fix: original asset objects are now cast during first load to avoid leaking originals where we shouldnt, #977

Author: AlmasB

fxgl/src/main/kotlin/com/almasb/fxgl/app/services/FXGLAssetLoaderService.kt

@@ -533,7 +533,7 @@ class FXGLAssetLoaderService : AssetLoaderService() {
                 cachedAssets[cacheKey] = loaded as Any
             }
 
-            loaded
+            data.cast(loaded as Any)
         } catch (e: Exception) {
             log.warning("Failed to load ${loadParams.url}", e)
             data.getDummy()
@@ -696,6 +696,12 @@ private class TextAssetLoader : AssetLoader<List<*>>(
         List::class.java,
         TEXT_DIR
 ) {
+    override fun cast(obj: Any): List<String> {
+        val list = obj as List<String>
+
+        return list.toList()
+    }
+
     override fun load(url: URL): List<String> = url.openStream().bufferedReader().readLines()
 
     override fun getDummy(): List<String> = emptyList()

fxgl/src/test/kotlin/com/almasb/fxgl/app/AssetLoaderServiceTest.kt

@@ -185,7 +185,8 @@ class AssetLoaderServiceTest {
 
         assertThat(lines.size, `is`(0))
 
-        assertTrue(assetLoader.loadText("test1.txt") === assetLoader.loadText("test1.txt"))
+        // ensure a new copy of the list is loaded so that original cannot be modified
+        assertTrue(assetLoader.loadText("test1.txt") !== assetLoader.loadText("test1.txt"))
     }
 
     @Test