build: merge shadow jar access wideners

buildSrc/src/FabricModTransform.kt

@@ -0,0 +1,80 @@
+import com.github.jengelman.gradle.plugins.shadow.transformers.ResourceTransformer
+import com.github.jengelman.gradle.plugins.shadow.transformers.TransformerContext
+import com.google.gson.Gson
+import com.google.gson.JsonObject
+import com.google.gson.JsonPrimitive
+import java.io.Serializable
+import net.fabricmc.accesswidener.AccessWidenerReader
+import net.fabricmc.accesswidener.AccessWidenerWriter
+import org.apache.tools.zip.ZipEntry
+import org.apache.tools.zip.ZipOutputStream
+import org.gradle.api.file.FileTreeElement
+import org.gradle.api.provider.Property
+import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.Internal
+
+open class FabricModTransform : ResourceTransformer {
+
+	enum class AccessWidenerInclusion : Serializable {
+		ALL,
+		NONE,
+	}
+
+	@get:Input
+	var mergeAccessWideners: AccessWidenerInclusion = AccessWidenerInclusion.ALL
+
+	@get:Internal
+	internal var mergedFmj: JsonObject? = null
+
+	@get:Internal
+	internal val foundAccessWideners = AccessWidenerWriter()
+
+	@get:Internal
+	internal var foundAnyAccessWidener = false
+
+	override fun canTransformResource(element: FileTreeElement): Boolean {
+		if (mergeAccessWideners == AccessWidenerInclusion.ALL && element.name.endsWith(".accesswidener"))
+			return true
+		return element.path == "fabric.mod.json"
+	}
+
+	override fun transform(context: TransformerContext) {
+		if (context.path.endsWith(".accesswidener")) {
+			foundAnyAccessWidener = true
+			// TODO: allow filtering for only those mentioned in a fabric.mod.json, potentially
+			context.inputStream.use { stream ->
+				AccessWidenerReader(foundAccessWideners).read(stream.bufferedReader())
+			}
+			return
+		}
+		// TODO: mixins.json relocations
+		val fmj = context.inputStream.use { stream ->
+			Gson().fromJson(stream.bufferedReader(), JsonObject::class.java)
+		}
+		val mergedFmj = this.mergedFmj
+		println("${fmj["id"]} is first? ${mergedFmj == null}")
+		if (mergedFmj == null) {
+			this.mergedFmj = fmj
+		} else {
+			// TODO: merge stuff
+		}
+	}
+
+	override fun hasTransformedResource(): Boolean {
+		return mergedFmj != null
+	}
+
+	override fun modifyOutputStream(os: ZipOutputStream, preserveFileTimestamps: Boolean) {
+		val mergedFmj = mergedFmj!!
+		if (foundAnyAccessWidener) {
+			val awFile = mergedFmj["accessWidener"]
+			require(awFile is JsonPrimitive && awFile.isString)
+			os.putNextEntry(ZipEntry(awFile.asString))
+			os.write(foundAccessWideners.write())
+			os.closeEntry()
+		}
+		os.putNextEntry(ZipEntry("fabric.mod.json"))
+		os.write(mergedFmj.toString().toByteArray())
+		os.closeEntry()
+	}
+}