Add setting to ignore object introduction dates

src/lang/english.txt

@@ -2476,6 +2476,9 @@ STR_CONFIG_SETTING_NO_EXPIRE_OBJECTS_AFTER_HELPTEXT             :Objects which w
 STR_CONFIG_SETTING_NO_EXPIRE_OBJECTS_AFTER_VALUE                :{NUM}
 STR_CONFIG_SETTING_NO_EXPIRE_OBJECTS_AFTER_ZERO                 :Off
 
+STR_CONFIG_SETTING_IGNORE_OBJECT_INTRO_DATES                    :Ignore object introduction dates: {STRING2}
+STR_CONFIG_SETTING_IGNORE_OBJECT_INTRO_DATES_HELPTEXT           :Set whether players are allowed to build objects before their introduction date.{}Does not apply to objects constructed during map generation.
+
 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

@@ -70,7 +70,7 @@ bool ObjectSpec::IsEverAvailable() const
  */
 bool ObjectSpec::WasEverAvailable() const
 {
-	return this->IsEverAvailable() && _date > this->introduction_date;
+	return this->IsEverAvailable() && (_date > this->introduction_date || (_settings_game.construction.ignore_object_intro_dates && !_generating_world));
 }
 
 /**

src/settings_gui.cpp

@@ -2089,6 +2089,7 @@ static SettingsContainer &GetSettingsTree()
 			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"));
+			limitations->Add(new SettingEntry("construction.ignore_object_intro_dates"));
 		}
 
 		SettingsPage *disasters = main->Add(new SettingsPage(STR_CONFIG_SETTING_ACCIDENTS));

src/settings_type.h

@@ -455,6 +455,7 @@ struct ConstructionSettings {
 	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
+	bool   ignore_object_intro_dates;        ///< allow players to build objects before their introduction dates (does not include during map generation)
 
 	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?

src/table/settings/settings.ini

@@ -2093,6 +2093,14 @@ cat      = SC_ADVANCED
 patxname = ""construction.no_expire_objects_after""
 post_cb  = [](auto) { InvalidateWindowClassesData(WC_BUILD_OBJECT, 0); }
 
+[SDT_BOOL]
+var      = construction.ignore_object_intro_dates
+def      = false
+str      = STR_CONFIG_SETTING_IGNORE_OBJECT_INTRO_DATES
+strhelp  = STR_CONFIG_SETTING_IGNORE_OBJECT_INTRO_DATES_HELPTEXT
+patxname = ""construction.ignore_object_intro_dates""
+post_cb  = [](auto) { InvalidateWindowClassesData(WC_BUILD_OBJECT, 0); }
+
 [SDT_BOOL]
 var      = station.adjacent_stations
 from     = SLV_62