Unfreeze block registry ourselves in tests

Author: embeddedt

fabric/src/test/java/org/embeddedt/modernfix/testing/util/BootstrapMinecraftExtension.java

@@ -1,12 +1,17 @@
 package org.embeddedt.modernfix.testing.util;
 
 import net.minecraft.DetectedVersion;
+import net.minecraft.core.MappedRegistry;
+import net.minecraft.core.registries.BuiltInRegistries;
 import net.minecraft.server.Bootstrap;
 import org.junit.jupiter.api.extension.AfterAllCallback;
 import org.junit.jupiter.api.extension.BeforeAllCallback;
 import org.junit.jupiter.api.extension.Extension;
 import org.junit.jupiter.api.extension.ExtensionContext;
 
+import java.lang.reflect.Field;
+import java.util.IdentityHashMap;
+
 /**
  * Simple extension to run vanilla bootstrap, inspired by AE2.
  */
@@ -15,6 +20,15 @@ public class BootstrapMinecraftExtension implements Extension, BeforeAllCallback
     public void beforeAll(ExtensionContext context) throws Exception {
         DetectedVersion.tryDetectVersion();
         Bootstrap.bootStrap();
+        // Allow blocks to be created in tests
+        Field field = MappedRegistry.class.getDeclaredField("unregisteredIntrusiveHolders");
+        field.setAccessible(true);
+        if(field.get(BuiltInRegistries.BLOCK) == null) {
+            field.set(BuiltInRegistries.BLOCK, new IdentityHashMap<>());
+            field = MappedRegistry.class.getDeclaredField("frozen");
+            field.setAccessible(true);
+            field.setBoolean(BuiltInRegistries.BLOCK, false);
+        }
     }
 
     @Override