added serde(default) to Transform

crates/bevy_transform/Cargo.toml

@@ -29,6 +29,7 @@ bevy_math = { path = "../bevy_math", version = "0.19.0-dev", default-features =
   "approx",
 ] }
 approx = "0.5.1"
+ron = "0.8"
 
 [features]
 # Turning off default features leaves you with a barebones

crates/bevy_transform/src/components/transform.rs

@@ -68,6 +68,7 @@ fn assert_is_normalized(message: &str, length_squared: f32) {
 /// [transform_example]: https://github.com/bevyengine/bevy/blob/latest/examples/transforms/transform.rs
 #[derive(Debug, PartialEq, Clone, Copy)]
 #[cfg_attr(feature = "serialize", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "serialize", serde(default))]
 #[cfg_attr(
     feature = "bevy-support",
     derive(Component),
@@ -670,3 +671,82 @@ impl Mul<Vec3> for Transform {
     reflect(Serialize, Deserialize)
 )]
 pub struct TransformTreeChanged;
+
+#[cfg(all(test, feature = "serialize"))]
+mod tests {
+    use super::*;
+    use ron;
+
+    // use "serialize" feature flag for these
+
+    // make sure an empty config will serialize and deserialize properly
+    #[test]
+    fn test_empty_transform_defaults() {
+        let ron_data = "()";
+
+        let transform: Transform = ron::de::from_str(ron_data).unwrap();
+
+        assert_eq!(transform, Transform::IDENTITY);
+    }
+
+    #[test]
+    fn test_missing_rotation_and_scale() {
+        let ron_data = r#"
+        (
+            translation: (5.0, -2.0, 10.0),
+        )
+    "#;
+
+        let transform: Transform = ron::de::from_str(ron_data).unwrap();
+
+        assert_eq!(transform.translation, Vec3::new(5.0, -2.0, 10.0));
+        assert_eq!(transform.rotation, Quat::IDENTITY);
+        assert_eq!(transform.scale, Vec3::ONE);
+    }
+
+    #[test]
+    fn test_only_scale_provided() {
+        let ron_data = r#"
+        (
+            scale: (3.0, 4.0, 5.0),
+        )
+    "#;
+
+        let transform: Transform = ron::de::from_str(ron_data).unwrap();
+
+        assert_eq!(transform.translation, Vec3::ZERO);
+        assert_eq!(transform.rotation, Quat::IDENTITY);
+        assert_eq!(transform.scale, Vec3::new(3.0, 4.0, 5.0));
+    }
+
+    // round trip
+    #[test]
+    fn test_roundtrip_preserves_values() {
+        let original = Transform {
+            translation: Vec3::new(1.0, 2.0, 3.0),
+            rotation: Quat::IDENTITY,
+            scale: Vec3::splat(2.0),
+        };
+
+        let ron = ron::ser::to_string(&original).unwrap();
+        let deserialized: Transform = ron::de::from_str(&ron).unwrap();
+
+        assert_eq!(original, deserialized);
+    }
+
+    #[test]
+    fn test_partial_values_mix() {
+        let ron_data = r#"
+        (
+            translation: (9.0, 8.0, 7.0),
+            scale: (0.5, 0.5, 0.5),
+        )
+    "#;
+
+        let transform: Transform = ron::de::from_str(ron_data).unwrap();
+
+        assert_eq!(transform.translation, Vec3::new(9.0, 8.0, 7.0));
+        assert_eq!(transform.scale, Vec3::splat(0.5));
+        assert_eq!(transform.rotation, Quat::IDENTITY);
+    }
+}