.github/workflows/release.yaml

@@ -1,95 +1,92 @@
 name: release
 
 on:
-  push:
+    push:
-    tags:
+        tags: ["v*", "workflow_dispatch"]
-      - "v*"
-  workflow_dispatch:
 
 permissions:
-  id-token: write
+    id-token: write
-  contents: write
+    contents: read
 
 jobs:
-  build:
+    build:
-    name: Build
+        name: Build
-    runs-on: ubuntu-latest
+        runs-on: ubuntu-latest
-    steps:
+        steps:
-      - name: Checkout Project
+            - name: Checkout Project
-        uses: actions/checkout@v4
+              uses: actions/checkout@v4
 
-      - name: Install Rokit
+            - name: Install Rokit
-        uses: CompeyDev/setup-rokit@v0.1.2
+              uses: CompeyDev/setup-rokit@v0.1.2
 
-      - name: Install Dependencies
+            - name: Install Dependencies
-        run: wally install
+              run: wally install
 
-      - name: Build
+            - name: Build
-        run: rojo build --output build.rbxm default.project.json
+              run: rojo build --output build.rbxm default.project.json
 
-      - name: Upload Build Artifact
+            - name: Upload Build Artifact
-        uses: actions/upload-artifact@v4
+              uses: actions/upload-artifact@v4
-        with:
+              with:
-          name: build
+                  name: build
-          path: build.rbxm
+                  path: build.rbxm
 
-  release:
+    release:
-    name: Release
+        name: Release
-    needs: build
+        needs: [build]
-    runs-on: ubuntu-latest
+        runs-on: ubuntu-latest
-    steps:
+        permissions:
-      - name: Checkout Project
+            contents: write
-        uses: actions/checkout@v4
+        steps:
+            - name: Checkout Project
+              uses: actions/checkout@v4
 
-      - name: Download Build
+            - name: Download Jecs Build
-        uses: actions/download-artifact@v4
+              uses: actions/download-artifact@v4
-        with:
+              with:
-          name: build
+                  name: build
-          path: build
+                  path: build
 
-      - name: Rename Build
+            - name: Rename Build
-        run: mv build/build.rbxm jecs.rbxm
+              run: mv build/build.rbxm jecs.rbxm
 
-      - name: Create Release
+            - name: Create Release
-        uses: softprops/action-gh-release@v1
+              uses: softprops/action-gh-release@v1
-        with:
+              with:
-          name: Jecs ${{ github.ref_name }}
+                  name: Jecs ${{ github.ref_name }}
-          tag_name: ${{ github.ref_name }}
+                  files: |
-          files: jecs.rbxm
+                      jecs.rbxm
 
-  publish-wally:
+    publish-wally:
-    name: Publish to Wally
+        name: Publish to Wally
-    needs: release
+        needs: [release]
-    runs-on: ubuntu-latest
+        runs-on: ubuntu-latest
-    steps:
+        steps:
-      - name: Checkout Project
+            - name: Checkout Project
-        uses: actions/checkout@v4
+              uses: actions/checkout@v4
 
-      - name: Install Rokit
+            - name: Install Rokit
-        uses: CompeyDev/setup-rokit@v0.1.2
+              uses: CompeyDev/setup-rokit@v0.1.2
 
-      - name: Wally Login
+            - name: Wally Login
-        run: wally login --token ${{ secrets.WALLY_AUTH_TOKEN }}
+              run: wally login --token ${{ secrets.WALLY_AUTH_TOKEN }}
 
-      - name: Publish
+            - name: Publish
-        run: wally publish
+              run: wally publish
 
-  publish-npm:
+    publish-npm:
-    name: Publish to NPM
+        name: Publish to NPM
-    needs: release
+        needs: [release]
-    runs-on: ubuntu-latest
+        runs-on: ubuntu-latest
-    steps:
+        steps:
-      - name: Checkout Project
+            - name: Checkout Project
-        uses: actions/checkout@v4
+              uses: actions/checkout@v4
 
-      - name: Setup Node
+            - name: Setup Node
-        uses: actions/setup-node@v4
+              uses: actions/setup-node@v4
-        with:
+              with:
-          node-version: "24"
+                  node-version: "24"
-          registry-url: "https://registry.npmjs.org"
+                  registry-url: "https://registry.npmjs.org"
 
-      - name: Install
+            - run: npm install
-        run: npm install
+            - run: npm publish
-
-      - name: Publish
-        run: npm publish

examples/networking/networking_recv.luau

@@ -48,6 +48,7 @@ end
 
 -- 	rel = ecs_ensure_entity(world, rel)
 -- 
+-- 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
 -- 	tgt = ecs_ensure_entity(world, tgt)
 
 -- 	return jecs.pair(rel, tgt)

how_to/999_temperance.luau

@@ -19,7 +19,7 @@ about the code base is lost, ability to work on it at the same level of quality
 is lost. Over time code quality will decline as code size grows.
 
 - Tacit knowledge is very hard to recover by looking at a maze of code,
-and it takes a long time to do so.
+and it takes
 
 - You will often hear that "every semantic distinction deserves its own
 component or tag". Sometimes this is correct. A well chosen component boundary

modules/OB/module.luau

@@ -193,6 +193,7 @@ local function monitors_new(query: jecs.Query<...any>): Monitor
 		if not r then return end
 
 		local src = r.archetype
+		if not src then return end
 
 		if not archetypes[src.id] then return end
 
@@ -286,6 +287,9 @@ local function monitors_new(query: jecs.Query<...any>): Monitor
 					end
 					local r = jecs.record(world, entity)
 					local archetype = r.archetype
+					if not archetype then
+						return
+					end
 
 					if archetypes[oldarchetype.id] and not archetypes[archetype.id] then
 						last_old_archetype = nil
@@ -305,6 +309,9 @@ local function monitors_new(query: jecs.Query<...any>): Monitor
 
 					local r = jecs.record(world, entity)
 					local archetype = r.archetype
+					if not archetype then
+						return
+					end
 					if last_old_archetype == archetype then
 						return
 					end
@@ -325,6 +332,9 @@ local function monitors_new(query: jecs.Query<...any>): Monitor
 					end
 					local r = jecs.record(world, entity)
 					local archetype = r.archetype
+					if not archetype then
+						return
+					end
 
 					if archetypes[oldarchetype.id] and not archetypes[archetype.id] then
 						callback_removed(entity)
@@ -339,6 +349,9 @@ local function monitors_new(query: jecs.Query<...any>): Monitor
 					end
 					local r = jecs.record(world, entity)
 					local archetype = r.archetype
+					if not archetype then
+						return
+					end
 					local dst = jecs.archetype_traverse_remove(world, id, archetype)
 
 					if archetypes[dst.id] then

modules/deserialize.luau

@@ -1,47 +0,0 @@
-local jecs = require("@jecs")
-
-local function ecs_ensure_entity(world: jecs.World, id: jecs.Entity<any>, ctx: {[jecs.Entity<any>]: jecs.Entity<any>})
-	local e = 0
-
-	local ser_id = id
-
-	local deser_id = ctx[ser_id]
-	if not deser_id then
-		if not world:exists(ser_id)
-			or (world:contains(ser_id) and not world:get(ser_id, jecs.Name))
-		then
-			deser_id = world:entity(id)
-		else
-			if world:contains(ser_id)  then
-				if world:has(ser_id, jecs.Name) then
-					deser_id = ser_id
-				else
-					deser_id = world:entity(ser_id)
-				end
-			else
-				if world:exists(ser_id) then
-					deser_id = world:entity()
-				else
-					deser_id = world:entity(ser_id)
-				end
-			end
-		end
-		ctx[ser_id] = deser_id
-	end
-
-	e = deser_id
-
-	return e
-end
-
-local function ecs_deser_pairs(world: jecs.World, rel, tgt, ctx)
-	rel = ecs_ensure_entity(world, rel, ctx)
-	tgt = ecs_ensure_entity(world, tgt, ctx)
-
-	return jecs.pair(rel, tgt)
-end
-
-return {
-	ecs_ensure_entity = ecs_ensure_entity,
-	ecs_deser_pairs = ecs_deser_pairs,
-}

modules/remotes.luau

@@ -0,0 +1,39 @@
+-- A simple way to safely type remote events without hassle
+
+local ReplicatedStorage = require("@game/ReplicatedStorage")
+local jecs = require("@jecs")
+local ty = require("./")
+
+type Remote<T...> = {
+	FireClient: (Remote<T...>, Player, T...) -> (),
+	FireAllClients: (Remote<T...>, T...) -> (),
+	FireServer: (Remote<T...>, T...) -> (),
+	OnServerEvent: RBXScriptSignal<(Player, T...)>,
+	OnClientEvent: RBXScriptSignal<T...>
+}
+
+local function stream_ensure(name)
+	local remote = ReplicatedStorage:FindFirstChild(name)
+	if not remote then
+		remote = Instance.new("RemoteEvent")
+		remote.Name = name
+		remote.Parent = ReplicatedStorage
+	end
+	return remote
+end
+
+local function datagram_ensure(name)
+	local remote = ReplicatedStorage:FindFirstChild(name)
+	if not remote then
+		remote = Instance.new("UnreliableRemoteEvent")
+		remote.Name = name
+		remote.Parent = ReplicatedStorage
+	end
+	return remote
+end
+
+
+return {
+	input = datagram_ensure("input") :: Remote<string>,
+	replication = stream_ensure("replication") :: Remote<snapshot>
+}

package.json

@@ -1,11 +1,11 @@
 {
 	"name": "@rbxts/jecs",
-	"version": "0.11.0",
+	"version": "0.10.2",
 	"description": "Stupidly fast Entity Component System",
 	"main": "src/jecs.luau",
 	"repository": {
 		"type": "git",
-		"url": "https://github.com/Ukendio/jecs"
+		"url": "git+https://github.com/ukendio/jecs.git"
 	},
 	"keywords": [],
 	"author": "Ukendio",

src/jecs.luau

@@ -156,7 +156,6 @@ type componentrecord = {
 	counts: { [i53]: number },
 	flags: number,
 	size: number,
-	cache: { number },
 
 	on_add: ((entity: i53, id: i53, value: any, oldarchetype: archetype) -> ())?,
 	on_change: ((entity: i53, id: i53, value: any, oldarchetype: archetype) -> ())?,
@@ -568,21 +567,17 @@ end
 
 local ECS_INTERNAL_ERROR_INCOMPATIBLE_ENTITY = "Entity is outside range"
 
-local function ENTITY_INDEX_NEW_ID(world: world): i53
+local function ENTITY_INDEX_NEW_ID(entity_index: entityindex): i53
-	local entity_index = world.entity_index
-	local ROOT_ARCHETYPE = world.ROOT_ARCHETYPE
 	local dense_array = entity_index.dense_array
 	local alive_count = entity_index.alive_count
 	local sparse_array = entity_index.sparse_array
 	local max_id = entity_index.max_id
-	local next_count = alive_count + 1
 
 	if alive_count < max_id then
-		local id = dense_array[next_count]
+		alive_count += 1
-		if id then 
+		entity_index.alive_count = alive_count
-			entity_index.alive_count = next_count
+		local id = dense_array[alive_count]
-			return id
+		return id
-		end
 	end
 
 	local id = max_id + 1
@@ -590,9 +585,10 @@ local function ENTITY_INDEX_NEW_ID(world: world): i53
 	ecs_assert(range_end == nil or id < range_end, ECS_INTERNAL_ERROR_INCOMPATIBLE_ENTITY)
 
 	entity_index.max_id = id
-	entity_index.alive_count = next_count
+	alive_count += 1
-	dense_array[next_count] = id
+	entity_index.alive_count = alive_count
-	sparse_array[id] = { dense = next_count, row = 0, archetype = ROOT_ARCHETYPE }
+	dense_array[alive_count] = id
+	sparse_array[id] = { dense = alive_count } :: record
 
 	return id
 end
@@ -919,7 +915,6 @@ local function id_record_create(
 		records = {},
 		counts = {},
 		flags = flags,
-		cache = {},
 
 		on_add = on_add,
 		on_change = on_change,
@@ -957,7 +952,6 @@ local function archetype_append_to_records(
 		idr_records[archetype_id] = index
 		idr_counts[archetype_id] = 1
 		columns_map[id] = column
-		table.insert(idr.cache, archetype_id)
 	else
 		local max_count = idr_counts[archetype_id] + 1
 		idr_counts[archetype_id] = max_count
@@ -1049,10 +1043,8 @@ local function world_range(world: world, range_begin: number, range_end: number?
 		for i = max_id + 1, range_begin do
 			dense_array[i] = i
 			sparse_array[i] = {
-				dense = 0,
+				dense = 0
-				row = 0,
+			} :: record
-				archetype = world.ROOT_ARCHETYPE
-			}
 		end
 		entity_index.max_id = range_begin
 		entity_index.alive_count = range_begin
@@ -1092,11 +1084,10 @@ local function find_archetype_without(
 ): archetype
 	local id_types = node.types
 	local at = table.find(id_types, id)
-	if at == nil then
+
-		return node
-	end
 	local dst = table.clone(id_types)
 	table.remove(dst, at)
+
 	return archetype_ensure(world, dst)
 end
 
@@ -1219,13 +1210,6 @@ local function archetype_destroy(world: world, archetype: archetype)
 	if archetype == world.ROOT_ARCHETYPE then
 		return
 	end
-	-- RAII / idempotent: already destroyed or still has entities → no-op
-	if world.archetypes[archetype.id] ~= archetype then
-		return
-	end
-	if #archetype.entities > 0 then
-		return
-	end
 
 	local component_index = world.component_index
 	local archetype_edges = world.archetype_edges
@@ -2577,7 +2561,7 @@ local function ecs_bulk_insert(world: world, entity: i53, ids: { i53 }, values:
 	end
 	local from = r.archetype
 	local component_index = world.component_index
-	if from == world.ROOT_ARCHETYPE then
+	if not from then
 		local dst_types = table.clone(ids)
 		table.sort(dst_types)
 
@@ -2665,8 +2649,6 @@ local function ecs_bulk_insert(world: world, entity: i53, ids: { i53 }, values:
 	end
 end
 
-local ON_REMOVE_STRUCTURAL_WARN = "jecs: on_remove must not perform structural changes (world:add/world:remove); this will be removed as a lint in future versions and can cause silent failures"
-
 local function ecs_bulk_remove(world: world, entity: i53, ids: { i53 })
 	local entity_index = world.entity_index
 	local r = entity_index_try_get(entity_index, entity)
@@ -2675,13 +2657,14 @@ local function ecs_bulk_remove(world: world, entity: i53, ids: { i53 })
 	end
 	local from = r.archetype
 	local component_index = world.component_index
+	if not from then
+		return
+	end
 
 	local remove: { [i53]: boolean } = {}
 
 	local columns_map = from.columns_map
 
-	local dst_types = table.clone(from.types) :: { i53 }
-
 	for i, id in ids do
 		if not columns_map[id] then
 			continue
@@ -2693,15 +2676,22 @@ local function ecs_bulk_remove(world: world, entity: i53, ids: { i53 })
 		local on_remove = idr.on_remove
 		if on_remove then
 			on_remove(entity, id)
-			if from ~= r.archetype then 
-				error(ON_REMOVE_STRUCTURAL_WARN)
-			end
 		end
+	end
+
+	local to = r.archetype
+	if from ~= to then
+		from = to
+	end
+
+	local dst_types = table.clone(from.types) :: { i53 }
+
+	for id in remove do
 		local at = table.find(dst_types, id)
 		table.remove(dst_types, at)
 	end
 
-	local to = archetype_ensure(world, dst_types)
+	to = archetype_ensure(world, dst_types)
 
 	if from ~= to then
 		entity_move(entity_index, entity, r, to)
@@ -2712,12 +2702,12 @@ local function world_new(DEBUG: boolean?)
 	local eindex_dense_array = {} :: { i53 }
 	local eindex_sparse_array = {} :: { record }
 
-	local entity_index: entityindex = {
+	local entity_index = {
 		dense_array = eindex_dense_array,
 		sparse_array = eindex_sparse_array,
 		alive_count = 0,
 		max_id = 0,
-	}
+	} :: entityindex
 
 	-- NOTE(marcus): with the way the component index is accessed, we want to
 	-- ensure that components range has fast access.
@@ -2757,6 +2747,31 @@ local function world_new(DEBUG: boolean?)
 		signals = signals,
 	} :: world
 
+
+	local function entity_index_new_id(entity_index: entityindex): i53
+		local alive_count = entity_index.alive_count
+		local max_id = entity_index.max_id
+
+		if alive_count < max_id then
+			alive_count += 1
+			entity_index.alive_count = alive_count
+			local id = eindex_dense_array[alive_count]
+			return id
+		end
+
+		local id = max_id + 1
+		local range_end = entity_index.range_end
+		ecs_assert(range_end == nil or id < range_end, ECS_INTERNAL_ERROR_INCOMPATIBLE_ENTITY)
+
+		entity_index.max_id = id
+		alive_count += 1
+		entity_index.alive_count = alive_count
+		eindex_dense_array[alive_count] = id
+		eindex_sparse_array[id] = { dense = alive_count } :: record
+
+		return id
+	end
+
 	local ROOT_ARCHETYPE = archetype_create(world, {}, "")
 	world.ROOT_ARCHETYPE = ROOT_ARCHETYPE
 
@@ -2886,7 +2901,9 @@ local function world_new(DEBUG: boolean?)
 			return
 		end
 
-		local src = record.archetype
+		local from: archetype = record.archetype
+		local ROOT_ARCHETYPE = ROOT_ARCHETYPE
+		local src = from or ROOT_ARCHETYPE
 		local column = src.columns_map[id]
 		if column then
 			local idr = component_index[id]
@@ -2916,9 +2933,9 @@ local function world_new(DEBUG: boolean?)
 							local id_types = src.types
 							if on_remove then
 								on_remove(entity, id_types[cr])
-								if src ~= record.archetype then
+								src = record.archetype
-									error(ON_REMOVE_STRUCTURAL_WARN)
+								id_types = src.types
-								end
+								cr = idr.records[src.id]
 							end
 
 							to = exclusive_traverse_add(src, cr, id)
@@ -2941,8 +2958,11 @@ local function world_new(DEBUG: boolean?)
 							if cr then
 								local id_types = src.types
 								on_remove(entity, id_types[cr])
-								if src ~= record.archetype then
+								local arche = record.archetype
-									error(ON_REMOVE_STRUCTURAL_WARN)
+								if src ~= arche then
+									id_types = arche.types
+									cr = idr.records[arche.id]
+									to = exclusive_traverse_add(arche, cr, id)
 								end
 							end
 						end
@@ -2961,9 +2981,7 @@ local function world_new(DEBUG: boolean?)
 				idr = component_index[id]
 			end
 
-			local ROOT_ARCHETYPE = ROOT_ARCHETYPE
+			if from then
-			local src_is_root_archetype = src == ROOT_ARCHETYPE
-			if not src_is_root_archetype then
 				-- If there was a previous archetype, then the entity needs to move the archetype
 				inner_entity_move(entity, record, to)
 			else
@@ -2990,7 +3008,9 @@ local function world_new(DEBUG: boolean?)
 			return
 		end
 
-		local src = record.archetype
+		local from = record.archetype
+		local ROOT_ARCHETYPE = ROOT_ARCHETYPE
+		local src = from or ROOT_ARCHETYPE
 		if src.columns_map[id] then
 			return
 		end
@@ -3012,9 +3032,10 @@ local function world_new(DEBUG: boolean?)
 						local id_types = src.types
 						if on_remove then
 							on_remove(entity, id_types[cr])
-							if src ~= record.archetype then 
+
-								error(ON_REMOVE_STRUCTURAL_WARN)
+							src = record.archetype
-							end
+							id_types = src.types
+							cr = idr.records[src.id]
 						end
 
 						to = exclusive_traverse_add(src, cr, id)
@@ -3060,9 +3081,7 @@ local function world_new(DEBUG: boolean?)
 			idr = component_index[id]
 		end
 
-		local ROOT_ARCHETYPE = ROOT_ARCHETYPE
+		if from then
-		local src_is_root_archetype = src == ROOT_ARCHETYPE
-		if not src_is_root_archetype then
 			inner_entity_move(entity, record, to)
 		else
 			if #to.types > 0 then
@@ -3085,6 +3104,9 @@ local function world_new(DEBUG: boolean?)
 		end
 
 		local archetype = record.archetype
+		if not archetype then
+			return nil
+		end
 
 		local columns_map = archetype.columns_map
 		local row = record.row
@@ -3142,8 +3164,7 @@ local function world_new(DEBUG: boolean?)
 		table.insert(listeners, fn)
 		return function()
 			local n = #listeners
-			local i = table.find(listeners, fn::Listener<any>)
+			local i = table.find(listeners, fn)
-			assert(i, "Listener not found, maybe you tried to disconnect it twice")
 			listeners[i] = listeners[n]
 			listeners[n] = nil
 		end
@@ -3188,8 +3209,7 @@ local function world_new(DEBUG: boolean?)
 		table.insert(listeners, fn)
 		return function()
 			local n = #listeners
-			local i = table.find(listeners, fn::Listener<any>)
+			local i = table.find(listeners, fn)
-			assert(i, "Listener not found, maybe you tried to disconnect it twice")
 			listeners[i] = listeners[n]
 			listeners[n] = nil
 		end
@@ -3234,7 +3254,6 @@ local function world_new(DEBUG: boolean?)
 		return function()
 			local n = #listeners
 			local i = table.find(listeners, fn::Listener<any>)
-			assert(i, "Listener not found, maybe you tried to disconnect it twice")
 			listeners[i] = listeners[n]
 			listeners[n] = nil
 		end
@@ -3307,13 +3326,10 @@ local function world_new(DEBUG: boolean?)
 	end
 
 	local function world_entity(world: world, entity: i53?): i53
-		local sparse_array = eindex_sparse_array
-		local dense_array = eindex_dense_array
-		
 		if entity then
 			local index = ECS_ID(entity)
 			local alive_count = entity_index.alive_count
-			local r = sparse_array[index]
+			local r = eindex_sparse_array[index]
 			if r then
 				local dense = r.dense
 
@@ -3323,17 +3339,17 @@ local function world_new(DEBUG: boolean?)
 					alive_count += 1
 					entity_index.alive_count = alive_count
 					r.dense = alive_count
-					dense_array[alive_count] = entity
+					eindex_dense_array[alive_count] = entity
 					return entity
 				end
 
 				-- If dense > 0, check if there's an existing entity at that position
-				local existing_entity = dense_array[dense]
+				local existing_entity = eindex_dense_array[dense]
 				if existing_entity and existing_entity ~= entity then
 					alive_count += 1
 					entity_index.alive_count = alive_count
 					r.dense = alive_count
-					dense_array[alive_count] = entity
+					eindex_dense_array[alive_count] = entity
 					return entity
 				end
 
@@ -3342,41 +3358,30 @@ local function world_new(DEBUG: boolean?)
 				local max_id = entity_index.max_id
 
 				if index > max_id then
+					-- Pre-populate all intermediate IDs to keep sparse_array as an array
 					for i = max_id + 1, index - 1 do
-						sparse_array[i] = { dense = 0, row = 0, archetype = ROOT_ARCHETYPE }
+						if not eindex_sparse_array[i] then
+							-- NOTE(marcus): We have to do this check to see if
+							-- they exist first because world:range() may have
+							-- pre-populated some slots already.
+						end
+
+						eindex_sparse_array[i] = { dense = 0 } :: record
 					end
 					entity_index.max_id = index
 				end
 
 				alive_count += 1
 				entity_index.alive_count = alive_count
-				dense_array[alive_count] = entity
+				eindex_dense_array[alive_count] = entity
 
-				r = { dense = alive_count, row = 0, archetype = ROOT_ARCHETYPE }
+				r = { dense = alive_count } :: record
-				sparse_array[index] = r
+				eindex_sparse_array[index] = r
 
 				return entity
 			end
 		end
-
+		return entity_index_new_id(entity_index)
-		local alive_count = entity_index.alive_count
-		local max_id = entity_index.max_id
-		local next_count = alive_count + 1
-		if alive_count < max_id then
-			entity = dense_array[next_count]
-			if entity then 
-				entity_index.alive_count = next_count
-				return entity
-			end
-		end
-		local id = max_id + 1
-		local range_end = entity_index.range_end
-		ecs_assert(range_end == nil or id < range_end, ECS_INTERNAL_ERROR_INCOMPATIBLE_ENTITY)
-		entity_index.max_id = id
-		entity_index.alive_count = next_count
-		dense_array[next_count] = id
-		sparse_array[id] = { dense = next_count, row = 0, archetype = ROOT_ARCHETYPE }
-		return id
 	end
 
 	local function world_remove(world: world, entity: i53, id: i53)
@@ -3386,6 +3391,10 @@ local function world_new(DEBUG: boolean?)
 		end
 		local from = record.archetype
 
+		if not from then
+			return
+		end
+
 		if from.columns_map[id] then
 			local idr = world.component_index[id]
 			local on_remove = idr.on_remove
@@ -3463,6 +3472,7 @@ local function world_new(DEBUG: boolean?)
 					for i = n, 1, -1 do
 						world_delete(world, entities[i])
 					end
+
 					archetype_destroy(world, idr_archetype)
 				end
 			else
@@ -3479,10 +3489,13 @@ local function world_new(DEBUG: boolean?)
 							local r = eindex_sparse_array[ECS_ID(e :: number)]
 							local from = r.archetype
 							if from ~= idr_archetype then
+								-- unfortunately the on_remove hook allows a window where `e` can have changed archetype
+								-- this is hypothetically not that expensive of an operation anyways
 								to = archetype_traverse_remove(world, entity, from)
 							end
 							inner_entity_move(e, r, to)
 						end
+
 						archetype_destroy(world, idr_archetype)
 					end
 				else
@@ -3495,6 +3508,7 @@ local function world_new(DEBUG: boolean?)
 							local e = entities[i]
 							entity_move(entity_index, e, eindex_sparse_array[ECS_ID(e :: number)], to)
 						end
+
 						archetype_destroy(world, idr_archetype)
 					end
 				end
@@ -3502,10 +3516,11 @@ local function world_new(DEBUG: boolean?)
 		end
 
 		if idr_t then
-			local to_remove = {} :: { [i53]: componentrecord }
+			local archetype_ids = idr_t.records
-			local cache = idr_t.cache
+            local to_remove = {}:: { [i53]: componentrecord}
-			for i = #cache, 1, -1 do 
+            local did_cascade_delete = false
-				local archetype_id = cache[i]
+
+			for archetype_id in archetype_ids do
 				local idr_t_archetype = archetypes[archetype_id]
 				if not idr_t_archetype then
 					continue
@@ -3519,14 +3534,20 @@ local function world_new(DEBUG: boolean?)
 					if not ECS_IS_PAIR(id) then
 						continue
 					end
-					local object = entity_index_get_alive(entity_index, ECS_PAIR_SECOND(id))
+					local object = entity_index_get_alive(
+					    entity_index, ECS_PAIR_SECOND(id))
 					if object ~= entity then
 						continue
 					end
 					local id_record = component_index[id]
-					local has_delete = bit32.btest(id_record.flags, ECS_ID_DELETE)
+					local flags = id_record.flags
-					if has_delete then
+					local flags_delete_mask = bit32.btest(flags, ECS_ID_DELETE)
-						deleted_any = true
+					if flags_delete_mask then
+                        for i = #entities, 1, -1 do
+						    local child = entities[i]
+						    world_delete(world, child)
+					    end
+                        deleted_any = true
 						break
 					else
                         to_remove[id] = id_record
@@ -3534,50 +3555,72 @@ local function world_new(DEBUG: boolean?)
 					end
 				end
 
-				if deleted_any then
+                if deleted_any then
-					for row = #entities, 1, -1 do
+                    did_cascade_delete = true
-						world_delete(world, entities[row])
+                    continue
-					end
+                end
-					archetype_destroy(world, idr_t_archetype)
-					continue
-				end
-				if remove_count == 1 then
-					local id, id_record = next(to_remove)
-					local to = archetype_traverse_remove(world, id::i53, idr_t_archetype)
-					local on_remove = id_record.on_remove
-					for row = #entities, 1, -1 do
-						local child = entities[row]
-						local r = entity_index_try_get_unsafe(child)::record
-						local dst = to
-						if on_remove then
-							on_remove(child, id :: i53)
-						end
-						inner_entity_move(child, r, dst)
-					end
-					archetype_destroy(world, idr_t_archetype)
-				else
-					local dst_types = table.clone(idr_t_archetype.types)
-					for id in to_remove do
-						table.remove(dst_types, table.find(dst_types, id))
-					end
 
-					local dst = archetype_ensure(world, dst_types)
+                if remove_count == 1 then
+                    local id, id_record = next(to_remove)
+                    local to_u = archetype_traverse_remove(world, id :: i53, idr_t_archetype)
+                    local on_remove = id_record.on_remove
+                    for i = #entities, 1, -1 do
+                        local child = entities[i]
+                        local r = entity_index_try_get_unsafe(child) :: record
+                        local to = to_u
+                        if on_remove then
+                            on_remove(child, id :: i53)
+                            local src = r.archetype
+                            if src ~= idr_t_archetype then
+                                to = archetype_traverse_remove(world, id::i53, src)
+                            end
+                        end
 
-					for row = #entities, 1, -1 do
+                        inner_entity_move(child, r, to)
-						local child = entities[row]
+                    end
-						local r = entity_index_try_get_unsafe(child) :: record
+                elseif remove_count > 1 then
-						for id, component_record in to_remove do
+                    local dst_types = table.clone(idr_t_types)
-							local on_remove = component_record.on_remove
+                    for id, component_record in to_remove do
-							if on_remove then
+                        table.remove(dst_types, table.find(dst_types, id))
-								on_remove(child, id)
+                    end
-							end
+
-						end
+                    local to_u = archetype_ensure(world, dst_types)
-						inner_entity_move(child, r, dst)
+                    for i = #entities, 1, -1 do
+                        local child = entities[i]
+                        local r = entity_index_try_get_unsafe(child) :: record
+
+                        local to = to_u
+                        for id, component_record in to_remove do
+                            local on_remove = component_record.on_remove
+                            if on_remove then
+                                on_remove(child, id)
+                                local src = r.archetype
+                                if src ~= idr_t_archetype then
+                                    to = archetype_traverse_remove(world, id, src)
+                                end
+                            end
+                        end
+
+                        inner_entity_move(child, r, to)
+                    end
+                end
+
+                table.clear(to_remove)
+				archetype_destroy(world, idr_t_archetype)
+			end
+
+			if did_cascade_delete then
+				for archetype_id in archetype_ids do
+					local idr_t_archetype = archetypes[archetype_id]
+					if not idr_t_archetype then
+						continue
+					end
+					local entities = idr_t_archetype.entities
+					for i = #entities, 1, -1 do
+						world_delete(world, entities[i])
 					end
 					archetype_destroy(world, idr_t_archetype)
 				end
-
-				table.clear(to_remove)
 			end
 		end
 
@@ -3632,11 +3675,14 @@ local function world_new(DEBUG: boolean?)
 						local r = entity_index_try_get_unsafe(e) :: record
 						inner_entity_move(e, r, node)
 					end
+
 					archetype_destroy(world, idr_r_archetype)
 				end
 			end
 		end
 
+
+
 		local dense = record.dense
 		local i_swap = entity_index.alive_count
 		entity_index.alive_count = i_swap - 1
@@ -3644,8 +3690,8 @@ local function world_new(DEBUG: boolean?)
 		local e_swap = eindex_dense_array[i_swap]
 		local r_swap = entity_index_try_get_any(e_swap) :: record
 		r_swap.dense = dense
-		record.archetype = ROOT_ARCHETYPE
+		record.archetype = nil :: any
-		record.row = 0
+		record.row = nil :: any
 		record.dense = i_swap
 
 		eindex_dense_array[dense] = e_swap
@@ -3667,8 +3713,8 @@ local function world_new(DEBUG: boolean?)
 			end
 		end
 		archetype_delete(world, record.archetype, record.row)
-		record.archetype = world.ROOT_ARCHETYPE
+		record.archetype = nil :: any
-		record.row = 0
+		record.row = nil :: any
 	end
 
 	local function world_exists(world: world, entity: i53): boolean
@@ -3827,7 +3873,7 @@ local function world_new(DEBUG: boolean?)
 	end
 
 	for i = 1, EcsRest do
-		ENTITY_INDEX_NEW_ID(world)
+		entity_index_new_id(entity_index)
 	end
 
 	for i = 1, max_component_id do
@@ -3863,7 +3909,7 @@ local function world_new(DEBUG: boolean?)
 	world_add(world, EcsOnDeleteTarget, EcsExclusive)
 
 	for i = EcsRest + 1, ecs_max_tag_id do
-		ENTITY_INDEX_NEW_ID(world)
+		entity_index_new_id(entity_index)
 	end
 
 	for i, bundle in ecs_metadata do
@@ -3881,7 +3927,7 @@ end
 
 local function ecs_is_tag(world: world, entity: i53): boolean
 	if ECS_IS_PAIR(entity) then
-		return ecs_is_tag(world, ecs_pair_first(world, entity)) and ecs_is_tag(world, ecs_pair_second(world, entity))
+		return ecs_is_tag(world, ecs_pair_first(world, entity)) or ecs_is_tag(world, ecs_pair_second(world, entity))
 	end
 	local idr = world.component_index[entity]
 	if idr then
@@ -3950,7 +3996,7 @@ local function entity_index_ensure(entity_index: entityindex, e: i53)
 end
 
 local function new(world: world)
-	local e = ENTITY_INDEX_NEW_ID(world)
+	local e = ENTITY_INDEX_NEW_ID(world.entity_index)
 	return e
 end
 
@@ -3968,7 +4014,7 @@ local function new_low_id(world: world)
 		end
 	end
 	if e == 0 or e >= HI_COMPONENT_ID then
-		e = ENTITY_INDEX_NEW_ID(world)
+		e = ENTITY_INDEX_NEW_ID(entity_index)
 	else
 		entity_index_ensure(entity_index, e)
 	end
@@ -3976,7 +4022,7 @@ local function new_low_id(world: world)
 end
 
 local function new_w_id(world: world, id: i53)
-	local e = ENTITY_INDEX_NEW_ID(world)
+	local e = ENTITY_INDEX_NEW_ID(world.entity_index)
 	world.add(world, e, id)
 	return e
 end

test/benches/visual/spawn.bench.luau

@@ -10,6 +10,7 @@ local mirror = require(ReplicatedStorage.mirror:Clone())
 return {
 	ParameterGenerator = function()
 		local ecs = jecs.world()
+		ecs:range(1000, 20000)
 		local mcs = mirror.World.new()
 		return ecs, mcs
 	end,
@@ -18,14 +19,14 @@ return {
 		Mirror = function(_, ecs, mcs)
 			for i = 1, 100 do
 
-				local _e = mcs:entity()
+				mcs:entity()
 			end
 		end,
 
 		Jecs = function(_, ecs, mcs)
 			for i = 1, 100 do
 
-				local _e = ecs:entity()
+				ecs:entity()
 			end
 		end,
 },

test/tests.luau

@@ -24,174 +24,6 @@ type Id<T=unknown> = jecs.Id<T>
 local entity_visualiser = require("@modules/entity_visualiser")
 local dwi = entity_visualiser.stringify
 
--- FOCUS()
-TEST("Stale to_remove", function()
-	local world = jecs.world()
-
-	local a = world:component()
-	local b = world:component()
-	local c = world:component()
-	local d = world:component()
-	local marker = world:component()
-
-	local target = world:entity()
-
-	local first = world:entity()
-	world:add(first, jecs.pair(a, target))
-	world:add(first, jecs.pair(b, target))
-	world:add(first, jecs.pair(jecs.ChildOf, target))
-
-	local second = world:entity()
-	world:add(second, jecs.pair(c, target))
-	world:add(second, jecs.pair(d, target))
-	world:add(second, marker)
-
-	print("-------")
-	world:delete(target)
-	print("-------")
-
-	CHECK(world:contains(second))
-	CHECK(world:has(second, marker))
-end)
-
--- FOCUS()
--- Exercises idr_t multi-remove path: entity has multiple pairs with same target (no cascade); delete target → both pairs removed, on_remove each called.
-TEST("Target delete: multi-remove path (removing_count > 1)", function()
-	local world = jecs.world()
-	local rel1 = world:entity()
-	local rel2 = world:entity()
-	local tag = world:component()
-	local target = world:entity()
-	local e = world:entity()
-	world:add(e, jecs.pair(rel1, target))
-	world:add(e, jecs.pair(rel2, target))
-	world:add(e, tag)
-	local removed_ids = {}
-	world:removed(rel1, function(_e, id) table.insert(removed_ids, id) end)
-	world:removed(rel2, function(_e, id) table.insert(removed_ids, id) end)
-	world:delete(target)
-	CHECK(world:contains(e))
-	CHECK(world:has(e, tag))
-	CHECK(not world:has(e, jecs.pair(rel1, target)))
-	CHECK(not world:has(e, jecs.pair(rel2, target)))
-	CHECK(#removed_ids == 2)
-end)
-
--- FOCUS()
-TEST("repro 2", function()
-	local sessionDeletedCount = 0
-	local slotDeletedCount = 0
-
-	for i = 1, 100 do
-		local world = jecs.world(true);
-
-		-- randomness
-		for _ = 1, i % 40 do
-			world:entity()
-		end
-
-		local ofMatch = world:component()
-		local ofTeam = world:component()
-		local ofRound = world:component()
-		local ownedBy = world:component()
-		local nextTeam = world:component()
-		local activeRound = world:component()
-		local team = world:component()
-		local session = world:component()
-		local round = world:component()
-
-		world:add(ofTeam, jecs.Exclusive)
-		world:add(ownedBy, jecs.Exclusive)
-		world:add(nextTeam, jecs.Exclusive)
-		
-		world:add(activeRound, jecs.Exclusive)
-
-		local slotEntity = world:entity()
-		local matchEntity = world:entity()
-		world:add(matchEntity, jecs.pair(jecs.ChildOf, slotEntity))
-
-		local teams = {}
-		for t = 1, 2 do
-			local teamEntity = world:entity()
-			world:add(teamEntity, team)
-			world:add(teamEntity, jecs.pair(jecs.ChildOf, matchEntity))
-			world:add(teamEntity, jecs.pair(ofMatch, matchEntity))
-			table.insert(teams, teamEntity)
-		end
-		world:add(matchEntity, jecs.pair(nextTeam, teams[1]))
-
-		local roundEntity = world:entity()
-		world:add(roundEntity, round)
-		world:add(roundEntity, jecs.pair(jecs.ChildOf, matchEntity))
-
-		-- doing something as simple as adding this pair causes error rate to change. When this isn't here, sessionDeletedCount drops from 100% to 80%.
-		world:add(matchEntity, jecs.pair(activeRound, roundEntity))
-
-		local sessions = {}
-		for j = 1, #teams do
-			-- random number of players on team
-			for _ = 1, 1 + (i % 5) do
-				local player = world:entity()
-
-				local sessionEntity = world:entity()
-				world:add(sessionEntity, session)
-				world:add(sessionEntity, jecs.pair(ofMatch, matchEntity))
-				world:add(sessionEntity, jecs.pair(ofTeam, teams[j]))
-
-				-- not adding this next pair makes sessionDeletedCount to drop to 0%??
-				world:add(sessionEntity, jecs.pair(ownedBy, player))
-				world:add(sessionEntity, jecs.pair(ofRound, roundEntity))
-				table.insert(sessions, sessionEntity)
-			end
-		end
-
-		world:delete(matchEntity)
-
-		-- session should stay alive after match deletion
-		for _, entity in sessions do
-			if not world:contains(entity) then
-				sessionDeletedCount += 1
-				break
-			end
-		end
-
-		if not world:contains(slotEntity) then
-			slotDeletedCount += 1
-			break
-		end
-	end
-
-	CHECK(sessionDeletedCount == 0)
-	CHECK(slotDeletedCount == 0)
-
-	if (sessionDeletedCount + slotDeletedCount > 0)then
-		print(`repro 2 incorrect session deletion count: {sessionDeletedCount}`)
-
-		-- this has never been above 0, but it's the issue i'm having
-		print(`repro 2 incorrect slot deletion count: {slotDeletedCount}`)
-	end
-end)
-TEST("migrating to real records", function() 
-	local world = jecs.world(true)
-	local e1 = world:entity()
-	local e2 = world:entity()
-	print(jecs.record(world, e1).row)
-	world:add(e1, jecs.pair(jecs.ChildOf, e2))
-	world:set(e1, jecs.Name, "hello")
-	CHECK(jecs.record(world, e1).row~=0)
-	CHECK(world:get(e1, jecs.Name)=="hello")
-	CHECK(world:has(e1, jecs.pair(jecs.ChildOf, jecs.Wildcard)))
-end)
-
-TEST("e2 is nil", function() 
-	local world = jecs.world(true)
-	local e1 = world:entity(1000)
-	local e2 = world:entity()
-	
-    CHECK(e1 and world:contains(e1))
-    CHECK(e2 and world:contains(e2))
-end)
--- FOCUS()
 TEST("reproduce idr_t nil archetype bug", function()
 	local world = jecs.world(true)
 
@@ -706,6 +538,44 @@ TEST("world:add()", function()
 		CHECK(world:has(e, pair(A, C)) == true)
 	end
 
+	do CASE "exclusive relations invoke on_remove hooks that should allow side effects"
+		local world = jecs.world()
+		local A = world:component()
+		local B = world:component()
+		local C = world:component()
+		local D = world:component()
+
+		world:add(A, jecs.Exclusive)
+		local call_count = 0
+		world:set(A, jecs.OnRemove, function(e, id)
+			call_count += 1
+			if call_count == 1 then
+				world:add(e, C)
+			else
+				world:add(e, D)
+			end
+		end)
+
+		local e = world:entity()
+		world:add(e, pair(A, B))
+		world:add(e, pair(A, C))
+
+		CHECK(world:has(e, pair(A, B)) == false)
+		CHECK(world:has(e, pair(A, C)) == true)
+		CHECK(world:has(e, C))
+
+
+		-- We have to ensure that it actually invokes hooks everytime it
+		-- traverses the archetype
+		e = world:entity()
+		world:add(e, pair(A, B))
+		world:add(e, pair(A, C))
+
+		CHECK(world:has(e, pair(A, B)) == false)
+		CHECK(world:has(e, pair(A, C)) == true)
+		CHECK(world:has(e, D))
+	end
+
 	do CASE "idempotent"
 		local world = jecs.world()
 		local d = dwi(world)
@@ -728,8 +598,8 @@ TEST("world:add()", function()
 		local e = world:entity()
 		-- An entity starts without an archetype or row
 		-- should therefore not need to copy over data
-		CHECK(d.tbl(e) == world.ROOT_ARCHETYPE)
+		CHECK(d.tbl(e) == nil)
-		CHECK(d.row(e) == 0)
+		CHECK(d.row(e) == nil)
 
 		local archetypes = #world.archetypes
 		-- This should create a new archetype
@@ -1163,6 +1033,24 @@ TEST("world:delete()", function()
 		-- CHECK(B_OnRemove_called)
 	end
 
+	do CASE "idr_t//remove//on_remove//changed_archetype@3123..3126"
+		local world = jecs.world()
+		local A = world:component()
+		local B = world:component()
+		world:set(A, jecs.OnRemove, function(entity, id)
+			world:set(entity, B, true)
+		end)
+
+		local e1 = world:entity()
+		local e2 = world:entity()
+		world:add(e2, pair(A, e2))
+		world:set(e2, pair(A, e1), true)
+
+		world:delete(e1)
+
+		CHECK(not world:has(e2, pair(A, e1)))
+	end
+
 	do CASE "pair(OnDelete, Delete)"
 	    local world = jecs.world()
 	    local ct = world:component()
@@ -1705,7 +1593,6 @@ TEST("world:added", function()
 	end
 end)
 
--- FOCUS()
 TEST("world:range()", function()
 
 	do CASE "spawn entity under min range"
@@ -3013,6 +2900,43 @@ TEST("world:set()", function()
 		CHECK(world:has(e, pair(A, C)) == true)
 	end
 
+	do CASE "exclusive relations invoke on_remove hooks that should allow side effects"
+		local world = jecs.world()
+		local A = world:component()
+		local B = world:component()
+		local C = world:component()
+		local D = world:component()
+
+		world:add(A, jecs.Exclusive)
+		local call_count = 0
+		world:set(A, jecs.OnRemove, function(e, id)
+			call_count += 1
+			if call_count == 1 then
+				world:set(e, C, true)
+			else
+				world:set(e, D, true)
+			end
+		end)
+
+		local e = world:entity()
+		world:set(e, pair(A, B), true)
+		world:set(e, pair(A, C), true)
+
+		CHECK(world:has(e, pair(A, B)) == false)
+		CHECK(world:has(e, pair(A, C)) == true)
+		CHECK(world:has(e, C))
+
+
+		-- We have to ensure that it actually invokes hooks everytime it
+		-- traverses the archetype
+		e = world:entity()
+		world:set(e, pair(A, B), true)
+		world:set(e, pair(A, C), true)
+
+		CHECK(world:has(e, pair(A, B)) == false)
+		CHECK(world:has(e, pair(A, C)) == true)
+		CHECK(world:has(e, D))
+	end
 	do CASE "archetype move"
 		local world = jecs.world()
 
@@ -3023,8 +2947,8 @@ TEST("world:set()", function()
 		local e = world:entity()
 		-- An entity starts without an archetype or row
 		-- should therefore not need to copy over data
-		CHECK(d.tbl(e) == world.ROOT_ARCHETYPE)
+		CHECK(d.tbl(e) == nil)
-		CHECK(d.row(e) == 0)
+		CHECK(d.row(e) == nil)
 
 		local archetypes = #world.archetypes
 		-- This should create a new archetype since it is the first
@@ -3360,7 +3284,7 @@ TEST("Hooks", function()
 			local B = world:component()
 			local e = world:entity()
 
-			world:set(A, jecs.OnRemove, function(entity: jecs.Entity)
+			world:set(A, jecs.OnRemove, function(entity)
 				world:set(entity, B, true)
 				CHECK(world:get(entity, A))
 				CHECK(world:get(entity, B))

wally.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ukendio/jecs"
-version = "0.11.0"
+version = "0.10.2"
 registry = "https://github.com/UpliftGames/wally-index"
 realm = "shared"
 license = "MIT"