[users] Move login validation to Config object

- add a loginNameStatus which is a QString (empty if things are ok)
  stating what's wrong with the loginName, if anything.

src/modules/users/Config.cpp

@@ -28,6 +28,10 @@
 
 #include <QFile>
 #include <QRegExp>
+#include <QRegExpValidator>
+
+static const QRegExp USERNAME_RX( "^[a-z_][a-z0-9_-]*[$]?$" );
+static constexpr const int USERNAME_MAX_LENGTH = 31;
 
 Config::Config( QObject* parent )
     : QObject( parent )
@@ -49,7 +53,7 @@ Config::setUserShell( const QString& shell )
 }
 
 static inline void
-setGS( const QString& key, const QString& group )
+insertInGlobalStorage( const QString& key, const QString& group )
 {
     auto* gs = Calamares::JobQueue::instance()->globalStorage();
     if ( !gs || group.isEmpty() )
@@ -62,14 +66,14 @@ setGS( const QString& key, const QString& group )
 void
 Config::setAutologinGroup( const QString& group )
 {
-    setGS( QStringLiteral( "autologinGroup" ), group );
+    insertInGlobalStorage( QStringLiteral( "autologinGroup" ), group );
     emit autologinGroupChanged( group );
 }
 
 void
 Config::setSudoersGroup( const QString& group )
 {
-    setGS( QStringLiteral( "sudoersGroup" ), group );
+    insertInGlobalStorage( QStringLiteral( "sudoersGroup" ), group );
     emit sudoersGroupChanged( group );
 }
 
@@ -82,7 +86,53 @@ Config::setLoginName( const QString& login )
         m_customLoginName = !login.isEmpty();
         m_loginName = login;
         emit loginNameChanged( login );
+        emit loginNameStatusChanged( loginNameStatus() );
+    }
+}
+
+const QStringList&
+Config::forbiddenLoginNames()
+{
+    static QStringList forbidden { "root" };
+    return forbidden;
+}
+
+QString
+Config::loginNameStatus() const
+{
+    // An empty login is "ok", even if it isn't really
+    if ( m_loginName.isEmpty() )
+    {
+        return QString();
+    }
+
+    QRegExpValidator validateEntireLoginName( USERNAME_RX );
+    QRegExpValidator validateFirstLetter( QRegExp( "[a-z_].*" ) );  // anchors are implicit in QRegExpValidator
+    int pos = -1;
+
+    if ( m_loginName.length() > USERNAME_MAX_LENGTH )
+    {
+        return tr( "Your username is too long." );
+    }
+    QString login( m_loginName );  // make a copy because validate() doesn't take const&
+    if ( validateFirstLetter.validate( login, pos ) == QValidator::Invalid )
+    {
+        return tr( "Your username must start with a lowercase letter or underscore." );
+    }
+    if ( validateEntireLoginName.validate( login, pos ) == QValidator::Invalid )
+    {
+        return tr( "Only lowercase letters, numbers, underscore and hyphen are allowed." );
     }
+
+    for ( const QString& badName : forbiddenLoginNames() )
+    {
+        if ( 0 == QString::compare( badName, m_loginName, Qt::CaseSensitive ) )
+        {
+            return tr( "'%1' is not allowed as user name." ).arg( badName );
+        }
+    }
+
+    return QString();
 }
 
 void
@@ -133,7 +183,6 @@ guessProductName()
 static QString
 makeLoginNameSuggestion( const QStringList& parts )
 {
-    static const QRegExp USERNAME_RX( "^[a-z_][a-z0-9_-]*[$]?$" );
     if ( parts.isEmpty() || parts.first().isEmpty() )
     {
         return QString();
@@ -199,6 +248,7 @@ Config::setFullName( const QString& name )
             {
                 m_loginName = login;
                 emit loginNameChanged( login );
+                emit loginNameStatusChanged( loginNameStatus() );
             }
         }
         if ( !m_customHostName )

src/modules/users/Config.h

@@ -35,6 +35,7 @@ class Config : public QObject
 
     Q_PROPERTY( QString fullName READ fullName WRITE setFullName NOTIFY fullNameChanged )
     Q_PROPERTY( QString loginName READ loginName WRITE setLoginName NOTIFY loginNameChanged )
+    Q_PROPERTY( QString loginNameStatus READ loginNameStatus NOTIFY loginNameStatusChanged )
 
     Q_PROPERTY( QString hostName READ hostName WRITE setHostName NOTIFY hostNameChanged )
 
@@ -60,10 +61,14 @@ public:
     QString fullName() const { return m_fullName; }
     /// The login name of the user
     QString loginName() const { return m_loginName; }
+    /// Status message about login -- empty for "ok"
+    QString loginNameStatus() const;
 
     /// The host name (name for the system)
     QString hostName() const { return m_hostName; }
 
+    static const QStringList& forbiddenLoginNames();
+
 public Q_SLOTS:
     /** @brief Sets the user's shell if possible
      *
@@ -94,6 +99,7 @@ signals:
     void sudoersGroupChanged( const QString& );
     void fullNameChanged( const QString& );
     void loginNameChanged( const QString& );
+    void loginNameStatusChanged( const QString& );
     void hostNameChanged( const QString& );
 
 private:

src/modules/users/UsersPage.cpp

@@ -46,7 +46,6 @@
 #include <QRegExp>
 #include <QRegExpValidator>
 
-static const QRegExp USERNAME_RX( "^[a-z_][a-z0-9_-]*[$]?$" );
 static const QRegExp HOSTNAME_RX( "^[a-zA-Z0-9][-a-zA-Z0-9_]*$" );
 static constexpr const int USERNAME_MAX_LENGTH = 31;
 static constexpr const int HOSTNAME_MIN_LENGTH = 2;
@@ -129,7 +128,7 @@ UsersPage::UsersPage( Config* config, QWidget* parent )
 
     connect( ui->textBoxLoginName, &QLineEdit::textEdited, config, &Config::setLoginName );
     connect( config, &Config::loginNameChanged, ui->textBoxLoginName, &QLineEdit::setText );
-    connect( config, &Config::loginNameChanged, this, &UsersPage::validateUsernameText );
+    connect( config, &Config::loginNameStatusChanged, this, &UsersPage::reportLoginNameStatus );
 
     setWriteRootPassword( true );
     ui->checkBoxReusePassword->setChecked( true );
@@ -277,55 +276,31 @@ UsersPage::onFullNameTextEdited( const QString& textRef )
     checkReady( isReady() );
 }
 
-
 void
-UsersPage::validateUsernameText( const QString& textRef )
+UsersPage::reportLoginNameStatus( const QString& status )
 {
-    QString text( textRef );
-    QRegExpValidator val_whole( USERNAME_RX );
-    QRegExpValidator val_start( QRegExp( "[a-z_].*" ) );  // anchors are implicit in QRegExpValidator
-    int pos = -1;
-
-    if ( text.isEmpty() )
-    {
-        ui->labelUsernameError->clear();
-        ui->labelUsername->clear();
-        m_readyUsername = false;
-    }
-    else if ( text.length() > USERNAME_MAX_LENGTH )
-    {
-        labelError( ui->labelUsername, ui->labelUsernameError, tr( "Your username is too long." ) );
-        m_readyUsername = false;
-    }
-    else if ( val_start.validate( text, pos ) == QValidator::Invalid )
-    {
-        labelError( ui->labelUsername,
-                    ui->labelUsernameError,
-                    tr( "Your username must start with a lowercase letter or underscore." ) );
-        m_readyUsername = false;
-    }
-    else if ( val_whole.validate( text, pos ) == QValidator::Invalid )
+    if ( status.isEmpty() )
     {
-        labelError( ui->labelUsername,
-                    ui->labelUsernameError,
-                    tr( "Only lowercase letters, numbers, underscore and hyphen are allowed." ) );
-        m_readyUsername = false;
-    }
-    else if ( 0 == QString::compare( "root", text, Qt::CaseSensitive ) )
-    {
-        labelError( ui->labelUsername, ui->labelUsernameError, tr( "'root' is not allowed as user name." ) );
-        m_readyUsername = false;
+        if ( m_config->loginName().isEmpty() )
+        {
+            ui->labelUsernameError->clear();
+            ui->labelUsername->clear();
+            m_readyUsername = false;
+        }
+        else
+        {
+            labelOk( ui->labelUsername, ui->labelUsernameError );
+            m_readyUsername = true;
+        }
     }
     else
     {
-        labelOk( ui->labelUsername, ui->labelUsernameError );
-        m_readyUsername = true;
+        labelError( ui->labelUsername, ui->labelUsernameError, status );
+        m_readyUsername = false;
     }
-
     emit checkReady( isReady() );
 }
 
-
 void
 UsersPage::validateHostnameText( const QString& textRef )
 {

src/modules/users/UsersPage.h

@@ -72,7 +72,7 @@ public:
 
 protected slots:
     void onFullNameTextEdited( const QString& );
-    void validateUsernameText( const QString& );
+    void reportLoginNameStatus( const QString& );
     void validateHostnameText( const QString& );
     void onPasswordTextChanged( const QString& );
     void onRootPasswordTextChanged( const QString& );