Add a null type for libeval / std::optional support

Fixes https://gitlab.com/kicad/code/kicad/-/issues/19158

common/libeval_compiler/libeval_compiler.cpp

@@ -115,6 +115,9 @@ bool VALUE::EqualTo( CONTEXT* aCtx, const VALUE* b ) const
     if( m_type == VT_UNDEFINED || b->m_type == VT_UNDEFINED )
         return false;
 
+    if( m_type == VT_NULL && b->m_type == VT_NULL )
+        return true;
+
     if( m_type == VT_NUMERIC && b->m_type == VT_NUMERIC )
     {
         return AsDouble() == b->AsDouble();

include/libeval_compiler/libeval_compiler.h

@@ -85,7 +85,8 @@ enum VAR_TYPE_T
     VT_STRING = 1,
     VT_NUMERIC,
     VT_UNDEFINED,
-    VT_PARSE_ERROR
+    VT_PARSE_ERROR,
+    VT_NULL
 };
 
 enum TOKEN_TYPE_T
@@ -210,6 +211,13 @@ public:
         m_isDeferredStr( false )
     {};
 
+    static VALUE* MakeNullValue()
+    {
+        VALUE* v = new VALUE();
+        v->m_type = VT_NULL;
+        return v;
+    }
+
     virtual ~VALUE()
     {};
 

pcbnew/dialogs/panel_setup_rules_help_9more_examples.h

@@ -94,7 +94,7 @@ _HKI( "### More Examples\n"
 "\n"
 "    # Disallow solder mask margin overrides\n"
 "    (rule \"disallow solder mask margin overrides\"\n"
-"        (constraint assertion \"A.Soldermask_Margin_Override == 0mm\")\n"
+"        (constraint assertion \"A.Soldermask_Margin_Override == null\")\n"
 "        (condition \"A.Type == 'Pad'\"))\n"
 "\n"
 "\n"

pcbnew/dialogs/panel_setup_rules_help_9more_examples.md

@@ -93,7 +93,7 @@
 
     # Disallow solder mask margin overrides
     (rule "disallow solder mask margin overrides"
-        (constraint assertion "A.Soldermask_Margin_Override == 0mm")
+        (constraint assertion "A.Soldermask_Margin_Override == null")
         (condition "A.Type == 'Pad'"))
 
 

pcbnew/pcbexpr_evaluator.cpp

@@ -272,6 +272,9 @@ LIBEVAL::VALUE* PCBEXPR_VAR_REF::GetValue( LIBEVAL::CONTEXT* aCtx )
 {
     PCBEXPR_CONTEXT* context = static_cast<PCBEXPR_CONTEXT*>( aCtx );
 
+    if( m_type == LIBEVAL::VT_NULL )
+        return LIBEVAL::VALUE::MakeNullValue();
+
     if( m_itemIndex == 2 )
         return new PCBEXPR_LAYER_VALUE( context->GetLayer() );
 
@@ -294,7 +297,17 @@ LIBEVAL::VALUE* PCBEXPR_VAR_REF::GetValue( LIBEVAL::CONTEXT* aCtx )
     {
         if( m_type == LIBEVAL::VT_NUMERIC )
         {
-            return new LIBEVAL::VALUE( (double) item->Get<int>( it->second ) );
+            if( m_isOptional )
+            {
+                auto val = item->Get<std::optional<int>>( it->second );
+
+                if( val.has_value() )
+                    return new LIBEVAL::VALUE( static_cast<double>( val.value() ) );
+
+                return LIBEVAL::VALUE::MakeNullValue();
+            }
+
+            return new LIBEVAL::VALUE( static_cast<double>( item->Get<int>( it->second ) ) );
         }
         else
         {
@@ -394,6 +407,13 @@ std::unique_ptr<LIBEVAL::VAR_REF> PCBEXPR_UCODE::CreateVarRef( const wxString& a
     PROPERTY_MANAGER& propMgr = PROPERTY_MANAGER::Instance();
     std::unique_ptr<PCBEXPR_VAR_REF> vref;
 
+    if( aVar.IsSameAs( wxT( "null" ), false ) )
+    {
+        vref = std::make_unique<PCBEXPR_VAR_REF>( 0 );
+        vref->SetType( LIBEVAL::VT_NULL );
+        return vref;
+    }
+
     // Check for a couple of very common cases and compile them straight to "object code".
 
     if( aField.CmpNoCase( wxT( "NetClass" ) ) == 0 )
@@ -464,6 +484,11 @@ std::unique_ptr<LIBEVAL::VAR_REF> PCBEXPR_UCODE::CreateVarRef( const wxString& a
                 {
                     vref->SetType( LIBEVAL::VT_NUMERIC );
                 }
+                if( prop->TypeHash() == TYPE_HASH( std::optional<int> ) )
+                {
+                    vref->SetType( LIBEVAL::VT_NUMERIC );
+                    vref->SetIsOptional();
+                }
                 else if( prop->TypeHash() == TYPE_HASH( bool ) )
                 {
                     vref->SetType( LIBEVAL::VT_NUMERIC );
@@ -475,7 +500,7 @@ std::unique_ptr<LIBEVAL::VAR_REF> PCBEXPR_UCODE::CreateVarRef( const wxString& a
                 else if ( prop->HasChoices() )
                 {   // it's an enum, we treat it as string
                     vref->SetType( LIBEVAL::VT_STRING );
-                    vref->SetIsEnum ( true );
+                    vref->SetIsEnum( true );
                 }
                 else
                 {

pcbnew/pcbexpr_evaluator.h

@@ -85,7 +85,8 @@ public:
     PCBEXPR_VAR_REF( int aItemIndex ) :
             m_itemIndex( aItemIndex ),
             m_type( LIBEVAL::VT_UNDEFINED ),
-            m_isEnum( false )
+            m_isEnum( false ),
+            m_isOptional( false )
     {}
 
     ~PCBEXPR_VAR_REF() {};
@@ -93,6 +94,9 @@ public:
     void SetIsEnum( bool s ) { m_isEnum = s; }
     bool IsEnum() const { return m_isEnum; }
 
+    void SetIsOptional( bool s = true ) { m_isOptional = s; }
+    bool IsOptional() const { return m_isOptional; }
+
     void SetType( LIBEVAL::VAR_TYPE_T type ) { m_type = type; }
     LIBEVAL::VAR_TYPE_T GetType() const override { return m_type; }
 
@@ -110,6 +114,7 @@ private:
     int                                         m_itemIndex;
     LIBEVAL::VAR_TYPE_T                         m_type;
     bool                                        m_isEnum;
+    bool                                        m_isOptional;
 };