[packagechooser] Rename internals

- pkgc -> packageChoice and similar for methods, variables
- document that this is the convenience value for one-selection
  QML modules, not a full model
- use std::optional to keep track of which one is being used.

src/modules/packagechooser/Config.cpp

@@ -100,8 +100,8 @@ Config::updateGlobalStorage( const QStringList& selected ) const
 {
     if ( m_method == PackageChooserMethod::Legacy )
     {
-        //QString value = selected.join( ',' );
+        QString value = selected.join( ',' );
-        QString value = ( m_pkgc );
+        // QString value = ( m_pkgc );
         Calamares::JobQueue::instance()->globalStorage()->insert( m_id, value );
         cDebug() << m_id << "selected" << value;
     }
@@ -119,16 +119,23 @@ Config::updateGlobalStorage( const QStringList& selected ) const
 }
 
 void
-Config::setPkgc( const QString& pkgc )
+Config::setPackageChoice( const QString& packageChoice )
 {
-    m_pkgc = pkgc;
+    if ( packageChoice.isEmpty() )
-    emit pkgcChanged( m_pkgc );
+    {
+        m_packageChoice.reset();
+    }
+    else
+    {
+        m_packageChoice = packageChoice;
+    }
+    emit packageChoiceChanged( m_packageChoice.value_or( QString() ) );
 }
 
 QString
 Config::prettyStatus() const
 {
-    return tr( "Install option: <strong>%1</strong>" ).arg( m_pkgc );
+    return tr( "Install option: <strong>%1</strong>" ).arg( m_packageChoice.value_or( tr( "None" ) ) );
 }
 
 static void
@@ -197,7 +204,7 @@ Config::setConfigurationMap( const QVariantMap& configurationMap )
                                              PackageChooserMode::Required );
     m_method = PackageChooserMethodNames().find( CalamaresUtils::getString( configurationMap, "method" ),
                                                  PackageChooserMethod::Legacy );
-    m_pkgc = CalamaresUtils::getString( configurationMap, "pkgc" );
+    setPackageChoice( CalamaresUtils::getString( configurationMap, "pkgc" ) );
 
     if ( m_method == PackageChooserMethod::Legacy )
     {

src/modules/packagechooser/Config.h

@@ -17,6 +17,7 @@
 #include "modulesystem/InstanceKey.h"
 
 #include <memory>
+#include <optional>
 
 enum class PackageChooserMode
 {
@@ -40,7 +41,16 @@ class Config : public Calamares::ModuleSystem::Config
 {
     Q_OBJECT
 
-    Q_PROPERTY( QString pkgc READ pkgc WRITE setPkgc NOTIFY pkgcChanged )
+    /** @brief This is the single-select package-choice
+     *
+     * For (QML) modules that support only a single selection and
+     * just want to do things in a straightforward pick-this-one
+     * way, the packageChoice property is a (the) way to go.
+     *
+     * Writing to this property means that any other form of package-
+     * choice or selection is ignored.
+     */
+    Q_PROPERTY( QString packageChoice READ packageChoice WRITE setPackageChoice NOTIFY packageChoiceChanged )
     Q_PROPERTY( QString prettyStatus READ prettyStatus NOTIFY prettyStatusChanged FINAL )
 
 public:
@@ -78,13 +88,13 @@ public:
     /// As updateGlobalStorage() with an empty selection list
     void fillGSSecondaryConfiguration() const { updateGlobalStorage( QStringList() ); }
 
-    QString pkgc() const { return m_pkgc; }
+    QString packageChoice() const { return m_packageChoice.value_or( QString() ); }
-    void setPkgc( const QString& pkgc );
+    void setPackageChoice( const QString& packageChoice );
 
     QString prettyStatus() const;
 
 signals:
-    void pkgcChanged( QString pkgc );
+    void packageChoiceChanged( QString packageChoice );
     void prettyStatusChanged();
 
 private:
@@ -99,8 +109,12 @@ private:
     QString m_id;
     /// Value to use for id if none is set in the config file
     Calamares::ModuleSystem::InstanceKey m_defaultId;
-    /// QML selection
+    /** @brief QML selection (for single-selection approaches)
-    QString m_pkgc;
+     *
+     * If there is no value, then there has been no selection.
+     * Reading the property will return an empty QString.
+     */
+    std::optional< QString > m_packageChoice;
 };