From ee96d82f2fc69b62b32b98ab7df21f642d9147a8 Mon Sep 17 00:00:00 2001
From: Marko Lindqvist <cazfi74@gmail.com>
Date: Wed, 4 Jan 2023 18:05:06 +0200
Subject: [PATCH 10/10] Check "Tile_Workable" effect after tile changes

Make cities to stop working tiles that they no longer
can work after terrain or extra change.

Reported by ihnatus

See osdn #44706

Signed-off-by: Marko Lindqvist <cazfi74@gmail.com>
---
 server/citytools.c |  2 +-
 server/maphand.c   | 24 ++++++++++++++++++++++--
 server/maphand.h   |  5 ++++-
 server/srv_main.c  |  8 ++++----
 server/unittools.c |  5 +++--
 5 files changed, 34 insertions(+), 10 deletions(-)

diff --git a/server/citytools.c b/server/citytools.c
index 4df06b2050..5ce828e143 100644
--- a/server/citytools.c
+++ b/server/citytools.c
@@ -1875,7 +1875,7 @@ void remove_city(struct city *pcity)
   /* At least sentried helicopters need to go idle, maybe others.
    * In alien ruleset, city center might have provided water source
    * for adjacent tile. */
-  unit_activities_cancel_all_illegal_area(pcenter);
+  tile_change_side_effects(pcenter);
 }
 
 /**************************************************************************
diff --git a/server/maphand.c b/server/maphand.c
index d8702da7e4..34905cfb8d 100644
--- a/server/maphand.c
+++ b/server/maphand.c
@@ -223,8 +223,7 @@ void climate_change(bool warming, int effect)
       check_terrain_change(ptile, old);
       update_tile_knowledge(ptile);
 
-      /* Check the unit activities. */
-      unit_activities_cancel_all_illegal_area(ptile);
+      tile_change_side_effects(ptile);
 
     } else if (old == new) {
       /* This counts toward a climate change although nothing is changed. */
@@ -2529,3 +2528,24 @@ void give_distorted_map(struct player *pfrom, struct player *pto,
 
   unbuffer_shared_vision(pto);
 }
+
+/**********************************************************************//**
+  Handle various side effects of the change on tile.
+  If a city was working the tile, that city might need refresh
+  after this call.
+
+  @param ptile         tile that has changed
+**************************************************************************/
+void tile_change_side_effects(struct tile *ptile)
+{
+  struct city *pcity = ptile->worked;
+
+  /* Check the unit activities. */
+  unit_activities_cancel_all_illegal_area(ptile);
+
+  if (pcity != NULL && !is_free_worked(pcity, ptile)
+      && get_city_tile_output_bonus(pcity, ptile, NULL, EFT_TILE_WORKABLE) <= 0) {
+    city_map_update_empty(pcity, ptile);
+    pcity->specialists[DEFAULT_SPECIALIST]++;
+  }
+}
diff --git a/server/maphand.h b/server/maphand.h
index affa680ca7..f151a8d89c 100644
--- a/server/maphand.h
+++ b/server/maphand.h
@@ -141,4 +141,7 @@ void destroy_extra(struct tile *ptile, struct extra_type *pextra);
 void give_distorted_map(struct player *pfrom, struct player *pto,
                         int prob, bool reveal_cities);
 
-#endif  /* FC__MAPHAND_H */
+void tile_change_side_effects(struct tile *ptile)
+  fc__attribute((nonnull (1)));
+
+#endif /* FC__MAPHAND_H */
diff --git a/server/srv_main.c b/server/srv_main.c
index d74ab9beba..0fb12a0e56 100644
--- a/server/srv_main.c
+++ b/server/srv_main.c
@@ -1600,9 +1600,9 @@ static void end_turn(void)
                         tile_link(ptile));
         }
 
-        /* Unit activities at the target tile and its neighbors may now
+        /* Activities at the target tile and its neighbors may now
          * be illegal because of present reqs. */
-        unit_activities_cancel_all_illegal_area(ptile);
+        tile_change_side_effects(ptile);
       }
     } whole_map_iterate_end;
   } extra_type_by_rmcause_iterate_end;
@@ -1628,9 +1628,9 @@ static void end_turn(void)
                         tile_link(ptile));
         }
 
-        /* Unit activities at the target tile and its neighbors may now
+        /* Activities at the target tile and its neighbors may now
          * be illegal because of !present reqs. */
-        unit_activities_cancel_all_illegal_area(ptile);
+        tile_change_side_effects(ptile);
       }
     } whole_map_iterate_end;
   } extra_type_by_cause_iterate_end;
diff --git a/server/unittools.c b/server/unittools.c
index 2a65095cb1..1660439bc2 100644
--- a/server/unittools.c
+++ b/server/unittools.c
@@ -1007,13 +1007,14 @@ static void update_unit_activity(struct unit *punit)
             && punit2->activity_target == act_tgt) {
           /* This unit was helping with the work just finished.
            * Mark it idle (already finished) so its "current"
-           * activity is not considered illegal below. */
+           * activity is not considered illegal
+           * in tile_change_side_effects() . */
           set_unit_activity(punit2, ACTIVITY_IDLE);
         }
       } unit_list_iterate_end;
     }
 
-    unit_activities_cancel_all_illegal_area(ptile);
+    tile_change_side_effects(ptile);
   }
 
   if (activity == ACTIVITY_FORTIFYING) {
-- 
2.39.0