Add downloadMojangMappings task

buildSrc/src/main/java/quilt/internal/constants/Extensions.java

@@ -8,4 +8,5 @@ public interface Extensions {
     String UNPICK = Constants.UNPICK_NAME;
     String GZ = "gz";
     String JSON = "json";
+    String TXT = "txt";
 }

buildSrc/src/main/java/quilt/internal/plugin/MinecraftJarsPlugin.java

@@ -12,6 +12,7 @@
 import quilt.internal.task.VersionParserConsumingTask;
 import quilt.internal.task.setup.DownloadMinecraftJarsTask;
 import quilt.internal.task.setup.DownloadMinecraftLibrariesTask;
+import quilt.internal.task.setup.DownloadMojangMappingsTask;
 import quilt.internal.task.setup.DownloadWantedVersionManifestTask;
 import quilt.internal.task.setup.ExtractServerJarTask;
 import quilt.internal.task.setup.MergeJarsTask;
@@ -98,9 +99,9 @@ protected MinecraftJarsExtension applyImpl(@NotNull Project project) {
                     downloadMinecraftJars.flatMap(DownloadMinecraftJarsTask::getServerBootstrapJar)
                 );
 
-                task.getExtractionDest().convention(
-                    this.provideMinecraftBuildFile(quiltExt.provideSuffixedMinecraftVersion("-server." + Extensions.JAR))
-                );
+                task.getExtractionDest().convention(this.provideMinecraftBuildFile(
+                    quiltExt.provideSuffixedMinecraftVersion("-server." + Extensions.JAR)
+                ));
             }
         );
 
@@ -112,9 +113,9 @@ protected MinecraftJarsExtension applyImpl(@NotNull Project project) {
 
                 task.getServerJar().convention(extractServerJar.flatMap(ExtractServerJarTask::getExtractionDest));
 
-                task.getMergedFile().convention(
-                    this.provideMinecraftBuildFile(quiltExt.provideSuffixedMinecraftVersion("-merged." + Extensions.JAR))
-                );
+                task.getMergedFile().convention(this.provideMinecraftBuildFile(
+                quiltExt.provideSuffixedMinecraftVersion("-merged." + Extensions.JAR)
+                ));
             }
         );
 
@@ -126,6 +127,20 @@ protected MinecraftJarsExtension applyImpl(@NotNull Project project) {
             }
         );
 
+        tasks.register(
+            DownloadMojangMappingsTask.DOWNLOAD_MOJANG_MAPPINGS_TASK_NAME,
+            DownloadMojangMappingsTask.class,
+            task -> {
+                task.getClientMappings().convention(
+                    this.getMinecraftBuildDir().map(dir -> dir.file("client." + Extensions.TXT))
+                );
+
+                task.getServerMappings().convention(
+                    this.getMinecraftBuildDir().map(dir -> dir.file("server." + Extensions.TXT))
+                );
+            }
+        );
+
         return project.getExtensions().create(
             MinecraftJarsExtension.NAME, MinecraftJarsExtension.class,
             new Tasks(mergeJars, downloadMinecraftLibraries)

buildSrc/src/main/java/quilt/internal/task/setup/DownloadMojangMappingsTask.java

@@ -0,0 +1,58 @@
+package quilt.internal.task.setup;
+
+import org.gradle.api.DefaultTask;
+import org.gradle.api.file.RegularFileProperty;
+import org.gradle.api.tasks.OutputFile;
+import org.gradle.api.tasks.TaskAction;
+import org.quiltmc.launchermeta.version.v1.Downloads;
+import quilt.internal.constants.Groups;
+import quilt.internal.plugin.MinecraftJarsPlugin;
+import quilt.internal.task.VersionParserConsumingTask;
+import quilt.internal.util.DownloadUtil;
+
+/**
+ * Downloads Mojang's client and server mappings for the passed {@linkplain #getVersionParser version}.
+ *
+ * @see <a href=https://minecraft.wiki/w/Obfuscation_map>Obfuscation map</a>
+ * @see MinecraftJarsPlugin MinecraftJarsPlugin's configureEach
+ */
+public abstract class DownloadMojangMappingsTask extends DefaultTask implements VersionParserConsumingTask {
+    /**
+     * {@linkplain org.gradle.api.tasks.TaskContainer#register Registered} by
+     * {@link MinecraftJarsPlugin MinecraftJarsPlugin}.
+     */
+    public static final String DOWNLOAD_MOJANG_MAPPINGS_TASK_NAME = "downloadMojangMappings";
+
+    @OutputFile
+    public abstract RegularFileProperty getClientMappings();
+
+    @OutputFile
+    public abstract RegularFileProperty getServerMappings();
+
+    public DownloadMojangMappingsTask() {
+        this.setGroup(Groups.SETUP);
+    }
+
+    @TaskAction
+    public void download() {
+        final Downloads downloads = this.getVersionParser().get().get().getDownloads();
+
+        downloads.getClientMappings().ifPresentOrElse(
+            clientMappings -> DownloadUtil.download(
+                clientMappings.getUrl(),
+                this.getClientMappings().get().getAsFile(),
+                false, this.getLogger()
+            ),
+            () -> this.getLogger().warn("No client mappings available")
+        );
+
+        downloads.getServerMappings().ifPresentOrElse(
+            serverMappings -> DownloadUtil.download(
+                serverMappings.getUrl(),
+                this.getServerMappings().get().getAsFile(),
+                false, this.getLogger()
+            ),
+            () -> this.getLogger().warn("No server mappings available")
+        );
+    }
+}