cease loading the same mappings file a million times

src/main/java/net/fabricmc/loom/providers/MappingsProvider.java

@@ -28,10 +28,14 @@ import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.util.Constants;
 import net.fabricmc.loom.util.DependencyProvider;
 import net.fabricmc.loom.util.Version;
+import net.fabricmc.mappings.Mappings;
 import net.fabricmc.stitch.commands.CommandProposeFieldNames;
 import org.gradle.api.Project;
 
 import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.lang.ref.SoftReference;
 import java.nio.file.FileSystem;
 import java.nio.file.FileSystems;
 import java.nio.file.Files;
@@ -50,9 +54,22 @@ public class MappingsProvider extends DependencyProvider {
 	private File MAPPINGS_DIR;
 	public File MAPPINGS_TINY_BASE;
 	public File MAPPINGS_TINY;
-
 	public File MAPPINGS_MIXIN_EXPORT;
 
+	private SoftReference<Mappings> mappings;
+
+	public Mappings getMappings() throws IOException {
+		if (mappings == null || mappings.get() == null) {
+			try (FileInputStream stream = new FileInputStream(MAPPINGS_TINY)) {
+				mappings = new SoftReference<>(
+						net.fabricmc.mappings.MappingsProvider.readTinyMappings(stream, false)
+				);
+			}
+		}
+		
+		return mappings.get();
+	}
+
 	@Override
 	public void provide(DependencyInfo dependency, Project project, LoomGradleExtension extension, Consumer<Runnable> postPopulationScheduler) throws Exception {
 		MinecraftProvider minecraftProvider = getDependencyManager().getProvider(MinecraftProvider.class);

src/main/java/net/fabricmc/loom/task/RemapJar.java

@@ -30,6 +30,7 @@ import org.gradle.api.tasks.OutputFile;
 import org.gradle.api.tasks.TaskAction;
 
 import java.io.File;
+import java.io.IOException;
 
 public class RemapJar extends DefaultLoomTask {
 	public File jar;
@@ -57,7 +58,7 @@ public class RemapJar extends DefaultLoomTask {
 	}
 
 	@TaskAction
-	public void remap() {
+	public void remap() throws IOException {
 		ModRemapper.remap(this, nestJar);
 	}
 }

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

@@ -47,7 +47,6 @@ public class MapJarsTiny {
 		LoomGradleExtension extension = project.getExtensions().getByType(LoomGradleExtension.class);
 		MappingsProvider mappingsProvider = extension.getMappingsProvider();
 
-		Path mappings = mappingsProvider.MAPPINGS_TINY.toPath();
 		Path[] classpath = mapProvider.getMapperPaths().stream()
 				.map(File::toPath)
 				.toArray(Path[]::new);
@@ -62,7 +61,7 @@ public class MapJarsTiny {
 			project.getLogger().lifecycle(":remapping minecraft (TinyRemapper, " + fromM + " -> " + toM + ")");
 
 			TinyRemapper remapper = TinyRemapper.newRemapper()
-					.withMappings(TinyUtils.createTinyMappingProvider(mappings, fromM, toM))
+					.withMappings(TinyRemapperMappingsHelper.create(mappingsProvider.getMappings(), fromM, toM))
 					.renameInvalidLocals(true)
 					.rebuildSourceFilenames(true)
 					.build();

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

@@ -44,6 +44,7 @@ import org.gradle.jvm.JvmLibrary;
 import org.gradle.language.base.artifact.SourcesArtifact;
 
 import java.io.File;
+import java.io.IOException;
 import java.util.Optional;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
@@ -116,7 +117,11 @@ public class ModCompileRemapper {
 			File output = new File(modStore, remappedFilename + ".jar");
 			if (!output.exists() || input.lastModified() <= 0 || input.lastModified() > output.lastModified()) {
 				//If the output doesn't exist, or appears to be outdated compared to the input we'll remap it
+				try {
 					ModProcessor.handleMod(input, output, project);
+				} catch (IOException e) {
+					throw new RuntimeException("Failed to remap mod", e);
+				}
 
 				if (!output.exists()){
 					throw new RuntimeException("Failed to remap mod");

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

@@ -56,7 +56,7 @@ import java.util.zip.ZipEntry;
 public class ModProcessor {
 	private static final Gson GSON = new Gson();
 
-	public static void handleMod(File input, File output, Project project){
+	public static void handleMod(File input, File output, Project project) throws IOException {
 		if(output.exists()){
 			output.delete();
 		}
@@ -64,11 +64,7 @@ public class ModProcessor {
 		readInstallerJson(input, project);
 		//Enable this if you want your nested jars to be extracted, this will extract **all** jars
 		if(project.getExtensions().getByType(LoomGradleExtension.class).extractJars){
-			try {
 			handleNestedJars(input, project);
-			} catch (IOException e) {
-				throw new RuntimeException("Failed to handle nested jar", e);
-			}
 		}
 		//Always strip the nested jars
 		stripNestedJars(output);
@@ -95,7 +91,7 @@ public class ModProcessor {
 		}
 	}
 
-	private static void processNestedJar(JarFile parentJar, String fileName, Project project){
+	private static void processNestedJar(JarFile parentJar, String fileName, Project project) throws IOException {
 		LoomGradleExtension extension = project.getExtensions().getByType(LoomGradleExtension.class);
 
 		JarEntry entry = parentJar.getJarEntry(fileName);
@@ -104,10 +100,8 @@ public class ModProcessor {
 		}
 
 		File nestedFile = new File(extension.getNestedModCache(), fileName.substring(fileName.lastIndexOf("/")));
-		try(InputStream jarStream = parentJar.getInputStream(entry)){
+		try(InputStream jarStream = parentJar.getInputStream(entry)) {
 			FileUtils.copy(jarStream, nestedFile);
-		} catch (IOException e) {
-			throw new RuntimeException(e);
 		}
 		File remappedFile = new File(extension.getRemappedModCache(), fileName.substring(fileName.lastIndexOf("/")));
 
@@ -133,7 +127,7 @@ public class ModProcessor {
 		}))});
 	}
 
-	private static void remapJar(File input, File output, Project project){
+	private static void remapJar(File input, File output, Project project) throws IOException {
 		LoomGradleExtension extension = project.getExtensions().getByType(LoomGradleExtension.class);
 		String fromM = "intermediary";
 		String toM = "named";
@@ -162,7 +156,7 @@ public class ModProcessor {
 		project.getLogger().lifecycle(":remapping " + input.getName() + " (TinyRemapper, " + fromM + " -> " + toM + ")");
 
 		TinyRemapper remapper = TinyRemapper.newRemapper()
-			.withMappings(TinyUtils.createTinyMappingProvider(mappings, fromM, toM))
+			.withMappings(TinyRemapperMappingsHelper.create(mappingsProvider.getMappings(), fromM, toM))
 			.build();
 
 		try (OutputConsumerPath outputConsumer = new OutputConsumerPath(Paths.get(output.getAbsolutePath()))) {
@@ -172,8 +166,6 @@ public class ModProcessor {
 			remapper.readClassPath(mcDeps);
 			remapper.readInputs(inputPath);
 			remapper.apply(outputConsumer);
-		} catch (Exception e){
-			throw new RuntimeException("Failed to remap JAR to " + toM, e);
 		} finally {
 			remapper.finish();
 		}

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

@@ -42,7 +42,7 @@ import java.util.List;
 
 public class ModRemapper {
 
-	public static void remap(RemapJar task, boolean nest) {
+	public static void remap(RemapJar task, boolean nest) throws IOException {
 		Project project = task.getProject();
 		LoomGradleExtension extension = project.getExtensions().getByType(LoomGradleExtension.class);
 
@@ -79,7 +79,8 @@ public class ModRemapper {
 		Path mixinMapPath = mixinMapFile.toPath();
 
 		TinyRemapper.Builder remapperBuilder = TinyRemapper.newRemapper();
-		remapperBuilder = remapperBuilder.withMappings(TinyUtils.createTinyMappingProvider(mappings, fromM, toM));
+
+		remapperBuilder = remapperBuilder.withMappings(TinyRemapperMappingsHelper.create(mappingsProvider.getMappings(), fromM, toM));
 		if (mixinMapFile.exists()) {
 			remapperBuilder = remapperBuilder.withMappings(TinyUtils.createTinyMappingProvider(mixinMapPath, fromM, toM));
 		}

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

@@ -62,9 +62,10 @@ public class SourceRemapper {
 		MappingsProvider mappingsProvider = extension.getMappingsProvider();
 
 		MappingSet mappings = extension.getOrCreateSrcMappingCache(toNamed ? 1 : 0, () -> {
-			try (FileInputStream stream = new FileInputStream(mappingsProvider.MAPPINGS_TINY)) {
+			try {
+				Mappings m = mappingsProvider.getMappings();
 				project.getLogger().lifecycle(":loading " + (toNamed ? "intermediary -> named" : "named -> intermediary") + " source mappings");
-				return new TinyReader(stream, toNamed ? "intermediary" : "named", toNamed ? "named" : "intermediary").read();
+				return new TinyReader(m, toNamed ? "intermediary" : "named", toNamed ? "named" : "intermediary").read();
 			} catch (Exception e) {
 				throw new RuntimeException(e);
 			}
@@ -140,19 +141,17 @@ public class SourceRemapper {
 	}
 
 	public static class TinyReader extends MappingsReader {
-		private final InputStream stream;
+		private final Mappings m;
 		private final String from, to;
 
-		public TinyReader(InputStream stream, String from, String to) {
-			this.stream = stream;
+		public TinyReader(Mappings m, String from, String to) {
+			this.m = m;
 			this.from = from;
 			this.to = to;
 		}
 
 		@Override
-		public MappingSet read(final MappingSet mappings) throws IOException {
-			Mappings m = net.fabricmc.mappings.MappingsProvider.readTinyMappings(stream, false);
-
+		public MappingSet read(final MappingSet mappings) {
 			for (ClassEntry entry : m.getClassEntries()) {
 				mappings.getOrCreateClassMapping(entry.get(from))
 						.setDeobfuscatedName(entry.get(to));

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

@@ -0,0 +1,53 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2016, 2017, 2018 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 net.fabricmc.mappings.*;
+import net.fabricmc.tinyremapper.IMappingProvider;
+import net.fabricmc.tinyremapper.MemberInstance;
+
+public class TinyRemapperMappingsHelper {
+	private TinyRemapperMappingsHelper() {
+
+	}
+
+	public static IMappingProvider create(Mappings mappings, String from, String to) {
+		return (classMap, fieldMap, methodMap) -> {
+			for (ClassEntry entry : mappings.getClassEntries()) {
+				classMap.put(entry.get(from), entry.get(to));
+			}
+
+			for (FieldEntry entry : mappings.getFieldEntries()) {
+				EntryTriple fromTriple = entry.get(from);
+				fieldMap.put(fromTriple.getOwner() + "/" + MemberInstance.getFieldId(fromTriple.getName(), fromTriple.getDesc()), entry.get(to).getName());
+			}
+
+			for (MethodEntry entry : mappings.getMethodEntries()) {
+				EntryTriple fromTriple = entry.get(from);
+				methodMap.put(fromTriple.getOwner() + "/" + MemberInstance.getMethodId(fromTriple.getName(), fromTriple.getDesc()), entry.get(to).getName());
+			}
+		};
+	}
+}