Guard Bukkit chunk unload path against reflection nulls and NPE loops

[Copilot]

ChunkUnloadEvent could repeatedly throw NullPointerException when AUTO_TRIM was enabled and reflection-backed chunk internals were unavailable or returned null. This caused unstable unload handling and noisy repeated failures on affected server/version combinations.

• unloadChunk defensive null handling

  • Added early returns when required reflection members are unavailable:
    • methodGetHandleChunk
    • mustNotSave
    • methodSetUnsaved
  • Added early returns when runtime reflection results are null:
    • NMS chunk handle (c)
    • mustNotSave.of(c) field executor

• onChunkUnload NPE containment

  • Wrapped AUTO_TRIM unload + subsequent chunk processing in an NPE guard so a single bad chunk/reflection path does not repeatedly surface exceptions on unload events.

• Example of new guard behavior

  if (this.methodGetHandleChunk == null || this.mustNotSave == null || this.methodSetUnsaved == null) {
      return false;
  }
  Object c = ...;
  if (c == null) {
      return false;
  }
  RefField.RefExecutor field = this.mustNotSave.of(c);
  if (field == null) {
      return false;
  }

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• jitpack.io
  • Triggering command: /usr/lib/jvm/temurin-21-jdk-amd64/bin/java /usr/lib/jvm/temurin-21-jdk-amd64/bin/java --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.lang.invoke=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED --add-opens=java.base/java.nio.charset=ALL-UNNAMED --add-opens=java.base/java.net=ALL-UNNAMED --add-opens=java.base/java.util.concurrent=ALL-UNNAMED --add-opens=java.base/java.util.concurrent.atomic=ALL-UNNAMED --add-opens=java.xml/javax.xml.namespace=ALL-UNNAMED --add-opens=java.base/java.time=ALL-UNNAMED -XX:+HeapDumpOnOutOfMemoryError -Xmx2048m -Dfile.encoding=UTF-8 -Duser.country -Duser.language=en -Duser.variant -cp (dns block)
• maven.enginehub.org
  • Triggering command: /usr/lib/jvm/temurin-17-jdk-amd64/bin/java /usr/lib/jvm/temurin-17-jdk-amd64/bin/java --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.lang.invoke=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED --add-opens=java.base/java.nio.charset=ALL-UNNAMED --add-opens=java.base/java.net=ALL-UNNAMED --add-opens=java.base/java.util.concurrent=ALL-UNNAMED --add-opens=java.base/java.util.concurrent.atomic=ALL-UNNAMED --add-opens=java.xml/javax.xml.namespace=ALL-UNNAMED --add-opens=java.base/java.time=ALL-UNNAMED -XX:+HeapDumpOnOutOfMemoryError -Xmx2048m -Dfile.encoding=UTF-8 -Duser.country -Duser.language=en -Duser.variant -cp (dns block)
  • Triggering command: /usr/lib/jvm/temurin-21-jdk-amd64/bin/java /usr/lib/jvm/temurin-21-jdk-amd64/bin/java --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.lang.invoke=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED --add-opens=java.base/java.nio.charset=ALL-UNNAMED --add-opens=java.base/java.net=ALL-UNNAMED --add-opens=java.base/java.util.concurrent=ALL-UNNAMED --add-opens=java.base/java.util.concurrent.atomic=ALL-UNNAMED --add-opens=java.xml/javax.xml.namespace=ALL-UNNAMED --add-opens=java.base/java.time=ALL-UNNAMED -XX:+HeapDumpOnOutOfMemoryError -Xmx2048m -Dfile.encoding=UTF-8 -Duser.country -Duser.language=en -Duser.variant -cp (dns block)

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Original prompt

The ChunkUnloadEvent handler in Bukkit/src/main/java/com/plotsquared/bukkit/listener/ChunkListener.java throws a java.lang.NullPointerException repeatedly when chunks are unloaded.

Root cause: In the onChunkUnload method, unloadChunk(world, chunk, true) is called when Settings.Chunk_Processor.AUTO_TRIM is enabled. Inside unloadChunk, the code calls this.methodGetHandleChunk.of(chunk).call(...) and this.mustNotSave.of(c) — but this.methodGetHandleChunk and/or this.mustNotSave can be null if the reflection-based initialization in the constructor failed (the catch block sets AUTO_TRIM = false but that happens after the fields were already not set). Also, the NMS object c returned by methodGetHandleChunk can itself be null on certain server versions/configurations.

Fix needed:

1. In unloadChunk, add null-checks for this.methodGetHandleChunk, this.mustNotSave, and the result c before proceeding. Return false early if any of these are null.
2. Also guard the onChunkUnload method: wrap the unloadChunk call (and the subsequent processChunk) in a try-catch for NullPointerException or add proper null guards so a single problematic chunk doesn't spam the error log.

The file to change is: Bukkit/src/main/java/com/plotsquared/bukkit/listener/ChunkListener.java