Add setting to disable object expiry after a given year

src/lang/english.txt

@@ -2471,6 +2471,11 @@ STR_CONFIG_SETTING_PURCHASE_LAND_PERMITTED_HELPTEXT             :Set whether com
 STR_CONFIG_SETTING_BUILD_OBJECT_PERMITTED                       :Permit bulk construction of objects: {STRING2}
 STR_CONFIG_SETTING_BUILD_OBJECT_PERMITTED_HELPTEXT              :Set whether companies are permitted to construct objects by area, instead of one at a time
 
+STR_CONFIG_SETTING_NO_EXPIRE_OBJECTS_AFTER                      :No objects expire after: {STRING2}
+STR_CONFIG_SETTING_NO_EXPIRE_OBJECTS_AFTER_HELPTEXT             :Objects which would otherwise expire after this year remain available forever
+STR_CONFIG_SETTING_NO_EXPIRE_OBJECTS_AFTER_VALUE                :{NUM}
+STR_CONFIG_SETTING_NO_EXPIRE_OBJECTS_AFTER_ZERO                 :Off
+
 STR_PURCHASE_LAND_PERMITTED_NO                                  :No
 STR_PURCHASE_LAND_PERMITTED_SINGLE                              :Yes, 1 tile at a time
 STR_PURCHASE_LAND_PERMITTED_AREA                                :Yes, large areas at a time

src/newgrf_object.cpp

@@ -80,7 +80,8 @@ bool ObjectSpec::WasEverAvailable() const
 bool ObjectSpec::IsAvailable() const
 {
 	return this->WasEverAvailable() &&
-			(_date < this->end_of_life_date || this->end_of_life_date < this->introduction_date + 365);
+			(_date < this->end_of_life_date || this->end_of_life_date < this->introduction_date + 365 ||
+			(_settings_game.construction.no_expire_objects_after != 0 && _cur_year >= _settings_game.construction.no_expire_objects_after));
 }
 
 /**

src/settings_gui.cpp

@@ -2088,6 +2088,7 @@ static SettingsContainer &GetSettingsTree()
 			limitations->Add(new SettingEntry("construction.allow_docks_under_bridges"));
 			limitations->Add(new SettingEntry("construction.purchase_land_permitted"));
 			limitations->Add(new SettingEntry("construction.build_object_area_permitted"));
+			limitations->Add(new SettingEntry("construction.no_expire_objects_after"));
 		}
 
 		SettingsPage *disasters = main->Add(new SettingsPage(STR_CONFIG_SETTING_ACCIDENTS));

src/settings_type.h

@@ -454,6 +454,7 @@ struct ConstructionSettings {
 	bool   allow_docks_under_bridges;        ///< allow docks under bridges
 	byte   purchase_land_permitted;          ///< whether and how purchasing land is permitted
 	bool   build_object_area_permitted;      ///< whether building objects by area is permitted
+	Year   no_expire_objects_after;          ///< do not expire objects after this year
 
 	uint32 terraform_per_64k_frames;         ///< how many tile heights may, over a long period, be terraformed per 65536 frames?
 	uint16 terraform_frame_burst;            ///< how many tile heights may, over a short period, be terraformed?
@@ -615,8 +616,8 @@ struct VehicleSettings {
 	uint8  freight_trains;                   ///< value to multiply the weight of cargo by
 	bool   dynamic_engines;                  ///< enable dynamic allocation of engine data
 	bool   never_expire_vehicles;            ///< never expire vehicles
-	Year   no_expire_vehicles_after;         ///< do not expire vehicles ater this year
-	Year   no_introduce_vehicles_after;      ///< do not introduce vehicles ater this year
+	Year   no_expire_vehicles_after;         ///< do not expire vehicles after this year
+	Year   no_introduce_vehicles_after;      ///< do not introduce vehicles after this year
 	byte   extend_vehicle_life;              ///< extend vehicle life by this many years
 	byte   road_side;                        ///< the side of the road vehicles drive on
 	uint8  plane_crashes;                    ///< number of plane crashes, 0 = none, 1 = reduced, 2 = normal

src/table/settings/settings.ini

@@ -2078,6 +2078,21 @@ str      = STR_CONFIG_SETTING_BUILD_OBJECT_PERMITTED
 strhelp  = STR_CONFIG_SETTING_BUILD_OBJECT_PERMITTED_HELPTEXT
 patxname = ""build_object_area_permitted.construction.build_object_area_permitted""
 
+[SDT_VAR]
+var      = construction.no_expire_objects_after
+type     = SLE_INT32
+flags    = SF_GUI_0_IS_SPECIAL
+def      = 0
+min      = MIN_YEAR
+max      = MAX_YEAR
+interval = 1
+str      = STR_CONFIG_SETTING_NO_EXPIRE_OBJECTS_AFTER
+strhelp  = STR_CONFIG_SETTING_NO_EXPIRE_OBJECTS_AFTER_HELPTEXT
+strval   = STR_CONFIG_SETTING_NO_EXPIRE_OBJECTS_AFTER_VALUE
+cat      = SC_ADVANCED
+patxname = ""construction.no_expire_objects_after""
+post_cb  = [](auto) { InvalidateWindowClassesData(WC_BUILD_OBJECT, 0); }
+
 [SDT_BOOL]
 var      = station.adjacent_stations
 from     = SLV_62