Fix spells crashing when they can't find a target. (#36507)

* Enable translation

* Change spell::random_valid_target to return an optional value.

This handles the case when no target point can be found.

Changed all callers accordingly to ignore the action when no target has been found.

* Fix wrong word used to describe what's wrong. Remember: spell != skill. They sound similar, but they are not exactly the same. Thanks for the reminder.

Co-Authored-By: Anton Burmistrov <Night_Pryanik@mail.ru>

src/activity_handlers.cpp

@@ -4440,14 +4440,19 @@ void activity_handlers::spellcasting_finish( player_activity *act, player *p )
             }
         } while( !target_is_valid );
     } else if( casting.has_flag( RANDOM_TARGET ) ) {
-        target = casting.random_valid_target( *p, p->pos() );
+        const cata::optional<tripoint> target_ = casting.random_valid_target( *p, p->pos() );
+        if( !target_ ) {
+            p->add_msg_if_player( m_bad, _( "Your spell can't find a suitable target." ) );
+            return;
+        }
+        target = *target_;
     }
 
     // no turning back now. it's all said and done.
     bool success = no_fail || rng_float( 0.0f, 1.0f ) >= casting.spell_fail( *p );
     int exp_gained = casting.casting_exp( *p );
     if( !success ) {
-        p->add_msg_if_player( m_bad, "You lose your concentration!" );
+        p->add_msg_if_player( m_bad, _( "You lose your concentration!" ) );
         if( !casting.is_max_level() && level_override == -1 ) {
             // still get some experience for trying
             casting.gain_exp( exp_gained / 5 );

src/magic.cpp

@@ -1092,10 +1092,9 @@ void spell::cast_all_effects( Creature &source, const tripoint &target ) const
             source.add_msg_if_player( sp.message() );
 
             if( sp.has_flag( RANDOM_TARGET ) ) {
-                if( _self ) {
-                    sp.cast_all_effects( source, sp.random_valid_target( source, source.pos() ) );
-                } else {
-                    sp.cast_all_effects( source, sp.random_valid_target( source, target ) );
+                if( const cata::optional<tripoint> new_target = sp.random_valid_target( source,
+                        _self ? source.pos() : target ) ) {
+                    sp.cast_all_effects( source, *new_target );
                 }
             } else {
                 if( _self ) {
@@ -1111,10 +1110,9 @@ void spell::cast_all_effects( Creature &source, const tripoint &target ) const
         for( const fake_spell &extra_spell : type->additional_spells ) {
             spell sp = extra_spell.get_spell( get_level() );
             if( sp.has_flag( RANDOM_TARGET ) ) {
-                if( extra_spell.self ) {
-                    sp.cast_all_effects( source, sp.random_valid_target( source, source.pos() ) );
-                } else {
-                    sp.cast_all_effects( source, sp.random_valid_target( source, target ) );
+                if( const cata::optional<tripoint> new_target = sp.random_valid_target( source,
+                        extra_spell.self ? source.pos() : target ) ) {
+                    sp.cast_all_effects( source, *new_target );
                 }
             } else {
                 if( extra_spell.self ) {
@@ -1127,20 +1125,20 @@ void spell::cast_all_effects( Creature &source, const tripoint &target ) const
     }
 }
 
-tripoint spell::random_valid_target( const Creature &caster, const tripoint &caster_pos ) const
+cata::optional<tripoint> spell::random_valid_target( const Creature &caster,
+        const tripoint &caster_pos ) const
 {
-    const std::set<tripoint> area = spell_effect::spell_effect_blast( *this, caster_pos, caster_pos,
-                                    range(), false );
     std::set<tripoint> valid_area;
-    for( const tripoint &target : area ) {
+    for( const tripoint &target : spell_effect::spell_effect_blast( *this, caster_pos, caster_pos,
+            range(), false ) ) {
         if( is_valid_target( caster, target ) ) {
             valid_area.emplace( target );
         }
     }
-    size_t rand_i = rng( 0, valid_area.size() - 1 );
-    auto iter = valid_area.begin();
-    std::advance( iter, rand_i );
-    return *iter;
+    if( valid_area.empty() ) {
+        return cata::nullopt;
+    }
+    return random_entry( valid_area );
 }
 
 // player

src/magic.h

@@ -402,7 +402,8 @@ class spell
         bool is_valid_effect_target( valid_target t ) const;
 
         // picks a random valid tripoint from @area
-        tripoint random_valid_target( const Creature &caster, const tripoint &caster_pos ) const;
+        cata::optional<tripoint> random_valid_target( const Creature &caster,
+                const tripoint &caster_pos ) const;
 };
 
 class known_magic