Parse null lists as empty lists instead

java/src/main/java/dev/emortal/api/liveconfigparser/adapter/NullListToEmptyFactory.java

@@ -0,0 +1,53 @@
+package dev.emortal.api.liveconfigparser.adapter;
+
+import com.google.gson.Gson;
+import com.google.gson.TypeAdapter;
+import com.google.gson.TypeAdapterFactory;
+import com.google.gson.reflect.TypeToken;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonToken;
+import com.google.gson.stream.JsonWriter;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+public final class NullListToEmptyFactory implements TypeAdapterFactory {
+    public static final NullListToEmptyFactory INSTANCE = new NullListToEmptyFactory();
+
+    private NullListToEmptyFactory() {
+    }
+
+    @Override
+    public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
+        Class<?> rawType = type.getRawType();
+
+        // Only handle List and ArrayList; let other factories handle different types
+        if (rawType != List.class && rawType != ArrayList.class) {
+            return null;
+        }
+
+        // Delegate which handles deserialization of non-null values, and serialization
+        TypeAdapter<T> delegate = gson.getDelegateAdapter(this, type);
+        return new TypeAdapter<>() {
+            @Override
+            public void write(JsonWriter out, T value) throws IOException {
+                delegate.write(out, value);
+            }
+
+            @Override
+            public T read(JsonReader in) throws IOException {
+                if (in.peek() == JsonToken.NULL) {
+                    in.nextNull();
+
+                    // Safe due to check at beginning of `create` method
+                    @SuppressWarnings("unchecked")
+                    T t = (T) new ArrayList<>();
+                    return t;
+                } else {
+                    return delegate.read(in);
+                }
+            }
+        };
+    }
+}

java/src/main/java/dev/emortal/api/liveconfigparser/configs/common/ConfigItem.java

@@ -1,7 +1,8 @@
 package dev.emortal.api.liveconfigparser.configs.common;
 
-import java.util.List;
 import org.jetbrains.annotations.NotNull;
 
+import java.util.List;
+
 public record ConfigItem(@NotNull String material, int slot, @NotNull String name, @NotNull List<String> lore) {
 }

java/src/main/java/dev/emortal/api/liveconfigparser/configs/gamemode/GameModeCollection.java

@@ -3,6 +3,7 @@
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 import dev.emortal.api.liveconfigparser.adapter.DurationAdapter;
+import dev.emortal.api.liveconfigparser.adapter.NullListToEmptyFactory;
 import dev.emortal.api.liveconfigparser.configs.ConfigCollection;
 import dev.emortal.api.liveconfigparser.parser.ConfigParser;
 import io.kubernetes.client.openapi.ApiClient;
@@ -41,6 +42,7 @@ private GameModeCollection(@NotNull Path localPath) throws IOException {
     private static final class Parser implements ConfigParser<GameModeConfig> {
         private static final Gson GSON = new GsonBuilder()
                 .registerTypeAdapter(Duration.class, new DurationAdapter().nullSafe())
+                .registerTypeAdapterFactory(NullListToEmptyFactory.INSTANCE)
                 .create();
 
         @Override