Ensure files are closed and outputs cleaned up when remapping.

src/main/java/net/fabricmc/loom/build/JarRemapper.java

@@ -25,6 +25,7 @@
 package net.fabricmc.loom.build;
 
 import java.io.IOException;
+import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -37,6 +38,7 @@ import java.util.function.BiFunction;
 import org.gradle.api.Action;
 import org.objectweb.asm.commons.Remapper;
 
+import net.fabricmc.loom.util.CloseableList;
 import net.fabricmc.stitch.util.Pair;
 import net.fabricmc.tinyremapper.IMappingProvider;
 import net.fabricmc.tinyremapper.InputTag;
@@ -89,8 +91,8 @@ public class JarRemapper {
 			remapper.readInputsAsync(tag, data.input);
 		}
 
-		List<OutputConsumerPath> outputConsumers = new ArrayList<>();
-
+		//noinspection MismatchedQueryAndUpdateOfCollection
+		try (CloseableList<OutputConsumerPath> outputConsumers = new CloseableList<>()) {
 			for (RemapData data : remapData) {
 				OutputConsumerPath outputConsumer = new OutputConsumerPath.Builder(data.output).build();
 				outputConsumers.add(outputConsumer);
@@ -102,9 +104,13 @@ public class JarRemapper {
 			}
 
 			remapper.finish();
+		} catch (Exception e) {
+			for (RemapData data : remapData) {
+				// Cleanup bad outputs
+				Files.deleteIfExists(data.output);
+			}
 
-		for (OutputConsumerPath outputConsumer : outputConsumers) {
-			outputConsumer.close();
+			throw new IOException("Failed to remap %s files".formatted(remapData.size()), e);
 		}
 
 		remapData.forEach(RemapData::complete);

src/main/java/net/fabricmc/loom/util/CloseableList.java

@@ -0,0 +1,52 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.util;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.util.ArrayList;
+
+public class CloseableList<T extends Closeable> extends ArrayList<T> implements Closeable {
+	@Override
+	public void close() throws IOException {
+		IOException exception = null;
+
+		for (T t : this) {
+			try {
+				t.close();
+			} catch (IOException e) {
+				if (exception == null) {
+					exception = new IOException("Failed to close list");
+				}
+
+				exception.addSuppressed(e);
+			}
+		}
+
+		if (exception != null) {
+			throw exception;
+		}
+	}
+}