Changed proguard rule for Hermes is not specified in the upgrade helper for 0.62.

[yghokim]

Feature Request

The new proguard rule for using Hermes:

-keep class com.facebook.jni.** { *; }

is not mentioned in the upgrade helper for 0.62.

Why it is needed

Omitting this update makes the Android release app with Hermes and Proguard crashes on startup:

FATAL EXCEPTION: create_react_context
java.lang.UnsatisfiedLinkError: couldn't find DSO to load: libhermes.so caused by: com.facebook.jni.NativeRunnable

[pvinis]

Where is that change exactly? I couldn't find this in a new project.

[yghokim]

In the React Native documentation of 0.61,
The Hermes setup page (https://reactnative.dev/docs/0.61/hermes) specified this Proguard rule:

-keep class com.facebook.hermes.unicode.** { *; }

In the documentation of 0.62 (https://reactnative.dev/docs/hermes), the Proguard rule is updated:

-keep class com.facebook.hermes.unicode.** { *; }
-keep class com.facebook.jni.** { *; }

I think this change was made because 0.62 uses Hermes 0.4.0.

However, I spent hours struggling with a crash bug because this Proguard.rule change was not specified in the update helper.

If it is specified somewhere, it should be more salient for developers who are using Hermes.

[lucasbento]

I wonder how we can add this to the upgrade-helper, I was thinking that we can add an inline comment here:

(reason is that we can only add inline comments on diffs)

And maybe add this issue at the top with a title like "Upgrade proguard rule for Hermes".

Thoughts on this @muclipse @pvinis?

[pvinis]

Right. I checked the proguard-rules.pro file, and you can also see here, there is nothing in there for hermes like the docs say. The way the upgrade-helper and purge work is that they diff the template between versions, so if there was no change, nothing will be shown. The change is in the documentation.

I feel this change might be more suitable in the releases changelog.

For now, probably the best we can do is what @lucasbento said, and we can add a comment or a note on the 0.62 upgrade helper.

[lucasbento]

Right. I checked the proguard-rules.pro file, and you can also see here , there is nothing in there for hermes like the docs say.

Yeah, this is probably because the template does not use Hermes by default.

I feel this change might be more suitable in the releases changelog .

Agreed, cc @alloy.

[yghokim]

I feel this change might be more suitable in the releases changelog .

I agree, @alloy.

Also,

we can add a comment or a note on the 0.62 upgrade helper.

cc @pvinis

Another good place would be adding a comment in the block comment in android/build.gradle (file) above:

project.ext.react = [
    enableHermes: false,  // clean and rebuild if changing
]

[alloy]

Hmm, yeah we actually went back and forth on this in the CHANGELOG react-native-community/releases#166 (comment) but dropped the ball in the end.

Thanks for the reminder, added this react-native-community/releases#182

[kelset]

Eloy's PR is now merged, I guess we can close this? :)

[lucasbento]

We still have some work to do on Upgrade-Helper side, will be done today

[lucasbento]

Added a comment to Upgrade-Helper to mention this change at react-native-community/upgrade-helper#224 and it should be up in prod in a few minutes.

Thank you so much for reporting this @muclipse, this will probably help a lot of people!

Thanks for the help here @pvinis & @alloy 🤗