Preserve ammo linkage on zone unload

src/activity_actor.cpp

@@ -6430,6 +6430,12 @@ void unload_loot_activity_actor::do_turn( player_activity &act, Character &you )
                     for( item *contained : it->first->all_items_top( item_pocket::pocket_type::MAGAZINE ) ) {
                         // no liquids don't want to spill stuff
                         if( !contained->made_of( phase_id::LIQUID ) && !contained->made_of( phase_id::GAS ) ) {
+                            if( it->first->is_ammo_belt() ) {
+                                if( it->first->type->magazine->linkage ) {
+                                    item link( *it->first->type->magazine->linkage, calendar::turn, contained->count() );
+                                    here.add_item_or_charges( src_loc, link );
+                                }
+                            }
                             move_item( you, *contained, contained->count(), src_loc, src_loc, this_veh, this_part );
                             it->first->remove_item( *contained );
                         }

src/activity_item_handling.cpp

@@ -2276,6 +2276,12 @@ void activity_on_turn_move_loot( player_activity &act, Character &you )
                         for( item *contained : it->first->all_items_top( item_pocket::pocket_type::MAGAZINE ) ) {
                             // no liquids don't want to spill stuff
                             if( !contained->made_of( phase_id::LIQUID ) && !contained->made_of( phase_id::GAS ) ) {
+                                if( it->first->is_ammo_belt() ) {
+                                    if( it->first->type->magazine->linkage ) {
+                                        item link( *it->first->type->magazine->linkage, calendar::turn, contained->count() );
+                                        here.add_item_or_charges( src_loc, link );
+                                    }
+                                }
                                 move_item( you, *contained, contained->count(), src_loc, src_loc, this_veh, this_part );
                                 it->first->remove_item( *contained );
                             }

tests/clzones_test.cpp

@@ -1,29 +1,97 @@
 #include <iosfwd>
 #include <vector>
 
+#include "activity_actor_definitions.h"
 #include "cata_catch.h"
 #include "clzones.h"
 #include "item.h"
 #include "item_category.h"
 #include "item_pocket.h"
 #include "map_helpers.h"
+#include "player_helpers.h"
 #include "point.h"
 #include "ret_val.h"
 #include "type_id.h"
 
 static const faction_id faction_your_followers( "your_followers" );
 
+static const itype_id itype_556( "556" );
+static const itype_id itype_ammolink223( "ammolink223" );
+static const itype_id itype_belt223( "belt223" );
+
 static const zone_type_id zone_type_LOOT_DRINK( "LOOT_DRINK" );
 static const zone_type_id zone_type_LOOT_FOOD( "LOOT_FOOD" );
 static const zone_type_id zone_type_LOOT_PDRINK( "LOOT_PDRINK" );
 static const zone_type_id zone_type_LOOT_PFOOD( "LOOT_PFOOD" );
+static const zone_type_id zone_type_zone_unload_all( "zone_unload_all" );
+
+static int count_items_or_charges( const tripoint src, const itype_id &id )
+{
+    int n = 0;
+    map_stack items = get_map().i_at( src );
+    for( const item &it : items ) {
+        if( it.typeId() == id ) {
+            n += it.count();
+        }
+    }
+    return n;
+}
+
+static void complete_activity( Character &u, const activity_actor &act )
+{
+    u.assign_activity( player_activity( act ) );
+    while( !u.activity.is_null() ) {
+        u.set_moves( u.get_speed() );
+        u.activity.do_turn( u );
+    }
+}
 
 static void create_tile_zone( const std::string &name, const zone_type_id &zone_type, tripoint pos )
 {
     zone_manager &zm = zone_manager::get_manager();
     zm.add( name, zone_type, faction_your_followers, false, true, pos, pos );
 }
 
+TEST_CASE( "zone unloading ammo belts", "[zones][items][ammo_belt][activities][unload]" )
+{
+    clear_avatar();
+    clear_map();
+
+    avatar &dummy = get_avatar();
+    map &here = get_map();
+
+    dummy.setpos( tripoint_east );
+    create_tile_zone( "Unload All", zone_type_zone_unload_all, tripoint_east );
+
+    item ammo_belt = item( itype_belt223, calendar::turn );
+
+    ammo_belt.ammo_set( ammo_belt.ammo_default() );
+
+    here.add_item_or_charges( tripoint_east, ammo_belt );
+
+    const auto get_belt_ammo_count = [&]() {
+        return here.items_with( tripoint_east, []( const item & it ) {
+            return it.typeId() == itype_belt223;
+        } ).front()->ammo_remaining();
+    };
+
+    const int belt_ammo_count_before_unload = get_belt_ammo_count();
+
+    CHECK( belt_ammo_count_before_unload == ammo_belt.ammo_capacity(
+               ammo_belt.loaded_ammo().ammo_type() ) );
+
+    complete_activity( dummy, unload_loot_activity_actor() );
+
+    THEN( "Check that the ammo and linkages were both unloaded" ) {
+        CHECK( count_items_or_charges( tripoint_east, itype_belt223 ) == 1 );
+        CHECK( count_items_or_charges( tripoint_east,
+                                       itype_ammolink223 ) == belt_ammo_count_before_unload );
+        CHECK( count_items_or_charges( tripoint_east, itype_556 ) == belt_ammo_count_before_unload );
+
+        CHECK( get_belt_ammo_count() == 0 );
+    }
+}
+
 // Comestibles sorting is a bit awkward. Unlike other loot, they're almost
 // always inside of a container, and their sort zone changes based on their
 // shelf life and whether the container prevents rotting.