Give immediate and complete error messages when there is a crash during startup (#4869)

src/main/java/net/minecraftforge/fml/client/CustomModLoadingErrorDisplayException.java

@@ -21,6 +21,7 @@ package net.minecraftforge.fml.client;
 
 import net.minecraft.client.gui.FontRenderer;
 import net.minecraft.client.gui.GuiErrorScreen;
+import net.minecraft.client.gui.GuiScreen;
 import net.minecraftforge.fml.common.EnhancedRuntimeException;
 import net.minecraftforge.fml.common.IFMLHandledException;
 import net.minecraftforge.fml.relauncher.Side;
@@ -37,7 +38,7 @@ import net.minecraftforge.fml.relauncher.SideOnly;
  *
  */
 @SideOnly(Side.CLIENT)
-public abstract class CustomModLoadingErrorDisplayException extends EnhancedRuntimeException implements IFMLHandledException
+public abstract class CustomModLoadingErrorDisplayException extends EnhancedRuntimeException implements IFMLHandledException, IDisplayableError
 {
     public CustomModLoadingErrorDisplayException() {
     }
@@ -72,4 +73,10 @@ public abstract class CustomModLoadingErrorDisplayException extends EnhancedRunt
     public abstract void drawScreen(GuiErrorScreen errorScreen, FontRenderer fontRenderer, int mouseRelX, int mouseRelY, float tickTime);
 
     @Override public void printStackTrace(EnhancedRuntimeException.WrappedPrintStream s){}; // Do Nothing unless the modder wants to.
+
+    @Override
+    public final GuiScreen createGui()
+    {
+        return new GuiCustomModLoadingErrorScreen(this);
+    }
 }

src/main/java/net/minecraftforge/fml/client/FMLClientHandler.java

@@ -112,6 +112,7 @@ import net.minecraftforge.registries.GameData;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.message.FormattedMessage;
 import org.lwjgl.LWJGLUtil;
 import org.lwjgl.input.Mouse;
 import org.lwjgl.opengl.Display;
@@ -171,19 +172,13 @@ public class FMLClientHandler implements IFMLSidedHandler
 
     private DummyModContainer optifineContainer;
 
+    @Deprecated // TODO remove in 1.13. mods are referencing this to get around client-only dependencies in old Forge versions
     private MissingModsException modsMissing;
 
-    private ModSortingException modSorting;
-
     private boolean loading = true;
 
-    private WrongMinecraftVersionException wrongMC;
+    @Nullable
-
+    private IDisplayableError errorToDisplay;
-    private CustomModLoadingErrorDisplayException customError;
-
-    private DuplicateModsFoundException dupesFound;
-
-    private MultipleModsErrored multipleModsErrored;
 
     private boolean serverShouldBeKilledQuietly;
 
@@ -209,7 +204,6 @@ public class FMLClientHandler implements IFMLSidedHandler
      * @param resourcePackList The resource pack list we will populate with mods
      * @param resourceManager The resource manager
      */
-    @SuppressWarnings("unchecked")
     public void beginMinecraftLoading(Minecraft minecraft, List<IResourcePack> resourcePackList, IReloadableResourceManager resourceManager, MetadataSerializer metaSerializer)
     {
         detectOptifine();
@@ -230,30 +224,11 @@ public class FMLClientHandler implements IFMLSidedHandler
         {
             Loader.instance().loadMods(injectedModContainers);
         }
-        catch (WrongMinecraftVersionException wrong)
+        catch (WrongMinecraftVersionException | DuplicateModsFoundException | MissingModsException | ModSortingException | CustomModLoadingErrorDisplayException | MultipleModsErrored e)
         {
-            wrongMC = wrong;
+            FMLLog.log.error("An exception was thrown, the game will display an error screen and halt.", e);
-        }
+            errorToDisplay = e;
-        catch (DuplicateModsFoundException dupes)
+            MinecraftForge.EVENT_BUS.shutdown();
-        {
-            dupesFound = dupes;
-        }
-        catch (MissingModsException missing)
-        {
-            modsMissing = missing;
-        }
-        catch (ModSortingException sorting)
-        {
-            modSorting = sorting;
-        }
-        catch (CustomModLoadingErrorDisplayException custom)
-        {
-            FMLLog.log.error("A custom exception was thrown by a mod, the game will now halt", custom);
-            customError = custom;
-        }
-        catch (MultipleModsErrored multiple)
-        {
-            multipleModsErrored = multiple;
         }
         catch (LoaderException le)
         {
@@ -274,8 +249,9 @@ public class FMLClientHandler implements IFMLSidedHandler
             if (le.getCause() instanceof CustomModLoadingErrorDisplayException)
             {
                 CustomModLoadingErrorDisplayException custom = (CustomModLoadingErrorDisplayException) le.getCause();
-                FMLLog.log.error("A custom exception was thrown by a mod, the game will now halt", custom);
+                FMLLog.log.error("A custom exception was thrown by a mod, the game will display an error screen and halt.", custom);
-                customError = custom;
+                errorToDisplay = custom;
+                MinecraftForge.EVENT_BUS.shutdown();
             }
             else
             {
@@ -284,6 +260,7 @@ public class FMLClientHandler implements IFMLSidedHandler
             }
         }
 
+        @SuppressWarnings("unchecked")
         Map<String,Map<String,String>> sharedModList = (Map<String, Map<String, String>>) Launch.blackboard.get("modList");
         if (sharedModList == null)
         {
@@ -332,7 +309,7 @@ public class FMLClientHandler implements IFMLSidedHandler
 
     public boolean hasError()
     {
-        return modsMissing != null || wrongMC != null || customError != null || dupesFound != null || modSorting != null || multipleModsErrored != null;
+        return errorToDisplay != null;
     }
 
     /**
@@ -356,8 +333,9 @@ public class FMLClientHandler implements IFMLSidedHandler
             if (le.getCause() instanceof CustomModLoadingErrorDisplayException)
             {
                 CustomModLoadingErrorDisplayException custom = (CustomModLoadingErrorDisplayException) le.getCause();
-                FMLLog.log.error("A custom exception was thrown by a mod, the game will now halt", custom);
+                FMLLog.log.error("A custom exception was thrown by a mod, the game will display an error screen and halt.", custom);
-                customError = custom;
+                errorToDisplay = custom;
+                MinecraftForge.EVENT_BUS.shutdown();
             }
             else
             {
@@ -369,6 +347,7 @@ public class FMLClientHandler implements IFMLSidedHandler
         // This call is being phased out for performance reasons in 1.12,
         // but we are keeping an option here in case something needs it for a little longer.
         // See https://github.com/MinecraftForge/MinecraftForge/pull/4032
+        // TODO remove in 1.13
         if (Boolean.parseBoolean(System.getProperty("fml.reloadResourcesOnStart", "false")))
         {
             client.refreshResources();
@@ -401,7 +380,7 @@ public class FMLClientHandler implements IFMLSidedHandler
         }
         loading = false;
         client.gameSettings.loadOptions(); //Reload options to load any mod added keybindings.
-        if (customError == null)
+        if (!hasError())
             Loader.instance().loadingComplete();
         SplashProgress.finish();
     }
@@ -439,29 +418,10 @@ public class FMLClientHandler implements IFMLSidedHandler
         // re-sync TEXTURE_2D, splash screen disables it with a direct GL call
         GlStateManager.disableTexture2D();
         GlStateManager.enableTexture2D();
-        if (wrongMC != null)
+        if (errorToDisplay != null)
         {
-            showGuiScreen(new GuiWrongMinecraft(wrongMC));
+            GuiScreen errorScreen = errorToDisplay.createGui();
-        }
+            showGuiScreen(errorScreen);
-        else if (modsMissing != null)
-        {
-            showGuiScreen(new GuiModsMissing(modsMissing));
-        }
-        else if (dupesFound != null)
-        {
-            showGuiScreen(new GuiDupesFound(dupesFound));
-        }
-        else if (modSorting != null)
-        {
-            showGuiScreen(new GuiSortingProblem(modSorting));
-        }
-        else if (customError != null)
-        {
-            showGuiScreen(new GuiCustomModLoadingErrorScreen(customError));
-        }
-        else if (multipleModsErrored != null)
-        {
-            showGuiScreen(new GuiMultipleModsErrored(multipleModsErrored));
         }
         else
         {
@@ -616,6 +576,10 @@ public class FMLClientHandler implements IFMLSidedHandler
         return client.getIntegratedServer();
     }
 
+    /**
+     * TODO remove in 1.13
+     */
+    @Deprecated
     public void displayMissingMods(Object modMissingPacket)
     {
 //        showGuiScreen(new GuiModsMissingForServer(modMissingPacket));
@@ -679,7 +643,8 @@ public class FMLClientHandler implements IFMLSidedHandler
             }
             catch (Exception e)
             {
-                throw new RuntimeException("An unexpected exception occurred constructing the custom resource pack for " + container.getName(), e);
+                FormattedMessage message = new FormattedMessage("An unexpected exception occurred constructing the custom resource pack for {} ({})", container.getName(), container.getModId());
+                throw new RuntimeException(message.getFormattedMessage(), e);
             }
         }
     }
@@ -698,14 +663,6 @@ public class FMLClientHandler implements IFMLSidedHandler
     @Override
     public void serverStopped()
     {
-        // If the server crashes during startup, it might hang the client - reset the client so it can abend properly.
-        MinecraftServer server = getServer();
-
-        if (server != null && !server.serverIsInRunLoop())
-        {
-//            ObfuscationReflectionHelper.setPrivateValue(MinecraftServer.class, server, true, "field_71296"+"_Q","serverIs"+"Running");
-        }
-
         GameData.revertToFrozen();
     }
 

src/main/java/net/minecraftforge/fml/client/IDisplayableError.java

@@ -0,0 +1,11 @@
+package net.minecraftforge.fml.client;
+
+import net.minecraft.client.gui.GuiScreen;
+import net.minecraftforge.fml.relauncher.Side;
+import net.minecraftforge.fml.relauncher.SideOnly;
+
+public interface IDisplayableError
+{
+    @SideOnly(Side.CLIENT)
+    GuiScreen createGui();
+}

src/main/java/net/minecraftforge/fml/common/DuplicateModsFoundException.java

@@ -23,8 +23,14 @@ import java.io.File;
 import java.util.Map.Entry;
 
 import com.google.common.collect.SetMultimap;
+import net.minecraft.client.gui.GuiScreen;
+import net.minecraftforge.fml.client.GuiDupesFound;
+import net.minecraftforge.fml.client.IDisplayableError;
+import net.minecraftforge.fml.relauncher.Side;
+import net.minecraftforge.fml.relauncher.SideOnly;
 
-public class DuplicateModsFoundException extends LoaderException {
+public class DuplicateModsFoundException extends LoaderException implements IDisplayableError
+{
     private static final long serialVersionUID = 1L;
     public SetMultimap<ModContainer,File> dupes;
 
@@ -42,4 +48,11 @@ public class DuplicateModsFoundException extends LoaderException {
         }
         stream.println("");
     }
+
+    @Override
+    @SideOnly(Side.CLIENT)
+    public GuiScreen createGui()
+    {
+        return new GuiDupesFound(this);
+    }
 }

src/main/java/net/minecraftforge/fml/common/FMLModContainer.java

@@ -36,6 +36,7 @@ import java.util.Map;
 import java.util.Properties;
 import java.util.Set;
 
+import com.google.common.base.Throwables;
 import net.minecraftforge.common.MinecraftForge;
 import net.minecraftforge.common.config.Config;
 import net.minecraftforge.common.config.ConfigManager;
@@ -73,6 +74,7 @@ import com.google.common.collect.Maps;
 import com.google.common.collect.SetMultimap;
 import com.google.common.eventbus.EventBus;
 import com.google.common.eventbus.Subscribe;
+import org.apache.logging.log4j.message.FormattedMessage;
 
 import javax.annotation.Nullable;
 
@@ -380,8 +382,7 @@ public class FMLModContainer implements ModContainer
     }
 
     @Nullable
-    @SuppressWarnings("unchecked")
+    private Method gatherAnnotations(Class<?> clazz)
-    private Method gatherAnnotations(Class<?> clazz) throws Exception
     {
         Method factoryMethod = null;
         for (Method m : clazz.getDeclaredMethods())
@@ -393,7 +394,9 @@ public class FMLModContainer implements ModContainer
                     if (m.getParameterTypes().length == 1 && FMLEvent.class.isAssignableFrom(m.getParameterTypes()[0]))
                     {
                         m.setAccessible(true);
-                        eventMethods.put((Class<? extends FMLEvent>)m.getParameterTypes()[0], m);
+                        @SuppressWarnings("unchecked")
+                        Class<? extends FMLEvent> parameterType = (Class<? extends FMLEvent>) m.getParameterTypes()[0];
+                        eventMethods.put(parameterType, m);
                     }
                     else
                     {
@@ -421,7 +424,7 @@ public class FMLModContainer implements ModContainer
         return factoryMethod;
     }
 
-    private void processFieldAnnotations(ASMDataTable asmDataTable) throws Exception
+    private void processFieldAnnotations(ASMDataTable asmDataTable) throws IllegalAccessException
     {
         SetMultimap<String, ASMData> annotations = asmDataTable.getAnnotationsFor(this);
 
@@ -503,86 +506,110 @@ public class FMLModContainer implements ModContainer
     @Subscribe
     public void constructMod(FMLConstructionEvent event)
     {
+        BlamingTransformer.addClasses(getModId(), candidate.getClassList());
+        ModClassLoader modClassLoader = event.getModClassLoader();
         try
         {
-            BlamingTransformer.addClasses(getModId(), candidate.getClassList());
-            ModClassLoader modClassLoader = event.getModClassLoader();
             modClassLoader.addFile(source);
-            modClassLoader.clearNegativeCacheFor(candidate.getClassList());
+        }
+        catch (MalformedURLException e)
+        {
+            FormattedMessage message = new FormattedMessage("{} Failed to add file to classloader: {}", getModId(), source);
+            throw new LoaderException(message.getFormattedMessage(), e);
+        }
+        modClassLoader.clearNegativeCacheFor(candidate.getClassList());
 
-            //Only place I could think to add this...
+        //Only place I could think to add this...
-            MinecraftForge.preloadCrashClasses(event.getASMHarvestedData(), getModId(), candidate.getClassList());
+        MinecraftForge.preloadCrashClasses(event.getASMHarvestedData(), getModId(), candidate.getClassList());
 
-            Class<?> clazz = Class.forName(className, true, modClassLoader);
+        Class<?> clazz;
+        try
+        {
+            clazz = Class.forName(className, true, modClassLoader);
+        }
+        catch (ClassNotFoundException e)
+        {
+            FormattedMessage message = new FormattedMessage("{} Failed load class: {}", getModId(), className);
+            throw new LoaderException(message.getFormattedMessage(), e);
+        }
 
-            Certificate[] certificates = clazz.getProtectionDomain().getCodeSource().getCertificates();
+        Certificate[] certificates = clazz.getProtectionDomain().getCodeSource().getCertificates();
-            ImmutableList<String> certList = CertificateHelper.getFingerprints(certificates);
+        ImmutableList<String> certList = CertificateHelper.getFingerprints(certificates);
-            sourceFingerprints = ImmutableSet.copyOf(certList);
+        sourceFingerprints = ImmutableSet.copyOf(certList);
 
-            String expectedFingerprint = (String)descriptor.get("certificateFingerprint");
+        String expectedFingerprint = (String)descriptor.get("certificateFingerprint");
 
-            fingerprintNotPresent = true;
+        fingerprintNotPresent = true;
 
-            if (expectedFingerprint != null && !expectedFingerprint.isEmpty())
+        if (expectedFingerprint != null && !expectedFingerprint.isEmpty())
+        {
+            if (!sourceFingerprints.contains(expectedFingerprint))
             {
-                if (!sourceFingerprints.contains(expectedFingerprint))
+                Level warnLevel = source.isDirectory() ? Level.TRACE : Level.ERROR;
-                {
+                FMLLog.log.log(warnLevel, "The mod {} is expecting signature {} for source {}, however there is no signature matching that description", getModId(), expectedFingerprint, source.getName());
-                    Level warnLevel = Level.ERROR;
-                    if (source.isDirectory())
-                    {
-                        warnLevel = Level.TRACE;
-                    }
-                    FMLLog.log.log(warnLevel, "The mod {} is expecting signature {} for source {}, however there is no signature matching that description", getModId(), expectedFingerprint, source.getName());
-                }
-                else
-                {
-                    certificate = certificates[certList.indexOf(expectedFingerprint)];
-                    fingerprintNotPresent = false;
-                }
-            }
-
-            @SuppressWarnings("unchecked")
-            List<Map<String, Object>> props = (List<Map<String, Object>>)descriptor.get("customProperties");
-            if (props != null)
-            {
-                com.google.common.collect.ImmutableMap.Builder<String, String> builder = ImmutableMap.builder();
-                for (Map<String, Object> p : props)
-                {
-                    builder.put((String)p.get("k"), (String)p.get("v"));
-                }
-                customModProperties = builder.build();
             }
             else
             {
-                customModProperties = EMPTY_PROPERTIES;
+                certificate = certificates[certList.indexOf(expectedFingerprint)];
+                fingerprintNotPresent = false;
             }
+        }
 
-            Boolean hasDisableableFlag = (Boolean)descriptor.get("canBeDeactivated");
+        @SuppressWarnings("unchecked")
-            boolean hasReverseDepends = !event.getReverseDependencies().get(getModId()).isEmpty();
+        List<Map<String, String>> props = (List<Map<String, String>>)descriptor.get("customProperties");
-            if (hasDisableableFlag != null && hasDisableableFlag)
+        if (props != null)
+        {
+            ImmutableMap.Builder<String, String> builder = ImmutableMap.builder();
+            for (Map<String, String> p : props)
             {
-                disableability = hasReverseDepends ? Disableable.DEPENDENCIES : Disableable.YES;
+                builder.put(p.get("k"), p.get("v"));
             }
-            else
+            customModProperties = builder.build();
-            {
+        }
-                disableability = hasReverseDepends ? Disableable.DEPENDENCIES : Disableable.RESTART;
+        else
-            }
+        {
-            Method factoryMethod = gatherAnnotations(clazz);
+            customModProperties = EMPTY_PROPERTIES;
-            modInstance = getLanguageAdapter().getNewInstance(this, clazz, modClassLoader, factoryMethod);
+        }
-            NetworkRegistry.INSTANCE.register(this, clazz, (String)(descriptor.getOrDefault("acceptableRemoteVersions", null)), event.getASMHarvestedData());
-            if (fingerprintNotPresent)
-            {
-                eventBus.post(new FMLFingerprintViolationEvent(source.isDirectory(), source, ImmutableSet.copyOf(this.sourceFingerprints), expectedFingerprint));
-            }
-            ProxyInjector.inject(this, event.getASMHarvestedData(), FMLCommonHandler.instance().getSide(), getLanguageAdapter());
-            AutomaticEventSubscriber.inject(this, event.getASMHarvestedData(), FMLCommonHandler.instance().getSide());
-            ConfigManager.sync(this.getModId(), Config.Type.INSTANCE);
 
+        Boolean hasDisableableFlag = (Boolean)descriptor.get("canBeDeactivated");
+        boolean hasReverseDepends = !event.getReverseDependencies().get(getModId()).isEmpty();
+        if (hasDisableableFlag != null && hasDisableableFlag)
+        {
+            disableability = hasReverseDepends ? Disableable.DEPENDENCIES : Disableable.YES;
+        }
+        else
+        {
+            disableability = hasReverseDepends ? Disableable.DEPENDENCIES : Disableable.RESTART;
+        }
+        Method factoryMethod = gatherAnnotations(clazz);
+        ILanguageAdapter languageAdapter = getLanguageAdapter();
+        try
+        {
+            modInstance = languageAdapter.getNewInstance(this, clazz, modClassLoader, factoryMethod);
+        }
+        catch (Exception e)
+        {
+            Throwables.throwIfUnchecked(e);
+            FormattedMessage message = new FormattedMessage("{} Failed to load new mod instance.", getModId());
+            throw new LoaderException(message.getFormattedMessage(), e);
+        }
+        NetworkRegistry.INSTANCE.register(this, clazz, (String)(descriptor.getOrDefault("acceptableRemoteVersions", null)), event.getASMHarvestedData());
+        if (fingerprintNotPresent)
+        {
+            eventBus.post(new FMLFingerprintViolationEvent(source.isDirectory(), source, ImmutableSet.copyOf(this.sourceFingerprints), expectedFingerprint));
+        }
+        ProxyInjector.inject(this, event.getASMHarvestedData(), FMLCommonHandler.instance().getSide(), languageAdapter);
+        AutomaticEventSubscriber.inject(this, event.getASMHarvestedData(), FMLCommonHandler.instance().getSide());
+        ConfigManager.sync(this.getModId(), Config.Type.INSTANCE);
+
+        try
+        {
             processFieldAnnotations(event.getASMHarvestedData());
         }
-        catch (Throwable e)
+        catch (IllegalAccessException e)
         {
-            controller.errorOccurred(this, e);
+            FormattedMessage message = new FormattedMessage("{} Failed to process field annotations.", getModId());
+            throw new LoaderException(message.getFormattedMessage(), e);
         }
     }
 

src/main/java/net/minecraftforge/fml/common/LoadController.java

@@ -20,15 +20,14 @@
 package net.minecraftforge.fml.common;
 
 import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
-import java.util.Map;
-import java.util.Map.Entry;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
-import net.minecraftforge.common.MinecraftForge;
 import net.minecraftforge.common.util.TextTable;
 import net.minecraftforge.fml.common.LoaderState.ModState;
 import net.minecraftforge.fml.common.ProgressManager.ProgressBar;
@@ -39,9 +38,10 @@ import net.minecraftforge.fml.common.event.FMLPreInitializationEvent;
 import net.minecraftforge.fml.common.event.FMLStateEvent;
 import net.minecraftforge.fml.common.versioning.ArtifactVersion;
 
-import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.ThreadContext;
+import org.apache.logging.log4j.message.FormattedMessage;
 
+import com.google.common.base.Throwables;
 import com.google.common.collect.ArrayListMultimap;
 import com.google.common.collect.BiMap;
 import com.google.common.collect.ImmutableBiMap;
@@ -53,9 +53,8 @@ import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 import com.google.common.collect.Multimap;
 import com.google.common.eventbus.EventBus;
+import com.google.common.eventbus.FMLThrowingEventBus;
 import com.google.common.eventbus.Subscribe;
-import com.google.common.eventbus.SubscriberExceptionHandler;
-import com.google.common.eventbus.SubscriberExceptionContext;
 
 import javax.annotation.Nullable;
 
@@ -63,11 +62,9 @@ public class LoadController
 {
     private Loader loader;
     private EventBus masterChannel;
-    private ImmutableMap<String,EventBus> eventChannels;
+    private ImmutableMap<String, EventBus> eventChannels;
     private LoaderState state;
     private Multimap<String, ModState> modStates = ArrayListMultimap.create();
-    private Multimap<String, Throwable> errors = ArrayListMultimap.create();
-    private Map<String, String> modNames = Maps.newHashMap();
     private List<ModContainer> activeModList = Lists.newArrayList();
     private ModContainer activeContainer;
     private BiMap<ModContainer, Object> modObjectList;
@@ -76,13 +73,13 @@ public class LoadController
     public LoadController(Loader loader)
     {
         this.loader = loader;
-        this.masterChannel = new EventBus(new SubscriberExceptionHandler()
+        this.masterChannel = new FMLThrowingEventBus((exception, context) -> {
-        {
+            Throwables.throwIfUnchecked(exception);
-            @Override
+            // should not happen, but add some extra context for checked exceptions
-            public void handleException(Throwable exception, SubscriberExceptionContext context)
+            Method method = context.getSubscriberMethod();
-            {
+            String parameterNames = Stream.of(method.getParameterTypes()).map(Class::getName).collect(Collectors.joining(", "));
-                FMLLog.log.error("Could not dispatch event: {} to {}", context.getSubscriberMethod(), exception);
+            String message = "Exception thrown during LoadController." + method.getName() + '(' + parameterNames + ')';
-            }
+            throw new LoaderExceptionModCrash(message, exception);
         });
         this.masterChannel.register(this);
 
@@ -97,14 +94,12 @@ public class LoadController
         String modId = mod.getModId();
         EventBus bus = temporary.remove(modId);
         bus.post(new FMLModDisabledEvent());
-        if (errors.get(modId).isEmpty())
+        eventChannels = ImmutableMap.copyOf(temporary);
-        {
+        modStates.put(modId, ModState.DISABLED);
-            eventChannels = ImmutableMap.copyOf(temporary);
+        modObjectList.remove(mod);
-            modStates.put(modId, ModState.DISABLED);
+        activeModList.remove(mod);
-            modObjectList.remove(mod);
-            activeModList.remove(mod);
-        }
     }
+
     @Subscribe
     public void buildModList(FMLLoadEvent event)
     {
@@ -112,15 +107,7 @@ public class LoadController
 
         for (final ModContainer mod : loader.getModList())
         {
-            //Create mod logger, and make the EventBus logger a child of it.
+            EventBus bus = new FMLThrowingEventBus((exception, context) -> this.errorOccurred(mod, exception));
-            EventBus bus = new EventBus(new SubscriberExceptionHandler()
-            {
-                @Override
-                public void handleException(final Throwable exception, final SubscriberExceptionContext context)
-                {
-                    LoadController.this.errorOccurred(mod, exception);
-                }
-            });
 
             boolean isActive = mod.registerBus(bus, this);
             if (isActive)
@@ -136,7 +123,6 @@ public class LoadController
                 modStates.put(mod.getModId(), ModState.UNLOADED);
                 modStates.put(mod.getModId(), ModState.DISABLED);
             }
-            modNames.put(mod.getModId(), mod.getName());
         }
 
         eventChannels = eventBus.build();
@@ -159,13 +145,13 @@ public class LoadController
         }
 
         LoaderState oldState = state;
-        state = state.transition(!errors.isEmpty());
+        state = state.transition(false);
         if (state != desiredState)
         {
             if (!forceState)
             {
-                FMLLog.log.fatal("Fatal errors were detected during the transition from {} to {}. Loading cannot continue", oldState, desiredState);
+                FormattedMessage message = new FormattedMessage("A fatal error occurred during the state transition from {} to {}. State became {} instead. Loading cannot continue.", oldState, desiredState, state);
-                throw throwStoredErrors();
+                throw new LoaderException(message.getFormattedMessage());
             }
             else
             {
@@ -178,60 +164,11 @@ public class LoadController
     @Deprecated // TODO remove in 1.13
     public void checkErrorsAfterAvailable()
     {
-        checkErrors();
     }
 
+    @Deprecated // TODO remove in 1.13
     public void checkErrors()
     {
-        if (errors.size() > 0)
-        {
-            FMLLog.log.fatal("Fatal errors were detected during {}. Loading cannot continue.", state);
-            MinecraftForge.EVENT_BUS.shutdown();
-            state = state.transition(true);
-            throw throwStoredErrors();
-        }
-    }
-
-    private RuntimeException throwStoredErrors()
-    {
-        Entry<String, Throwable> toThrow = null;
-        StringBuilder sb = new StringBuilder();
-        printModStates(sb);
-        FMLLog.log.fatal(sb.toString());
-        if (errors.size() > 0)
-        {
-            FMLLog.log.fatal("The following problems were captured during this phase");
-            for (Entry<String, Throwable> entry : errors.entries())
-            {
-                String modId = entry.getKey();
-                String modName = modNames.get(modId);
-                Throwable error = entry.getValue();
-                FMLLog.log.error("Caught exception from {} ({})", modId, modName, error);
-                if (error instanceof IFMLHandledException)
-                {
-                    toThrow = entry;
-                }
-                else if (toThrow == null)
-                {
-                    toThrow = entry;
-                }
-            }
-        }
-
-        if (toThrow == null)
-        {
-            FMLLog.log.fatal("The ForgeModLoader state engine has become corrupted. Probably, a state was missed by and invalid modification to a base class" +
-                    "ForgeModLoader depends on. This is a critical error and not recoverable. Investigate any modifications to base classes outside of" +
-                    "ForgeModLoader, especially Optifine, to see if there are fixes available.");
-            throw new RuntimeException("The ForgeModLoader state engine is invalid");
-        }
-        else
-        {
-            String modId = toThrow.getKey();
-            String modName = modNames.get(modId);
-            String errMsg = String.format("Caught exception from %s (%s)", modName, modId);
-            throw new LoaderExceptionModCrash(errMsg, toThrow.getValue());
-        }
     }
 
     @Nullable
@@ -244,6 +181,7 @@ public class LoadController
     {
         activeContainer = container;
     }
+
     @Subscribe
     public void propogateStateMessage(FMLEvent stateEvent)
     {
@@ -263,10 +201,10 @@ public class LoadController
     private void sendEventToModContainer(FMLEvent stateEvent, ModContainer mc)
     {
         String modId = mc.getModId();
-        Collection<String> requirements =  mc.getRequirements().stream().map(ArtifactVersion::getLabel).collect(Collectors.toCollection(HashSet::new));
+        Collection<String> requirements = mc.getRequirements().stream().map(ArtifactVersion::getLabel).collect(Collectors.toCollection(HashSet::new));
         for (ArtifactVersion av : mc.getDependencies())
         {
-            if (av.getLabel()!= null && requirements.contains(av.getLabel()) && modStates.containsEntry(av.getLabel(),ModState.ERRORED))
+            if (av.getLabel() != null && requirements.contains(av.getLabel()) && modStates.containsEntry(av.getLabel(), ModState.ERRORED))
             {
                 FMLLog.log.error("Skipping event {} and marking errored mod {} since required dependency {} has errored", stateEvent.getEventType(), modId, av.getLabel());
                 modStates.put(modId, ModState.ERRORED);
@@ -283,14 +221,7 @@ public class LoadController
         activeContainer = null;
         if (stateEvent instanceof FMLStateEvent)
         {
-            if (!errors.containsKey(modId))
+            modStates.put(modId, ((FMLStateEvent) stateEvent).getModState());
-            {
-                modStates.put(modId, ((FMLStateEvent)stateEvent).getModState());
-            }
-            else
-            {
-                modStates.put(modId, ModState.ERRORED);
-            }
         }
     }
 
@@ -299,7 +230,7 @@ public class LoadController
         ImmutableBiMap.Builder<ModContainer, Object> builder = ImmutableBiMap.builder();
         for (ModContainer mc : activeModList)
         {
-            if (!mc.isImmutable() && mc.getMod()!=null)
+            if (!mc.isImmutable() && mc.getMod() != null)
             {
                 builder.put(mc, mc.getMod());
                 List<String> packages = mc.getOwnedPackages();
@@ -308,13 +239,10 @@ public class LoadController
                     packageOwners.put(pkg, mc);
                 }
             }
-            if (mc.getMod()==null && !mc.isImmutable() && state!=LoaderState.CONSTRUCTING)
+            if (mc.getMod() == null && !mc.isImmutable() && state != LoaderState.CONSTRUCTING)
             {
-                FMLLog.log.fatal("There is a severe problem with {} - it appears not to have constructed correctly", mc.getModId());
+                FormattedMessage message = new FormattedMessage("There is a severe problem with {} ({}) - it appears not to have constructed correctly", mc.getName(), mc.getModId());
-                if (state != LoaderState.CONSTRUCTING)
+                this.errorOccurred(mc, new RuntimeException(message.getFormattedMessage()));
-                {
-                    this.errorOccurred(mc, new RuntimeException());
-                }
             }
         }
         return builder.build();
@@ -322,14 +250,19 @@ public class LoadController
 
     public void errorOccurred(ModContainer modContainer, Throwable exception)
     {
+        String modId = modContainer.getModId();
+        String modName = modContainer.getName();
+        modStates.put(modId, ModState.ERRORED);
         if (exception instanceof InvocationTargetException)
         {
-            errors.put(modContainer.getModId(), exception.getCause());
+            exception = exception.getCause();
         }
-        else
+        if (exception instanceof LoaderException) // avoid wrapping loader exceptions multiple times
         {
-            errors.put(modContainer.getModId(), exception);
+            throw (LoaderException) exception;
         }
+        FormattedMessage message = new FormattedMessage("Caught exception from {} ({})", modName, modId);
+        throw new LoaderExceptionModCrash(message.getFormattedMessage(), exception);
     }
 
     public void printModStates(StringBuilder ret)
@@ -374,15 +307,16 @@ public class LoadController
 
     public void distributeStateMessage(Class<?> customEvent)
     {
+        Object eventInstance;
         try
         {
-            masterChannel.post(customEvent.newInstance());
+            eventInstance = customEvent.newInstance();
         }
-        catch (Exception e)
+        catch (InstantiationException | IllegalAccessException e)
         {
-            FMLLog.log.error("An unexpected exception", e);
+            throw new LoaderException("Failed to create new event instance for " + customEvent.getName(), e);
-            throw new LoaderException(e);
         }
+        masterChannel.post(eventInstance);
     }
 
     public BiMap<ModContainer, Object> getModObjectList()
@@ -400,8 +334,9 @@ public class LoadController
         return this.state == state;
     }
 
-    boolean hasReachedState(LoaderState state) {
+    boolean hasReachedState(LoaderState state)
-        return this.state.ordinal()>=state.ordinal() && this.state!=LoaderState.ERRORED;
+    {
+        return this.state.ordinal() >= state.ordinal() && this.state != LoaderState.ERRORED;
     }
 
     void forceState(LoaderState newState)
@@ -419,7 +354,7 @@ public class LoadController
             {
                 continue;
             }
-            String pkg = c.getName().substring(0,idx);
+            String pkg = c.getName().substring(0, idx);
             if (packageOwners.containsKey(pkg))
             {
                 return packageOwners.get(pkg).get(0);
@@ -428,6 +363,7 @@ public class LoadController
 
         return null;
     }
+
     private FMLSecurityManager accessibleManager = new FMLSecurityManager();
 
     class FMLSecurityManager extends SecurityManager

src/main/java/net/minecraftforge/fml/common/Loader.java

@@ -547,9 +547,10 @@ public class Loader
         ObjectHolderRegistry.INSTANCE.findObjectHolders(new ASMDataTable());
         modController.forceActiveContainer(containers[0]);
     }
+
     /**
      * Called from the hook to start mod loading. We trigger the
-     * {@link #identifyMods()} and Constructing, Preinitalization, and Initalization phases here. Finally,
+     * {@link #identifyMods(List)} and Constructing, Preinitalization, and Initalization phases here. Finally,
      * the mod list is frozen completely and is consider immutable from then on.
      * @param injectedModContainers containers to inject
      */
@@ -624,7 +625,6 @@ public class Loader
         ItemStackHolderInjector.INSTANCE.findHolders(discoverer.getASMTable());
         CapabilityManager.INSTANCE.injectCapabilities(discoverer.getASMTable());
         modController.distributeStateMessage(LoaderState.PREINITIALIZATION, discoverer.getASMTable(), canonicalConfigDir);
-        modController.checkErrors();
         GameData.fireRegistryEvents(rl -> !rl.equals(GameData.RECIPES));
         FMLCommonHandler.instance().fireSidedRegistryEvents();
         ObjectHolderRegistry.INSTANCE.applyObjectHolders();
@@ -750,7 +750,6 @@ public class Loader
         progressBar.step("Finishing up");
         modController.transition(LoaderState.AVAILABLE, false);
         modController.distributeStateMessage(LoaderState.AVAILABLE);
-        modController.checkErrors();
         GameData.freezeData();
         FMLLog.log.info("Forge Mod Loader has successfully loaded {} mod{}", mods.size(), mods.size() == 1 ? "" : "s");
         progressBar.step("Completing Minecraft initialization");

src/main/java/net/minecraftforge/fml/common/MissingModsException.java

@@ -28,9 +28,15 @@ import java.util.Set;
 import java.util.stream.Collectors;
 
 import com.google.common.base.Preconditions;
-import net.minecraftforge.fml.common.versioning.ArtifactVersion;
 
-public class MissingModsException extends EnhancedRuntimeException
+import net.minecraft.client.gui.GuiScreen;
+import net.minecraftforge.fml.client.GuiModsMissing;
+import net.minecraftforge.fml.client.IDisplayableError;
+import net.minecraftforge.fml.common.versioning.ArtifactVersion;
+import net.minecraftforge.fml.relauncher.Side;
+import net.minecraftforge.fml.relauncher.SideOnly;
+
+public class MissingModsException extends EnhancedRuntimeException implements IDisplayableError
 {
     private static final long serialVersionUID = 1L;
     private final String id;
@@ -101,6 +107,13 @@ public class MissingModsException extends EnhancedRuntimeException
         stream.println("");
     }
 
+    @Override
+    @SideOnly(Side.CLIENT)
+    public GuiScreen createGui()
+    {
+        return new GuiModsMissing(this);
+    }
+
     public static class MissingModInfo
     {
         private final ArtifactVersion acceptedVersion;
@@ -132,4 +145,5 @@ public class MissingModsException extends EnhancedRuntimeException
             return required;
         }
     }
+
 }

src/main/java/net/minecraftforge/fml/common/MultipleModsErrored.java

@@ -21,7 +21,13 @@ package net.minecraftforge.fml.common;
 
 import java.util.List;
 
-public class MultipleModsErrored extends EnhancedRuntimeException
+import net.minecraft.client.gui.GuiScreen;
+import net.minecraftforge.fml.client.GuiMultipleModsErrored;
+import net.minecraftforge.fml.client.IDisplayableError;
+import net.minecraftforge.fml.relauncher.Side;
+import net.minecraftforge.fml.relauncher.SideOnly;
+
+public class MultipleModsErrored extends EnhancedRuntimeException implements IDisplayableError
 {
     public final List<WrongMinecraftVersionException> wrongMinecraftExceptions;
     public final List<MissingModsException> missingModsExceptions;
@@ -31,6 +37,13 @@ public class MultipleModsErrored extends EnhancedRuntimeException
         this.missingModsExceptions = missingModsExceptions;
     }
 
+    @Override
+    @SideOnly(Side.CLIENT)
+    public GuiScreen createGui()
+    {
+        return new GuiMultipleModsErrored(this);
+    }
+
     @Override
     protected void printStackTrace(WrappedPrintStream stream)
     {

src/main/java/net/minecraftforge/fml/common/WrongMinecraftVersionException.java

@@ -19,7 +19,13 @@
 
 package net.minecraftforge.fml.common;
 
-public class WrongMinecraftVersionException extends EnhancedRuntimeException
+import net.minecraft.client.gui.GuiScreen;
+import net.minecraftforge.fml.client.GuiWrongMinecraft;
+import net.minecraftforge.fml.client.IDisplayableError;
+import net.minecraftforge.fml.relauncher.Side;
+import net.minecraftforge.fml.relauncher.SideOnly;
+
+public class WrongMinecraftVersionException extends EnhancedRuntimeException implements IDisplayableError
 {
     private static final long serialVersionUID = 1L;
     public ModContainer mod;
@@ -42,4 +48,10 @@ public class WrongMinecraftVersionException extends EnhancedRuntimeException
         stream.println("");
     }
 
+    @Override
+    @SideOnly(Side.CLIENT)
+    public GuiScreen createGui()
+    {
+        return new GuiWrongMinecraft(this);
+    }
 }

src/main/java/net/minecraftforge/fml/common/eventhandler/FMLThrowingEventBus.java

@@ -0,0 +1,52 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016.
+ *
+ * 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.fml.common.eventhandler;
+
+import com.google.common.eventbus.EventBus;
+import com.google.common.eventbus.SubscriberExceptionHandler;
+
+/**
+ * Event bus that allows exceptions thrown by the exception handler to propagate.
+ * TODO remove this in 1.13 and stop using the guava event bus
+ */
+public class FMLThrowingEventBus extends EventBus
+{
+    public FMLThrowingEventBus(final SubscriberExceptionHandler exceptionHandler)
+    {
+        super((exception, context) -> {
+            try
+            {
+                exceptionHandler.handleException(exception, context);
+            }
+            catch (final Throwable t)
+            {
+                // this is a hack to break out of the catch statement in EventBus.handleSubscriberException
+                throw new RuntimeException()
+                {
+                    @Override
+                    public String toString()
+                    {
+                        throw t;
+                    }
+                };
+            }
+        });
+    }
+}

src/main/java/net/minecraftforge/fml/common/toposort/ModSortingException.java

@@ -21,10 +21,15 @@ package net.minecraftforge.fml.common.toposort;
 
 import java.util.Set;
 
+import net.minecraft.client.gui.GuiScreen;
+import net.minecraftforge.fml.client.GuiSortingProblem;
+import net.minecraftforge.fml.client.IDisplayableError;
 import net.minecraftforge.fml.common.EnhancedRuntimeException;
 import net.minecraftforge.fml.common.ModContainer;
+import net.minecraftforge.fml.relauncher.Side;
+import net.minecraftforge.fml.relauncher.SideOnly;
 
-public class ModSortingException extends EnhancedRuntimeException
+public class ModSortingException extends EnhancedRuntimeException implements IDisplayableError
 {
     private static final long serialVersionUID = 1L;
 
@@ -76,4 +81,11 @@ public class ModSortingException extends EnhancedRuntimeException
         }
     }
 
+
+    @Override
+    @SideOnly(Side.CLIENT)
+    public GuiScreen createGui()
+    {
+        return new GuiSortingProblem(this);
+    }
 }