Don't do a sided-test on a footprint which has no side.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/15284

pcbnew/collectors.cpp

@@ -271,10 +271,10 @@ INSPECT_RESULT GENERAL_COLLECTOR::Inspect( EDA_ITEM* aTestItem, void* aTestData
 
     if( footprint )
     {
-        if( m_Guide->IgnoreFootprintsOnBack() && ( footprint->GetLayer() == B_Cu ) )
+        if( m_Guide->IgnoreFootprintsOnBack() && footprint->GetSide() == B_Cu )
             return INSPECT_RESULT::CONTINUE;
 
-        if( m_Guide->IgnoreFootprintsOnFront() && ( footprint->GetLayer() == F_Cu ) )
+        if( m_Guide->IgnoreFootprintsOnFront() && footprint->GetSide() == F_Cu )
             return INSPECT_RESULT::CONTINUE;
     }
 

pcbnew/dialogs/dialog_board_statistics.cpp

@@ -217,10 +217,13 @@ void DIALOG_BOARD_STATISTICS::getDataFromPCB()
         {
             if( ( footprint->GetAttributes() & line.attribute_mask ) == line.attribute_value )
             {
-                if( footprint->IsFlipped() )
-                    line.backSideQty++;
-                else
-                    line.frontSideQty++;
+                switch( footprint->GetSide() )
+                {
+                case F_Cu: line.frontSideQty++;                  break;
+                case B_Cu: line.backSideQty++;                   break;
+                default:   /* unsided: user-layers only, etc. */ break;
+                }
+
                 break;
             }
         }

pcbnew/footprint.cpp

@@ -989,6 +989,7 @@ const BOX2I FOOTPRINT::GetBoundingBox( bool aIncludeText, bool aIncludeInvisible
     std::vector<PCB_TEXT*> texts;
     const BOARD* board = GetBoard();
     bool         isFPEdit = board && board->IsFootprintHolder();
+    PCB_LAYER_ID footprintSide = GetSide();
 
     if( board )
     {
@@ -1029,8 +1030,9 @@ const BOX2I FOOTPRINT::GetBoundingBox( bool aIncludeText, bool aIncludeInvisible
             continue;
         }
 
-        // If we're not including text then drop annotations as well
-        if( !aIncludeText )
+        // If we're not including text then drop annotations as well -- unless, of course, it's
+        // an unsided footprint -- in which case it's likely to be nothing *but* annotations.
+        if( !aIncludeText && footprintSide != UNDEFINED_LAYER )
         {
             if( BaseType( item->Type() ) == PCB_DIMENSION_T )
                 continue;
@@ -1287,7 +1289,13 @@ void FOOTPRINT::GetMsgPanelInfo( EDA_DRAW_FRAME* aFrame, std::vector<MSG_PANEL_I
     }
 
     // aFrame is the board editor:
-    aList.emplace_back( _( "Board Side" ), IsFlipped() ? _( "Back (Flipped)" ) : _( "Front" ) );
+
+    switch( GetSide() )
+    {
+    case F_Cu: aList.emplace_back( _( "Board Side" ), _( "Front" ) );          break;
+    case B_Cu: aList.emplace_back( _( "Board Side" ), _( "Back (Flipped)" ) ); break;
+    default:   /* unsided: user-layers only, etc. */                           break;
+    }
 
     auto addToken = []( wxString* aStr, const wxString& aAttr )
                     {
@@ -1334,6 +1342,37 @@ void FOOTPRINT::GetMsgPanelInfo( EDA_DRAW_FRAME* aFrame, std::vector<MSG_PANEL_I
 }
 
 
+PCB_LAYER_ID FOOTPRINT::GetSide() const
+{
+    if( const BOARD* board = GetBoard() )
+    {
+        if( board->IsFootprintHolder() )
+            return UNDEFINED_LAYER;
+    }
+
+    // Test pads first; they're the most likely to return a quick answer.
+    for( PAD* pad : m_pads )
+    {
+        if( ( LSET::SideSpecificMask() & pad->GetLayerSet() ).any() )
+            return GetLayer();
+    }
+
+    for( BOARD_ITEM* item : m_drawings )
+    {
+        if( LSET::SideSpecificMask().test( item->GetLayer() ) )
+            return GetLayer();
+    }
+
+    for( ZONE* zone : m_zones )
+    {
+        if( ( LSET::SideSpecificMask() & zone->GetLayerSet() ).any() )
+            return GetLayer();
+    }
+
+    return UNDEFINED_LAYER;
+}
+
+
 bool FOOTPRINT::IsOnLayer( PCB_LAYER_ID aLayer ) const
 {
     // If we have any pads, fall back on normal checking

pcbnew/footprint.h

@@ -350,6 +350,12 @@ public:
      */
     bool IsFlipped() const { return GetLayer() == B_Cu; }
 
+    /**
+     * Use instead of IsFlipped() when you also need to account for unsided footprints (those
+     * purely on user-layers, etc.).
+     */
+    PCB_LAYER_ID GetSide() const;
+
     /**
      * @copydoc BOARD_ITEM::IsOnLayer
      */

pcbnew/tools/pcb_selection_tool.cpp

@@ -2605,16 +2605,20 @@ bool PCB_SELECTION_TOOL::Selectable( const BOARD_ITEM* aItem, bool checkVisibili
 
     if( aItem->Type() == PCB_FOOTPRINT_T )
     {
+        const FOOTPRINT* footprint = static_cast<const FOOTPRINT*>( aItem );
+
         // In footprint editor, we do not want to select the footprint itself.
         if( m_isFootprintEditor )
             return false;
 
         // Allow selection of footprints if some part of the footprint is visible.
-        const FOOTPRINT* footprint = static_cast<const FOOTPRINT*>( aItem );
-        LSET             boardSide = footprint->IsFlipped() ? LSET::BackMask() : LSET::FrontMask();
+        if( footprint->GetSide() != UNDEFINED_LAYER && !m_skip_heuristics )
+        {
+            LSET boardSide = footprint->IsFlipped() ? LSET::BackMask() : LSET::FrontMask();
 
-        if( !( visibleLayers() & boardSide ).any() && !m_skip_heuristics )
-            return false;
+            if( !( visibleLayers() & boardSide ).any() )
+                return false;
+        }
 
         // If the footprint has no items except the reference and value fields, include the
         // footprint in the selections.