paste features: don't skip primary key fields, use default value if present,

otherwise value of pasted feature (fixes #9489)

Author: jef-n

src/app/qgisapp.cpp

@@ -5742,11 +5742,9 @@ void QgisApp::editPaste( QgsMapLayer *destinationLayer )
   for ( int idx = 0; idx < fields.count(); ++idx )
   {
     int dst = pasteVectorLayer->fieldNameIndex( fields[idx].name() );
-    if ( dst < 0 || pkAttrList.contains( dst ) )
-    {
-      // skip primary key attributes
+    if ( dst < 0 )
       continue;
-    }
+
     remap.insert( idx, dst );
   }
 
@@ -5763,6 +5761,14 @@ void QgisApp::editPaste( QgsMapLayer *destinationLayer )
       if ( dst < 0 )
         continue;
 
+      // use default value for primary key fields if it's NOT NULL
+      if ( pkAttrList.contains( dst ) )
+      {
+        dstAttr[ dst ] = pasteVectorLayer->dataProvider()->defaultValue( dst );
+	if( !dstAttr[ dst ].isNull() )
+	  continue;
+      }
+
       dstAttr[ dst ] = srcAttr[ src ];
     }