PCB: import from netlist, save, and load unit info from footprints

For upcoming gate swap feature

common/pcb.keywords

@@ -370,6 +370,9 @@ true
 tstamp
 type
 units
+unit
+pins
+num
 units_format
 unlocked
 user

pcbnew/netlist_reader/board_netlist_updater.cpp

@@ -1166,6 +1166,67 @@ bool BOARD_NETLIST_UPDATER::updateComponentPadConnections( FOOTPRINT* aFootprint
 }
 
 
+bool BOARD_NETLIST_UPDATER::updateComponentUnits( FOOTPRINT* aFootprint, COMPONENT* aNewComponent )
+{
+    // Build the footprint-side representation from the netlist component
+    std::vector<FOOTPRINT::FP_UNIT_INFO> newUnits;
+
+    for( const COMPONENT::UNIT_INFO& u : aNewComponent->GetUnitInfo() )
+        newUnits.push_back( { u.m_unitName, u.m_pins } );
+
+    const std::vector<FOOTPRINT::FP_UNIT_INFO>& curUnits = aFootprint->GetUnitInfo();
+
+    auto unitsEqual = []( const std::vector<FOOTPRINT::FP_UNIT_INFO>& a,
+                          const std::vector<FOOTPRINT::FP_UNIT_INFO>& b )
+        {
+            if( a.size() != b.size() )
+                return false;
+
+            for( size_t i = 0; i < a.size(); ++i )
+            {
+                if( a[i].m_unitName != b[i].m_unitName )
+                    return false;
+
+                if( a[i].m_pins != b[i].m_pins )
+                    return false;
+            }
+
+            return true;
+        };
+
+    if( unitsEqual( curUnits, newUnits ) )
+        return false;
+
+    wxString msg;
+
+    if( m_isDryRun )
+    {
+        msg.Printf( _( "Update %s unit metadata." ), aFootprint->GetReference() );
+        m_reporter->Report( msg, RPT_SEVERITY_ACTION );
+        return false; // no actual change on board during dry run
+    }
+
+    // Create a copy only if the footprint has not been added during this update
+    FOOTPRINT* copy = nullptr;
+
+    if( !m_commit.GetStatus( aFootprint ) )
+    {
+        copy = static_cast<FOOTPRINT*>( aFootprint->Clone() );
+        copy->SetParentGroup( nullptr );
+    }
+
+    aFootprint->SetUnitInfo( newUnits );
+
+    msg.Printf( _( "Updated %s unit metadata." ), aFootprint->GetReference() );
+    m_reporter->Report( msg, RPT_SEVERITY_ACTION );
+
+    if( copy )
+        m_commit.Modified( aFootprint, copy );
+
+    return true;
+}
+
+
 void BOARD_NETLIST_UPDATER::cacheCopperZoneConnections()
 {
     for( ZONE* zone : m_board->Zones() )
@@ -1567,6 +1628,7 @@ bool BOARD_NETLIST_UPDATER::UpdateNetlist( NETLIST& aNetlist )
                     updateFootprintGroup( tmp, component );
                     updateComponentPadConnections( tmp, component );
                     updateComponentClass( tmp, component );
+                    updateComponentUnits( tmp, component );
 
                     sheetPaths.insert( footprint->GetSheetname() );
                 }
@@ -1593,6 +1655,7 @@ bool BOARD_NETLIST_UPDATER::UpdateNetlist( NETLIST& aNetlist )
                 updateFootprintGroup( footprint, component );
                 updateComponentPadConnections( footprint, component );
                 updateComponentClass( footprint, component );
+                updateComponentUnits( footprint, component );
 
                 sheetPaths.insert( footprint->GetSheetname() );
             }

pcbnew/netlist_reader/board_netlist_updater.h

@@ -121,6 +121,8 @@ private:
 
     void updateComponentClass( FOOTPRINT* aFootprint, COMPONENT* aNewComponent );
 
+    bool updateComponentUnits( FOOTPRINT* aFootprint, COMPONENT* aNewComponent );
+
     void cacheCopperZoneConnections();
 
     bool updateCopperZoneNets( NETLIST& aNetlist );

pcbnew/pcb_io/kicad_sexpr/pcb_io_kicad_sexpr.cpp

@@ -1238,6 +1238,26 @@ void PCB_IO_KICAD_SEXPR::format( const FOOTPRINT* aFootprint ) const
     if( !aFootprint->GetSheetfile().empty() )
         m_out->Print( "(sheetfile %s)", m_out->Quotew( aFootprint->GetSheetfile() ).c_str() );
 
+    // Emit unit info for gate swapping metadata (flat pin list form)
+    if( !aFootprint->GetUnitInfo().empty() )
+    {
+        m_out->Print( "(units" );
+
+        for( const FOOTPRINT::FP_UNIT_INFO& u : aFootprint->GetUnitInfo() )
+        {
+            m_out->Print( "(unit (name %s)", m_out->Quotew( u.m_unitName ).c_str() );
+            m_out->Print( "(pins" );
+
+            for( const wxString& n : u.m_pins )
+                m_out->Print( " %s", m_out->Quotew( n ).c_str() );
+
+            m_out->Print( ")" ); // </pins>
+            m_out->Print( ")" ); // </unit>
+        }
+
+        m_out->Print( ")" ); // </units>
+    }
+
     if( aFootprint->GetLocalSolderMaskMargin().has_value() )
     {
         m_out->Print( "(solder_mask_margin %s)",

pcbnew/pcb_io/kicad_sexpr/pcb_io_kicad_sexpr.h

@@ -191,7 +191,8 @@ class PCB_IO_KICAD_SEXPR;   // forward decl
 //#define SEXPR_BOARD_FILE_VERSION    20250818  // Support for custom layer counts in footprints
 //#define SEXPR_BOARD_FILE_VERSION    20250829  // Support Rounded Rectangles
 //#define SEXPR_BOARD_FILE_VERSION    20250901  // PCB points
-#define SEXPR_BOARD_FILE_VERSION      20250907  // uuids for tables
+//#define SEXPR_BOARD_FILE_VERSION    20250907  // uuids for tables
+#define SEXPR_BOARD_FILE_VERSION      20250909  // footprint unit metadata (units/pins)
 
 #define BOARD_FILE_HOST_VERSION       20200825  ///< Earlier files than this include the host tag
 #define LEGACY_ARC_FORMATTING         20210925  ///< These were the last to use old arc formatting

pcbnew/pcb_io/kicad_sexpr/pcb_io_kicad_sexpr_parser.cpp

@@ -4758,6 +4758,68 @@ FOOTPRINT* PCB_IO_KICAD_SEXPR_PARSER::parseFOOTPRINT_unchecked( wxArrayString* a
             NeedRIGHT();
             break;
 
+        case T_units:
+        {
+            std::vector<FOOTPRINT::FP_UNIT_INFO> unitInfos;
+
+            // (units (unit (name "A") (pins "1" "2" ...)) ...)
+            for( token = NextTok(); token != T_RIGHT; token = NextTok() )
+            {
+                if( token == T_LEFT )
+                    token = NextTok();
+
+                if( token == T_unit )
+                {
+                    FOOTPRINT::FP_UNIT_INFO info;
+
+                    for( token = NextTok(); token != T_RIGHT; token = NextTok() )
+                    {
+                        if( token == T_LEFT )
+                            token = NextTok();
+
+                        if( token == T_name )
+                        {
+                            NeedSYMBOLorNUMBER();
+                            info.m_unitName = FromUTF8();
+                            NeedRIGHT();
+                        }
+                        else if( token == T_pins )
+                        {
+                            // Parse a flat list of quoted numbers or symbols until ')'
+                            for( token = NextTok(); token != T_RIGHT; token = NextTok() )
+                            {
+                                if( token == T_STRING || token == T_NUMBER )
+                                {
+                                    info.m_pins.emplace_back( FromUTF8() );
+                                }
+                                else
+                                {
+                                    Expecting( "pin number" );
+                                }
+                            }
+                        }
+                        else
+                        {
+                            // Unknown sub-token inside unit; skip its list if any
+                            skipCurrent();
+                        }
+                    }
+
+                    unitInfos.push_back( info );
+                }
+                else
+                {
+                    // Unknown entry under units; skip
+                    skipCurrent();
+                }
+            }
+
+            if( !unitInfos.empty() )
+                footprint->SetUnitInfo( unitInfos );
+
+            break;
+        }
+
         case T_autoplace_cost90:
         case T_autoplace_cost180:
             parseInt( "legacy auto-place cost" );