two-way sync: allow changedProperties to be null to avoid array/object issues

plugin/src/ApiContext.lua

@@ -158,19 +158,35 @@ end
 function ApiContext:write(patch)
 	local url = ("%s/api/write"):format(self.__baseUrl)
 
-	local body = {
-		sessionId = self.__sessionId,
-		removed = patch.removed,
-		updated = patch.updated,
-	}
+	local updated = {}
+	for _, update in ipairs(patch.updated) do
+		local fixedUpdate = {
+			id = update.id,
+			changedName = update.changedName,
+		}
+
+		if next(update.changedProperties) ~= nil then
+			fixedUpdate.changedProperties = update.changedProperties
+		end
+
+		table.insert(updated, fixedUpdate)
+	end
 
 	-- Only add the 'added' field if the table is non-empty, or else Roblox's
 	-- JSON implementation will turn the table into an array instead of an
 	-- object, causing API validation to fail.
+	local added
 	if next(patch.added) ~= nil then
-		body.added = patch.added
+		added = patch.added
 	end
 
+	local body = {
+		sessionId = self.__sessionId,
+		removed = patch.removed,
+		updated = updated,
+		added = added,
+	}
+
 	body = Http.jsonEncode(body)
 
 	return Http.post(url, body)

src/web/interface.rs

@@ -34,8 +34,10 @@ pub struct InstanceUpdate {
     pub id: RbxId,
     pub changed_name: Option<String>,
     pub changed_class_name: Option<String>,
+
     // TODO: Transform from HashMap<String, Option<_>> to something else, since
     // null will get lost when decoding from JSON in some languages.
+    #[serde(default)]
     pub changed_properties: HashMap<String, Option<RbxValue>>,
     pub changed_metadata: Option<InstanceMetadata>,
 }