Symbol editor: fix crash caused by broken root symbol name.

The symbol editor selection criteria did not include LIB_FIELD objects
which allowed the root symbol name to be changed causing broken derived
symbol links.  Disable the symbols fields from being edited when a
derived part is shown in the editor to prevent this.

Add a missing warning that deleting a root symbol used to derive other
symbols would also delete all derived symbols from a library.  Give the
user a chance to cancel the delete operation in this case.

Fixes kicad/code/kicad#3654

eeschema/libedit/lib_manager.cpp

@@ -642,6 +642,15 @@ void LIB_MANAGER::GetRootSymbolNames( const wxString& aLibraryName,
 }
 
 
+bool LIB_MANAGER:: HasDerivedSymbols( const wxString& aSymbolName,
+                                      const wxString& aLibraryName )
+{
+    LIB_BUFFER& libBuf = getLibraryBuffer( aLibraryName );
+
+    return libBuf.HasDerivedSymbols( aSymbolName );
+}
+
+
 wxString LIB_MANAGER::getLibraryName( const wxString& aFilePath )
 {
     wxFileName fn( aFilePath );

eeschema/libedit/lib_manager.h

@@ -290,6 +290,14 @@ public:
 
     void GetRootSymbolNames( const wxString& aLibName, wxArrayString& aRootSymbolNames );
 
+    /**
+     * Check if symbol \a aSymbolName in library \a aLibraryName is a root symbol that
+     * has derived symbols.
+     *
+     * @return true if \aSymbolName in \a aLibraryName has derived symbols.
+     */
+    bool HasDerivedSymbols( const wxString& aSymbolName, const wxString& aLibraryName );
+
 private:
     ///> Extracts library name basing on the file name
     static wxString getLibraryName( const wxString& aFilePath );

eeschema/libedit/libedit.cpp

@@ -460,7 +460,7 @@ void LIB_EDIT_FRAME::savePartAs()
 
         if( new_lib.IsEmpty() )
         {
-            DisplayError( NULL, _( "No library specified.  Symbol could not be saved." ) );
+            DisplayError( this, _( "No library specified.  Symbol could not be saved." ) );
             return;
         }
 
@@ -471,7 +471,7 @@ void LIB_EDIT_FRAME::savePartAs()
 
         if( new_name.IsEmpty() )
         {
-            DisplayError( NULL, _( "No symbol name specified.  Symbol could not be saved." ) );
+            DisplayError( this, _( "No symbol name specified.  Symbol could not be saved." ) );
             return;
         }
 
@@ -487,7 +487,6 @@ void LIB_EDIT_FRAME::savePartAs()
         LIB_PART new_part( *part );
         new_part.SetName( new_name );
 
-        fixDuplicateAliases( &new_part, new_lib );
         m_libMgr->UpdatePart( &new_part, new_lib );
         SyncLibraries( false );
         m_treePane->GetLibTree()->SelectLibId( LIB_ID( new_lib, new_part.GetName() ) );
@@ -539,13 +538,33 @@ void LIB_EDIT_FRAME::DeletePartFromLibrary()
     LIB_ID libId = getTargetLibId();
 
     if( m_libMgr->IsPartModified( libId.GetLibItemName(), libId.GetLibNickname() )
-        && !IsOK( this, _( wxString::Format( "Component %s has been modified\n"
+        && !IsOK( this, _( wxString::Format( "The symbol \"%s\" has been modified\n"
                                              "Do you want to remove it from the library?",
                                              libId.GetUniStringLibItemName() ) ) ) )
     {
         return;
     }
 
+    if( m_libMgr->HasDerivedSymbols( libId.GetLibItemName(), libId.GetLibNickname() ) )
+    {
+        wxString msg;
+
+        msg.Printf( _( "The symbol \"%s\" is used to derive other symbols.\n"
+                       "Deleting this symbol will delete all of the symbols derived from it.\n\n"
+                       "Do you wish to delete this symbol and all of it's derivatives?" ),
+                    libId.GetLibItemName().wx_str() );
+
+        wxMessageDialog::ButtonLabel yesButtonLabel( _( "Delete Symbol" ) );
+        wxMessageDialog::ButtonLabel noButtonLabel( _( "Keep Symbol" ) );
+
+        wxMessageDialog dlg( this, msg, _( "Warning" ),
+                             wxYES_NO | wxYES_DEFAULT | wxICON_QUESTION | wxCENTER );
+        dlg.SetYesNoLabels( yesButtonLabel, noButtonLabel );
+
+        if( dlg.ShowModal() == wxID_NO )
+            return;
+    }
+
     if( isCurrentPart( libId ) )
         emptyScreen();
 

eeschema/tools/ee_selection_tool.cpp

@@ -1083,17 +1083,31 @@ bool EE_SELECTION_TOOL::doSelectionMenu( EE_COLLECTOR* aCollector )
 bool EE_SELECTION_TOOL::Selectable( const EDA_ITEM* aItem, bool checkVisibilityOnly ) const
 {
     // NOTE: in the future this is where eeschema layer/itemtype visibility will be handled
+    LIB_EDIT_FRAME* editFrame = dynamic_cast< LIB_EDIT_FRAME* >( m_frame );
+
+    wxCHECK( editFrame, false );
 
     switch( aItem->Type() )
     {
     case SCH_PIN_T:
-        if( !static_cast<const SCH_PIN*>( aItem )->IsVisible() && !m_frame->GetShowAllPins() )
+        if( !static_cast<const SCH_PIN*>( aItem )->IsVisible() && !editFrame->GetShowAllPins() )
             return false;
         break;
 
     case LIB_PART_T:    // In libedit we do not want to select the symbol itself.
         return false;
 
+    case LIB_FIELD_T:
+    {
+        LIB_PART*       currentPart = editFrame->GetCurPart();
+
+        // Nothing in derived symbols is editable at the moment.
+        if( currentPart && currentPart->IsAlias() )
+            return false;
+
+        break;
+    }
+
     case LIB_ARC_T:
     case LIB_CIRCLE_T:
     case LIB_TEXT_T:
@@ -1102,7 +1116,6 @@ bool EE_SELECTION_TOOL::Selectable( const EDA_ITEM* aItem, bool checkVisibilityO
     case LIB_BEZIER_T:
     case LIB_PIN_T:
     {
-        LIB_EDIT_FRAME* editFrame = (LIB_EDIT_FRAME*) m_frame;
         LIB_ITEM*       lib_item = (LIB_ITEM*) aItem;
 
         if( lib_item->GetUnit() && lib_item->GetUnit() != editFrame->GetUnit() )
@@ -1113,6 +1126,7 @@ bool EE_SELECTION_TOOL::Selectable( const EDA_ITEM* aItem, bool checkVisibilityO
 
         break;
     }
+
     case SCH_MARKER_T:  // Always selectable
         return true;