From 6922019ed980a08e79cfa4960540362d4f8b8e3b Mon Sep 17 00:00:00 2001
From: Ukendio <ukendio@gmail.com>
Date: Sun, 27 Apr 2025 04:13:49 +0200
Subject: [PATCH] Short circuit return for non zero generation entities

---
 jecs.luau       | 48 ++++++++++++++++++------------------------------
 test/tests.luau | 41 +++++++++++++++++++++++++++--------------
 2 files changed, 45 insertions(+), 44 deletions(-)

diff --git a/jecs.luau b/jecs.luau
index 7bfeb68..b22bd70 100644
--- a/jecs.luau
+++ b/jecs.luau
@@ -772,39 +772,27 @@ local function world_entity(world: ecs_world_t, entity: i53?): i53
 		local r = sparse_array[index]
 		if r then
 			local dense = r.dense
-			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
+			if dense and r.dense ~= 0 then
+				local any = dense_array[dense]
+				if any ~= entity then
+					if dense > alive_count then
+						alive_count += 1
+						entity_index.alive_count = alive_count
+						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] = any
+						dense_array[dense] = e_swap
+					end
+					return any
 				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
+			else
+				r.dense = index
+				dense_array[index] = entity
 				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
-
-			r_swap.dense = dense
-			r.dense = alive_count
-			dense_array[alive_count] = any
-			dense_array[dense] = e_swap
-			return any
 		else
 			for i = max_id + 1, index do
 				sparse_array[i]	= { dense = i } :: ecs_record_t
diff --git a/test/tests.luau b/test/tests.luau
index c055c6e..bbef91d 100644
--- a/test/tests.luau
+++ b/test/tests.luau
@@ -659,6 +659,7 @@ 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)
@@ -667,27 +668,39 @@ TEST("world:entity()", function()
 		CHECK(world:contains(e2))
 
 		-- world:print_entity_index()
-		local e3 = world:entity(275)
+		print("-----")
+		local e3 = world:entity(375)
+		world:entity(376)
+		print("-----")
 
-		CHECK(e3 == 275)
+		print(e3)
+		CHECK(e3 == 375)
 		CHECK(world:contains(e3))
 
-		CHECK(e3 == world:entity(e3))
-
 		world:delete(e3)
 
-		local e3v1 = world:entity(275)
-		CHECK(not world:contains(275))
+		print("-------call 1-------")
+		local e3v1 = world:entity(375)
+		CHECK(not world:contains(375))
 		CHECK(jecs.ECS_GENERATION(e3v1) == 1)
-		CHECK(jecs.ECS_ID(e3v1) == 275)
-
-
+		CHECK(jecs.ECS_ID(e3v1) == 375)
 		CHECK(world:contains(e3v1))
-		-- world:print_entity_index()
-		world:entity(e3)
-
-		world:entity(e3)
-		world:entity(275)
+		print("-------call 2-------")
+		world:entity(382)
+		world:delete(382)
+		world:entity(376)
+		world:delete(e3v1)
+		print("--------------------")
+		print("-------call 3-------")
+		local e3v2 = world:entity(375)
+		CHECK(jecs.ECS_GENERATION(e3v2) == 2)
+		CHECK(jecs.ECS_ID(e3v2) == 375)
+		CHECK(not world:contains(e3v1))
+		CHECK(world:contains(e3v2))
+		print("----------------------")
+		print("-----call 4-------")
+		CHECK(world:entity(375) == e3v2)
+		print("------call 5")
 	end
 	local N = 2^8