Add options in list config widget for how to deal with empty rows

Allow NULL or empty array

src/gui/CMakeLists.txt

@@ -163,6 +163,7 @@ set(QGIS_GUI_SRCS
   editorwidgets/qgskeyvaluewidgetwrapper.cpp
   editorwidgets/qgslistwidgetfactory.cpp
   editorwidgets/qgslistwidgetwrapper.cpp
+  editorwidgets/qgslistconfigdlg.cpp
   editorwidgets/qgsmultiedittoolbutton.cpp
   editorwidgets/qgsrangeconfigdlg.cpp
   editorwidgets/qgsrangewidgetwrapper.cpp

src/gui/editorwidgets/qgslistconfigdlg.cpp

@@ -0,0 +1,40 @@
+/***************************************************************************
+    qgslistconfigdlg.cpp
+     --------------------------------------
+    Date                 : 9.2020
+    Copyright            : (C) 2020 Stephen Knox
+    Email                : stephenknox73 at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgslistconfigdlg.h"
+
+QgsListConfigDlg::QgsListConfigDlg( QgsVectorLayer *vl, int fieldIdx, QWidget *parent )
+  : QgsEditorConfigWidget( vl, fieldIdx, parent )
+{
+  setupUi( this );
+  connect( mNullBehavior, &QGroupBox::toggled, this, &QgsEditorConfigWidget::changed );
+}
+
+
+QVariantMap QgsListConfigDlg::config()
+{
+  QVariantMap cfg;
+
+  cfg.insert( QStringLiteral( "EmptyIsNull" ), mEmptyisNull->isChecked() );
+  cfg.insert( QStringLiteral( "EmptyIsEmptyArray" ), mEmptyisEmptyArray->isChecked() );
+
+  return cfg;
+}
+
+void QgsListConfigDlg::setConfig( const QVariantMap &config )
+{
+  mEmptyisNull->setChecked( config.value( QStringLiteral( "EmptyIsNull" ) ).toBool() );
+  mEmptyisEmptyArray->setChecked( config.value( QStringLiteral( "EmptyIsEmptyArray" ) ).toBool() );
+}

src/gui/editorwidgets/qgslistconfigdlg.h

@@ -0,0 +1,51 @@
+/***************************************************************************
+    qgstexteditconfigdlg.h
+     --------------------------------------
+    Date                 : 9.2020
+    Copyright            : (C) 2020 Stephen Knox
+    Email                : stephenknox73 at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSLISTCONFIGDLG_H
+#define QGSLISTCONFIGDLG_H
+
+#include "ui_qgslistconfigdlg.h"
+
+#include "qgseditorconfigwidget.h"
+#include "qgis_gui.h"
+
+SIP_NO_FILE
+
+/**
+ * A configuration dialog for the List Widget class
+ * \ingroup gui
+ * \class QgsListConfigDlg
+ * \note not available in Python bindings
+ *
+ * \since QGIS 3.16
+ */
+class GUI_EXPORT QgsListConfigDlg : public QgsEditorConfigWidget, private Ui::QgsListConfigDlg
+{
+    Q_OBJECT
+
+  public:
+
+    /**
+     * Constructor for QgsListConfigDlg, with the specified \a vector layer and field index.
+     */
+    explicit QgsListConfigDlg( QgsVectorLayer *vl, int fieldIdx, QWidget *parent = nullptr );
+
+    // QgsEditorConfigWidget interface
+  public:
+    QVariantMap config() override;
+    void setConfig( const QVariantMap &config ) override;
+};
+
+#endif // QGSLISTCONFIGDLG_H

src/gui/editorwidgets/qgslistwidgetfactory.cpp

@@ -15,7 +15,7 @@
 
 #include "qgslistwidgetfactory.h"
 #include "qgslistwidgetwrapper.h"
-#include "qgsdummyconfigdlg.h"
+#include "qgslistconfigdlg.h"
 #include "qgsfields.h"
 #include "qgsvectorlayer.h"
 #include "qgseditorwidgetregistry.h"
@@ -35,10 +35,7 @@ QgsEditorWidgetWrapper *QgsListWidgetFactory::create( QgsVectorLayer *vl, int fi
 
 QgsEditorConfigWidget *QgsListWidgetFactory::configWidget( QgsVectorLayer *vl, int fieldIdx, QWidget *parent ) const
 {
-  Q_UNUSED( vl )
-  Q_UNUSED( fieldIdx )
-  Q_UNUSED( parent )
-  return new QgsDummyConfigDlg( vl, fieldIdx, parent, QObject::tr( "List field" ) );
+  return new QgsListConfigDlg( vl, fieldIdx, parent );
 }
 
 unsigned int QgsListWidgetFactory::fieldScore( const QgsVectorLayer *vl, int fieldIdx ) const

src/gui/editorwidgets/qgslistwidgetwrapper.cpp

@@ -71,6 +71,10 @@ QVariant QgsListWidgetWrapper::value() const
   QVariant::Type type = field().type();
   if ( !mWidget ) return QVariant( type );
   const QVariantList list = mWidget->list();
+  if ( list.size() == 0 && config( QStringLiteral( "EmptyIsNull" ) ).toBool() )
+  {
+    return QVariant( );
+  }
   if ( type == QVariant::StringList )
   {
     QStringList result;
@@ -80,14 +84,7 @@ QVariant QgsListWidgetWrapper::value() const
   }
   else
   {
-    if ( list.size() == 0 )
-    {
-      return QVariant( );
-    }
-    else
-    {
-      return list;
-    }
+    return list;
   }
 }
 

src/ui/editorwidgets/qgslistconfigdlg.ui

@@ -0,0 +1,50 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>QgsListConfigDlg</class>
+ <widget class="QWidget" name="QgsListConfigDlg">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>400</width>
+    <height>78</height>
+   </rect>
+  </property>
+  <property name="windowTitle">
+   <string notr="true">Form</string>
+  </property>
+  <layout class="QGridLayout" name="gridLayout">
+   <item row="0" column="0">
+    <widget class="QGroupBox" name="mNullBehavior">
+     <property name="title">
+      <string>Treatment of Empty Cells</string>
+     </property>
+     <layout class="QFormLayout" name="formLayout_2">
+      <item row="0" column="0">
+       <widget class="QRadioButton" name="mEmptyisNull">
+        <property name="text">
+         <string>NULL</string>
+        </property>
+        <property name="checked">
+         <bool>true</bool>
+        </property>
+       </widget>
+      </item>
+      <item row="0" column="1">
+       <widget class="QRadioButton" name="mEmptyisEmptyArray">
+        <property name="text">
+         <string>Empty Array</string>
+        </property>
+        <property name="checked">
+         <bool>false</bool>
+        </property>
+       </widget>
+      </item>
+     </layout>
+    </widget>
+   </item>
+  </layout>
+ </widget>
+ <resources/>
+ <connections/>
+</ui>