Fixes Shell Bell inlcuding heal amount from Future Sight when triggered

src/battle_script_commands.c

@@ -2456,7 +2456,9 @@ static void Cmd_datahpupdate(void)
                 }
 
                 // Record damage for Shell Bell
-                if (gSpecialStatuses[battler].shellBellDmg == 0 && !(gHitMarker & HITMARKER_PASSIVE_DAMAGE))
+                if (gSpecialStatuses[gBattlerTarget].shellBellDmg == IGNORE_SHELL_BELL)
+                    gSpecialStatuses[battler].shellBellDmg = 0;
+                else if (gSpecialStatuses[battler].shellBellDmg == 0 && !(gHitMarker & HITMARKER_PASSIVE_DAMAGE))
                     gSpecialStatuses[battler].shellBellDmg = gHpDealt;
 
                 // Note: While physicalDmg/specialDmg below are only distinguished between for Counter/Mirror Coat, they are

test/battle/hold_effect/shell_bell.c

@@ -0,0 +1,28 @@
+#include "global.h"
+#include "test/battle.h"
+
+SINGLE_BATTLE_TEST("Shell Bell does not activate on Future Sight if the original user is on the field")
+{
+    s16 damage = 0;
+    s16 healed = 0;
+
+    GIVEN {
+        PLAYER(SPECIES_WOBBUFFET) { HP(1); Item(ITEM_SHELL_BELL); }
+        OPPONENT(SPECIES_WYNAUT);
+    } WHEN {
+        TURN { MOVE(player, MOVE_FUTURE_SIGHT); }
+        TURN {}
+        TURN {}
+        TURN { MOVE(player, MOVE_DRAGON_RAGE); }
+    } SCENE {
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_FUTURE_SIGHT, player);
+        MESSAGE("The opposing Wynaut took the Future Sight attack!");
+        HP_BAR(opponent);
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_DRAGON_RAGE, player);
+        HP_BAR(opponent, captureDamage: &damage);
+        ANIMATION(ANIM_TYPE_GENERAL, B_ANIM_HELD_ITEM_EFFECT, player);
+        HP_BAR(player, captureDamage: &healed);
+    } THEN {
+        EXPECT_MUL_EQ(damage, Q_4_12(-0.25), healed);
+    }
+}