Add extra_datagen_resources folder for runtime datagen (#484)

docs/README.md

@@ -27,6 +27,27 @@ MI can generate most of these resources for you if you ask it to.
   - This will make sure that MI will automatically load the resources generated in the previous step.
 - Profit!
 
+#### More info regarding runtime datagen
+Runtime datagen works by running the data generators during the end of MI startup.
+- It uses `modern_industrialization/runtime_datagen` to produce all the files that are automatically generated.
+  - These files include loot tables, most recipes, or material textures, for example.
+- The files that are **different** from those in the jar then get copied to `modern_industrialization/generated_resources`.
+- Finally, MI injects a hidden data and resource pack with maximum priority to load these resources into the game.
+
+Runtime datagen will only use the resources from the MI jar and the base vanilla assets.
+**It will not use any resource pack, as it runs too early.**
+
+However, files can be placed in the `modern_industrialization/extra_datagen_resources` folder if they are needed during datagen,
+and they take precedence over the files in the MI jar.
+At the moment, this only works for textures.
+Here are some examples to get you started:
+- Placing a texture in `modern_industrialization/extra_datagen_resources/assets/modern_industrialization/textures/materialsets/common/plate.png`
+  will change the texture of most plates.
+- The `datagen_texture_overrides` exists to manually override textures produced by datagen, for example specific material textures.
+  Placing a texture in `modern_industrialization/extra_datagen_resources/assets/modern_industrialization/datagen_texture_overrides/item/aluminum_plate.png`
+  will change the texture of the aluminum plate only.
+- Refer to the contents of the MI .jar for more details on the file structure.
+
 ### Adding new machines
 Refer to [ADDING_MACHINES.md](ADDING_MACHINES.md) for more information on how to add machines via KubeJS.
 

src/client/java/aztech/modern_industrialization/datagen/texture/TexturesProvider.java

@@ -41,6 +41,7 @@
 import java.io.File;
 import java.io.IOException;
 import java.nio.file.Path;
+import java.util.ArrayList;
 import java.util.List;
 import net.fabricmc.fabric.api.datagen.v1.FabricDataGenerator;
 import net.fabricmc.fabric.api.resource.ResourcePackActivationType;
@@ -63,19 +64,24 @@ public record TexturesProvider(FabricDataGenerator dataGenerator, boolean runtim
 
     @Override
     public void run(CachedOutput cache) {
-        PackResources miResources;
+        var packs = new ArrayList<PackResources>();
+
+        packs.add(new DefaultClientPackResources(ClientPackSource.BUILT_IN, new AssetIndex(new File(""), "")));
+
         if (runtimeDatagen) {
+            // MI jar
             ModContainer container = FabricLoader.getInstance().getModContainer(ModernIndustrialization.MOD_ID).get();
-            miResources = ModNioResourcePack.create(new ResourceLocation("fabric", container.getMetadata().getId()),
-                    container.getMetadata().getName(), container, null, PackType.CLIENT_RESOURCES, ResourcePackActivationType.ALWAYS_ENABLED);
+            packs.add(ModNioResourcePack.create(new ResourceLocation("fabric", container.getMetadata().getId()),
+                    container.getMetadata().getName(), container, null, PackType.CLIENT_RESOURCES, ResourcePackActivationType.ALWAYS_ENABLED));
+
+            // extra_datagen_resources folder
+            var extra = FabricLoader.getInstance().getGameDir().resolve("modern_industrialization").resolve("extra_datagen_resources");
+            packs.add(new FolderPackResources(extra.toFile()));
         } else {
             var nonGeneratedResources = dataGenerator.getOutputFolder().resolve("../../main/resources").toFile();
-            miResources = new FolderPackResources(nonGeneratedResources);
+            packs.add(new FolderPackResources(nonGeneratedResources));
         }
 
-        var packs = List.of(
-                new DefaultClientPackResources(ClientPackSource.BUILT_IN, new AssetIndex(new File(""), "")),
-                miResources);
         try (var fallbackProvider = new MultiPackResourceManager(PackType.CLIENT_RESOURCES, packs)) {
             generateTextures(cache, fallbackProvider);
         }

src/main/java/aztech/modern_industrialization/misc/runtime_datagen/RuntimeDataGen.java

@@ -47,6 +47,18 @@ public static void run(Consumer<FabricDataGenerator> config) {
 
     private static void runInner(Consumer<FabricDataGenerator> config) throws Exception {
         var miFolder = FabricLoader.getInstance().getGameDir().resolve("modern_industrialization");
+
+        // Create some relevant texture folders because I'm sure some people will forget it
+        var datagenOverridesFolder = miFolder.resolve("extra_datagen_resources");
+        Files.createDirectories(datagenOverridesFolder
+                .resolve("assets")
+                .resolve("modern_industrialization")
+                .resolve("textures"));
+        Files.createDirectories(datagenOverridesFolder
+                .resolve("assets")
+                .resolve("modern_industrialization")
+                .resolve("datagen_texture_overrides"));
+
         var dataOutput = miFolder.resolve("runtime_datagen");
 
         ModernIndustrialization.LOGGER.info("Starting MI runtime data generation");