Add counterpart to setCanonicalProperty for reading

plugin/src/getCanonicalProperty.lua

@@ -0,0 +1,37 @@
+local RbxDom = require(script.Parent.Parent.RbxDom)
+
+--[[
+	Attempts to set a property on the given instance.
+]]
+local function getCanonincalProperty(instance, propertyName)
+	local descriptor = RbxDom.findCanonicalPropertyDescriptor(instance.ClassName, propertyName)
+
+	-- We can skip unknown properties; they're not likely reflected to Lua.
+	--
+	-- A good example of a property like this is `Model.ModelInPrimary`, which
+	-- is serialized but not reflected to Lua.
+	if descriptor == nil then
+		return false, "unknown property"
+	end
+
+	if descriptor.scriptability == "None" or descriptor.scriptability == "Write" then
+		return false, "unreadable property"
+	end
+
+	local success, err = descriptor:read(instance)
+
+	if not success then
+		-- If we don't have permission to read a property, we can chalk that up
+		-- to our database being out of date and the engine being right.
+		if err.kind == RbxDom.Error.Kind.Roblox and err.extra:find("lacking permission") then
+			return false, "permission error"
+		end
+
+		local message = ("Invalid property %s.%s: %s"):format(descriptor.className, descriptor.name, tostring(err))
+		error(message, 2)
+	end
+
+	return true
+end
+
+return getCanonincalProperty