Simplify GaudiSequencer

- re-use Gaudi::Details::ostream_joiner
- avoid heap allocation
- avoid recursive variadic pack expansion

GaudiAlg/src/lib/GaudiSequencer.cpp

 // Include files
+#include <initializer_list>
+#include <tuple>
 
 // from Gaudi
 #include "GaudiAlg/GaudiSequencer.h"
@@ -11,41 +13,38 @@ namespace
 
   bool isDefault( const std::string& s ) { return s.empty(); }
 
+  template <typename Container>
+  bool veto( const Container* props, const char* name )
+  { // avoid changing properties explicitly present in the JOS...
+    return props &&
+           std::any_of( begin( *props ), end( *props ), [name]( const auto* prop ) { return prop->name() == name; } );
+  }
+
+  template <typename F, typename... Args>
+  void for_each_arg( F&& f, Args&&... args )
+  {
+    // the std::initializer_list only exists to provide a 'context' in which to
+    // expand the variadic pack
+    (void)std::initializer_list<int>{( f( std::forward<Args>( args ) ), 0 )...};
+  }
+
   // utility class to populate some properties in the job options service
   // for a given instance name in case those options are not explicitly
   // set a-priori (effectively inheriting their values from the GaudiSequencer)
   class populate_JobOptionsSvc_t
   {
-    std::vector<std::unique_ptr<Gaudi::Details::PropertyBase>> m_props;
+    std::vector<std::string> m_props;
     IJobOptionsSvc* m_jos;
     std::string m_name;
 
-    template <typename T>
-    void process( T&& t )
-    {
-      static_assert( std::tuple_size<T>::value == 2, "Expecting an std::tuple key-value pair" );
-      using type   = std::decay_t<std::tuple_element_t<1, T>>;
-      using prop_t = Gaudi::Property<type>;
-      if ( !isDefault( std::get<1>( t ) ) )
-        m_props.push_back( std::make_unique<prop_t>( std::get<0>( t ), std::get<1>( t ) ) );
-    }
-    template <typename T, typename... Args>
-    void process( T&& t, Args&&... args )
+    template <typename Properties, typename Key, typename Value>
+    void addPropertyToCatalogue( const Properties* props, const std::tuple<Key, Value>& arg )
     {
-      process( std::forward<T>( t ) );
-      process( std::forward<Args>( args )... );
-    }
-    void check_veto()
-    { // avoid changing properties expliclty present in the JOS...
-      const auto* props = m_jos->getProperties( m_name );
-      if ( !props ) return;
-      for ( const auto& i : *props ) {
-        auto j = std::find_if( std::begin( m_props ), std::end( m_props ),
-                               [&i]( const auto& prop ) { return prop->name() == i->name(); } );
-        if ( j == std::end( m_props ) ) continue;
-        m_props.erase( j );
-        if ( m_props.empty() ) break; // done!
-      }
+      const auto& key   = std::get<0>( arg );
+      const auto& value = std::get<1>( arg );
+      if ( isDefault( value ) || veto( props, key ) ) return;
+      m_jos->addPropertyToCatalogue( m_name, Gaudi::Property<std::decay_t<Value>>{key, value} ).ignore();
+      m_props.push_back( key );
     }
 
   public:
@@ -53,30 +52,16 @@ namespace
     populate_JobOptionsSvc_t( std::string name, IJobOptionsSvc* jos, Args&&... args )
         : m_jos{jos}, m_name{std::move( name )}
     {
-      process( std::forward<Args>( args )... );
-      if ( !m_props.empty() ) check_veto();
-      std::for_each( std::begin( m_props ), std::end( m_props ),
-                     [&]( const auto& i ) { m_jos->addPropertyToCatalogue( m_name, *i ).ignore(); } );
+      const auto* props = m_jos->getProperties( m_name );
+      for_each_arg( [&]( auto&& arg ) { this->addPropertyToCatalogue( props, std::forward<decltype( arg )>( arg ) ); },
+                    std::forward<Args>( args )... );
     }
     ~populate_JobOptionsSvc_t()
     {
-      std::for_each( std::begin( m_props ), std::end( m_props ),
-                     [&]( const auto& i ) { m_jos->removePropertyFromCatalogue( m_name, i->name() ).ignore(); } );
+      std::for_each( begin( m_props ), end( m_props ),
+                     [&]( const std::string& key ) { m_jos->removePropertyFromCatalogue( m_name, key ).ignore(); } );
     }
   };
-
-  template <typename Stream, typename Container, typename Separator, typename Transform>
-  Stream& ostream_joiner( Stream& os, const Container& c, Separator sep, Transform trans )
-  {
-    auto first = std::begin( c );
-    auto last  = std::end( c );
-    if ( first != last ) {
-      os << trans( *first );
-      ++first;
-    }
-    for ( ; first != last; ++first ) os << sep << trans( *first );
-    return os;
-  }
 }
 
 //-----------------------------------------------------------------------------
@@ -203,7 +188,6 @@ StatusCode GaudiSequencer::execute()
 //=============================================================================
 StatusCode GaudiSequencer::finalize()
 {
-
   if ( msgLevel( MSG::DEBUG ) ) debug() << "==> Finalize" << endmsg;
   return GaudiAlgorithm::finalize();
 }
@@ -213,7 +197,6 @@ StatusCode GaudiSequencer::finalize()
 //=========================================================================
 StatusCode GaudiSequencer::beginRun()
 {
-
   if ( !isEnabled() ) return StatusCode::SUCCESS;
   if ( msgLevel( MSG::DEBUG ) ) debug() << "==> beginRun" << endmsg;
   return StatusCode::SUCCESS;
@@ -224,7 +207,6 @@ StatusCode GaudiSequencer::beginRun()
 //=========================================================================
 StatusCode GaudiSequencer::endRun()
 {
-
   if ( !isEnabled() ) return StatusCode::SUCCESS;
   if ( msgLevel( MSG::DEBUG ) ) debug() << "==> endRun" << endmsg;
   return StatusCode::SUCCESS;
@@ -235,7 +217,6 @@ StatusCode GaudiSequencer::endRun()
 //=========================================================================
 StatusCode GaudiSequencer::decodeNames()
 {
-
   StatusCode final = StatusCode::SUCCESS;
   m_entries.clear();
 
@@ -273,19 +254,15 @@ StatusCode GaudiSequencer::decodeNames()
     // propagate the sub-algorithm into own state.
     if ( result.isSuccess() && Gaudi::StateMachine::INITIALIZED <= FSMState() && myIAlg &&
          Gaudi::StateMachine::INITIALIZED > myIAlg->FSMState() ) {
-      StatusCode sc = myIAlg->sysInitialize();
-      if ( sc.isFailure() ) {
-        result = sc;
-      }
+      StatusCode sc                = myIAlg->sysInitialize();
+      if ( sc.isFailure() ) result = sc;
     }
 
     // propagate the sub-algorithm into own state.
     if ( result.isSuccess() && Gaudi::StateMachine::RUNNING <= FSMState() && myIAlg &&
          Gaudi::StateMachine::RUNNING > myIAlg->FSMState() ) {
-      StatusCode sc = myIAlg->sysStart();
-      if ( sc.isFailure() ) {
-        result = sc;
-      }
+      StatusCode sc                = myIAlg->sysStart();
+      if ( sc.isFailure() ) result = sc;
     }
 
     //== Is it an Algorithm ?  Strange test...
@@ -311,11 +288,12 @@ StatusCode GaudiSequencer::decodeNames()
   MsgStream& msg = info();
   if ( m_modeOR ) msg << "OR ";
   msg << "Member list: ";
-  ostream_joiner( msg, m_entries, ", ", []( const AlgorithmEntry& e ) {
-    Algorithm* alg  = e.algorithm();
-    std::string typ = System::typeinfoName( typeid( *alg ) );
-    return ( alg->name() == typ ) ? alg->name() : ( typ + "/" + alg->name() );
-  } );
+  GaudiUtils::details::ostream_joiner(
+      msg, m_entries, ", ", []( auto& os, const AlgorithmEntry& e ) -> decltype( auto ) {
+        Algorithm* alg  = e.algorithm();
+        std::string typ = System::typeinfoName( typeid( *alg ) );
+        return os << ( alg->name() == typ ? alg->name() : ( typ + "/" + alg->name() ) );
+      } );
   if ( !isDefault( context() ) ) msg << ", with context '" << context() << "'";
   if ( !isDefault( rootInTES() ) ) msg << ", with rootInTES '" << rootInTES() << "'";
   msg << endmsg;
@@ -329,15 +307,11 @@ StatusCode GaudiSequencer::decodeNames()
 void GaudiSequencer::membershipHandler( Gaudi::Details::PropertyBase& /* p */ )
 {
   // no action for not-yet initialized sequencer
-  if ( Gaudi::StateMachine::INITIALIZED > FSMState() ) {
-    return;
-  } // RETURN
+  if ( Gaudi::StateMachine::INITIALIZED > FSMState() ) return; // RETURN
 
   decodeNames().ignore();
 
-  if ( !m_measureTime ) {
-    return;
-  } // RETURN
+  if ( !m_measureTime ) return; // RETURN
 
   // add the entries into timer table:
 
@@ -367,14 +341,12 @@ std::ostream& GaudiSequencer::toControlFlowExpression( std::ostream& os ) const
   if ( m_entries.size() > 1 ) os << "seq(";
 
   const auto op    = m_modeOR ? " | " : " & ";
-  const auto first = begin( m_entries );
   const auto last  = end( m_entries );
-  auto iterator    = first;
-  while ( iterator != last ) {
+  const auto first = begin( m_entries );
+  for ( auto iterator = first; iterator != last; ++iterator ) {
     if ( iterator != first ) os << op;
     if ( iterator->reverse() ) os << "~";
     iterator->algorithm()->toControlFlowExpression( os );
-    ++iterator;
   }
 
   if ( m_entries.size() > 1 ) os << ")";