[1.17.1] Custom Language Provider is not loaded due to NPE

[Kotori316]

Minecraft 1.17.1, Forge 37.0.2

I'm developing a custom language provider for Scala. I created the jar as the same way as 1.16.5, but Minecraft crashes with this error.

Spoiler

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "net.minecraftforge.forgespi.language.IModFileInfo.moduleName()" because the return value of "net.minecraftforge.forgespi.locating.IModFile.getModFileInfo()" is null
    at MC-BOOTSTRAP/[email protected]/net.minecraftforge.fml.loading.moddiscovery.ModJarMetadata.name(ModJarMetadata.java:53)
    at [email protected]/cpw.mods.jarhandling.impl.Jar.name(Jar.java:212)
    at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197)
    at java.base/java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948)
    at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
    at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
    at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:550)
    at java.base/java.util.stream.AbstractPipeline.evaluateToArrayNode(AbstractPipeline.java:260)
    at java.base/java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:616)
    at java.base/java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:622)
    at java.base/java.util.stream.ReferencePipeline.toList(ReferencePipeline.java:627)
    at MC-BOOTSTRAP/[email protected]/cpw.mods.modlauncher.ModuleLayerHandler.buildLayer(ModuleLayerHandler.java:69)
    at MC-BOOTSTRAP/[email protected]/cpw.mods.modlauncher.ModuleLayerHandler.buildLayer(ModuleLayerHandler.java:82)
    at MC-BOOTSTRAP/[email protected]/cpw.mods.modlauncher.Launcher.run(Launcher.java:93)
    at MC-BOOTSTRAP/[email protected]/cpw.mods.modlauncher.Launcher.main(Launcher.java:77)
    at MC-BOOTSTRAP/[email protected]/cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:26)
    at MC-BOOTSTRAP/[email protected]/cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:23)
    at [email protected]/cpw.mods.bootstraplauncher.BootstrapLauncher.main(BootstrapLauncher.java:84)

NPE happens in the call of SecureJar#name, which calls JarMetadata#name.

The default lang loaders(javafml, mclangage, etc.) is provided with SimpleJarMetadata or ModuleJarMetadata, where JarMetadata#name must return valid value.

But jars in mods dir have ModJarMetadata. In the class, JarMetadata#name fails if modFile.getModFileInfo() is null. For mod jar(FMLModType is MOD), the field(modFile.modFileInfo) is set in construction but for LANGPROVIDER the field remains null.

 

What I did

• Created a class that implements `IModLanguageProvider`
• Made a service provider file at META-INF/services/net.minecraftforge.forgespi.language.IModLanguageProvider
  • It contains the class name that implements `net.minecraftforge.forgespi.language.IModLanguageProvider`
• Created other classes such as Mod Container, Language Target.
• Then, I made a jar file.

Content of MANIFEST.MF in jar. I know "Main-Class" is not needed for Minecraft. It's for my test. I think "FMLModType" must be "LANGPROVIDER" if I want to create language provider, as the same way in 1.16.5.

Spoiler

Manifest-Version: 1.0
FMLModType: LANGPROVIDER
Specification-Title: SLP
Specification-Vendor: Kotori316
Specification-Version: 1
Implementation-Title: SLP
Implementation-Version: 2.13.6-build-1
Implementation-Vendor: Kotori316
Implementation-Timestamp: 2021-07-27T15:07:10.803099700Z
Main-Class: com.kotori316.scala_lib.Main

 

EDIT: The PR https://github.com/MinecraftForge/MinecraftForge/pull/7947 will solve this problem.

Edited July 30, 2021 by Kotori316