Merge pull request #39479 from akien-mga/classdb-default-property-unique

Object: Add usage hint to instantiate Object properties in editor

2 files changed, 18 insertions, 1 deletions

diff --git a/core/class_db.cpp b/core/class_db.cpp
index eed9ec17cb..05c9850c39 100644
--- a/core/class_db.cpp
+++ b/core/class_db.cpp
@@ -1386,7 +1386,23 @@ Variant ClassDB::class_get_default_property_value(const StringName &p_class, con
 	if (r_valid != nullptr) {
 		*r_valid = true;
 	}
-	return default_values[p_class][p_property];
+
+	Variant var = default_values[p_class][p_property];
+
+#ifdef DEBUG_ENABLED
+	// Some properties may have an instantiated Object as default value,
+	// (like Path2D's `curve` used to have), but that's not a good practice.
+	// Instead, those properties should use PROPERTY_USAGE_EDITOR_INSTANTIATE_OBJECT
+	// to be auto-instantiated when created in the editor.
+	if (var.get_type() == Variant::OBJECT) {
+		Object *obj = var.get_validated_object();
+		if (obj) {
+			WARN_PRINT(vformat("Instantiated %s used as default value for %s's \"%s\" property.", obj->get_class(), p_class, p_property));
+		}
+	}
+#endif
+
+	return var;
 }
 
 RWLock *ClassDB::lock = nullptr;
diff --git a/core/object.h b/core/object.h
index 95662f6208..5b46a0f93a 100644
--- a/core/object.h
+++ b/core/object.h
@@ -124,6 +124,7 @@ enum PropertyUsageFlags {
 	PROPERTY_USAGE_RESOURCE_NOT_PERSISTENT = 1 << 24,
 	PROPERTY_USAGE_KEYING_INCREMENTS = 1 << 25, // Used in inspector to increment property when keyed in animation player
 	PROPERTY_USAGE_DEFERRED_SET_RESOURCE = 1 << 26, // when loading, the resource for this property can be set at the end of loading
+	PROPERTY_USAGE_EDITOR_INSTANTIATE_OBJECT = 1 << 27, // For Object properties, instantiate them when creating in editor.
 
 	PROPERTY_USAGE_DEFAULT = PROPERTY_USAGE_STORAGE | PROPERTY_USAGE_EDITOR | PROPERTY_USAGE_NETWORK,
 	PROPERTY_USAGE_DEFAULT_INTL = PROPERTY_USAGE_STORAGE | PROPERTY_USAGE_EDITOR | PROPERTY_USAGE_NETWORK | PROPERTY_USAGE_INTERNATIONALIZED,