JSC from this library can't be installed on IOS

[tux2nicolae]

We do have an IOS AppClip which has a hard size constraint, the app can't weight more than 15MB.

Due to this constraint, as much as we would like we can't use hermes engine because it adds extra space in our app clip, we relied on the JSC since it is already available in IOS so it does not add extra space.

But after upgrading to react-native 0.82.1 it seems we can't use it anymore.

---

When using

ENV['USE_THIRD_PARTY_JSC'] = '1'
ENV['USE_HERMES'] = '0'

You can't install pods due to these issues

react/react-native#54267
react/react-native#54268

Repro provided by @anta-semenov

https://github.com/anta-semenov/react-native-circular-dependencies

[npcomplete415]

This technically affects:

s.dependency "React-jsitooling"
s.dependency "React-cxxreact"
s.dependency "React-jsiexecutor"

being called from within React-Jsc (https://github.com/react-native-community/javascriptcore/blob/main/React-jsc.podspec)

and you can't get rid of it because they are actually being used by https://github.com/react-native-community/javascriptcore/blob/7ee642d93058d0322773b80607a79ae9c7ff813f/ios/RCTJscInstance.h

not sure whats the best way to address this.

[tux2nicolae]

Seems like the JSC support is completely broken right now

[MPiccinato]

Anyone been able to make any progress with this? It seems with React Native 0.84.0-rc.3 the pods install fine but then there is a whole bunch of compiler issues, getting past those is a bit problematic and then it just crashes if I do get it to run.

[trentrand]

I also need JSC engine to get my App Clip under 15MB. Trimmed out everything to get my app down to 15.6MB. Then I tried going to SDK 55 beta for the remaining KBs, but the app went +2.1MB (15.6MB → 17.9MB).

• +0.1MB increase from transition of Hermes Framework → HermesVM Framework.
• +2.0MB increase of app binary

Very disappointing. So my last hope is switching to JSC.

[trentrand]

I spent four days trying to make this work on RN 0.81 and 0.83, but it fails because Hermes is still assumed in multiple RN/Expo modules at compile time, even with USE_THIRD_PARTY_JSC=1 and USE_HERMES=0. That forces an endless chain of invasive patches, which I couldn’t fully resolve and which will almost certainly keep breaking on updates.

IMO your best opportunity is to update the build target to 17.0, giving you a 100 MB maximum uncompressed App Clip binary (with restrictions: cannot support physical invocations through App Clip Codes, QR codes, NFC tags).

If you're like me and must use NFC, good luck. I added JS Bundle compression to react-native-app-clips, and the rest of the savings will be from meticulously trimming out replaceable node_modules and Pods. Expo Atlas and Xcode > Build Phases > [CP] Copy Pods Resources are good sources to hunt for opportunities.

The general React Native community does not care about app size.

[npcomplete415]

I reached the same conclusion so and based on sentiment of both expo and react native repos; it seems like it's a lost cause to attempt a fix.

[tux2nicolae]

That's disappointing, over the last 5 years being in the react-native ecosystem, a good portion of time was tweaking, patching, hacking, updating and synchronising library's to just have a working product, especially with the transition to new architecture, in the past months the things started to go in the right direction but there is still such a mess we just can't move forward due to some stupid bugs (sorry for these words, I know there is a lot of work and a lot of nice people involved) but as a bussines we are really reconsidering at this point the react-native itself as the most appropriate framework for our product, especially with the new AI era where we can't resist to managers and competition itself because we just can't justify the migration cost anymore.

If you guys happen to find any workarounds or anything on this, please share it here if you can, your help will be really appreciated.

[tux2nicolae]

I noticed @Saadnajmi made some commits a few hours ago, I'm curious how is Microsoft able to use this library at all?

[Saadnajmi]

We're on an older version of React Native, have our own fork (React Native macOS), our own custom hosting layer (I.E: We don't use ReactNativeFactory or whatever) and are currently in the process of upgrading to 0.81 and may need to make some fixes.

My initial impression from upgrading though is that React Native does not really support using this library of that USE_THIRD_PARTY_JSC flag at all. Turning that flag on will make code in React Native just not compile. It's pretty clear to me JSC is no longer supported, this repo just moved what existed inside React Native into a separate repo and maybe worked for one release (0.79?) but not after. For React Native macOS, I expect I'll need to make some fixes to support JSC on 0.81. Your best bet is to switch to Hermes, we have that on our backlog, closer to the front, but noooot quite there yet :/

[tux2nicolae]

We managed to make it compile and run on 0.84.1, for anyone interested please check our fork https://github.com/crisposoft/javascriptcore

[npcomplete415]

Nice work! Out of curiosity have you tested this with expo? That was my other concern that expo will continue to be broken.

[tux2nicolae]

Unfortunately we don't use expo in our project and implicitly i did not tested it