From e16e4a04e4e56070bc30c6e701db879cd31f07e3 Mon Sep 17 00:00:00 2001
From: Ukendio <ukendio@gmail.com>
Date: Mon, 15 Sep 2025 23:15:11 +0200
Subject: [PATCH] Enlist starting archetypes

---
 addons/ob.luau      |  9 +++++++++
 test/addons/ob.luau | 17 +++++++++++++++++
 test/tests.luau     |  1 -
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/addons/ob.luau b/addons/ob.luau
index eb7f0e4..6b8ecfd 100755
--- a/addons/ob.luau
+++ b/addons/ob.luau
@@ -22,6 +22,7 @@ local function observers_new<T...>(
 ): Observer<T...>
 	query:cached()
 
+
 	local world = (query :: Query<T...> & { world: World }).world
 	callback = callback
 
@@ -42,6 +43,10 @@ local function observers_new<T...>(
 
 	local entity_index = world.entity_index :: any
 
+	for _, archetype in query:archetypes() do
+		archetypes[archetype.id] = true
+	end
+
 	local function emplaced<T, a>(
 		entity: jecs.Entity<T>,
 		id: jecs.Id<a>,
@@ -132,6 +137,10 @@ local function monitors_new<T...>(query: Query<T...>): Observer<T...>
 	observer_on_delete.callback = function(archetype)
 		archetypes[archetype.id] = nil
 	end
+
+	for _, archetype in query:archetypes() do
+		archetypes[archetype.id] = true
+	end
 	local entity_index = world.entity_index :: any
 
 	local callback_added: ((jecs.Entity) -> ())?
diff --git a/test/addons/ob.luau b/test/addons/ob.luau
index aab623a..dd38dd0 100755
--- a/test/addons/ob.luau
+++ b/test/addons/ob.luau
@@ -7,6 +7,23 @@ local ob = require("@addons/ob")
 
 TEST("addons/ob", function()
 	local world = jecs.world()
+	do CASE "should match against archetypes that were already created"
+		local A = world:component()
+
+		local e1 = world:entity()
+		world:add(e1, A)
+
+		local monitor = ob.monitor(world:query(A))
+		local c = 1
+		monitor.added(function()
+			c += 1
+		end)
+
+		world:remove(e1, A)
+		world:add(e1, A)
+		CHECK(c==2)
+	end
+
 	do CASE "Should support query:without()"
 		local A = world:component()
 		local B = world:component()
diff --git a/test/tests.luau b/test/tests.luau
index b223754..528ee7f 100755
--- a/test/tests.luau
+++ b/test/tests.luau
@@ -1365,7 +1365,6 @@ TEST("world:added", function()
 	end
 
 	do CASE ""
-		local world = jecs.world()
 		local IsNearby = world:component()
 		world:set(IsNearby, jecs.Name, "IsNearby")
 		local person1, person2 = world:entity(), world:entity()