[libcalamares] Convenience for logging subentries

For methods that log a bunch of things, and which want to
consistently use SubEntry, but don't know when the **first**
log entry is within the method, Logger::Once can be used
to log one regular message (with function info) and the
rest are subentries.

src/libcalamares/utils/Logger.h

@@ -22,6 +22,8 @@
 
 namespace Logger
 {
+class Once;
+
 struct FuncSuppressor
 {
     explicit constexpr FuncSuppressor( const char[] );
@@ -58,6 +60,7 @@ public:
     virtual ~CDebug();
 
     friend CDebug& operator<<( CDebug&&, const FuncSuppressor& );
+    friend CDebug& operator<<( CDebug&&, Once& );
 
 private:
     QString m_msg;
@@ -286,6 +289,33 @@ operator<<( QDebug& s, const Pointer& p )
     s << '@' << p.ptr << Quote;
     return s;
 }
+
+class Once
+{
+public:
+    Once()
+        : m( true )
+    {
+    }
+    friend CDebug& operator<<( CDebug&&, Once& );
+
+private:
+    bool m = false;
+};
+
+inline CDebug&
+operator<<( CDebug&& s, Once& o )
+{
+    if ( o.m )
+    {
+        o.m = false;
+        return s;
+    }
+    s.m_funcinfo = nullptr;
+    s << SubEntry;
+    return s;
+}
+
 }  // namespace Logger
 
 #define cDebug() Logger::CDebug( Logger::LOGDEBUG, Q_FUNC_INFO )

src/libcalamaresui/modulesystem/ModuleManager.cpp

@@ -61,7 +61,6 @@ ModuleManager::init()
     QTimer::singleShot( 0, this, &ModuleManager::doInit );
 }
 
-
 void
 ModuleManager::doInit()
 {
@@ -72,6 +71,7 @@ ModuleManager::doInit()
     // the module name, and must contain a settings file named module.desc.
     // If at any time the module loading procedure finds something unexpected, it
     // silently skips to the next module or search path. --Teo 6/2014
+    Logger::Once deb;
     for ( const QString& path : m_paths )
     {
         QDir currentDir( path );
@@ -88,12 +88,12 @@ ModuleManager::doInit()
                     QFileInfo descriptorFileInfo( currentDir.absoluteFilePath( QLatin1String( "module.desc" ) ) );
                     if ( !descriptorFileInfo.exists() )
                     {
-                        cDebug() << bad_descriptor << descriptorFileInfo.absoluteFilePath() << "(missing)";
+                        cDebug() << deb << bad_descriptor << descriptorFileInfo.absoluteFilePath() << "(missing)";
                         continue;
                     }
                     if ( !descriptorFileInfo.isReadable() )
                     {
-                        cDebug() << bad_descriptor << descriptorFileInfo.absoluteFilePath() << "(unreadable)";
+                        cDebug() << deb << bad_descriptor << descriptorFileInfo.absoluteFilePath() << "(unreadable)";
                         continue;
                     }
 
@@ -118,12 +118,12 @@ ModuleManager::doInit()
         }
         else
         {
-            cDebug() << "ModuleManager module search path does not exist:" << path;
+            cDebug() << deb << "ModuleManager module search path does not exist:" << path;
         }
     }
     // At this point m_availableDescriptorsByModuleName is filled with
     // the modules that were found in the search paths.
-    cDebug() << "Found" << m_availableDescriptorsByModuleName.count() << "modules";
+    cDebug() << deb << "Found" << m_availableDescriptorsByModuleName.count() << "modules";
     QTimer::singleShot( 10, this, &ModuleManager::initDone );
 }