Add diff task for paperweight development

paperweight-core/src/main/kotlin/PaperweightCore.kt

@@ -62,6 +62,16 @@ class PaperweightCore : Plugin<Project> {
         target.configurations.create(DECOMPILER_CONFIG)
         target.configurations.create(PAPERCLIP_CONFIG)
 
+        if (target.providers.gradleProperty("paperweight.dev").forUseAtConfigurationTime().orNull == "true") {
+            target.tasks.register<CreateDiffOutput>("diff") {
+                inputDir.convention(ext.paper.paperServerDir.map { it.dir("src/main/java") })
+                val prop = target.providers.gradleProperty("paperweight.diff.output").forUseAtConfigurationTime()
+                if (prop.isPresent) {
+                    baseDir.convention(target.layout.projectDirectory.dir(prop))
+                }
+            }
+        }
+
         val tasks = AllTasks(target)
 
         val devBundleTasks = DevBundleTasks(target)

paperweight-lib/src/main/kotlin/tasks/CreateDiffOutput.kt

@@ -0,0 +1,63 @@
+/*
+ * paperweight is a Gradle plugin for the PaperMC project.
+ *
+ * Copyright (c) 2021 Kyle Wood (DenWav)
+ *                    Contributors
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation;
+ * version 2.1 only, no later versions.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301
+ * USA
+ */
+
+package io.papermc.paperweight.tasks
+
+import io.papermc.paperweight.util.*
+import org.gradle.api.file.DirectoryProperty
+import org.gradle.api.provider.Property
+import org.gradle.api.tasks.InputDirectory
+import org.gradle.api.tasks.Internal
+import org.gradle.api.tasks.OutputDirectory
+import org.gradle.api.tasks.TaskAction
+import org.gradle.api.tasks.UntrackedTask
+import org.gradle.api.tasks.options.Option
+
+@UntrackedTask(because = "Always copy files")
+abstract class CreateDiffOutput : BaseTask() {
+
+    @get:InputDirectory
+    abstract val inputDir: DirectoryProperty
+
+    @get:OutputDirectory
+    abstract val outputDir: DirectoryProperty
+
+    @get:Internal
+    abstract val baseDir: DirectoryProperty
+
+    @get:Internal
+    @get:Option(option = "target", description = "Directory name of the diff output")
+    abstract val target: Property<String>
+
+    override fun init() {
+        baseDir.convention(layout.cacheDir("paperweight/diff"))
+        outputDir.convention(baseDir.flatMap { it.dir(target) })
+    }
+
+    @TaskAction
+    fun run() {
+        val output = outputDir.path
+
+        output.deleteRecursively()
+        inputDir.path.copyRecursivelyTo(output)
+    }
+}

paperweight-lib/src/main/kotlin/util/utils.kt

@@ -45,8 +45,6 @@ import java.util.Optional
 import java.util.concurrent.ThreadLocalRandom
 import kotlin.io.path.*
 import org.cadixdev.lorenz.merge.MergeResult
-import org.cadixdev.lorenz.model.ClassMapping
-import org.cadixdev.lorenz.model.MemberMapping
 import org.gradle.api.Project
 import org.gradle.api.Task
 import org.gradle.api.file.FileCollection
@@ -81,7 +79,7 @@ inline fun <reified T> Gson.fromJson(any: Any): T = when (any) {
 }
 
 val ProjectLayout.cache: Path
-    get() = projectDirectory.file(".gradle/$CACHE_PATH").path
+    get() = projectDirectory.dir(".gradle/$CACHE_PATH").path
 
 fun ProjectLayout.cacheDir(path: String) = projectDirectory.dir(".gradle/$CACHE_PATH").dir(path)
 fun ProjectLayout.initSubmodules() {
@@ -238,9 +236,6 @@ fun findOutputDir(baseFile: Path): Path {
     return dir
 }
 
-val MemberMapping<*, *>.parentClass: ClassMapping<*, *>
-    get() = parent as ClassMapping<*, *>
-
 private val emptyMergeResult = MergeResult(null)
 fun <T> emptyMergeResult(): MergeResult<T?> {
     @Suppress("UNCHECKED_CAST")