How can I make "R8's optimization of ServiceLoader" take effect?

[whataa]

This question is mainly about the initialization of android Dispatchers.Main, it has been discussed a long time ago, see #878 .
If I understand correctly, the final solution should be to rely on R8 to optimize ServiceLoader, see ServiceLoaderRewriter

But the problem I encountered is that after R8 processing, the bytecode of MainDispatcherLoader is still the corresponding source code, not the expected, I really don’t know what else I need to pay attention to, need help.

expect:

Arrays.asList(new MainDispatcherFactory[] { new AndroidDispatcherFactory() }).iterator()

actual:

I have confirmed that optimization is not turned off, no -dontoptimize, and all rules in configuration.txt containing the kotlinx keyword come from the coroutines only.

env:

• Gradle: 8.8
• AGP: 8.5.0
• kotlin: 2.0.21
• coroutine: 1.7.1
• JDK: 17
• OS: Mac OS X
• arch: aarch64
• R8: 8.5.10 (build d827614db6c8c0c52724a1b4850d00da8e51177a from go/r8bot (luci-r8-custom-ci-archive-0-p93x))

[dkhalanskyjb]

Hi! Would it be possible for you to provide a self-contained project where the issue reproduces, along with build instructions for it? There are many moving parts in Android build configurations, so it would greatly simplify the process of reproducing this if we had some code on our hands.

[whataa]

Thank you, the "self-contained project" you mentioned inspired me. I put the all rules from configuration.txt generated by our project into a new demo project and repeatedly executed r8 by excluding half the rules each time, finally found that the rule causing the problem is as follows:

-keep,allowobfuscation interface * {
    <methods>;
}
# or
-keepnames class kotlinx.coroutines.internal.MainDispatcherFactory {}

[dkhalanskyjb]

@whataa, I think it's reasonable that these two rules negate the effect of ServiceLoader optimization for MainDispatcherFactory. After all, R8 was explicitly to keep these ServiceLoader-only entities. I don't see this as a bug. Do you see this differently?

[whataa]

It's really hard to know why until figure out the two rules above. It's not a bug, I'll close it.