From 3f8b178f88081b48f94710e58e1763a55e1878f8 Mon Sep 17 00:00:00 2001
From: Lucien Greathouse <me@lpghatguy.com>
Date: Thu, 14 Nov 2019 18:18:38 -0800
Subject: [PATCH] Add support for computing property and name changes in
 hydration patch computation

---
 plugin/src/Reconciler.lua | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/plugin/src/Reconciler.lua b/plugin/src/Reconciler.lua
index 66762e0d..456ed2aa 100644
--- a/plugin/src/Reconciler.lua
+++ b/plugin/src/Reconciler.lua
@@ -9,6 +9,7 @@ local t = require(script.Parent.Parent.t)
 local InstanceMap = require(script.Parent.InstanceMap)
 local Types = require(script.Parent.Types)
 local invariant = require(script.Parent.invariant)
+local getCanonicalProperty = require(script.Parent.getCanonicalProperty)
 local setCanonicalProperty = require(script.Parent.setCanonicalProperty)
 
 --[[
@@ -287,8 +288,36 @@ function Reconciler:__hydrateInternal(apiInstances, id, instance, hydratePatch)
 		end
 	end
 
-	-- TODO: Measure differences in properties and add them to
-	-- hydratePatch.updates
+	local changedName = nil
+	local changedProperties = {}
+
+	if apiInstance.Name ~= instance.Name then
+		changedName = apiInstance.Name
+	end
+
+	for propertyName, virtualValue in pairs(apiInstance.Properties) do
+		local success, existingValue = getCanonicalProperty(instance, propertyName)
+
+		if success then
+			local decodedValue = self:__decodeApiValue(virtualValue)
+
+			if existingValue ~= decodedValue then
+				changedProperties[propertyName] = virtualValue
+			end
+		end
+	end
+
+	-- If any properties differed from the virtual instance we read, add it to
+	-- the hydrate patch so that we can catch up.
+	if changedName ~= nil or next(changedProperties) ~= nil then
+		table.insert(hydratePatch.updated, {
+			id = id,
+			changedName = changedName,
+			changedClassName = nil,
+			changedProperties = changedProperties,
+			changedMetadata = nil,
+		})
+	end
 
 	local existingChildren = instance:GetChildren()