Refactor encoding logic in ChangeBatcher and improve matching depth handling

- Simplified the `isReadable` condition in `encodeService` for better readability.
- Updated the `ServiceChunk` structure to conditionally include properties and references only if they exist, enhancing data efficiency.
- Introduced a `MAX_SCORING_DEPTH` constant in the matching module to limit recursion depth, improving performance and preventing potential stack overflow issues.
- Refactored the `computePairCost` and `matchChildren` functions to incorporate the new depth parameter, ensuring accurate cost calculations during matching.

These changes enhance the clarity and efficiency of the encoding and matching processes, contributing to overall performance improvements.

plugin/src/ChangeBatcher/encodeService.lua

@@ -24,8 +24,7 @@ return function(service: Instance)
 				continue
 			end
 
-			local isReadable = propertyMeta.scriptability == "ReadWrite"
-				or propertyMeta.scriptability == "Read"
+			local isReadable = propertyMeta.scriptability == "ReadWrite" or propertyMeta.scriptability == "Read"
 			local doesSerialize = propertyMeta.serialization ~= "DoesNotSerialize"
 
 			if isReadable and doesSerialize then
@@ -66,10 +65,15 @@ return function(service: Instance)
 		end
 	end
 
-	return {
+	local chunk = {
 		className = service.ClassName,
 		data = data,
-		properties = properties,
-		refs = refs,
 	}
+	if next(properties) then
+		chunk.properties = properties
+	end
+	if next(refs) then
+		chunk.refs = refs
+	end
+	return chunk
 end

plugin/src/Reconciler/matching.lua

@@ -25,6 +25,7 @@ local RbxDom = require(Packages.RbxDom)
 local trueEquals = require(script.Parent.trueEquals)
 
 local UNMATCHED_PENALTY = 10000
+local MAX_SCORING_DEPTH = 3
 
 -- ================================================================
 -- Types
@@ -341,7 +342,8 @@ local function computePairCost(
 	virtualId: string,
 	studioInstance: Instance,
 	virtualInstances: VirtualInstances,
-	bestSoFar: number
+	bestSoFar: number,
+	depth: number
 ): number
 	local vc = session.costCache[virtualId]
 	if vc then
@@ -365,7 +367,7 @@ local function computePairCost(
 	local sCache = cacheStudio(studioInstance, classKeys, vCache.extraProps, refPropNames)
 
 	local cost = countOwnDiffs(vCache, sCache, classKeys)
-	if cost >= bestSoFar then
+	if cost >= bestSoFar or depth >= MAX_SCORING_DEPTH then
 		return cost
 	end
 
@@ -378,8 +380,15 @@ local function computePairCost(
 		elseif #studioKids == 0 then
 			cost += #validVChildren * UNMATCHED_PENALTY
 		else
-			local childResult =
-				matchChildren(session, validVChildren, studioKids, virtualInstances, virtualId, studioInstance)
+			local childResult = matchChildren(
+				session,
+				validVChildren,
+				studioKids,
+				virtualInstances,
+				virtualId,
+				studioInstance,
+				depth + 1
+			)
 			cost += childResult.totalCost
 		end
 	end
@@ -400,8 +409,10 @@ matchChildren = function(
 	studioChildren: { Instance },
 	virtualInstances: VirtualInstances,
 	parentVirtualId: string?,
-	parentStudioInstance: Instance?
+	parentStudioInstance: Instance?,
+	depth: number?
 ): MatchResult
+	depth = depth or 0
 	if parentVirtualId and parentStudioInstance then
 		local pc = session.matchCache[parentVirtualId]
 		if pc then
@@ -522,7 +533,7 @@ matchChildren = function(
 				pairIdx += 1
 				local cost = countOwnDiffs(vCache, sCache, classKeys)
 
-				if cost < bestSoFar then
+				if cost < bestSoFar and depth < MAX_SCORING_DEPTH then
 					local validVChildren = vCache.validChildren
 					local studioKids = sCache.children
 
@@ -538,7 +549,8 @@ matchChildren = function(
 								studioKids,
 								virtualInstances,
 								virtualChildren[vi],
-								sCache.instance
+								sCache.instance,
+								depth + 1
 							)
 							cost += childResult.totalCost
 						end
@@ -591,7 +603,7 @@ matchChildren = function(
 
 	local totalCost = 0
 	for _, pair in ipairs(matched) do
-		totalCost += computePairCost(session, pair.virtualId, pair.studioInstance, virtualInstances, math.huge)
+		totalCost += computePairCost(session, pair.virtualId, pair.studioInstance, virtualInstances, math.huge, depth)
 	end
 	totalCost += (#unmatchedVirtual + #unmatchedStudio) * UNMATCHED_PENALTY
 

src/syncback/matching.rs

@@ -251,6 +251,7 @@ struct ScoringMatchResult {
 /// Match children by reference for scoring purposes (non-consuming).
 /// Groups by (Name, ClassName), instant-matches 1:1 groups, and scores
 /// ambiguous groups using `compute_change_count` (mutually recursive).
+#[allow(clippy::too_many_arguments)]
 fn match_children_for_scoring(
     new_children: &[Ref],
     old_children: &[Ref],

src/syncback/property_filter.rs

@@ -62,11 +62,7 @@ pub fn filter_properties_with_stats<'inst>(
         }
         if !sync_unscriptable {
             let mut current = class_data;
-            loop {
-                let data = match current {
-                    Some(d) => d,
-                    None => break,
-                };
+            while let Some(data) = current {
                 if let Some(prop_data) = data.properties.get(prop_name.as_str()) {
                     if matches!(prop_data.scriptability, Scriptability::None) {
                         return true;

tests/tests/live_syncback.rs

@@ -316,7 +316,7 @@ fn parity_multiple_services_with_properties() {
 #[test]
 fn parity_camera_not_synced() {
     let camera_child = InstanceBuilder::new("Camera").with_name("Camera");
-    let chunks = vec![make_service_chunk_full(
+    let chunks = [make_service_chunk_full(
         "Workspace",
         vec![],
         vec![("CurrentCamera", "Camera", "Camera")],
@@ -698,7 +698,7 @@ fn roundtrip_build_syncback_rebuild() {
                 .iter()
                 .map(|&r| {
                     let c = dom_a.get_by_ref(r).unwrap();
-                    (c.name.clone(), c.class.clone(), r)
+                    (c.name.clone(), c.class, r)
                 })
                 .collect();
             children_a.sort_by(|a, b| (&a.0, &a.1).cmp(&(&b.0, &b.1)));
@@ -708,7 +708,7 @@ fn roundtrip_build_syncback_rebuild() {
                 .iter()
                 .map(|&r| {
                     let c = dom_b.get_by_ref(r).unwrap();
-                    (c.name.clone(), c.class.clone(), r)
+                    (c.name.clone(), c.class, r)
                 })
                 .collect();
             children_b.sort_by(|a, b| (&a.0, &a.1).cmp(&(&b.0, &b.1)));