assume migration is always to a property on the same class

Author: krakow10

rbx_binary/src/core.rs

@@ -402,13 +402,14 @@ impl<'db> PropertyDescriptors<'db> {
     }
 }
 
-/// Find both the canonical and serialized property descriptors for a given
-/// class and property name pair. These might be the same descriptor!
+/// Find the superclass which contains the specified property,
+/// extract the canonical and serialized property descriptors,
+/// and return both.
 pub fn find_property_descriptors<'db>(
     database: &'db ReflectionDatabase<'db>,
     class_descriptor: Option<&'db ClassDescriptor<'db>>,
     property_name: &str,
-) -> Option<PropertyDescriptors<'db>> {
+) -> Option<(&'db ClassDescriptor<'db>, PropertyDescriptors<'db>)> {
     // Checking the class descriptor is ugly without an optional
     // return value, and all the call sites need this precise logic.
     let class_descriptor = class_descriptor?;
@@ -425,7 +426,8 @@ pub fn find_property_descriptors<'db>(
 
     // Extract the canonical and serialized property descriptors
     // from the class and property descriptors
-    PropertyDescriptors::new(class, prop)
+    let descriptors = PropertyDescriptors::new(class, prop)?;
+    Some((class, descriptors))
 }
 
 /// Given the canonical property descriptor for a logical property along with

rbx_binary/src/deserializer/state.rs

@@ -104,7 +104,7 @@ fn find_canonical_property<'de>(
     // find_property_descriptors accepts Option<ClassDescriptor>
     let class_descriptor = database.classes.get(class_name);
     match find_property_descriptors(database, class_descriptor, prop_name) {
-        Some(descriptors) => {
+        Some((_, descriptors)) => {
             // If this descriptor is known but wasn't supposed to be
             // serialized, we should skip it.
             //

rbx_binary/src/serializer/state.rs

@@ -25,7 +25,8 @@ use rbx_reflection::{
 use crate::{
     chunk::ChunkBuilder,
     core::{
-        find_property_descriptors, RbxWriteExt, FILE_MAGIC_HEADER, FILE_SIGNATURE, FILE_VERSION,
+        find_property_descriptors, PropertyDescriptors, RbxWriteExt, FILE_MAGIC_HEADER,
+        FILE_SIGNATURE, FILE_VERSION,
     },
     types::Type,
     Serializer,
@@ -346,7 +347,7 @@ impl<'dom, 'db, W: Write> SerializerState<'dom, 'db, W> {
 
             let database = self.serializer.database;
             match find_property_descriptors(database, type_info.class_descriptor, prop_name) {
-                Some(descriptors) => {
+                Some((superclass_descriptor, descriptors)) => {
                     // For any properties that do not serialize, we can skip
                     // adding them to the set of type_infos.
                     let serialized = match descriptors.serialized {
@@ -360,11 +361,16 @@ impl<'dom, 'db, W: Write> SerializerState<'dom, 'db, W> {
                                 // information of the new property instead of the old
                                 // property, because migrated properties should not
                                 // serialize
-                                let new_descriptors = find_property_descriptors(
-                                    database,
-                                    type_info.class_descriptor,
-                                    &prop_migration.new_property_name,
-                                );
+                                //
+                                // Assume that the migration will always be
+                                // directed to a property on the same class.
+                                // This avoids re-walking the superclasses.
+                                let new_descriptors = superclass_descriptor
+                                    .properties
+                                    .get(prop_migration.new_property_name.as_str())
+                                    .and_then(|prop| {
+                                        PropertyDescriptors::new(superclass_descriptor, prop)
+                                    });
 
                                 migration = Some(prop_migration);