/react-reconciler/src/ReactFiberWorkLoop.js
index 5fafd8de5c903..d045fa08496e1 100644
--- a/packages/react-reconciler/src/ReactFiberWorkLoop.js
+++ b/packages/react-reconciler/src/ReactFiberWorkLoop.js
@@ -3792,12 +3792,9 @@ function commitDoubleInvokeEffectsInDEV(
   hasPassiveEffects: boolean,
 ) {
   if (__DEV__) {
-    if (useModernStrictMode) {
+    if (useModernStrictMode && root.tag !== LegacyRoot) {
       let doubleInvokeEffects = true;
 
-      if (root.tag === LegacyRoot && !(root.current.mode & StrictLegacyMode)) {
-        doubleInvokeEffects = false;
-      }
       if (
         root.tag === ConcurrentRoot &&
         !(root.current.mode & (StrictLegacyMode | StrictEffectsMode))
diff --git a/packages/shared/ReactFeatureFlags.js b/packages/shared/ReactFeatureFlags.js
index 67862a4f14288..3d8a7cf563bc8 100644
--- a/packages/shared/ReactFeatureFlags.js
+++ b/packages/shared/ReactFeatureFlags.js
@@ -147,7 +147,7 @@ export const disableJavaScriptURLs = false;
 // Modern <StrictMode /> behaviour aligns more with what components
 // components will encounter in production, especially when used With <Offscreen />.
 // TODO: clean up legacy <StrictMode /> once tests pass WWW.
-export const useModernStrictMode = false;
+export const useModernStrictMode = __NEXT_MAJOR__;
 
 // Not ready to break experimental yet.
 // Remove IE and MsApp specific workarounds for innerHTML