jecs.luau

@@ -772,24 +772,39 @@ local function world_entity(world: ecs_world_t, entity: i53?): i53
 		local r = sparse_array[index]
 		if r then
 			local dense = r.dense
-			if dense and r.dense ~= 0 then
-				if dense < alive_count then
-					return entity
-				end
-			else
-				r.dense = index
+			if not dense or dense == 0 then
 				dense = index
 			end
+			local any = dense_array[dense]
+			if any == entity then
+				if alive_count > dense then
+					r.dense = dense
+					return entity
+				end
+				local e_swap = dense_array[alive_count]
+				local r_swap = sparse_array[alive_count]
+				r_swap.dense = dense
+				r.dense = alive_count
+				dense_array[alive_count] = entity
+				dense_array[dense] = e_swap
+				return entity
+			end
+
+			-- assert(any ~= 0) should never happen
+
+			local e_swap = dense_array[alive_count]
+			local r_swap = sparse_array[alive_count]
+
+			if dense <= alive_count then
+				alive_count += 1
+				entity_index.alive_count = alive_count
+			end
 
-			local e_swap = dense_array[dense]
-			local r_swap = entity_index_try_get_any(entity_index, e_swap) :: ecs_record_t
-			alive_count += 1
-			entity_index.alive_count = alive_count
 			r_swap.dense = dense
 			r.dense = alive_count
+			dense_array[alive_count] = any
 			dense_array[dense] = e_swap
-			dense_array[alive_count] = entity
-			return entity
+			return any
 		else
 			for i = max_id + 1, index do
 				sparse_array[i]	= { dense = i } :: ecs_record_t

test/tests.luau

@@ -659,13 +659,35 @@ end)
 TEST("world:entity()", function()
 	do CASE "desired id"
 		local world = jecs.world()
-		world:range(400, 1000)
 		local id = world:entity()
 		local e = world:entity(id + 5)
 		CHECK(e == id + 5)
 		CHECK(world:contains(e))
 		local e2 = world:entity()
 		CHECK(world:contains(e2))
+
+		-- world:print_entity_index()
+		local e3 = world:entity(275)
+
+		CHECK(e3 == 275)
+		CHECK(world:contains(e3))
+
+		CHECK(e3 == world:entity(e3))
+
+		world:delete(e3)
+
+		local e3v1 = world:entity(275)
+		CHECK(not world:contains(275))
+		CHECK(jecs.ECS_GENERATION(e3v1) == 1)
+		CHECK(jecs.ECS_ID(e3v1) == 275)
+
+
+		CHECK(world:contains(e3v1))
+		-- world:print_entity_index()
+		world:entity(e3)
+
+		world:entity(e3)
+		world:entity(275)
 	end
 	local N = 2^8