Merge 918231a1ad into 9d83c3bc13

Prevent invalidation during removal of pairs with deleted targe

.gitignore

@@ -65,3 +65,7 @@ drafts/
 
 # Luau tools
 profile.*
+
+# Patch files
+
+*.patch

.luaurc

@@ -1,8 +1,9 @@
 {
     "aliases": {
         "jecs": "jecs",
-        "testkit": "test/testkit",
-        "mirror": "mirror"
+        "testkit": "tools/testkit",
+        "mirror": "mirror",
+        "tools": "tools",
     },
     "languageMode": "strict"
 }

benches/visual/despawn.bench.luau

@@ -5,41 +5,60 @@ local ReplicatedStorage = game:GetService("ReplicatedStorage")
 local Matter = require(ReplicatedStorage.DevPackages.Matter)
 local ecr = require(ReplicatedStorage.DevPackages.ecr)
 local jecs = require(ReplicatedStorage.Lib)
+local pair = jecs.pair
 local newWorld = Matter.World.new()
 local ecs = jecs.World.new()
+local mirror = require(ReplicatedStorage.mirror)
+local mcs = mirror.World.new()
 
-local A, B = Matter.component(), Matter.component()
-local C, D = ecs:component(), ecs:component()
+local C1 = ecs:component()
+local C2 = ecs:entity()
+ecs:add(C2, pair(jecs.OnDeleteTarget, jecs.Delete))
+local C3 = ecs:entity()
+ecs:add(C3, pair(jecs.OnDeleteTarget, jecs.Delete))
+local C4 = ecs:entity()
+ecs:add(C4, pair(jecs.OnDeleteTarget, jecs.Delete))
+local E1 = mcs:component()
+local E2 = mcs:entity()
+mcs:add(E2, pair(jecs.OnDeleteTarget, jecs.Delete))
+local E3 = mcs:entity()
+mcs:add(E3, pair(jecs.OnDeleteTarget, jecs.Delete))
+local E4 = mcs:entity()
+mcs:add(E4, pair(jecs.OnDeleteTarget, jecs.Delete))
+
+local registry2 = ecr.registry()
 
 return {
 	ParameterGenerator = function()
-		local matter_entities = {}
-		local jecs_entities = {}
-		local entities = {
-			matter = matter_entities,
-			jecs = jecs_entities,
-		}
+		local j = ecs:entity()
+		ecs:set(j, C1, true)
+		local m = mcs:entity()
+		mcs:set(m, E1, true)
 		for i = 1, 1000 do
-			table.insert(matter_entities, newWorld:spawn(A(), B()))
-			local e = ecs:entity()
-			ecs:set(e, C, {})
-			ecs:set(e, D, {})
-			table.insert(jecs_entities, e)
+			local friend1 = ecs:entity()
+			local friend2 = mcs:entity()
+
+			ecs:add(friend1, pair(C2, j))
+			ecs:add(friend1, pair(C3, j))
+			ecs:add(friend1, pair(C4, j))
+
+			mcs:add(friend2, pair(E2, m))
+			mcs:add(friend2, pair(E3, m))
+			mcs:add(friend2, pair(E4, m))
 		end
-		return entities
+		return {
+			m = m,
+			j = j,
+		}
 	end,
 
 	Functions = {
-		Matter = function(_, entities)
-			for _, entity in entities.matter do
-				newWorld:despawn(entity)
-			end
+		Mirror = function(_, a)
+			mcs:delete(a.m)
 		end,
 
-		Jecs = function(_, entities)
-			for _, entity in entities.jecs do
-				ecs:delete(entity)
-			end
+		Jecs = function(_, a)
+			ecs:delete(a.j)
 		end,
 	},
 }

benches/visual/insertion.bench.luau

@@ -28,22 +28,22 @@ local B6 = ecr.component()
 local B7 = ecr.component()
 local B8 = ecr.component()
 
-local C1 = ecs:entity()
-local C2 = ecs:entity()
-local C3 = ecs:entity()
-local C4 = ecs:entity()
-local C5 = ecs:entity()
-local C6 = ecs:entity()
-local C7 = ecs:entity()
-local C8 = ecs:entity()
-local E1 = mcs:entity()
-local E2 = mcs:entity()
-local E3 = mcs:entity()
-local E4 = mcs:entity()
-local E5 = mcs:entity()
-local E6 = mcs:entity()
-local E7 = mcs:entity()
-local E8 = mcs:entity()
+local C1 = ecs:component()
+local C2 = ecs:component()
+local C3 = ecs:component()
+local C4 = ecs:component()
+local C5 = ecs:component()
+local C6 = ecs:component()
+local C7 = ecs:component()
+local C8 = ecs:component()
+local E1 = mcs:component()
+local E2 = mcs:component()
+local E3 = mcs:component()
+local E4 = mcs:component()
+local E5 = mcs:component()
+local E6 = mcs:component()
+local E7 = mcs:component()
+local E8 = mcs:component()
 
 local registry2 = ecr.registry()
 return {
@@ -52,48 +52,30 @@ return {
 	end,
 
 	Functions = {
-		Matter = function()
-			local e = newWorld:spawn()
+		Mirror = function()
+			local e = mcs:entity()
 			for i = 1, 5000 do
-				newWorld:insert(
-					e,
-					A1({ value = true }),
-					A2({ value = true }),
-					A3({ value = true }),
-					A4({ value = true }),
-					A5({ value = true }),
-					A6({ value = true }),
-					A7({ value = true }),
-					A8({ value = true })
-				)
+				mcs:set(e, E1, false)
+				mcs:set(e, E2, false)
+				mcs:set(e, E3, false)
+				mcs:set(e, E4, false)
+				mcs:set(e, E5, false)
+				mcs:set(e, E6, false)
+				mcs:set(e, E7, false)
+				mcs:set(e, E8, false)
 			end
 		end,
-
-		ECR = function()
-			local e = registry2.create()
-			for i = 1, 5000 do
-				registry2:set(e, B1, { value = false })
-				registry2:set(e, B2, { value = false })
-				registry2:set(e, B3, { value = false })
-				registry2:set(e, B4, { value = false })
-				registry2:set(e, B5, { value = false })
-				registry2:set(e, B6, { value = false })
-				registry2:set(e, B7, { value = false })
-				registry2:set(e, B8, { value = false })
-			end
-		end,
-
 		Jecs = function()
 			local e = ecs:entity()
 			for i = 1, 5000 do
-				ecs:set(e, C1, { value = false })
-				ecs:set(e, C2, { value = false })
-				ecs:set(e, C3, { value = false })
-				ecs:set(e, C4, { value = false })
-				ecs:set(e, C5, { value = false })
-				ecs:set(e, C6, { value = false })
-				ecs:set(e, C7, { value = false })
-				ecs:set(e, C8, { value = false })
+				ecs:set(e, C1, false)
+				ecs:set(e, C2, false)
+				ecs:set(e, C3, false)
+				ecs:set(e, C4, false)
+				ecs:set(e, C5, false)
+				ecs:set(e, C6, false)
+				ecs:set(e, C7, false)
+				ecs:set(e, C8, false)
 			end
 		end,
 	},

benches/visual/remove.bench.luau

@@ -0,0 +1,49 @@
+--!optimize 2
+--!native
+
+local ReplicatedStorage = game:GetService("ReplicatedStorage")
+local Matter = require(ReplicatedStorage.DevPackages.Matter)
+local ecr = require(ReplicatedStorage.DevPackages.ecr)
+local jecs = require(ReplicatedStorage.Lib)
+local pair = jecs.pair
+local ecs = jecs.World.new()
+local mirror = require(ReplicatedStorage.mirror)
+local mcs = mirror.World.new()
+
+local C1 = ecs:component()
+local C2 = ecs:entity()
+ecs:add(C2, pair(jecs.OnDeleteTarget, jecs.Delete))
+local C3 = ecs:entity()
+ecs:add(C3, pair(jecs.OnDeleteTarget, jecs.Delete))
+local C4 = ecs:entity()
+ecs:add(C4, pair(jecs.OnDeleteTarget, jecs.Delete))
+local E1 = mcs:component()
+local E2 = mcs:entity()
+mcs:add(E2, pair(jecs.OnDeleteTarget, jecs.Delete))
+local E3 = mcs:entity()
+mcs:add(E3, pair(jecs.OnDeleteTarget, jecs.Delete))
+local E4 = mcs:entity()
+mcs:add(E4, pair(jecs.OnDeleteTarget, jecs.Delete))
+
+return {
+	ParameterGenerator = function()
+	end,
+
+	Functions = {
+		Mirror = function()
+			local m = mcs:entity()
+			for i = 1, 100 do
+				mcs:add(m, E3)
+				mcs:remove(m, E3)
+			end
+		end,
+
+		Jecs = function()
+			local j = ecs:entity()
+			for i = 1, 100 do
+				ecs:add(j, C3)
+				ecs:remove(j, C3)
+			end
+		end,
+	},
+}

demo/src/ReplicatedStorage/track.luau

@@ -0,0 +1,48 @@
+local events = {}
+
+local function trackers_invoke(event, component, entity, ...)
+	local trackers = events[event][component]
+	if not trackers then
+		return
+	end
+
+	for _, tracker in trackers do
+		tracker(entity, data)
+	end
+end
+
+local function trackers_init(event, component, fn)
+	local ob = events[event]
+
+	return {
+		connect = function(component, fn)
+			local trackers = ob[component]
+			if not trackers then
+				trackers = {}
+				ob[component] = trackers
+			end
+
+			table.insert(trackers, fn)
+		end,
+		invoke = function(component, ...)
+			trackers_invoke(event, component, ...)
+		end
+	}
+	return function(component, fn)
+		local trackers = ob[component]
+		if not trackers then
+			trackers = {}
+			ob[component] = trackers
+		end
+
+		table.insert(trackers, fn)
+	end
+end
+
+local trackers = {
+	emplace = trackers_init("emplace"),
+	add = trackers_init("added"),
+	remove = trackers_init("removed")
+}
+
+return trackers

demo/wally.toml

@@ -5,4 +5,4 @@ registry = "https://github.com/UpliftGames/wally-index"
 realm = "shared"
 
 [dependencies]
-jabby = "alicesaidhi/jabby@0.2.0-rc.9"
+jabby = "alicesaidhi/jabby@0.2.2"

jecs.luau

@@ -46,7 +46,7 @@ export type Record = {
 }
 
 type IdRecord = {
-	columns: { number },
+	cache: { number },
 	counts: { number },
 	flags: number,
 	size: number,
@@ -90,60 +90,35 @@ local EcsOnArchetypeCreate =        HI_COMPONENT_ID + 12
 local EcsOnArchetypeDelete =        HI_COMPONENT_ID + 13
 local EcsRest =                     HI_COMPONENT_ID + 14
 
-local ECS_PAIR_FLAG =                                0x8
-local ECS_ID_FLAGS_MASK =                           0x10
-local ECS_ENTITY_MASK =              bit32.lshift(1, 24)
-local ECS_GENERATION_MASK =          bit32.lshift(1, 16)
-
 local ECS_ID_DELETE =                        0b0000_0001
 local ECS_ID_IS_TAG =                        0b0000_0010
 local ECS_ID_HAS_ON_ADD =                    0b0000_0100
 local ECS_ID_HAS_ON_SET =                    0b0000_1000
 local ECS_ID_HAS_ON_REMOVE =                 0b0001_0000
 local ECS_ID_MASK =                          0b0000_0000
--- stylua: ignore end
-local NULL_ARRAY = table.freeze({}) :: Column
 
-local function FLAGS_ADD(is_pair: boolean): number
-	local flags = 0x0
+local ECS_ENTITY_MASK =              bit32.lshift(1, 24)
+local ECS_GENERATION_MASK =          bit32.lshift(1, 16)
 
-	if is_pair then
-		flags = bit32.bor(flags, ECS_PAIR_FLAG) -- HIGHEST bit in the ID.
-	end
-	if false then
-		flags = bit32.bor(flags, 0x4) -- Set the second flag to true
-	end
-	if false then
-		flags = bit32.bor(flags, 0x2) -- Set the third flag to true
-	end
-	if false then
-		flags = bit32.bor(flags, 0x1) -- LAST BIT in the ID.
-	end
+local NULL_ARRAY = table.freeze({})
 
-	return flags
-end
 
-local function ECS_COMBINE(source: number, target: number): i53
-	return (source * 268435456) + (target * ECS_ID_FLAGS_MASK)
+local function ECS_COMBINE(id: number, generation: number): i53
+	return id + (generation * ECS_ENTITY_MASK)
 end
+local ECS_PAIR_OFFSET = 2^48
 
 local function ECS_IS_PAIR(e: number): boolean
-	return if e > ECS_ENTITY_MASK then (e % ECS_ID_FLAGS_MASK) // ECS_PAIR_FLAG ~= 0 else false
-end
-
--- HIGH 24 bits LOW 24 bits
-local function ECS_GENERATION(e: i53): i24
-	return if e > ECS_ENTITY_MASK then (e // ECS_ID_FLAGS_MASK) % ECS_GENERATION_MASK else 0
+	return e > ECS_PAIR_OFFSET
 end
 
 local function ECS_GENERATION_INC(e: i53)
 	if e > ECS_ENTITY_MASK then
-		local flags = e // ECS_ID_FLAGS_MASK
-		local id = flags // ECS_ENTITY_MASK
-		local generation = flags % ECS_GENERATION_MASK
+		local id = e % ECS_ENTITY_MASK
+		local generation = e // ECS_ENTITY_MASK
 
 		local next_gen = generation + 1
-		if next_gen > ECS_GENERATION_MASK then
+		if next_gen >= ECS_GENERATION_MASK then
 			return id
 		end
 
@@ -152,22 +127,23 @@ local function ECS_GENERATION_INC(e: i53)
 	return ECS_COMBINE(e, 1)
 end
 
--- FIRST gets the high ID
-local function ECS_ENTITY_T_HI(e: i53): i24
-	return if e > ECS_ENTITY_MASK then (e // ECS_ID_FLAGS_MASK) % ECS_ENTITY_MASK else e
-end
-
--- SECOND
 local function ECS_ENTITY_T_LO(e: i53): i24
-	return if e > ECS_ENTITY_MASK then (e // ECS_ID_FLAGS_MASK) // ECS_ENTITY_MASK else e
+	return e % ECS_ENTITY_MASK
 end
 
-local function _STRIP_GENERATION(e: i53): i24
-	return ECS_ENTITY_T_LO(e)
+local function ECS_GENERATION(e: i53)
+	return e // ECS_ENTITY_MASK
+end
+
+local function ECS_ENTITY_T_HI(e: i53): i24
+	return e // ECS_ENTITY_MASK
 end
 
 local function ECS_PAIR(pred: i53, obj: i53): i53
-	return ECS_COMBINE(ECS_ENTITY_T_LO(pred), ECS_ENTITY_T_LO(obj)) + FLAGS_ADD(--[[isPair]] true) :: i53
+	pred %= ECS_ENTITY_MASK
+	obj %= ECS_ENTITY_MASK
+
+	return obj + (pred * 2^24) + ECS_PAIR_OFFSET
 end
 
 local function entity_index_try_get_any(entity_index: EntityIndex, entity: number): Record?
@@ -236,14 +212,14 @@ local function entity_index_new_id(entity_index: EntityIndex): i53
 	return id
 end
 
--- ECS_PAIR_FIRST, gets the relationship target / obj / HIGH bits
 local function ecs_pair_first(world, e)
-	return entity_index_get_alive(world.entity_index, ECS_ENTITY_T_LO(e))
+	local pred = (e - ECS_PAIR_OFFSET) // ECS_ENTITY_MASK
+	return entity_index_get_alive(world.entity_index, pred)
 end
 
--- ECS_PAIR_SECOND gets the relationship / pred / LOW bits
 local function ecs_pair_second(world, e)
-	return entity_index_get_alive(world.entity_index, ECS_ENTITY_T_HI(e))
+	local obj = (e - ECS_PAIR_OFFSET) % ECS_ENTITY_MASK
+	return entity_index_get_alive(world.entity_index, obj)
 end
 
 local function query_match(query, archetype: Archetype)
@@ -476,11 +452,11 @@ local function world_target(world: World, entity: i53, relation: i24, index: num
 		return nil
 	end
 
-	if nth >= count then
-		nth = nth + count + 1
+	if nth > count then
+		nth = nth + count
 	end
 
-	local tr = idr.columns[archetype_id]
+	local tr = idr.cache[archetype_id]
 
 	nth = archetype.types[nth + tr]
 
@@ -537,7 +513,7 @@ local function id_record_ensure(world: World, id: number): IdRecord
 
 		idr = {
 			size = 0,
-			columns = {},
+			cache = {},
 			counts = {},
 			flags = flags,
 			hooks = {
@@ -562,7 +538,7 @@ local function archetype_append_to_records(
 	local archetype_id = archetype.id
 	local archetype_records = archetype.records
 	local archetype_counts = archetype.counts
-	local idr_columns = idr.columns
+	local idr_columns = idr.cache
 	local idr_counts = idr.counts
 	local tr = idr_columns[archetype_id]
 	if not tr then
@@ -860,16 +836,16 @@ local function world_set(world: World, entity: i53, id: i53, data: unknown): ()
 		end
 	end
 
-	local on_add = idr_hooks.on_add
-	if on_add then
-		on_add(entity)
-	end
-
 	local tr = to.records[id]
 	local column = to.columns[tr]
 
 	column[record.row] = data
 
+	local on_add = idr_hooks.on_add
+	if on_add then
+		on_add(entity)
+	end
+
 	local on_set = idr_hooks.on_set
 	if on_set then
 		on_set(entity, data)
@@ -899,15 +875,16 @@ local function world_remove(world: World, entity: i53, id: i53)
 	if not from then
 		return
 	end
-	local to = archetype_traverse_remove(world, id, from)
 
-	if from ~= to then
+	if from.records[id] then
 		local idr = world.component_index[id]
 		local on_remove = idr.hooks.on_remove
 		if on_remove then
 			on_remove(entity)
 		end
 
+		local to = archetype_traverse_remove(world, id, record.archetype)
+
 		entity_move(entity_index, entity, record, to)
 	end
 end
@@ -1063,7 +1040,7 @@ local function archetype_destroy(world: World, archetype: Archetype)
 
 	for id in records do
 		local idr = component_index[id]
-		idr.columns[archetype_id] = nil :: any
+		idr.cache[archetype_id] = nil :: any
 		idr.counts[archetype_id] = nil
 		idr.size -= 1
 		records[id] = nil :: any
@@ -1122,7 +1099,7 @@ do
 		if idr then
 			local flags = idr.flags
 			if bit32.band(flags, ECS_ID_DELETE) ~= 0 then
-				for archetype_id in idr.columns do
+				for archetype_id in idr.cache do
 					local idr_archetype = archetypes[archetype_id]
 
 					local entities = idr_archetype.entities
@@ -1134,7 +1111,7 @@ do
 					archetype_destroy(world, idr_archetype)
 				end
 			else
-				for archetype_id in idr.columns do
+				for archetype_id in idr.cache do
 					local idr_archetype = archetypes[archetype_id]
 					local entities = idr_archetype.entities
 					local n = #entities
@@ -1147,55 +1124,66 @@ do
 			end
 		end
 
-		local sparse_array = entity_index.sparse_array
 		local dense_array = entity_index.dense_array
 
 		if idr_t then
-			for archetype_id in idr_t.columns do
-				local children = {}
+			local children
+			local ids
+			local count = 0
+			local archetype_ids = idr_t.cache
+			for archetype_id in archetype_ids do
 				local idr_t_archetype = archetypes[archetype_id]
-
 				local idr_t_types = idr_t_archetype.types
-
-				for _, child in idr_t_archetype.entities do
-					table.insert(children, child)
-				end
-
-				local n = #children
+				local entities = idr_t_archetype.entities
+				local removal_queued = false
 
 				for _, id in idr_t_types do
 					if not ECS_IS_PAIR(id) then
 						continue
 					end
 					local object = ecs_pair_second(world, id)
-					if object == delete then
+					if object ~= delete then
+						continue
+					end
 					local id_record = component_index[id]
 					local flags = id_record.flags
 					local flags_delete_mask: number = bit32.band(flags, ECS_ID_DELETE)
 					if flags_delete_mask ~= 0 then
-							for i = n, 1, -1 do
-								world_delete(world, children[i])
+						for i = #entities, 1, -1 do
+							local child = entities[i]
+							world_delete(world, child)
 						end
 						break
 					else
-							local on_remove = id_record.hooks.on_remove
-							local to = archetype_traverse_remove(world, id, idr_t_archetype)
-							local empty = #to.types == 0
-							for i = n, 1, -1 do
-								local child = children[i]
-								if on_remove then
-									on_remove(child)
+					    if not ids then
+							ids = {}
 						end
-								local r = sparse_array[ECS_ENTITY_T_LO(child)]
-								if not empty then
-									entity_move(entity_index, child, r, to)
+						ids[id] = true
+						removal_queued = true
 					end
 				end
+
+				if not removal_queued then
+					continue
+				end
+				if not children then
+					children = {}
+				end
+				local n = #entities
+				table.move(entities, 1, n, count + 1, children)
+				count += n
+			end
+
+			if ids then
+				for id in ids do
+					for _, child in children do
+						world_remove(world, child, id)
 					end
 				end
 			end
 
-				archetype_destroy(world, idr_t_archetype)
+			for archetype_id in archetype_ids do
+				archetype_destroy(world, archetypes[archetype_id])
 			end
 		end
 
@@ -2096,7 +2084,7 @@ local function world_query(world: World, ...)
 		return q
 	end
 
-	for archetype_id in idr.columns do
+	for archetype_id in idr.cache do
 		local compatibleArchetype = archetypes[archetype_id]
 		if #compatibleArchetype.entities == 0 then
 			continue
@@ -2130,9 +2118,9 @@ local function world_each(world: World, id): () -> ()
 		return NOOP
 	end
 
-	local idr_columns = idr.columns
+	local idr_cache = idr.cache
 	local archetypes = world.archetypes
-	local archetype_id = next(idr_columns, nil) :: number
+	local archetype_id = next(idr_cache, nil) :: number
 	local archetype = archetypes[archetype_id]
 	if not archetype then
 		return NOOP
@@ -2144,7 +2132,7 @@ local function world_each(world: World, id): () -> ()
 	return function(): any
 		local entity = entities[row]
 		while not entity do
-			archetype_id = next(idr_columns, archetype_id) :: number
+			archetype_id = next(idr_cache, archetype_id) :: number
 			if not archetype_id then
 				return
 			end
@@ -2402,51 +2390,44 @@ export type World = {
 	observable: any,
 
 	--- Creates a new entity
-	entity: (self: World) -> Entity,
+	entity: (self: World, id: Entity?) -> Entity,
 	--- Creates a new entity located in the first 256 ids.
 	--- These should be used for static components for fast access.
 	component: <T>(self: World) -> Entity<T>,
 	--- Gets the target of an relationship. For example, when a user calls
 	--- `world:target(id, ChildOf(parent), 0)`, you will obtain the parent entity.
-	target: <T, U>(self: World, id: Entity<T>, relation: Entity<U>, index: number?) -> Entity?,
+	target: (self: World, id: Entity, relation: Id, index: number?) -> Entity?,
 	--- Deletes an entity and all it's related components and relationships.
-	delete: <T>(self: World, id: Entity<T>) -> (),
+	delete: (self: World, id: Entity) -> (),
 
 	--- Adds a component to the entity with no value
-	add: <T, U>(self: World, id: Entity<T>, component: Id<U>) -> (),
+	add: <T>(self: World, id: Entity, component: Id) -> (),
 	--- Assigns a value to a component on the given entity
-	set: <T, U>(self: World, id: Entity<T>, component: Id<U>, data: U) -> (),
+	set: <T>(self: World, id: Entity, component: Id<T>, data: T) -> (),
 
 	cleanup: (self: World) -> (),
 	-- Clears an entity from the world
-	clear: <T>(self: World, id: Entity<T>) -> (),
+	clear: (self: World, id: Entity) -> (),
 	--- Removes a component from the given entity
-	remove: <T, U>(self: World, id: Entity<T>, component: Id<U>) -> (),
+	remove: (self: World, id: Entity, component: Id) -> (),
 	--- Retrieves the value of up to 4 components. These values may be nil.
-	get: (<T, A>(self: World, id: Entity<T>, Id<A>) -> A?)
-		& (<T, A, B>(self: World, id: Entity<T>, Id<A>, Id<B>) -> (A?, B?))
-		& (<T, A, B, C>(self: World, id: Entity<T>, Id<A>, Id<B>, Id<C>) -> (A?, B?, C?))
-		& <T, A, B, C, D>(self: World, id: Entity<T>, Id<A>, Id<B>, Id<C>, Id<D>) -> (A?, B?, C?, D?),
+	get: (<A>(self: World, id: Entity, Id<A>) -> A?)
+		& (<A, B>(self: World, id: Entity, Id<A>, Id<B>) -> (A?, B?))
+		& (<A, B, C>(self: World, id: Entity, Id<A>, Id<B>, Id<C>) -> (A?, B?, C?))
+		& <A, B, C, D>(self: World, id: Entity, Id<A>, Id<B>, Id<C>, Id<D>) -> (A?, B?, C?, D?),
 
 	--- Returns whether the entity has the ID.
-	has: (<T, U>(self: World, entity: Entity<T>, ...Id<U>) -> boolean)
-		& (<T, U, V>(self: World, entity: Entity<T>, Id<U>, Id<V>) -> boolean)
-		& (<T, U, V, W>(self: World, entity: Entity<T>, Id<U>, Id<V>, Id<W>) -> boolean)
-		& (<T, U, V, W, X>(self: World, entity: Entity<T>, Id<U>, Id<V>, Id<W>, Id<X>) -> boolean)
-		& (<T, U, V, W, X, Y>(self: World, entity: Entity<T>, Id<U>, Id<V>, Id<W>, Id<X>, Id<Y>) -> boolean)
-		& (<T, U, V, W, X, Y, Z>(self: World, entity: Entity<T>, Id<U>, Id<V>, Id<W>, Id<X>, Id<Y>, Id<Z>) -> boolean)
-		& (<T, U, V, W, X, Y, Z, A>(self: World, entity: Entity<T>, Id<U>, Id<V>, Id<W>, Id<X>, Id<Y>, Id<Z>, Id<A>) -> boolean)
-		& (<T, U, V, W, X, Y, Z, A>(self: World, entity: Entity<T>, Id<U>, Id<V>, Id<W>, Id<X>, Id<Y>, Id<Z>, Id<A>, ...unknown) -> boolean),
+	has: (self: World, entity: Entity, ...Id) -> boolean,
 
 	--- Get parent (target of ChildOf relationship) for entity. If there is no ChildOf relationship pair, it will return nil.
-	parent: <T>(self: World, entity: Entity<T>) -> Entity,
+	parent:(self: World, entity: Entity) -> Entity,
 
 	--- Checks if the world contains the given entity
-	contains: <T>(self: World, entity: Entity<T>) -> boolean,
+	contains:(self: World, entity: Entity) -> boolean,
 
-	each: <T>(self: World, id: Id<T>) -> () -> Entity,
+	each: (self: World, id: Id) -> () -> Entity,
 
-	children: <T>(self: World, id: Id<T>) -> () -> Entity,
+	children: (self: World, id: Id) -> () -> Entity,
 
 	--- Searches the world for entities that match a given query
 	query: (<A>(World, Id<A>) -> Query<A>)
@@ -2477,6 +2458,7 @@ export type World = {
 
 return {
 	World = World :: { new: () -> World },
+	world = World.new :: () -> World,
 
 	OnAdd = EcsOnAdd :: Entity<(entity: Entity) -> ()>,
 	OnRemove = EcsOnRemove :: Entity<(entity: Entity) -> ()>,
@@ -2500,6 +2482,8 @@ return {
 	ECS_GENERATION = ECS_GENERATION,
 	ECS_ID_IS_WILDCARD = ECS_ID_IS_WILDCARD,
 
+	ECS_ID_DELETE = ECS_ID_DELETE,
+
 	IS_PAIR = ECS_IS_PAIR,
 	pair_first = ecs_pair_first,
 	pair_second = ecs_pair_second,

test/devtools_test.luau

@@ -0,0 +1,25 @@
+local jecs = require("@jecs")
+local pair = jecs.pair
+local ChildOf = jecs.ChildOf
+local lifetime_tracker_add = require("@tools/lifetime_tracker")
+local pe = require("@tools/entity_visualiser").prettify
+local world = lifetime_tracker_add(jecs.world(), {padding_enabled=false})
+local FriendsWith = world:component()
+local _1 = world:print_snapshot()
+local e1 = world:entity()
+local e2 = world:entity()
+world:delete(e2)
+
+local _2 = world:print_snapshot()
+local e3 = world:entity()
+world:add(e3, pair(ChildOf, e1))
+local e4 = world:entity()
+world:add(e4, pair(FriendsWith, e3))
+local _3 = world:print_snapshot()
+world:delete(e1)
+world:delete(e3)
+local _4 = world:print_snapshot()
+world:print_entity_index()
+world:entity()
+world:entity()
+local _5 = world:print_snapshot()

test/tests.luau

@@ -26,6 +26,50 @@ local N = 2 ^ 8
 type World = jecs.World
 type Entity<T=nil> = jecs.Entity<T>
 
+local c = {
+	white_underline = function(s: any)
+		return `\27[1;4m{s}\27[0m`
+	end,
+
+	white = function(s: any)
+		return `\27[37;1m{s}\27[0m`
+	end,
+
+	green = function(s: any)
+		return `\27[32;1m{s}\27[0m`
+	end,
+
+	red = function(s: any)
+		return `\27[31;1m{s}\27[0m`
+	end,
+
+	yellow = function(s: any)
+		return `\27[33;1m{s}\27[0m`
+	end,
+
+	red_highlight = function(s: any)
+		return `\27[41;1;30m{s}\27[0m`
+	end,
+
+	green_highlight = function(s: any)
+		return `\27[42;1;30m{s}\27[0m`
+	end,
+
+	gray = function(s: any)
+		return `\27[30;1m{s}\27[0m`
+	end,
+}
+
+local function pe(e)
+	local gen = ECS_GENERATION(e)
+	return c.green(`e{ECS_ID(e)}`)..c.yellow(`v{gen}`)
+end
+
+local function pp(e)
+	local gen = ECS_GENERATION(e)
+	return c.green(`e{ECS_ID(e)}`)..c.yellow(`v{jecs.ECS_ENTITY_T_HI(e)}`)
+end
+
 local function debug_world_inspect(world: World)
 	local function record(e): jecs.Record
 		return entity_index_try_get_any(world.entity_index, e) :: any
@@ -67,10 +111,63 @@ local function debug_world_inspect(world: World)
 	}
 end
 
+local dwi = debug_world_inspect
+
 local function name(world, e)
 	return world:get(e, jecs.Name)
 end
 
+TEST("#repro", function()
+	local world = world_new()
+
+	local function getTargets(relation)
+		local tgts = {}
+		local pairwildcard = pair(relation, jecs.Wildcard)
+		for _, archetype in world:query(pairwildcard):archetypes() do
+			local tr = archetype.records[pairwildcard]
+			local count = archetype.counts[pairwildcard]
+			local types = archetype.types
+			for _, entity in archetype.entities do
+			    for i = 0, count - 1 do
+				    local tgt = jecs.pair_second(world, types[i + tr])
+				    table.insert(tgts, tgt)
+			    end
+			end
+		end
+		return tgts
+	end
+
+	local Attacks = world:component()
+	local Eats = world:component()
+
+	local function setAttacksAndEats(entity1, entity2)
+		world:add(entity1, pair(Attacks, entity2))
+		world:add(entity1, pair(Eats, entity2))
+	end
+
+	local e1 = world:entity()
+	local e2 = world:entity()
+	local e3 = world:entity()
+	setAttacksAndEats(e3, e1)
+	setAttacksAndEats(e3, e2)
+	setAttacksAndEats(e1, e2)
+	local d = dwi(world)
+	world:delete(e2)
+	local types1 = { pair(Attacks, e1), pair(Eats, e1) }
+	table.sort(types1)
+
+
+	CHECK(d.tbl(e1).type == "")
+	CHECK(d.tbl(e3).type == table.concat(types1, "_"))
+
+	for _, entity in getTargets(Attacks) do
+		CHECK(entity == e1)
+	end
+	for _, entity in getTargets(Eats) do
+		CHECK(entity == e1)
+	end
+end)
+
 TEST("archetype", function()
 	local archetype_traverse_add = jecs.archetype_traverse_add
 	local archetype_traverse_remove = jecs.archetype_traverse_remove
@@ -140,6 +237,9 @@ TEST("world:cleanup()", function()
 	CHECK(#archetype_index["1_2_3"].entities == 1)
 end)
 
+local pe = require("@tools/entity_visualiser").prettify
+local lifetime_tracker_add = require("@tools/lifetime_tracker")
+
 TEST("world:entity()", function()
 	do
 		CASE("unique IDs")
@@ -1199,6 +1299,7 @@ TEST("world:delete", function()
 			world:delete(e)
 		end)
 
+		local d = debug_world_inspect(world)
 		for i, friend in friends do
 			CHECK(not world:has(friend, pair(FriendsWith, e)))
 			CHECK(world:has(friend, Health))
@@ -1274,10 +1375,15 @@ TEST("world:target", function()
 		world:add(e, pair(C, D))
 
 		CHECK(pair(A, B) < pair(A, C))
-		CHECK(pair(A, E) < pair(B, C))
+		CHECK(pair(A, C) < pair(A, D))
+		CHECK(pair(C, A) < pair(C, D))
 
 		local records = debug_world_inspect(world).records(e)
 		CHECK(jecs.pair_first(world, pair(B, C)) == B)
+		local r = jecs.entity_index_try_get(world.entity_index, e)
+		local archetype = r.archetype
+		local counts = archetype.counts
+		CHECK(counts[pair(A, __)] == 4)
 		CHECK(records[pair(B, C)] > records[pair(A, E)])
 		CHECK(world:target(e, A, 0) == B)
 		CHECK(world:target(e, A, 1) == C)
@@ -1287,6 +1393,28 @@ TEST("world:target", function()
 		CHECK(world:target(e, B, 1) == D)
 		CHECK(world:target(e, C, 0) == D)
 		CHECK(world:target(e, C, 1) == nil)
+
+		-- for id in archetype.records do
+		-- 	local f = world:get(ecs_pair_first(world, id), jecs.Name)
+		-- 	local s = world:get(ecs_pair_second(world, id), jecs.Name)
+		-- 	print(`({f}, {s})`)
+		-- end
+		--
+
+		CHECK(archetype.records[pair(A, B)] == 1)
+		CHECK(archetype.records[pair(A, C)] == 2)
+		CHECK(archetype.records[pair(A, D)] == 3)
+		CHECK(archetype.records[pair(A, E)] == 4)
+		-- print("(A, B)", archetype.records[pair(A, B)])
+		-- print("(A, C)", archetype.records[pair(A, C)])
+		-- print("(A, D)", archetype.records[pair(A, D)])
+		-- print("(A, E)", archetype.records[pair(A, E)])
+
+		-- print(pair(A, D), pair(B, C))
+		-- print("(B, C)", archetype.records[pair(B, C)])
+
+		CHECK(world:target(e, C, 0) == D)
+		CHECK(world:target(e, C, 1) == nil)
 	end
 
 	do
@@ -1377,11 +1505,12 @@ TEST("Hooks", function()
 			local world = jecs.World.new()
 			local A = world:component() :: Entity<boolean>
 			local e1 = world:entity()
-			world:add(e1, A)
 			world:set(A, jecs.OnRemove, function(entity)
 				CHECK(e1 == entity)
-				CHECK(not world:has(e1, A))
+				CHECK(world:has(e1, A))
 			end)
+			world:add(e1, A)
+
 			world:remove(e1, A)
 			CHECK(not world:has(e1, A))
 		end
@@ -1401,7 +1530,7 @@ TEST("Hooks", function()
 			world:set(e, A, true)
 			world:remove(e, A)
 			CHECK(not world:get(e, A))
-			CHECK(not world:get(e, B))
+			CHECK(world:get(e, B))
 		end
 	end
 end)
@@ -1469,18 +1598,18 @@ TEST("repro", function()
 	do CASE "#1"
 		local world = world_new()
 		local reproEntity = world:component()
-		local components = { Cooldown = world:component() :: jecs.Id<number> }
+		local components = { Cooldown = world:component() :: jecs.Entity<number> }
 		world:set(reproEntity, components.Cooldown, 2)
 
 		local function updateCooldowns(dt: number)
 			local toRemove = {}
 
-			for id, cooldown in world:query(components.Cooldown):iter() do
+			local it = world:query(components.Cooldown):iter()
+			for id, cooldown in it do
 				cooldown -= dt
 
 				if cooldown <= 0 then
 					table.insert(toRemove, id)
-					print("removing")
 					-- world:remove(id, components.Cooldown)
 				else
 					world:set(id, components.Cooldown, cooldown)
@@ -1529,6 +1658,10 @@ TEST("wildcard query", function()
 
 		local entity = world:entity()
 
+		local p = pair(Relation, A)
+		CHECK(jecs.pair_first(world, p) == Relation)
+		CHECK(jecs.pair_second(world, p) == A)
+		local w = dwi(world)
 		world:add(entity, pair(Relation, A))
 
 		local counter = 0

tools/ansi.luau

@@ -0,0 +1,33 @@
+return {
+	white_underline = function(s: any)
+		return `\27[1;4m{s}\27[0m`
+	end,
+
+	white = function(s: any)
+		return `\27[37;1m{s}\27[0m`
+	end,
+
+	green = function(s: any)
+		return `\27[32;1m{s}\27[0m`
+	end,
+
+	red = function(s: any)
+		return `\27[31;1m{s}\27[0m`
+	end,
+
+	yellow = function(s: any)
+		return `\27[33;1m{s}\27[0m`
+	end,
+
+	red_highlight = function(s: any)
+		return `\27[41;1;30m{s}\27[0m`
+	end,
+
+	green_highlight = function(s: any)
+		return `\27[42;1;30m{s}\27[0m`
+	end,
+
+	gray = function(s: any)
+		return `\27[30;1m{s}\27[0m`
+	end,
+}

tools/entity_visualiser.luau

@@ -0,0 +1,43 @@
+local jecs = require("@jecs")
+local ECS_GENERATION = jecs.ECS_GENERATION
+local ECS_ID = jecs.ECS_ID
+local ansi = require("@tools/ansi")
+
+local function pe(e: any)
+	local gen = ECS_GENERATION(e)
+	return ansi.green(`e{ECS_ID(e)}`)..ansi.yellow(`v{gen}`)
+end
+
+local function name(world: jecs.World, id: any)
+	return world:get(id, jecs.Name) or `${id}`
+end
+
+local function components(world: jecs.World, entity: any)
+	local r = jecs.entity_index_try_get(world.entity_index, entity)
+	if not r then
+		return false
+	end
+
+	local archetype = r.archetype
+	local row = r.row
+	print(`Entity {pe(entity)}`)
+	print("-----------------------------------------------------")
+	for i, column in archetype.columns do
+		local component = archetype.types[i]
+		local n
+		if jecs.IS_PAIR(component) then
+			n = `({name(world, jecs.pair_first(world, component))}, {name(world, jecs.pair_second(world, component))})`
+		else
+			n = name(world, component)
+		end
+		local data = column[row] or "TAG"
+		print(`| {n} | {data} |`)
+	end
+	print("-----------------------------------------------------")
+	return true
+end
+
+return {
+	components = components,
+	prettify = pe,
+}

tools/lifetime_tracker.luau

@@ -0,0 +1,215 @@
+local jecs = require("@jecs")
+local ECS_GENERATION = jecs.ECS_GENERATION
+local ECS_ID = jecs.ECS_ID
+local __ = jecs.Wildcard
+local pair = jecs.pair
+
+local prettify = require("@tools/entity_visualiser").prettify
+
+local pe = prettify
+local ansi = require("@tools/ansi")
+
+function print_centered_entity(entity, width: number)
+    local entity_str = tostring(entity)
+    local entity_length = #entity_str
+
+    local padding_total = width - 2 - entity_length
+
+    local padding_left = math.floor(padding_total / 2)
+    local padding_right = padding_total - padding_left
+
+    local centered_str = string.rep(" ", padding_left) .. entity_str .. string.rep(" ", padding_right)
+
+    print("|" .. centered_str .. "|")
+end
+
+local function name(world, e)
+	return world:get(world, e, jecs.Name) or pe(e)
+end
+local padding_enabled = false
+local function pad()
+	if padding_enabled then
+		print("")
+	end
+end
+
+local function lifetime_tracker_add(world: jecs.World, opt)
+	local entity_index = world.entity_index
+	local dense_array = entity_index.dense_array
+	local component_index = world.component_index
+
+	local ENTITY_RANGE = (jecs.Rest :: any) + 1
+
+	local w = setmetatable({}, { __index = world })
+
+	padding_enabled = opt.padding_enabled
+
+	local world_entity = world.entity
+	w.entity = function(self, entity)
+		if entity then
+			return world_entity(world, entity)
+		end
+		local will_recycle = entity_index.max_id ~= entity_index.alive_count
+		local e = world_entity(world)
+		if will_recycle then
+			print(`*recycled {pe(e)}`)
+		else
+			print(`*created {pe(e)}`)
+		end
+		pad()
+		return e
+	end
+	w.print_entity_index = function(self)
+		local max_id = entity_index.max_id
+		local alive_count = entity_index.alive_count
+		local alive = table.move(dense_array, 1+jecs.Rest::any, alive_count, 1, {})
+		local dead = table.move(dense_array, alive_count + 1, max_id, 1, {})
+
+		local sep = "|--------|"
+		if #alive > 0 then
+			print("|-alive--|")
+			for i = 1, #alive do
+				local e = pe(alive[i])
+				print_centered_entity(e, 32)
+				print(sep)
+			end
+			print("\n")
+		end
+
+		if #dead > 0 then
+			print("|--dead--|")
+			for i = 1, #dead do
+				print_centered_entity(pe(dead[i]), 32)
+				print(sep)
+			end
+		end
+		pad()
+	end
+	local timelines = {}
+	w.print_snapshot = function(self)
+		local timeline = #timelines + 1
+		local entity_column_width = 10
+		local status_column_width = 8
+
+		local header = string.format("| %-" .. entity_column_width .. "s |", "Entity")
+		for i = 1, timeline do
+			header = header .. string.format(" %-" .. status_column_width .. "s |", string.format("T%d", i))
+		end
+
+		local max_id = entity_index.max_id
+		local alive_count = entity_index.alive_count
+		local alive = table.move(dense_array, 1+jecs.Rest::any, alive_count, 1, {})
+		local dead = table.move(dense_array, alive_count + 1, max_id, 1, {})
+
+		local data = {}
+		print("-------------------------------------------------------------------")
+		print(header)
+
+		-- Store the snapshot data for this timeline
+		for i = ENTITY_RANGE, max_id do
+			if dense_array[i] then
+				local entity = dense_array[i]
+				local id = ECS_ID(entity)
+				local status = "alive"
+				if not world:contains(entity) then
+					status = "dead"
+				end
+				data[id] = status
+			end
+		end
+
+		table.insert(timelines, data)
+
+		-- Create a table to hold entity data for sorting
+		local entities = {}
+		for i = ENTITY_RANGE, max_id do
+			if dense_array[i] then
+				local entity = dense_array[i]
+				local id = ECS_ID(entity)
+				-- Push entity and id into the new `entities` table
+				table.insert(entities, {entity = entity, id = id})
+			end
+		end
+
+		-- Sort the entities by ECS_ID
+		table.sort(entities, function(a, b)
+			return a.id < b.id
+		end)
+
+		-- Print the sorted rows
+		for _, entity_data in ipairs(entities) do
+			local entity = entity_data.entity
+			local id = entity_data.id
+			local status = "alive"
+			if id > alive_count then
+				status = "dead"
+			end
+			local row = string.format("| %-" .. entity_column_width .. "s     |", pe(entity))
+			for j = 1, timeline do
+				local timeline_data = timelines[j]
+				local entity_data = timeline_data[id]
+				if entity_data then
+					row = row .. string.format(" %-" .. status_column_width .. "s |", entity_data)
+				else
+					row = row .. string.format(" %-" .. status_column_width .. "s |", "-")
+				end
+			end
+			print(row)
+		end
+		print("-------------------------------------------------------------------")
+		pad()
+	end
+	local world_add = world.add
+	local relations = {}
+	w.add = function(self, entity: any, component: any)
+		world_add(world, entity, component)
+		if jecs.IS_PAIR(component) then
+			local relation = jecs.pair_first(world, component)
+			local target = jecs.pair_second(world, component)
+			print(`*added ({pe(relation)}, {pe(target)}) to {pe(entity)}`)
+			pad()
+		end
+
+	end
+
+	local world_delete = world.delete
+	w.delete = function(self, e)
+		world_delete(world, e)
+
+		local idr_t = component_index[pair(__, e)]
+		if idr_t then
+			for archetype_id in idr_t.cache do
+				local archetype = world.archetypes[archetype_id]
+				for _, id in archetype.types do
+					if not jecs.IS_PAIR(id) then
+						continue
+					end
+					local object = jecs.pair_second(world, id)
+					if object ~= e then
+						continue
+					end
+					local id_record = component_index[id]
+					local flags = id_record.flags
+					local flags_delete_mask: number = bit32.band(flags, jecs.ECS_ID_DELETE)
+					if flags_delete_mask ~= 0 then
+						for _, entity in archetype.entities do
+							print(`*deleted dependant {pe(entity)} of {pe(e)}`)
+							pad()
+						end
+						break
+					else
+						for _, entity in archetype.entities do
+							print(`*removed dependency ({pe(jecs.pair_first(world, id))}, {pe(object)}) from {pe(entity)}`)
+						end
+					end
+				end
+			end
+		end
+
+		print(`*deleted {pe(e)}`)
+		pad()
+	end
+	return w
+end
+
+return lifetime_tracker_add