Version

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@rbxts/jecs",
-	"version": "0.9.0-rc.6",
+	"version": "0.9.0-rc.7",
 	"description": "Stupidly fast Entity Component System",
 	"main": "jecs.luau",
 	"repository": {

wally.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ukendio/jecs"
-version = "0.9.0-rc.6"
+version = "0.9.0-rc.7"
 registry = "https://github.com/UpliftGames/wally-index"
 realm = "shared"
 license = "MIT"

werewitch.luau

@@ -0,0 +1,66 @@
+local jecs = require("@jecs")
+
+local world = jecs.world()
+local pair = jecs.pair
+
+local IsA = world:entity()
+
+local traits = {
+	IsA = IsA
+}
+
+world:set(IsA, jecs.OnAdd, function(component, id)
+	local second = jecs.pair_second(world, id)
+	assert(second ~= component, "circular")
+
+	local is_tag = jecs.is_tag(world, second)
+	world:added(component, function(entity, _, value)
+		if is_tag then
+			world:add(entity, second)
+		else
+			world:set(entity, second, value)
+		end
+	end)
+
+	world:removed(component, function(entity)
+		world:remove(entity, second)
+	end)
+
+	if not is_tag then
+		world:changed(component, function(entity, _, value)
+			world:set(entity, second, value)
+		end)
+	end
+
+	local r = jecs.record(world, second) :: jecs.Record
+	local archetype = r.archetype
+	if not archetype then
+		return
+	end
+	local types = archetype.types
+
+	for _, id in types do
+		if jecs.is_tag(world, id) then
+			world:add(component, id)
+		else
+			local metadata = world:get(second, id)
+			if not world:has(component, id) then
+				world:set(component, id, metadata)
+			end
+		end
+	end
+
+	-- jecs.bulk_insert(world, component, ids, values)
+end)
+
+local Witch = world:entity()
+local Werewolf = world:entity()
+
+local WereWitch = world:entity()
+world:add(WereWitch, pair(IsA, Witch))
+world:add(WereWitch, pair(IsA, Werewolf))
+
+local e = world:entity()
+world:add(e, WereWitch)
+print(world:has(e, pair(IsA, Witch))) -- false
+print(world:has(e, Witch)) -- true