Merge remote-tracking branch 'ALongStringOfNumbers/recipeConditions' into AE2-Omnifactory

src/main/java/appeng/core/api/definitions/ApiBlocks.java

@@ -616,7 +616,12 @@ public final class ApiBlocks implements IBlocks
 
 	private static IBlockDefinition makeStairs( String registryName, FeatureFactory registry, IBlockDefinition block )
 	{
-		return registry.block( registryName, () -> new BlockStairCommon( block.maybeBlock().get(), block.identifier() ) )
+		if( !block.maybeBlock().isPresent() )
+		{
+			return new BlockDefinition( registryName, null, null );
+		}
+
+		IBlockDefinition stairs = registry.block( registryName, () -> new BlockStairCommon( block.maybeBlock().get(), block.identifier() ) )
 				.features( AEFeature.DECORATIVE_BLOCKS )
 				.rendering( new BlockRenderingCustomizer()
 				{
@@ -629,6 +634,10 @@ public final class ApiBlocks implements IBlocks
 					}
 				} )
 				.build();
+
+		Verify.verify(stairs.maybeBlock().isPresent());
+
+		return stairs;
 	}
 
 	@Override

src/main/java/appeng/recipes/factories/conditions/PartExists.java

@@ -0,0 +1,36 @@
+package appeng.recipes.factories.conditions;
+
+import appeng.core.Api;
+import appeng.core.AppEng;
+import com.google.gson.JsonObject;
+import net.minecraft.util.JsonUtils;
+import net.minecraftforge.common.crafting.IConditionFactory;
+import net.minecraftforge.common.crafting.JsonContext;
+
+import java.util.function.BooleanSupplier;
+
+public class PartExists implements IConditionFactory {
+
+    private static final String JSON_MATERIAL_KEY = "part";
+
+    @Override
+    public BooleanSupplier parse(JsonContext jsonContext, JsonObject jsonObject )
+    {
+        final boolean result;
+
+        if( JsonUtils.isString( jsonObject, JSON_MATERIAL_KEY ) )
+        {
+            final String part = JsonUtils.getString( jsonObject, JSON_MATERIAL_KEY );
+            final Object item = Api.INSTANCE.registries().recipes().resolveItem( AppEng.MOD_ID, part );
+
+            result = item != null;
+        }
+        else
+        {
+            result = false;
+        }
+
+        return () -> result;
+
+    }
+}