feat: fluids in datagen without compile-time existence

src/main/java/com/simibubi/create/content/processing/recipe/ProcessingRecipeBuilder.java

@@ -7,6 +7,7 @@ import java.util.function.Consumer;
 import com.google.gson.JsonArray;
 import com.google.gson.JsonObject;
 import com.simibubi.create.foundation.data.SimpleDatagenIngredient;
+import com.simibubi.create.foundation.data.recipe.DatagenFluidStack;
 import com.simibubi.create.foundation.data.recipe.Mods;
 import com.simibubi.create.foundation.fluid.FluidHelper;
 import com.simibubi.create.foundation.fluid.FluidIngredient;
@@ -129,6 +130,10 @@ public class ProcessingRecipeBuilder<T extends ProcessingRecipe<?>> {
 		return this;
 	}
 
+	public ProcessingRecipeBuilder<T> require(Mods mod, String fluid, int amount) {
+		return require(new FluidIngredient.DatagenFluidIngredient(mod.asResource(fluid), amount));
+	}
+
 	public ProcessingRecipeBuilder<T> require(Fluid fluid, int amount) {
 		return require(FluidIngredient.fromFluid(fluid, amount));
 	}
@@ -183,6 +188,10 @@ public class ProcessingRecipeBuilder<T extends ProcessingRecipe<?>> {
 		return this;
 	}
 
+	public ProcessingRecipeBuilder<T> output(Mods mod, String fluid, int amount) {
+		return output(new DatagenFluidStack(mod.asResource(fluid), amount));
+	}
+
 	public ProcessingRecipeBuilder<T> output(Fluid fluid, int amount) {
 		fluid = FluidHelper.convertToStill(fluid);
 		return output(new FluidStack(fluid, amount));

src/main/java/com/simibubi/create/foundation/data/recipe/DatagenFluidStack.java

@@ -0,0 +1,29 @@
+package com.simibubi.create.foundation.data.recipe;
+
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.material.Fluids;
+import net.minecraftforge.fluids.FluidStack;
+
+import org.jetbrains.annotations.ApiStatus;
+
+/**
+ * Used to represent fluid outputs in recipe datagen without needing the fluid to exist at runtime.
+ */
+@ApiStatus.Internal
+public final class DatagenFluidStack extends FluidStack {
+	private final ResourceLocation actualFluid;
+
+	public DatagenFluidStack(ResourceLocation fluid, int amount) {
+		// This fluid is a farce
+		super(Fluids.WATER, amount);
+		actualFluid = fluid;
+	}
+
+	/**
+	 * Supersedes the result of getFluid() for the purpose of obtaining a string representation of the fluid
+	 * @return String value of the actual fluid's ResourceLocation
+	 */
+	public String getActualFluid(){
+		return actualFluid.toString();
+	}
+}

src/main/java/com/simibubi/create/foundation/fluid/FluidHelper.java

@@ -11,6 +11,7 @@ import com.simibubi.create.content.fluids.tank.CreativeFluidTankBlockEntity;
 import com.simibubi.create.content.fluids.transfer.GenericItemEmptying;
 import com.simibubi.create.content.fluids.transfer.GenericItemFilling;
 import com.simibubi.create.foundation.blockEntity.SmartBlockEntity;
+import com.simibubi.create.foundation.data.recipe.DatagenFluidStack;
 import com.simibubi.create.foundation.utility.Pair;
 import com.simibubi.create.foundation.utility.RegisteredObjects;
 
@@ -53,11 +54,11 @@ public class FluidHelper {
 	public static boolean isLava(Fluid fluid) {
 		return convertToStill(fluid) == Fluids.LAVA;
 	}
-	
+
 	public static boolean isSame(FluidStack fluidStack, FluidStack fluidStack2) {
 		return fluidStack.getFluid() == fluidStack2.getFluid();
 	}
-	
+
 	public static boolean isSame(FluidStack fluidStack, Fluid fluid) {
 		return fluidStack.getFluid() == fluid;
 	}
@@ -133,8 +134,9 @@ public class FluidHelper {
 
 	public static JsonElement serializeFluidStack(FluidStack stack) {
 		JsonObject json = new JsonObject();
-		json.addProperty("fluid", RegisteredObjects.getKeyOrThrow(stack.getFluid())
-			.toString());
+		json.addProperty("fluid", stack instanceof DatagenFluidStack datagenFluidStack ?
+				datagenFluidStack.getActualFluid() :
+				RegisteredObjects.getKeyOrThrow(stack.getFluid()).toString());
 		json.addProperty("amount", stack.getAmount());
 		if (stack.hasTag())
 			json.addProperty("nbt", stack.getTag()

src/main/java/com/simibubi/create/foundation/fluid/FluidIngredient.java

@@ -26,6 +26,8 @@ import net.minecraft.world.level.material.Fluid;
 import net.minecraftforge.fluids.FluidStack;
 import net.minecraftforge.registries.ForgeRegistries;
 
+import org.jetbrains.annotations.ApiStatus;
+
 public abstract class FluidIngredient implements Predicate<FluidStack> {
 
 	public static final FluidIngredient EMPTY = new FluidStackIngredient();
@@ -256,4 +258,55 @@ public abstract class FluidIngredient implements Predicate<FluidStack> {
 
 	}
 
+	/**
+	 * Used to represent fluid inputs in recipe datagen without needing the fluid to exist at runtime.
+	 */
+	@ApiStatus.Internal
+	public static final class DatagenFluidIngredient extends FluidIngredient{
+
+		private final ResourceLocation fluid;
+
+        public DatagenFluidIngredient(ResourceLocation fluid, int amountRequired) {
+            this.fluid = fluid;
+			this.amountRequired = amountRequired;
+        }
+
+        @Override
+		protected boolean testInternal(FluidStack t) {
+			return false;
+		}
+
+		@Override
+		protected void readInternal(FriendlyByteBuf buffer) {
+
+		}
+
+		@Override
+		protected void writeInternal(FriendlyByteBuf buffer) {
+
+		}
+
+		@Override
+		protected void readInternal(JsonObject json) {
+
+		}
+
+		@Override
+		protected void writeInternal(JsonObject json) {
+
+		}
+
+		@Override
+		protected List<FluidStack> determineMatchingFluidStacks() {
+			return null;
+		}
+
+		@Override
+		public JsonObject serialize() {
+			JsonObject json = super.serialize();
+			json.addProperty("fluid", fluid.toString());
+			return json;
+		}
+	}
+
 }