From 315dd62bd98437342403f93d32f87dc017c3a2e0 Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Wed, 27 Mar 2024 19:25:03 +0000
Subject: [PATCH] Fix Vehicle::CopyVehicleConfigAndStatistics not releasing
 unit number

See: https://github.com/OpenTTD/OpenTTD/issues/12388
---
 src/train_cmd.cpp  |  3 +--
 src/vehicle.cpp    | 11 +++++++++++
 src/vehicle_base.h |  3 +++
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
index 5d2a3e8417..5915e96305 100644
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -2225,8 +2225,7 @@ CommandCost CmdMoveRailVehicle(TileIndex tile, DoCommandFlag flags, uint32_t p1,
 			}
 			/* Remove stuff not valid anymore for non-front engines. */
 			DeleteVehicleOrders(src);
-			Company::Get(src->owner)->freeunits[src->type].ReleaseID(src->unitnumber);
-			src->unitnumber = 0;
+			src->ReleaseUnitNumber();
 			if (!_settings_game.vehicle.non_leading_engines_keep_name) {
 				src->name.clear();
 			}
diff --git a/src/vehicle.cpp b/src/vehicle.cpp
index 22d23d5019..d5a80ea368 100644
--- a/src/vehicle.cpp
+++ b/src/vehicle.cpp
@@ -3710,6 +3710,17 @@ void Vehicle::ResetRefitCaps()
 	for (Vehicle *v = this; v != nullptr; v = v->Next()) v->refit_cap = v->cargo_cap;
 }
 
+/**
+ * Release the vehicle's unit number.
+ */
+void Vehicle::ReleaseUnitNumber()
+{
+	if (this->unitnumber != 0) {
+		Company::Get(this->owner)->freeunits[this->type].ReleaseID(this->unitnumber);
+		this->unitnumber = 0;
+	}
+}
+
 static bool ShouldVehicleContinueWaiting(Vehicle *v)
 {
 	if (v->GetNumOrders() < 1) return false;
diff --git a/src/vehicle_base.h b/src/vehicle_base.h
index 89a4a00bf5..951e658b60 100644
--- a/src/vehicle_base.h
+++ b/src/vehicle_base.h
@@ -907,6 +907,8 @@ public:
 
 	void ResetRefitCaps();
 
+	void ReleaseUnitNumber();
+
 	/**
 	 * Copy certain configurations and statistics of a vehicle after successful autoreplace/renew
 	 * The function shall copy everything that cannot be copied by a command (like orders / group etc),
@@ -917,6 +919,7 @@ public:
 	{
 		this->CopyConsistPropertiesFrom(src);
 
+		this->ReleaseUnitNumber();
 		this->unitnumber = src->unitnumber;
 
 		this->current_order = src->current_order;