Include vanilla resources in final jar

src/main/kotlin/Paperweight.kt

@@ -128,6 +128,12 @@ class Paperweight : Plugin<Project> {
         val applyMergedAt by tasks.registering<ApplyAccessTransform> {
             inputJar.set(vanillaTasks.fixJar.flatMap { it.outputJar })
             atFile.set(spigotTasks.mergeGeneratedAts.flatMap { it.outputFile })
+        }
+
+        val copyResources by tasks.registering<CopyResources> {
+            inputJar.set(applyMergedAt.flatMap { it.outputJar })
+            vanillaJar.set(generalTasks.downloadServerJar.flatMap { it.outputJar })
+            includes.set(listOf("/data/**", "/assets/**", "version.json", "yggdrasil_session_pubkey.der", "pack.mcmeta"))
 
             outputJar.set(cache.resolve(Constants.FINAL_REMAPPED_JAR))
         }
@@ -135,7 +141,7 @@ class Paperweight : Plugin<Project> {
         val decompileJar by tasks.registering<RunForgeFlower> {
             executable.fileProvider(configurations.named(Constants.DECOMPILER_CONFIG).map { it.singleFile })
 
-            inputJar.set(applyMergedAt.flatMap { it.outputJar })
+            inputJar.set(copyResources.flatMap { it.outputJar })
             libraries.set(vanillaTasks.downloadMcLibraries.flatMap { it.outputDir })
         }
 

src/main/kotlin/tasks/CopyResources.kt

@@ -0,0 +1,43 @@
+package io.papermc.paperweight.tasks
+
+import io.papermc.paperweight.util.file
+import io.papermc.paperweight.util.zip
+import org.gradle.api.file.RegularFileProperty
+import org.gradle.api.provider.ListProperty
+import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.InputFile
+import org.gradle.api.tasks.OutputFile
+import org.gradle.api.tasks.TaskAction
+
+abstract class CopyResources : BaseTask() {
+    @get:InputFile
+    abstract val inputJar: RegularFileProperty
+    @get:InputFile
+    abstract val vanillaJar: RegularFileProperty
+    @get:Input
+    abstract val includes: ListProperty<String>
+
+    @get:OutputFile
+    abstract val outputJar: RegularFileProperty
+
+    @TaskAction
+    fun run() {
+        val out = outputJar.file
+        val target = out.resolveSibling("${out.name}.dir")
+        target.mkdirs()
+
+        fs.copy {
+            from(archives.zipTree(vanillaJar)) {
+                for (inc in this@CopyResources.includes.get()) {
+                    include(inc)
+                }
+            }
+            into(target)
+            from(archives.zipTree(inputJar))
+            into(target)
+        }
+
+        zip(target, outputJar)
+        target.deleteRecursively()
+    }
+}