add updateMappings task

src/main/java/net/fabricmc/loom/LoomGradlePlugin.java

@@ -64,6 +64,10 @@ public class LoomGradlePlugin extends AbstractPlugin {
 		tasks.register("cleanLoomBinaries", CleanLoomBinaries.class);
 		tasks.register("cleanLoomMappings", CleanLoomMappings.class);
 
+		tasks.register("updateMappings", UpdateMappingsTask.class, t -> {
+			t.getOutputs().upToDateWhen((o) -> false);
+		});
+
 		tasks.register("remapJar", RemapJar.class);
 
 		tasks.register("genSourcesDecompile", FernFlowerTask.class, t -> {

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

@@ -30,7 +30,7 @@ import org.gradle.api.tasks.OutputFile;
 
 import java.io.File;
 
-public abstract class AbstractDecompileTask extends DefaultLoomTask {
+public abstract class AbstractDecompileTask extends AbstractLoomTask {
     private Object input;
     private Object output;
     private Object lineMapFile;

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

@@ -26,9 +26,9 @@ package net.fabricmc.loom.task;
 
 import org.gradle.api.DefaultTask;
 
-public abstract class DefaultLoomTask extends DefaultTask {
+public abstract class AbstractLoomTask extends DefaultTask {
 
-	public DefaultLoomTask() {
+	public AbstractLoomTask() {
 		setGroup("fabric");
 	}
 

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

@@ -39,11 +39,11 @@ import java.util.Collections;
 import java.util.List;
 import java.util.function.Function;
 
-public abstract class RunTaskBase extends JavaExec {
+public abstract class AbstractRunTask extends JavaExec {
     private final Function<Project, RunConfig> configProvider;
     private RunConfig config;
 
-    public RunTaskBase(Function<Project, RunConfig> config) {
+    public AbstractRunTask(Function<Project, RunConfig> config) {
         super();
         setGroup("fabric");
         this.configProvider = config;

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

@@ -28,7 +28,7 @@ import net.fabricmc.loom.LoomGradleExtension;
 import org.gradle.api.Project;
 import org.gradle.api.tasks.TaskAction;
 
-public class CleanLoomBinaries extends DefaultLoomTask {
+public class CleanLoomBinaries extends AbstractLoomTask {
     @TaskAction
     public void run() {
         Project project = this.getProject();

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

@@ -32,7 +32,7 @@ import org.gradle.api.tasks.TaskAction;
 import java.io.IOException;
 import java.nio.file.Files;
 
-public class CleanLoomMappings extends DefaultLoomTask {
+public class CleanLoomMappings extends AbstractLoomTask {
     @TaskAction
     public void run() {
         Project project = this.getProject();

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

@@ -31,7 +31,7 @@ import org.gradle.api.tasks.TaskAction;
 
 import java.io.IOException;
 
-public class DownloadAssetsTask extends DefaultLoomTask {
+public class DownloadAssetsTask extends AbstractLoomTask {
 	@TaskAction
 	public void downloadAssets() throws IOException {
 		Project project = this.getProject();

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

@@ -33,7 +33,7 @@ import java.io.File;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 
-public class GenEclipseRunsTask extends DefaultLoomTask {
+public class GenEclipseRunsTask extends AbstractLoomTask {
 
     @TaskAction
     public void genRuns() throws IOException {

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

@@ -46,7 +46,7 @@ import javax.xml.transform.stream.StreamResult;
 import java.io.File;
 import java.io.IOException;
 
-public class GenIdeaProjectTask extends DefaultLoomTask {
+public class GenIdeaProjectTask extends AbstractLoomTask {
 
 	@TaskAction
 	public void genIdeaRuns() throws IOException, ParserConfigurationException, SAXException, TransformerException {

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

@@ -41,7 +41,7 @@ import java.util.List;
 // https://marketplace.visualstudio.com/items?itemName=redhat.java
 // https://marketplace.visualstudio.com/items?itemName=vscjava.vscode-java-debug
 // https://marketplace.visualstudio.com/items?itemName=vscjava.vscode-java-pack
-public class GenVsCodeProjectTask extends DefaultLoomTask {
+public class GenVsCodeProjectTask extends AbstractLoomTask {
 
     @TaskAction
     public void genRuns() {

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

@@ -33,7 +33,7 @@ import org.gradle.api.tasks.TaskAction;
 import java.io.File;
 import java.io.IOException;
 
-public class RemapJar extends DefaultLoomTask {
+public class RemapJar extends AbstractLoomTask {
 	public File jar;
 	public File destination;
 	public boolean nestJar = true;

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

@@ -29,7 +29,6 @@ import net.fabricmc.loom.util.LineNumberRemapper;
 import net.fabricmc.loom.util.progress.ProgressLogger;
 import net.fabricmc.stitch.util.StitchUtil;
 import org.gradle.api.Project;
-import org.gradle.api.file.FileCollection;
 import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.InputFile;
 import org.gradle.api.tasks.OutputFile;
@@ -37,10 +36,8 @@ import org.gradle.api.tasks.TaskAction;
 
 import java.io.File;
 import java.io.IOException;
-import java.nio.file.Files;
-import java.nio.file.Path;
 
-public class RemapLineNumbersTask extends DefaultLoomTask {
+public class RemapLineNumbersTask extends AbstractLoomTask {
     private Object input;
     private Object output;
     private Object lineMapFile;

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

@@ -31,7 +31,7 @@ import org.gradle.api.tasks.TaskAction;
 
 import java.io.File;
 
-public class RemapSourcesJar extends DefaultLoomTask {
+public class RemapSourcesJar extends AbstractLoomTask {
 	public File jar;
 	public File destinationJar;
 	public String direction = "intermediary";

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

@@ -24,19 +24,9 @@
 
 package net.fabricmc.loom.task;
 
-import net.fabricmc.loom.LoomGradleExtension;
-import net.fabricmc.loom.providers.MappingsProvider;
-import net.fabricmc.loom.util.Constants;
-import net.fabricmc.loom.util.MinecraftVersionInfo;
-import net.fabricmc.loom.util.OperatingSystem;
 import net.fabricmc.loom.util.RunConfig;
-import org.gradle.api.tasks.JavaExec;
 
-import java.io.File;
+public class RunClientTask extends AbstractRunTask {
-import java.util.ArrayList;
-import java.util.List;
-
-public class RunClientTask extends RunTaskBase {
 	public RunClientTask() {
 		super(RunConfig::clientRunConfig);
 	}

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

@@ -24,16 +24,9 @@
 
 package net.fabricmc.loom.task;
 
-import net.fabricmc.loom.LoomGradleExtension;
-import net.fabricmc.loom.util.Constants;
 import net.fabricmc.loom.util.RunConfig;
-import org.gradle.api.tasks.JavaExec;
 
-import java.io.File;
+public class RunServerTask extends AbstractRunTask {
-import java.util.ArrayList;
-import java.util.List;
-
-public class RunServerTask extends RunTaskBase {
 	public RunServerTask() {
 		super(RunConfig::serverRunConfig);
 	}

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

@@ -0,0 +1,145 @@
+/*
+ * 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.task;
+
+import net.fabricmc.loom.LoomGradleExtension;
+import net.fabricmc.loom.util.Constants;
+import net.fabricmc.mappings.*;
+import org.cadixdev.lorenz.MappingSet;
+import org.cadixdev.lorenz.io.MappingsReader;
+import org.cadixdev.mercury.Mercury;
+import org.cadixdev.mercury.remapper.MercuryRemapper;
+import org.gradle.api.Project;
+import org.gradle.api.tasks.TaskAction;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+
+public class UpdateMappingsTask extends AbstractLoomTask {
+    @TaskAction
+    public void doTask() throws Throwable {
+        Project project = getProject();
+        LoomGradleExtension extension = project.getExtensions().getByType(LoomGradleExtension.class);
+
+        project.getLogger().lifecycle(":loading mappings");
+
+        File mappingsFile = new File((String) project.getProperties().get("targetMappingsFile"));
+        File inputDir = new File((String) project.getProperties().get("inputDir"));
+        File outputDir = new File((String) project.getProperties().get("outputDir"));
+
+        Mappings sourceMappings = extension.getMappingsProvider().getMappings();
+        Mappings targetMappings;
+
+        try (FileInputStream stream = new FileInputStream(mappingsFile)) {
+            targetMappings = net.fabricmc.mappings.MappingsProvider.readTinyMappings(stream, false);
+        }
+
+        project.getLogger().lifecycle(":joining mappings");
+        MappingSet mappingSet = new MappingsJoiner(sourceMappings, targetMappings, "intermediary", "named").read();
+
+        project.getLogger().lifecycle(":remapping");
+        Mercury mercury = new Mercury();
+
+        for (File file : project.getConfigurations().getByName(Constants.MINECRAFT_DEPENDENCIES).getFiles()) {
+            mercury.getClassPath().add(file.toPath());
+        }
+
+        for (File file : project.getConfigurations().getByName(Constants.COMPILE_MODS_MAPPED).getFiles()) {
+            mercury.getClassPath().add(file.toPath());
+        }
+
+        mercury.getClassPath().add(extension.getMinecraftMappedProvider().MINECRAFT_MAPPED_JAR.toPath());
+        mercury.getClassPath().add(extension.getMinecraftMappedProvider().MINECRAFT_INTERMEDIARY_JAR.toPath());
+
+        mercury.getProcessors().add(MercuryRemapper.create(mappingSet));
+
+        try {
+            mercury.rewrite(inputDir.toPath(), outputDir.toPath());
+        } catch (Exception e) {
+            project.getLogger().warn("Could not remap fully!", e);
+        }
+
+        project.getLogger().lifecycle(":cleaning file descriptors");
+        System.gc();
+    }
+
+    public static class MappingsJoiner extends MappingsReader {
+        private final Mappings sourceMappings, targetMappings;
+        private final String fromNamespace, toNamespace;
+
+        public MappingsJoiner(Mappings sourceMappings, Mappings targetMappings, String fromNamespace, String toNamespace) {
+            this.sourceMappings = sourceMappings;
+            this.targetMappings = targetMappings;
+            this.fromNamespace = fromNamespace;
+            this.toNamespace = toNamespace;
+        }
+
+        @Override
+        public MappingSet read(MappingSet mappings) throws IOException {
+            Map<String, ClassEntry> targetClasses = new HashMap<>();
+            Map<EntryTriple, FieldEntry> targetFields = new HashMap<>();
+            Map<EntryTriple, MethodEntry> targetMethods = new HashMap<>();
+
+            targetMappings.getClassEntries().forEach((c) -> targetClasses.put(c.get(fromNamespace), c));
+            targetMappings.getFieldEntries().forEach((c) -> targetFields.put(c.get(fromNamespace), c));
+            targetMappings.getMethodEntries().forEach((c) -> targetMethods.put(c.get(fromNamespace), c));
+
+            for (ClassEntry entry : sourceMappings.getClassEntries()) {
+                String from = entry.get(toNamespace);
+                String to = targetClasses.getOrDefault(entry.get(fromNamespace), entry).get(toNamespace);
+
+                mappings.getOrCreateClassMapping(from).setDeobfuscatedName(to);
+            }
+
+            for (FieldEntry entry : sourceMappings.getFieldEntries()) {
+                EntryTriple fromEntry = entry.get(toNamespace);
+                EntryTriple toEntry = targetFields.getOrDefault(entry.get(fromNamespace), entry).get(toNamespace);
+
+                mappings.getOrCreateClassMapping(fromEntry.getOwner())
+                        .getOrCreateFieldMapping(fromEntry.getName(), fromEntry.getDesc())
+                        .setDeobfuscatedName(toEntry.getName());
+            }
+
+            for (MethodEntry entry : sourceMappings.getMethodEntries()) {
+                EntryTriple fromEntry = entry.get(toNamespace);
+                EntryTriple toEntry = targetMethods.getOrDefault(entry.get(fromNamespace), entry).get(toNamespace);
+
+                mappings.getOrCreateClassMapping(fromEntry.getOwner())
+                        .getOrCreateMethodMapping(fromEntry.getName(), fromEntry.getDesc())
+                        .setDeobfuscatedName(toEntry.getName());
+            }
+
+            return mappings;
+        }
+
+        @Override
+        public void close() throws IOException {
+
+        }
+    }
+}