An exception occurs when R8 is enabled and FAST_SERVICE_LOADER_ENABLED is set to false.

[JayneVong]

Describe the bug

AGP：8.11.1
R8：8.11.18
Kotlin：1.9.0
Kotlinx-coroutines-android：1.9.0

Caused by java.lang.IllegalStateException
Module with the Main dispatcher is missing. Add dependency providing the Main dispatcher, e.g. 'kotlinx-coroutines-android' and ensure it has the same version as 'kotlinx-coroutines-core'

Caused by java.lang.IllegalStateException: Module with the Main dispatcher is missing. Add dependency providing the Main dispatcher, e.g. 'kotlinx-coroutines-android' and ensure it has the same version as 'kotlinx-coroutines-core'
at kotlinx.coroutines.internal.MainDispatchersKt.throwMissingMainDispatcherException(MainDispatchers.kt:81)
at kotlinx.coroutines.internal.MainDispatchersKt.createMissingDispatcher(MainDispatchers.kt:78)
at kotlinx.coroutines.internal.MainDispatchersKt.createMissingDispatcher$default(MainDispatchers.kt:76)
at kotlinx.coroutines.internal.MainDispatcherLoader.loadMainDispatcher(MainDispatchers.kt:39)
at kotlinx.coroutines.internal.MainDispatcherLoader.(MainDispatchers.kt:22)
at kotlinx.coroutines.Dispatchers.getMain(Dispatchers.kt:57)
at androidx.lifecycle.LifecycleKt.getCoroutineScope(Lifecycle.kt:300)
at androidx.lifecycle.LifecycleOwnerKt.getLifecycleScope(LifecycleOwner.kt:45)
at com.dami.vipkid.engine.login.verify.VerifyCodeFragment.initData(VerifyCodeFragment.kt:166)
at com.dami.vipkid.engine.base.view.BaseFragment.onViewCreated(BaseFragment.java:84)
at androidx.fragment.app.Fragment.performViewCreated(Fragment.java:3128)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:552)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:261)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1899)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1817)
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1760)
at androidx.fragment.app.FragmentManager$5.run(FragmentManager.java:547)
at android.os.Handler.handleCallback(Handler.java:958)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loopOnce(Looper.java:205)
at android.os.Looper.loop(Looper.java:294)
at android.app.ActivityThread.main(ActivityThread.java:8500)
at java.lang.reflect.Method.invoke(Method.java)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:640)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1026)

[JayneVong]

This issue frequently occurs on [Transsion] devices, but we cannot reproduce it currently as we don't have access to such a device.

[JayneVong]

The obfuscated content：

/* loaded from: classes2.dex */
public final class MainDispatcherLoader {
private static final boolean FAST_SERVICE_LOADER_ENABLED = false;

@NotNull
public static final MainDispatcherLoader INSTANCE;

@JvmField
@NotNull
public static final c2 dispatcher;

static {
    MainDispatcherLoader mainDispatcherLoader = new MainDispatcherLoader();
    INSTANCE = mainDispatcherLoader;
    a0.f("kotlinx.coroutines.fast.service.loader", true);
    dispatcher = mainDispatcherLoader.loadMainDispatcher();
}

private MainDispatcherLoader() {
}

private final c2 loadMainDispatcher() {
    Object next;
    c2 e10;
    try {
        List u10 = SequencesKt___SequencesKt.u(SequencesKt__SequencesKt.c(ServiceLoader.load(MainDispatcherFactory.class, MainDispatcherFactory.class.getClassLoader()).iterator()));
        Iterator it2 = u10.iterator();
        if (it2.hasNext()) {
            next = it2.next();
            if (it2.hasNext()) {
                int loadPriority = ((MainDispatcherFactory) next).getLoadPriority();
                do {
                    Object next2 = it2.next();
                    int loadPriority2 = ((MainDispatcherFactory) next2).getLoadPriority();
                    if (loadPriority < loadPriority2) {
                        next = next2;
                        loadPriority = loadPriority2;
                    }
                } while (it2.hasNext());
            }
        } else {
            next = null;
        }
        MainDispatcherFactory mainDispatcherFactory = (MainDispatcherFactory) next;
        if (mainDispatcherFactory != null && (e10 = p.e(mainDispatcherFactory, u10)) != null) {
            return e10;
        }
        return p.b(null, null, 3, null);
    } catch (Throwable th) {
        return p.b(th, null, 2, null);
    }
}

}

[dkhalanskyjb]

Hello! Since the issue only occurs on specific devices, please use the Android issue tracker for this: in kotlinx.coroutines, we don't have any logic like "if this is a Transsion device, fail". I've also read through the obfuscated code, and it looks entirely reasonable, so the problem probably happens not during the obfuscation but at some later point. I don't see what our library can do about the problem.

Of course, if it turns out we can do something to work around this issue, let us know, and we'll reopen the issue!

[JayneVong]

Is it possible to remove the following rule from the file coroutines.pro: -assumenosideeffects class kotlinx.coroutines.internal.MainDispatcherLoader { boolean FAST_SERVICE_LOADER_ENABLED return false; }? Because using the Fast Service Loader hasn't caused any issues.

[dkhalanskyjb]

@JayneVong, if your project is using those coroutines.pro rules, then something is wrong with the minification: the only reason FAST_SERVICE_LOADER_ENABLED is false is that R8 can skip service loading, which as we can see, is still present in the obfuscated code for some reason. Could you please provide a project where the issue reproduces, that is, where the obfuscated code keeps the ServiceLoader.load(MainDispatcherFactory.class, MainDispatcherFactory.class.getClassLoader()) call?

[JayneVong]

This file configuration contains our final obfuscation configuration for the project. Because FAST_SERVICE_LOADER_ENABLED is forced to false, R8 optimization removes the call to FastServiceLoader, meaning that ServiceLoader is always used instead of FastServiceLoader.

Refer to the coroutines source code: source code

val factories = if (FAST_SERVICE_LOADER_ENABLED) {
FastServiceLoader.loadMainDispatcherFactory()
} else {
// We are explicitly using the
// `ServiceLoader.load(MyClass::class.java, MyClass::class.java.classLoader).iterator()`
// form of the ServiceLoader call to enable R8 optimization when compiled on Android.
ServiceLoader.load(
MainDispatcherFactory::class.java,
MainDispatcherFactory::class.java.classLoader
).iterator().asSequence().toList()
}

Unfortunately, I cannot reproduce this issue on my test device. This issue originated from Firebase Crashlytics, and here is the original error report: https://github.com/JayneVong/resource/blob/master/com.vipkid.ark.international.parent_issue_d117a48fc4a650153e8480ec1ea30f09_crash_session_68D43B6F019A00015E838770698A2B5B_DNE_0_v2_stacktrace.txt

[dkhalanskyjb]

@JayneVong, this is not what I mean. The minified version in #4533 (comment) is incorrect, it shouldn't look like this. Here's what it looks like in my sample project:

package q;

import java.util.Iterator;
import java.util.List;
import o.O;

public final class s {

    public static final O f144a;

    static {
        int i2 = x.f147a;
        z.b("kotlinx.coroutines.fast.service.loader", true);
        f144a = a();
    }

    private static O a() {
        List c2;
        Object next;
        O c3;
        try {
            c2 = m.c.c(m.c.a(r.a())); // <------- THIS IS IMPORTANT
            Iterator it = c2.iterator();
            if (it.hasNext()) {
                next = it.next();
                if (it.hasNext()) {
                    int loadPriority = ((q) next).getLoadPriority();
                    do {
                        Object next2 = it.next();
                        int loadPriority2 = ((q) next2).getLoadPriority();
                        if (loadPriority < loadPriority2) {
                            next = next2;
                            loadPriority = loadPriority2;
                        }
                    } while (it.hasNext());
                }
            } else {
                next = null;
            }
            q qVar = (q) next;
            if (qVar != null && (c3 = t.c(qVar, c2)) != null) {
                return c3;
            }
            t.a(null, 3);
            throw null;
        } catch (Throwable th) {
            t.a(th, 2);
            throw null;
        }
    }
}

package q;

import java.util.Arrays;
import java.util.Iterator;
import java.util.ServiceConfigurationError;
import kotlinx.coroutines.android.AndroidDispatcherFactory;

public abstract /* synthetic */ class r {
    public static /* synthetic */ Iterator a() {
        try {
            return Arrays.asList(new AndroidDispatcherFactory()).iterator(); // <---- THIS IS IMPORTANT
        } catch (Throwable th) {
            throw new ServiceConfigurationError(th.getMessage(), th);
        }
    }
}

As you can see, no ServiceLoader is called, because that call is supposed to be optimized by R8. For some reason, in your project, this doesn't happen. Could you please share a project whose minified version includes a call to ServiceLoader.load?