Custom JarJar tasks cannot be registered after applying UserDevPlugin

Introduction

I need to create two separate tasks of JarJar type. However, after a long investigation, I've found out that such custom tasks should be created (and disabled) before applying UserDevPlugin.

Examples

Let's take a look at two examples.

apply<UserDevPlugin>()

tasks.create<JarJar>("clientJarJar") {
    enabled = false
}

This won't compile as Gradle reports the following error:

Stacktrace

```java * Exception is: org.gradle.api.plugins.InvalidPluginException: An exception occurred applying plugin request [id: 'net.mattermc.mod'] Caused by: org.gradle.api.internal.AbstractMutationGuard$IllegalMutationException: DefaultTaskContainer#create(String, Class) on task set cannot be executed in the current context. at org.gradle.api.internal.AbstractMutationGuard.createIllegalStateException(AbstractMutationGuard.java:39) at org.gradle.api.internal.AbstractMutationGuard.assertMutationAllowed(AbstractMutationGuard.java:27) at org.gradle.api.internal.DefaultDomainObjectCollection.assertMutable(DefaultDomainObjectCollection.java:458) at org.gradle.api.internal.tasks.DefaultTaskContainer.create(DefaultTaskContainer.java:277) at org.gradle.api.internal.tasks.DefaultTaskContainer.maybeCreate(DefaultTaskContainer.java:266) at org.gradle.api.internal.tasks.DefaultTaskContainer.maybeCreate(DefaultTaskContainer.java:75) at net.minecraftforge.gradle.userdev.UserDevPlugin.lambda$createReobfExtension$33(UserDevPlugin.java:348) at org.gradle.api.internal.FactoryNamedDomainObjectContainer.doCreate(FactoryNamedDomainObjectContainer.java:93) at org.gradle.api.internal.AbstractNamedDomainObjectContainer.create(AbstractNamedDomainObjectContainer.java:78) at org.gradle.api.internal.AbstractNamedDomainObjectContainer.create(AbstractNamedDomainObjectContainer.java:56) at net.minecraftforge.gradle.userdev.UserDevPlugin.lambda$apply$31(UserDevPlugin.java:338) at org.gradle.configuration.internal.DefaultUserCodeApplicationContext$CurrentApplication$1.execute(DefaultUserCodeApplicationContext.java:123) at org.gradle.api.internal.DefaultCollectionCallbackActionDecorator$BuildOperationEmittingAction$1.run(DefaultCollectionCallbackActionDecorator.java:110) at org.gradle.internal.operations.DefaultBuildOperationRunner$1.execute(DefaultBuildOperationRunner.java:29) at org.gradle.internal.operations.DefaultBuildOperationRunner$1.execute(DefaultBuildOperationRunner.java:26) at org.gradle.internal.operations.DefaultBuildOperationRunner$2.execute(DefaultBuildOperationRunner.java:66) at org.gradle.internal.operations.DefaultBuildOperationRunner$2.execute(DefaultBuildOperationRunner.java:59) at org.gradle.internal.operations.DefaultBuildOperationRunner.execute(DefaultBuildOperationRunner.java:157) at org.gradle.internal.operations.DefaultBuildOperationRunner.execute(DefaultBuildOperationRunner.java:59) at org.gradle.internal.operations.DefaultBuildOperationRunner.run(DefaultBuildOperationRunner.java:47) at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:68) at org.gradle.api.internal.DefaultCollectionCallbackActionDecorator$BuildOperationEmittingAction.execute(DefaultCollectionCallbackActionDecorator.java:107) at org.gradle.api.internal.DefaultMutationGuard$2.execute(DefaultMutationGuard.java:44) at org.gradle.api.internal.DefaultMutationGuard$2.execute(DefaultMutationGuard.java:44) at org.gradle.api.internal.collections.CollectionFilter$1.execute(CollectionFilter.java:59) at org.gradle.internal.ImmutableActionSet$SetWithManyActions.execute(ImmutableActionSet.java:329) at org.gradle.api.internal.DefaultDomainObjectCollection.doAdd(DefaultDomainObjectCollection.java:262) at org.gradle.api.internal.DefaultNamedDomainObjectCollection.doAdd(DefaultNamedDomainObjectCollection.java:113) at org.gradle.api.internal.DefaultDomainObjectCollection.add(DefaultDomainObjectCollection.java:251) at org.gradle.api.internal.tasks.DefaultTaskContainer.addInternal(DefaultTaskContainer.java:752) at org.gradle.api.internal.tasks.DefaultTaskContainer.addTask(DefaultTaskContainer.java:253) at org.gradle.api.internal.tasks.DefaultTaskContainer.access$400(DefaultTaskContainer.java:76) at org.gradle.api.internal.tasks.DefaultTaskContainer$2.call(DefaultTaskContainer.java:298) ... 199 more ```

We can observe that it fails with DefaultTaskContainer#create(String, Class) on task set cannot be executed in the current context. which points to reobfExtension's NamedDomainObjectContainer#create.

Now let's examine the following example.

tasks.create<JarJar>("clientJarJar") {
    enabled = false
}

apply<UserDevPlugin>()

This will work and build will succeed.

Conclusion

If I understand correctly, the build fails due to improper order of reobf task generation and configuration.

MinecraftForge / ForgeGradle