From c368ebb5e74632bc622534b37cd1447b97281e20 Mon Sep 17 00:00:00 2001
From: "Dylan K. Taylor" <odigiman@gmail.com>
Date: Tue, 10 Nov 2020 16:45:20 +0000
Subject: [PATCH 1/3] InventoryTransaction: beware of conflicting slot change
 actions with the same origin/target these types of chains would never
 normally occur, but they've been seen in the wild. Attempting to resolve such
 chains has exponentially increasing complexity.

---
 .../transaction/InventoryTransaction.php      | 31 +++++++++++++------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/src/pocketmine/inventory/transaction/InventoryTransaction.php b/src/pocketmine/inventory/transaction/InventoryTransaction.php
index b85395785..053a15712 100644
--- a/src/pocketmine/inventory/transaction/InventoryTransaction.php
+++ b/src/pocketmine/inventory/transaction/InventoryTransaction.php
@@ -230,21 +230,34 @@ class InventoryTransaction{
 	protected function findResultItem(Item $needOrigin, array $possibleActions) : ?Item{
 		assert(count($possibleActions) > 0);
 
+		$candidate = null;
+		$newList = $possibleActions;
 		foreach($possibleActions as $i => $action){
 			if($action->getSourceItem()->equalsExact($needOrigin)){
-				$newList = $possibleActions;
+				if($candidate !== null){
+					/*
+					 * we found multiple possible actions that match the origin action
+					 * this means that there are multiple ways that this chain could play out
+					 * if we cared so much about this, we could build all the possible chains in parallel and see which
+					 * variation managed to complete the chain, but this has an extremely high complexity which is not
+					 * worth the trouble for this scenario (we don't usually expect to see chains longer than a couple
+					 * of actions in here anyway), and might still result in multiple possible results.
+					 */
+					return null;
+				}
+				$candidate = $action;
 				unset($newList[$i]);
-				if(count($newList) === 0){
-					return $action->getTargetItem();
-				}
-				$result = $this->findResultItem($action->getTargetItem(), $newList);
-				if($result !== null){
-					return $result;
-				}
 			}
 		}
+		if($candidate === null){
+			//chaining is not possible with this origin, none of the actions are valid
+			return null;
+		}
 
-		return null;
+		if(count($newList) === 0){
+			return $candidate->getTargetItem();
+		}
+		return $this->findResultItem($candidate->getTargetItem(), $newList);
 	}
 
 	/**

From e8b6b56330c8918b911ccc48e88a88b1e2cd201c Mon Sep 17 00:00:00 2001
From: "Dylan K. Taylor" <odigiman@gmail.com>
Date: Tue, 10 Nov 2020 16:48:18 +0000
Subject: [PATCH 2/3] Release 3.15.4

---
 changelogs/3.15.md             | 3 +++
 src/pocketmine/VersionInfo.php | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/changelogs/3.15.md b/changelogs/3.15.md
index 364fd298d..a9ed9cb2c 100644
--- a/changelogs/3.15.md
+++ b/changelogs/3.15.md
@@ -49,3 +49,6 @@ Plugin developers should **only** update their required API to this version if y
 - `Maximum memory (system)` is no longer reported in `/status` due to having a misleading output (it was the same as the current memory usage).
 - The `Player Chunk Send` timer on timings reports now actually reports measurements of chunk sending, not chunk loading.
 - A new parent timer `World Load` has been added to timings reports, which aggregates timings from `syncChunkLoad` and subtimings from all worlds.
+
+# 3.15.4
+- Fixed a bug in the inventory transaction system that caused the server to freeze under some circumstances.
diff --git a/src/pocketmine/VersionInfo.php b/src/pocketmine/VersionInfo.php
index f0e73f017..ea250f4f8 100644
--- a/src/pocketmine/VersionInfo.php
+++ b/src/pocketmine/VersionInfo.php
@@ -34,5 +34,5 @@ const _VERSION_INFO_INCLUDED = true;
 
 const NAME = "PocketMine-MP";
 const BASE_VERSION = "3.15.4";
-const IS_DEVELOPMENT_BUILD = true;
+const IS_DEVELOPMENT_BUILD = false;
 const BUILD_NUMBER = 0;

From 574b7f6343886def824522e286dc497d905c5b3f Mon Sep 17 00:00:00 2001
From: "Dylan K. Taylor" <odigiman@gmail.com>
Date: Tue, 10 Nov 2020 16:48:18 +0000
Subject: [PATCH 3/3] 3.15.5 is next

---
 src/pocketmine/VersionInfo.php | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/pocketmine/VersionInfo.php b/src/pocketmine/VersionInfo.php
index ea250f4f8..7626b0092 100644
--- a/src/pocketmine/VersionInfo.php
+++ b/src/pocketmine/VersionInfo.php
@@ -33,6 +33,6 @@ if(defined('pocketmine\_VERSION_INFO_INCLUDED')){
 const _VERSION_INFO_INCLUDED = true;
 
 const NAME = "PocketMine-MP";
-const BASE_VERSION = "3.15.4";
-const IS_DEVELOPMENT_BUILD = false;
+const BASE_VERSION = "3.15.5";
+const IS_DEVELOPMENT_BUILD = true;
 const BUILD_NUMBER = 0;