Add support for optional tag values to Tag.Builder

Add optional tag values to data gen test
Fix data gen test not running by correcting gui_light value

src/main/java/net/minecraftforge/common/ForgeHooks.java

@@ -39,6 +39,7 @@ import com.google.common.collect.Lists;
 import com.google.common.collect.Queues;
 import com.google.common.collect.Sets;
 import com.google.gson.Gson;
+import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonParseException;
@@ -118,6 +119,7 @@ import net.minecraft.world.dimension.DimensionType;
 import net.minecraft.world.storage.loot.LootContext;
 import net.minecraft.world.storage.loot.LootTable;
 import net.minecraft.world.storage.loot.LootTableManager;
+import net.minecraftforge.common.data.IOptionalTagEntry;
 import net.minecraftforge.common.loot.IGlobalLootModifier;
 import net.minecraftforge.common.loot.LootModifierManager;
 import net.minecraftforge.common.util.BlockSnapshot;
@@ -1095,12 +1097,9 @@ public class ForgeHooks
             {
                 String s = JSONUtils.getString(entry, "value");
                 if (!s.startsWith("#"))
-                {
-                    T value = valueGetter.apply(new ResourceLocation(s)).orElse(null);
-                    if (value != null)
-                        builder.add(value);
-                } else
-                    builder.add(new OptionalTagEntry<>(new ResourceLocation(s.substring(1))));
+                    builder.addOptional(valueGetter, Collections.singleton(new ResourceLocation(s)));
+                else
+                    builder.addOptionalTag(new ResourceLocation(s.substring(1)));
             }
         }
 
@@ -1114,7 +1113,7 @@ public class ForgeHooks
                     T value = valueGetter.apply(new ResourceLocation(s)).orElse(null);
                     if (value != null)
                     {
-                        Tag.ITagEntry<T> dummyEntry = new Tag.ListEntry<>(Collections.singletonList(value));
+                        Tag.ITagEntry<T> dummyEntry = new Tag.ListEntry<>(Collections.singleton(value));
                         builder.remove(dummyEntry);
                     }
                 } else
@@ -1126,35 +1125,6 @@ public class ForgeHooks
         }
     }
 
-    private static class OptionalTagEntry<T> extends Tag.TagEntry<T>
-    {
-        private Tag<T> resolvedTag = null;
-
-        OptionalTagEntry(ResourceLocation referent)
-        {
-            super(referent);
-        }
-
-        @Override
-        public boolean resolve(@Nonnull Function<ResourceLocation, Tag<T>> resolver)
-        {
-            if (this.resolvedTag == null)
-            {
-                this.resolvedTag = resolver.apply(this.getSerializedId());
-            }
-            return true; // never fail if resolver returns null
-        }
-
-        @Override
-        public void populate(@Nonnull Collection<T> items)
-        {
-            if (this.resolvedTag != null)
-            {
-                items.addAll(this.resolvedTag.getAllElements());
-            }
-        }
-    }
-
     private static final Map<IDataSerializer<?>, DataSerializerEntry> serializerEntries = GameData.getSerializerMap();
     //private static final ForgeRegistry<DataSerializerEntry> serializerRegistry = (ForgeRegistry<DataSerializerEntry>) ForgeRegistries.DATA_SERIALIZERS;
     // Do not reimplement this ^ it introduces a chicken-egg scenario by classloading registries during bootstrap

src/main/java/net/minecraftforge/common/data/IOptionalTagEntry.java

@@ -0,0 +1,8 @@
+package net.minecraftforge.common.data;
+
+import net.minecraft.tags.Tag.ITagEntry;
+
+public interface IOptionalTagEntry<T> extends ITagEntry<T>
+{
+
+}

src/main/java/net/minecraftforge/common/extensions/IForgeTagBuilder.java

@@ -0,0 +1,85 @@
+package net.minecraftforge.common.extensions;
+
+import java.util.Collection;
+import java.util.Optional;
+import java.util.function.Function;
+
+import javax.annotation.Nonnull;
+
+import com.google.gson.JsonArray;
+
+import net.minecraft.tags.Tag;
+import net.minecraft.util.ResourceLocation;
+import net.minecraftforge.common.data.IOptionalTagEntry;
+
+public interface IForgeTagBuilder<T>
+{    
+    default Tag.Builder<T> addOptional(Function<ResourceLocation, Optional<T>> valueGetter, Collection<ResourceLocation> locations)
+    {
+        return ((Tag.Builder<T>)this).add(new OptionalListEntry<>(locations, valueGetter));
+    }
+
+    default Tag.Builder<T> addOptionalTag(ResourceLocation tag)
+    {
+        return ((Tag.Builder<T>)this).add(new OptionalTagEntry<>(tag));
+    }
+}
+
+class OptionalListEntry<T> implements IOptionalTagEntry<T>
+{
+    private final Collection<ResourceLocation> names;
+    private final Function<ResourceLocation, Optional<T>> valueGetter;
+
+    OptionalListEntry(Collection<ResourceLocation> names, Function<ResourceLocation, Optional<T>> valueGetter)
+    {
+        this.names = names;
+        this.valueGetter = valueGetter;
+    }
+
+    @Override
+    public void populate(Collection<T> itemsIn)
+    {
+        for (ResourceLocation rl : names)
+        {
+            valueGetter.apply(rl).ifPresent(itemsIn::add);
+        }
+    }
+
+    @Override
+    public void serialize(JsonArray array, Function<T, ResourceLocation> getNameForObject)
+    {
+        for (ResourceLocation rl : names)
+        {
+            array.add(rl.toString());
+        }
+    }
+}
+
+class OptionalTagEntry<T> extends Tag.TagEntry<T> implements IOptionalTagEntry<T>
+{
+    private Tag<T> resolvedTag = null;
+
+    OptionalTagEntry(ResourceLocation referent)
+    {
+        super(referent);
+    }
+
+    @Override
+    public boolean resolve(@Nonnull Function<ResourceLocation, Tag<T>> resolver)
+    {
+        if (this.resolvedTag == null)
+        {
+            this.resolvedTag = resolver.apply(this.getSerializedId());
+        }
+        return true; // never fail if resolver returns null
+    }
+
+    @Override
+    public void populate(@Nonnull Collection<T> items)
+    {
+        if (this.resolvedTag != null)
+        {
+            items.addAll(this.resolvedTag.getAllElements());
+        }
+    }
+}

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

@@ -24,7 +24,6 @@ import com.mojang.blaze3d.systems.RenderSystem;
 
 import net.minecraft.client.MainWindow;
 import net.minecraft.client.Minecraft;
-import net.minecraft.client.gui.AbstractGui;
 import net.minecraft.util.math.MathHelper;
 import net.minecraftforge.fml.loading.progress.StartupMessageManager;
 import org.apache.commons.lang3.tuple.Pair;