Add fabric-loader-junit to allow unit testing of transformed classes.

[modmuss50]

PR to support testing mods with JUnit.

This PR publishes a new fabric-loader-junit maven artifact. This can be setup like so:

dependencies {
	testImplementation "net.fabricmc:fabric-loader-junit:${project.loader_version}"
}

test {
	useJUnitPlatform()
}

Eclipse / Visual Studio code are not currently supported, users of those IDEs must run the tests via Gradle. Gradle 8 MUST also be used to support this, hence why this PR updates loader to use Gradle 8.0-rc2.

Previous discussion: FabricMC/fabric-loom#742
Doucmentation: https://junit.org/junit5/docs/snapshot/user-guide/#launcher-api-launcher-interceptors-custom
Junit PR adding this: junit-team/junit5#3091

[modmuss50]

This should now be ready, Gradle 8 has now been released so im happy to merge this pending no other requested changes 👍

[modmuss50]

Going to merge this, I think for now its fair to call this "experimental" as its using a lot of new Junit and Gradle tech with limitations. As this is an advanced dev only feature I am less worried about having to maintain this far into the future if Junit or anything else changes in the future.

[md5]

This is great timing! I was just updating a mod that I wrote against 1.17 and started getting this error in my JUnit tests:

java.lang.IllegalAccessError: class net.minecraft.registry.SimpleRegistry tried to access method 'void net.minecraft.registry.entry.RegistryEntry$Reference.setRegistryKey(net.minecraft.registry.RegistryKey)' (net.minecraft.registry.SimpleRegistry and net.minecraft.registry.entry.RegistryEntry$Reference are in unnamed module of loader 'app')

It turns out that SimpleRegistry and RegistryEntry$Reference are actually in the same package in the official mappings, so package private access to setRegistryKey works there, but in the YARN mappings they are in different packages, resulting in the IllegalAccessError. Since this breaking change appears to have been made in FabricMC/yarn#3396, I made a comment over there.

Adding fabric-loader-junit seems to have worked around that problem, but I started getting a different error now:

org.gradle.api.internal.tasks.testing.TestSuiteExecutionException: Could not execute test class 'io.appropriate.minecraft.mods.durability.DurabilityCheckerTests'.
	at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:54)
	at [email protected]/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at [email protected]/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at [email protected]/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at [email protected]/java.lang.reflect.Method.invoke(Method.java:568)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
	at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
	at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)
	at jdk.proxy1/jdk.proxy1.$Proxy2.processTestClass(Unknown Source)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker$2.run(TestWorker.java:176)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:129)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:100)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:60)
	at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56)
	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:113)
	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:65)
	at app//worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
	at app//worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)
Caused by: java.lang.RuntimeException: Mixin transformation of io.appropriate.minecraft.mods.durability.DurabilityCheckerTests failed
	at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:427)
	at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.tryLoadClass(KnotClassDelegate.java:323)
	at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.loadClass(KnotClassDelegate.java:218)
	at net.fabricmc.loader.impl.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:112)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520)
	at java.base/java.lang.Class.forName0(Native Method)
	at java.base/java.lang.Class.forName(Class.java:467)
	at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor.loadClass(JUnitPlatformTestClassProcessor.java:135)
	at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor.access$100(JUnitPlatformTestClassProcessor.java:58)
	at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.execute(JUnitPlatformTestClassProcessor.java:100)
	at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.execute(JUnitPlatformTestClassProcessor.java:90)
	at org.gradle.api.internal.tasks.testing.junit.AbstractJUnitTestClassProcessor.processTestClass(AbstractJUnitTestClassProcessor.java:60)
	at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:52)
	... 18 more
Caused by: java.lang.ExceptionInInitializerError
	at net.fabricmc.loader.api.FabricLoader.getInstance(FabricLoader.java:41)
	at net.fabricmc.fabric.impl.client.indigo.IndigoMixinConfigPlugin.loadIfNeeded(IndigoMixinConfigPlugin.java:45)
	at net.fabricmc.fabric.impl.client.indigo.IndigoMixinConfigPlugin.shouldApplyIndigo(IndigoMixinConfigPlugin.java:60)
	at net.fabricmc.fabric.impl.client.indigo.IndigoMixinConfigPlugin.shouldApplyMixin(IndigoMixinConfigPlugin.java:79)
	at org.spongepowered.asm.mixin.transformer.PluginHandle.shouldApplyMixin(PluginHandle.java:132)
	at org.spongepowered.asm.mixin.transformer.MixinInfo.shouldApplyMixin(MixinInfo.java:988)
	at org.spongepowered.asm.mixin.transformer.MixinInfo.readDeclaredTargets(MixinInfo.java:953)
	at org.spongepowered.asm.mixin.transformer.MixinInfo.<init>(MixinInfo.java:882)
	at org.spongepowered.asm.mixin.transformer.MixinConfig.prepareMixins(MixinConfig.java:852)
	at org.spongepowered.asm.mixin.transformer.MixinConfig.prepare(MixinConfig.java:781)
	at org.spongepowered.asm.mixin.transformer.MixinProcessor.prepareConfigs(MixinProcessor.java:540)
	at org.spongepowered.asm.mixin.transformer.MixinProcessor.select(MixinProcessor.java:462)
	at org.spongepowered.asm.mixin.transformer.MixinProcessor.checkSelect(MixinProcessor.java:438)
	at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:290)
	at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:234)
	at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:202)
	at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:422)
	... 30 more
Caused by: java.lang.IllegalStateException: trying to load net.fabricmc.loader.impl.FabricLoaderImpl from target class loader
	at net.fabricmc.loader.impl.util.LoaderUtil.verifyNotInTargetCl(LoaderUtil.java:51)
	at net.fabricmc.loader.impl.FabricLoaderImpl.<clinit>(FabricLoaderImpl.java:539)
	... 47 more

I'm hoping that someone more familiar with the internals will have a clearer idea than I do of what the cause may be. My PR with the updates to go from 1.17 to 1.19 is at appropriate/durability-alert-mod#2, but it doesn't seem like the changes I'm making there are causing this since the tests work for the 1.17 version of the mod.

[md5]

It seems like perhaps FabricLoader.getInstance() needs to be called in launcherSessionOpened before setting the current thread's context ClassLoader or in the constructor of FabricLoaderLauncherSessionListener.

[modmuss50]

Hi, @md5 I think this might be caused by having fabric-loader on the classpath twice. Due to a change made to skip remapping loader its quite easy for a dep to pull in an older version of loader and remap it. I see you have alteast 2 mods that you depend on, a workaround for now is to exclude the fabric-loader transitive dep from them.

[md5]

Hi, @md5 I think this might be caused by having fabric-loader on the classpath twice. Due to a change made to skip remapping loader its quite easy for a dep to pull in an older version of loader and remap it. I see you have alteast 2 mods that you depend on, a workaround for now is to exclude the fabric-loader transitive dep from them.

Thanks @modmuss50! appropriate/durability-alert-mod@47178fa fixed things up