[libcalamares] Refactor settings-loading some more

- Load instances list in a separate method
 - Load sequence list in a separate method
 - Don't rely on QASSERT, explicitly throw if something is missing.

src/libcalamares/Settings.cpp

@@ -114,33 +114,13 @@ interpretModulesSearch( const bool debugMode, const QStringList& rawPaths, QStri
     }
 }
 
-Settings::Settings( const QString& settingsFilePath,
-                    bool debugMode,
-                    QObject* parent )
-    : QObject( parent )
-    , m_debug( debugMode )
-    , m_doChroot( true )
-    , m_promptInstall( false )
-    , m_disableCancel( false )
-{
-    cDebug() << "Using Calamares settings file at" << settingsFilePath;
-    QFile file( settingsFilePath );
-    if ( file.exists() && file.open( QFile::ReadOnly | QFile::Text ) )
-    {
-        QByteArray ba = file.readAll();
-
-        try
+static void
+interpretInstances( const YAML::Node& node, Settings::InstanceDescriptionList& customInstances )
 {
-            YAML::Node config = YAML::Load( ba.constData() );
-            Q_ASSERT( config.IsMap() );
-
-            interpretModulesSearch( debugMode, CalamaresUtils::yamlToStringList( config[ "modules-search" ] ), m_modulesSearchPaths );
-
     // Parse the custom instances section
-            if ( config[ "instances" ] )
+    if ( node )
     {
-                QVariant instancesV
-                        = CalamaresUtils::yamlToVariant( config[ "instances" ] ).toList();
+        QVariant instancesV = CalamaresUtils::yamlToVariant( node ).toList();
         if ( instancesV.type() == QVariant::List )
         {
             const auto instances = instancesV.toList();
@@ -150,7 +130,7 @@ Settings::Settings( const QString& settingsFilePath,
                     continue;
                 QVariantMap instancesVListItemMap =
                         instancesVListItem.toMap();
-                        QMap< QString, QString > instanceMap;
+                Settings::InstanceDescription instanceMap;
                 for ( auto it = instancesVListItemMap.constBegin();
                         it != instancesVListItemMap.constEnd(); ++it )
                 {
@@ -158,17 +138,22 @@ Settings::Settings( const QString& settingsFilePath,
                         continue;
                     instanceMap.insert( it.key(), it.value().toString() );
                 }
-                        m_customModuleInstances.append( instanceMap );
+                customInstances.append( instanceMap );
+            }
         }
     }
 }
 
+static void
+interpretSequence( const YAML::Node& node, Settings::ModuleSequence& moduleSequence )
+{
     // Parse the modules sequence section
-            Q_ASSERT( config[ "sequence" ] ); // It better exist!
+    if ( node )
     {
-                QVariant sequenceV
-                        = CalamaresUtils::yamlToVariant( config[ "sequence" ] );
-                Q_ASSERT( sequenceV.type() == QVariant::List );
+        QVariant sequenceV = CalamaresUtils::yamlToVariant( node );
+        if ( !( sequenceV.type() == QVariant::List ) )
+            throw YAML::Exception( YAML::Mark(), "sequence key does not have a list-value" );
+
         const auto sequence = sequenceV.toList();
         for ( const QVariant& sequenceVListItem : sequence )
         {
@@ -187,10 +172,37 @@ Settings::Settings( const QString& settingsFilePath,
                                             .toMap()
                                             .value( thisActionS )
                                             .toStringList();
-                    m_modulesSequence.append( qMakePair( thisAction,
+            moduleSequence.append( qMakePair( thisAction,
                                                     thisActionRoster ) );
         }
     }
+    else
+        throw YAML::Exception( YAML::Mark(), "sequence key is missing" );
+}
+
+Settings::Settings( const QString& settingsFilePath,
+                    bool debugMode,
+                    QObject* parent )
+    : QObject( parent )
+    , m_debug( debugMode )
+    , m_doChroot( true )
+    , m_promptInstall( false )
+    , m_disableCancel( false )
+{
+    cDebug() << "Using Calamares settings file at" << settingsFilePath;
+    QFile file( settingsFilePath );
+    if ( file.exists() && file.open( QFile::ReadOnly | QFile::Text ) )
+    {
+        QByteArray ba = file.readAll();
+
+        try
+        {
+            YAML::Node config = YAML::Load( ba.constData() );
+            Q_ASSERT( config.IsMap() );
+
+            interpretModulesSearch( debugMode, CalamaresUtils::yamlToStringList( config[ "modules-search" ] ), m_modulesSearchPaths );
+            interpretInstances( config[ "instances" ], m_customModuleInstances );
+            interpretSequence( config[ "sequence" ], m_modulesSequence );
 
             m_brandingComponentName = requireString( config, "branding" );
             m_promptInstall = requireBool( config, "prompt-install", false );