Make Loot Table data generators more reusable for modders.

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

@@ -0,0 +1,145 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2019.
+ *
+ * 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.common.data;
+
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.function.Supplier;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+
+import net.minecraft.block.Block;
+import net.minecraft.data.DataGenerator;
+import net.minecraft.data.DirectoryCache;
+import net.minecraft.data.IDataProvider;
+import net.minecraft.enchantment.Enchantment;
+import net.minecraft.entity.EntityType;
+import net.minecraft.item.Item;
+import net.minecraft.item.ItemStack;
+import net.minecraft.potion.Effect;
+import net.minecraft.world.biome.Biome;
+
+public abstract class LanguageProvider implements IDataProvider {
+    private static final Gson GSON = (new GsonBuilder()).setPrettyPrinting().disableHtmlEscaping().create();
+    private final Map<String, String> data = new TreeMap<>();
+    private final DataGenerator gen;
+    private final String modid;
+    private final String locale;
+
+    public LanguageProvider(DataGenerator gen, String modid, String locale) {
+        this.gen = gen;
+        this.modid = modid;
+        this.locale = locale;
+    }
+
+    protected abstract void addTranslations();
+
+    @Override
+    public void act(DirectoryCache cache) throws IOException {
+        addTranslations();
+        if (!data.isEmpty())
+            save(cache, data, this.gen.getOutputFolder().resolve("assets/" + modid + "/lang/" + locale + ".json"));
+    }
+
+    @Override
+    public String getName() {
+        return "Languages: " + locale;
+    }
+
+    private void save(DirectoryCache cache, Object object, Path target) throws IOException {
+        String data = GSON.toJson(object);
+        String hash = IDataProvider.HASH_FUNCTION.hashUnencodedChars(data).toString();
+        if (!Objects.equals(cache.getPreviousHash(target), hash) || !Files.exists(target)) {
+           Files.createDirectories(target.getParent());
+
+           try (BufferedWriter bufferedwriter = Files.newBufferedWriter(target)) {
+              bufferedwriter.write(data);
+           }
+        }
+
+        cache.func_208316_a(target, hash);
+    }
+
+    protected void addBlock(Supplier<Block> key, String name) {
+        add(key.get(), name);
+    }
+
+    protected void add(Block key, String name) {
+        add(key.getTranslationKey(), name);
+    }
+
+    protected void addItem(Supplier<Item> key, String name) {
+        add(key.get(), name);
+    }
+
+    protected void add(Item key, String name) {
+        add(key.getTranslationKey(), name);
+    }
+
+    protected void addItemStack(Supplier<ItemStack> key, String name) {
+        add(key.get(), name);
+    }
+
+    protected void add(ItemStack key, String name) {
+        add(key.getTranslationKey(), name);
+    }
+
+    protected void addEnchantment(Supplier<Enchantment> key, String name) {
+        add(key.get(), name);
+    }
+
+    protected void add(Enchantment key, String name) {
+        add(key.getName(), name);
+    }
+
+    protected void addBiome(Supplier<Biome> key, String name) {
+        add(key.get(), name);
+    }
+
+    protected void add(Biome key, String name) {
+        add(key.getTranslationKey(), name);
+    }
+
+    protected void addEffect(Supplier<Effect> key, String name) {
+        add(key.get(), name);
+    }
+
+    protected void add(Effect key, String name) {
+        add(key.getName(), name);
+    }
+
+    protected void addEntityType(Supplier<EntityType<?>> key, String name) {
+        add(key.get(), name);
+    }
+
+    protected void add(EntityType<?> key, String name) {
+        add(key.getTranslationKey(), name);
+    }
+
+    protected void add(String key, String value) {
+        if (data.put(key, value) != null)
+            throw new IllegalStateException("Duplicate translation key " + key);
+    }
+}

src/main/java/net/minecraftforge/registries/DeferredRegister.java

@@ -24,10 +24,13 @@ import net.minecraftforge.event.RegistryEvent;
 import net.minecraftforge.eventbus.api.IEventBus;
 import net.minecraftforge.fml.RegistryObject;
 
+import java.util.Collection;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Objects;
+import java.util.Set;
 import java.util.function.Supplier;
 
 /**
@@ -55,7 +58,8 @@ public class DeferredRegister<T extends IForgeRegistryEntry<T>>
 {
     private final IForgeRegistry<T> type;
     private final String modid;
-    private Map<RegistryObject<T>, Supplier<? extends T>> entries = new LinkedHashMap<>();
+    private final Map<RegistryObject<T>, Supplier<? extends T>> entries = new LinkedHashMap<>();
+    private final Set<RegistryObject<T>> entriesView = Collections.unmodifiableSet(entries.keySet());
 
     public DeferredRegister(IForgeRegistry<T> reg, String modid)
     {
@@ -94,6 +98,14 @@ public class DeferredRegister<T extends IForgeRegistryEntry<T>>
         bus.addListener(this::addEntries);
     }
 
+    /**
+     * @return The unmodifiable view of registered entries. Useful for bulk operations on all values.
+     */
+    public Collection<RegistryObject<T>> getEntries()
+    {
+        return entriesView;
+    }
+
     private void addEntries(RegistryEvent.Register<?> event)
     {
         if (event.getGenericType() == this.type.getRegistrySuperType())