Some tweaks to get the launcher working.

src/main/java/net/minecraftforge/client/extensions/IForgeKeybinding.java

@@ -1,3 +1,22 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2018.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
 package net.minecraftforge.client.extensions;
 
 import javax.annotation.Nonnull;

src/main/java/net/minecraftforge/fml/loading/DefaultModInfos.java

@@ -23,10 +23,15 @@ import com.electronwill.nightconfig.core.file.FileConfig;
 import net.minecraftforge.fml.language.IModInfo;
 import net.minecraftforge.fml.loading.moddiscovery.ModInfo;
 
+import java.io.IOException;
+import java.net.URI;
 import java.net.URISyntaxException;
+import java.nio.file.FileSystems;
 import java.nio.file.Paths;
 import java.util.Arrays;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Objects;
 
 public class DefaultModInfos
 {
@@ -35,12 +40,17 @@ public class DefaultModInfos
         FileConfig forgemod;
         try
         {
-            minecraftmod = FileConfig.of(Paths.get(DefaultModInfos.class.getClassLoader().getResource("minecraftmod.toml").toURI()));
+            final URI jarFileURI = DefaultModInfos.class.getClassLoader().getResource("minecraftmod.toml").toURI();
+            if (Objects.equals(jarFileURI.getScheme(), "jar")) {
+                // Initialize the filesystem for the forge jar, because otherwise this barfs?
+                FileSystems.newFileSystem(jarFileURI, new HashMap<>());
+            }
+            minecraftmod = FileConfig.of(Paths.get(jarFileURI));
             forgemod = FileConfig.of(Paths.get(DefaultModInfos.class.getClassLoader().getResource("forgemod.toml").toURI()));
             minecraftmod.load();
             forgemod.load();
         }
-        catch (URISyntaxException | NullPointerException e)
+        catch (IOException | URISyntaxException | NullPointerException e)
         {
             throw new RuntimeException("Missing toml configs for minecraft and forge!", e);
         }

src/main/java/net/minecraftforge/fml/loading/FMLClientLaunchProvider.java

@@ -23,11 +23,32 @@ import cpw.mods.modlauncher.api.ILaunchHandlerService;
 import cpw.mods.modlauncher.api.ITransformingClassLoader;
 import net.minecraftforge.api.distmarker.Dist;
 
+import java.net.URISyntaxException;
 import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Arrays;
+import java.util.List;
 import java.util.concurrent.Callable;
 
 public class FMLClientLaunchProvider extends FMLCommonLaunchHandler implements ILaunchHandlerService
 {
+    private static final Path forgePath;
+    private static final Path mcPath;
+    private static final List<String> SKIPPACKAGES = Arrays.asList(
+            "joptsimple.", "org.lwjgl.", "com.mojang.", "com.google.",
+            "org.apache.commons.", "io.netty.", "net.minecraftforge.fml.loading.", "net.minecraftforge.fml.language.",
+            "net.minecraftforge.eventbus.", "it.unimi.dsi.fastutil.", "net.minecraftforge.api.",
+            "paulscode.sound.", "com.ibm.icu.", "sun.", "gnu.trove.", "com.electronwill.nightconfig.",
+            "net.minecraftforge.fml.common.versioning."
+    );
+    static {
+        try {
+            forgePath = Paths.get(FMLClientLaunchProvider.class.getProtectionDomain().getCodeSource().getLocation().toURI());
+            mcPath = forgePath.resolveSibling("minecraft.jar");
+        } catch (URISyntaxException e) {
+            throw new RuntimeException("Unable to locate myself!");
+        }
+    }
     @Override
     public String name()
     {
@@ -37,13 +58,16 @@ public class FMLClientLaunchProvider extends FMLCommonLaunchHandler implements I
     @Override
     public Path[] identifyTransformationTargets()
     {
-        return new Path[0];
+        return new Path[] {mcPath, forgePath};
     }
 
     @Override
     public Callable<Void> launchService(String[] arguments, ITransformingClassLoader launchClassLoader)
     {
         return () -> {
+            super.beforeStart(launchClassLoader, forgePath);
+            launchClassLoader.addTargetPackageFilter(cn -> SKIPPACKAGES.stream().noneMatch(cn::startsWith));
+            Class.forName("net.minecraft.client.main.Main", true, launchClassLoader.getInstance()).getMethod("main", String[].class).invoke(null, (Object)arguments);
             return null;
         };
     }

src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModDiscoverer.java

@@ -27,6 +27,7 @@ import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
@@ -62,7 +63,7 @@ public class ModDiscoverer {
 
         FMLLoader.getLanguageLoadingProvider().addAdditionalLanguages(modFiles.get(ModFile.Type.LANGPROVIDER));
         BackgroundScanHandler backgroundScanHandler = new BackgroundScanHandler();
-        final List<ModFile> mods = modFiles.get(ModFile.Type.MOD);
+        final List<ModFile> mods = modFiles.getOrDefault(ModFile.Type.MOD, Collections.emptyList());
         for (Iterator<ModFile> iterator = mods.iterator(); iterator.hasNext(); )
         {
             ModFile mod = iterator.next();