Patch VanillaPackResources.getResource since it's still an issue

src/main/java/org/embeddedt/modernfix/core/config/ModernFixEarlyConfig.java

@@ -17,7 +17,7 @@ public class ModernFixEarlyConfig {
         // Defines the default rules which can be configured by the user or other mods.
         // You must manually add a rule for any new mixins not covered by an existing package rule.
         this.addMixinRule("core", true); // TODO: Don't actually allow the user to disable this
-        this.addMixinRule("perf.modern_resourcepacks", false);
+        this.addMixinRule("perf.modern_resourcepacks", true);
         this.addMixinRule("feature.branding", true);
         this.addMixinRule("feature.measure_time", true);
         this.addMixinRule("feature.reduce_loading_screen_freezes", false);

src/main/java/org/embeddedt/modernfix/mixin/perf/modern_resourcepacks/VanillaPackResourcesMixin.java

@@ -0,0 +1,36 @@
+package org.embeddedt.modernfix.mixin.perf.modern_resourcepacks;
+
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.packs.PackType;
+import net.minecraft.server.packs.VanillaPackResources;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Overwrite;
+import org.spongepowered.asm.mixin.Shadow;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Map;
+
+@Mixin(VanillaPackResources.class)
+public class VanillaPackResourcesMixin {
+    @Shadow @Final private static Map<PackType, Path> ROOT_DIR_BY_TYPE;
+
+    /**
+     * @author embeddedt
+     * @reason avoid going through the module class loader when we know exactly what path this resource should come
+     * from
+     */
+    @Overwrite
+    protected InputStream getResourceAsStream(PackType type, ResourceLocation location) {
+        Path rootPath = ROOT_DIR_BY_TYPE.get(type);
+        Path targetPath = rootPath.resolve(location.getNamespace() + "/" + location.getPath());
+        try {
+            return Files.newInputStream(targetPath);
+        } catch(IOException e) {
+            return null;
+        }
+    }
+}

src/main/resources/modernfix.mixins.json

@@ -7,6 +7,7 @@
   "refmap": "modernfix.refmap.json",
   "mixins": [
     "bugfix.edge_chunk_not_saved.ChunkManagerMixin",
+    "perf.modern_resourcepacks.VanillaPackResourcesMixin",
     "perf.remove_biome_temperature_cache.BiomeMixin",
     "perf.reduce_blockstate_cache_rebuilds.GameDataMixin",
     "perf.reduce_blockstate_cache_rebuilds.BlockCallbacksMixin",