Do we still need to set reactNativeReleaseLevel to experimental to enable the DISABLE_COMMIT_PAUSING_MECHANISM FF?

[TowhidKashem]

I remember having to set the release level in app.config.js to "experimental" in order to enable the DISABLE_COMMIT_PAUSING_MECHANISM feature flag:

      [
        'expo-build-properties',
        {
          ios: {
            deploymentTarget: '16.4',
            ccacheEnabled: true,
            networkInspector: true,

            // this enables the `preventShadowTreeCommitExhaustion` FF in react-native
            // it's needed for the `DISABLE_COMMIT_PAUSING_MECHANISM` FF to work in reanimated
            // - https://docs.swmansion.com/react-native-reanimated/docs/guides/feature-flags/#disable_commit_pausing_mechanism
            // - https://reactnative.dev/docs/releases/release-levels
            reactNativeReleaseLevel: 'experimental'
          }
        }
      ]

is this still necessary? I would prefer not to enable it due to stability concerns since this is a production app. But I still want to take advantage of the performance benefits that come with this FF. Seeing as how this FF was released a little while ago, I was wondering if the experimental release level is still necessary?

And if so, is there some way to enable some experimental features and not all of them in a blanket way like how the above is doing? That way we could just enable the minimum settings needed to make DISABLE_COMMIT_PAUSING_MECHANISM work and not anything extra thereby reducing the surface area for issues...

[tomekzaw]

@TowhidKashem Yes, DISABLE_COMMIT_PAUSING_MECHANISM Reanimated static feature flags still requires preventShadowTreeCommitExhaustion React Native feature flag to be enabled, that's why reactNativeReleaseLevel needs to be set to experimental. I understand your concerns with the app stability. @j-piasecki is working on a revamp of shadow tree commit mechanism which is expected to be out in RN 0.85.

[j-piasecki]

To clarify, if it lands in 0.85, it will likely end up in the experimental level as well.

[TowhidKashem]

Thanks and good to know! 👍

[TowhidKashem]

Hey I was just wondering if you guys think something this is a bad idea (off the top of your head):

diff --git a/node_modules/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlagsOverridesOSSStable.h b/node_modules/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlagsOverridesOSSStable.h
index 1a3bce0..94856e9 100644
--- a/node_modules/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlagsOverridesOSSStable.h
+++ b/node_modules/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlagsOverridesOSSStable.h
@@ -33,5 +33,9 @@ class ReactNativeFeatureFlagsOverridesOSSStable : public ReactNativeFeatureFlags
   {
     return true;
   }
+  bool preventShadowTreeCommitExhaustion() override
+  {
+    return true;
+  }
 };
 } // namespace facebook::react

I used claude to write this react-native patch to enable just the preventShadowTreeCommitExhaustion flag without needing to set releaseLevel to "experimental". But don't know if this will work or cause other problems, in case this flag needs other things from experimental mode to work properly?

[tomekzaw]

@TowhidKashem Yes, this would work, just don't forget to build react-native from source for the changes to take effect.

[TowhidKashem]

great, will do that then, thanks!