C++17: Replace auxiliary::Option with std::optional

* Replace auxiliary::Option with std::optional

include/openPMD/IO/ADIOS/ADIOS2IOHandler.hpp

@@ -29,7 +29,6 @@
 #include "openPMD/IO/IOTask.hpp"
 #include "openPMD/IO/InvalidatableFile.hpp"
 #include "openPMD/auxiliary/JSON_internal.hpp"
-#include "openPMD/auxiliary/Option.hpp"
 #include "openPMD/backend/Writable.hpp"
 #include "openPMD/config.hpp"
 #include "openPMD/IterationEncoding.hpp"
@@ -47,6 +46,7 @@
 #include <future>
 #include <iostream>
 #include <memory> // shared_ptr
+#include <optional>
 #include <set>
 #include <string>
 #include <unordered_map>
@@ -320,11 +320,11 @@ class ADIOS2IOHandlerImpl
      * @return first parameter: the operators, second parameters: whether
      * operators have been configured
      */
-    auxiliary::Option< std::vector< ParameterizedOperator > >
+    std::optional< std::vector< ParameterizedOperator > >
     getOperators( json::TracingJSON config );
 
     // use m_config
-    auxiliary::Option< std::vector< ParameterizedOperator > >
+    std::optional< std::vector< ParameterizedOperator > >
     getOperators();
 
     std::string
@@ -367,7 +367,7 @@ class ADIOS2IOHandlerImpl
 
     // Helper methods.
 
-    auxiliary::Option< adios2::Operator >
+    std::optional< adios2::Operator >
     getCompressionOperator( std::string const & compression );
 
     /*
@@ -1227,7 +1227,7 @@ namespace detail
 
     private:
         ADIOS2IOHandlerImpl * m_impl;
-        auxiliary::Option< adios2::Engine > m_engine; //! ADIOS engine
+        std::optional< adios2::Engine > m_engine; //! ADIOS engine
         /**
          * The ADIOS2 engine type, to be passed to adios2::IO::SetEngine
          */
@@ -1343,8 +1343,8 @@ namespace detail
          * the map that would be returned by a call to
          * IO::Available(Attributes|Variables).
          */
-        auxiliary::Option< AttributeMap_t > m_availableAttributes;
-        auxiliary::Option< AttributeMap_t > m_availableVariables;
+        std::optional< AttributeMap_t > m_availableAttributes;
+        std::optional< AttributeMap_t > m_availableVariables;
 
         /*
          * finalize() will set this true to avoid running twice.

include/openPMD/IO/HDF5/HDF5IOHandlerImpl.hpp

@@ -25,9 +25,9 @@
 #   include "openPMD/IO/AbstractIOHandlerImpl.hpp"
 
 #   include "openPMD/auxiliary/JSON_internal.hpp"
-#   include "openPMD/auxiliary/Option.hpp"
 
 #   include <hdf5.h>
+#   include <optional>
 #   include <unordered_map>
 #   include <unordered_set>
 #endif
@@ -88,7 +88,7 @@ namespace openPMD
             std::string name;
             hid_t id;
         };
-        auxiliary::Option< File > getFile( Writable * );
+        std::optional< File > getFile( Writable * );
     }; // HDF5IOHandlerImpl
 #else
     class HDF5IOHandlerImpl

include/openPMD/Iteration.hpp

@@ -20,7 +20,6 @@
  */
 #pragma once
 
-#include "openPMD/auxiliary/Option.hpp"
 #include "openPMD/auxiliary/Variant.hpp"
 #include "openPMD/backend/Attributable.hpp"
 #include "openPMD/backend/Container.hpp"
@@ -29,6 +28,8 @@
 #include "openPMD/ParticleSpecies.hpp"
 #include "openPMD/Streaming.hpp"
 
+#include <optional>
+
 
 namespace openPMD
 {
@@ -100,7 +101,7 @@ namespace internal
          * Information on a parsing request that has not yet been executed.
          * Otherwise empty.
          */
-        auxiliary::Option< DeferredParseAccess > m_deferredParseAccess{};
+        std::optional< DeferredParseAccess > m_deferredParseAccess{};
     };
 }
 /** @brief  Logical compilation of data from one snapshot (e.g. a single simulation cycle).

include/openPMD/ReadIterations.hpp

@@ -23,6 +23,8 @@
 #include "openPMD/Iteration.hpp"
 #include "openPMD/Series.hpp"
 
+#include <optional>
+
 namespace openPMD
 {
 /**
@@ -51,7 +53,7 @@ class SeriesIterator
 {
     using iteration_index_t = IndexedIteration::index_t;
 
-    using maybe_series_t = auxiliary::Option< Series >;
+    using maybe_series_t = std::optional< Series >;
 
     maybe_series_t m_series;
     iteration_index_t m_currentIteration = 0;

include/openPMD/Series.hpp

@@ -30,7 +30,6 @@
 #include "openPMD/IterationEncoding.hpp"
 #include "openPMD/Streaming.hpp"
 #include "openPMD/WriteIterations.hpp"
-#include "openPMD/auxiliary/Option.hpp"
 #include "openPMD/auxiliary/Variant.hpp"
 #include "openPMD/backend/Attributable.hpp"
 #include "openPMD/backend/Container.hpp"
@@ -42,6 +41,7 @@
 #endif
 
 #include <map>
+#include <optional>
 #include <string>
 
 // expose private and protected members for invasive testing
@@ -85,7 +85,7 @@ class SeriesData : public AttributableData
      * This ensures that Series::writeIteration() always returns
      * the same instance.
      */
-    auxiliary::Option< WriteIterations > m_writeIterations;
+    std::optional< WriteIterations > m_writeIterations;
     /**
      * Needed if reading a single iteration of a file-based series.
      * Users may specify the concrete filename of one iteration instead of the
@@ -95,7 +95,7 @@ class SeriesData : public AttributableData
      * Instead, the user-specified filename should be used directly.
      * Store that filename in the following Option to indicate this situation.
      */
-    auxiliary::Option< std::string > m_overrideFilebasedFilename;
+    std::optional< std::string > m_overrideFilebasedFilename;
     /**
      * Name of the iteration without filename suffix.
      * In case of file-based iteration encoding, with expansion pattern.

include/openPMD/WriteIterations.hpp

@@ -21,9 +21,10 @@
 #pragma once
 
 #include "openPMD/Iteration.hpp"
-#include "openPMD/auxiliary/Option.hpp"
 #include "openPMD/backend/Container.hpp"
 
+#include <optional>
+
 
 namespace openPMD
 {
@@ -61,7 +62,7 @@ class WriteIterations
     struct SharedResources
     {
         iterations_t iterations;
-        auxiliary::Option< uint64_t > currentlyOpen;
+        std::optional< uint64_t > currentlyOpen;
 
         SharedResources( iterations_t );
         ~SharedResources();

include/openPMD/auxiliary/JSON_internal.hpp

@@ -24,11 +24,12 @@
 #include "openPMD/config.hpp"
 
 #include "openPMD/Error.hpp"
-#include "openPMD/auxiliary/Option.hpp"
 
 #include <nlohmann/json.hpp>
 #include <toml.hpp>
 
+#include <optional>
+
 #if openPMD_HAVE_MPI
 #   include <mpi.h>
 #endif
@@ -223,12 +224,12 @@ namespace json
      * If it is a bool, convert it to either "0" or "1".
      * If it is not a literal, return an empty option.
      */
-    auxiliary::Option< std::string > asStringDynamic( nlohmann::json const & );
+    std::optional< std::string > asStringDynamic( nlohmann::json const & );
 
     /**
      * Like asStringDynamic(), but convert the string to lowercase afterwards.
      */
-    auxiliary::Option< std::string >
+    std::optional< std::string >
     asLowerCaseStringDynamic( nlohmann::json const & );
 
     /**

include/openPMD/openPMD.hpp

@@ -56,7 +56,6 @@ namespace openPMD {}
 #include "openPMD/auxiliary/Date.hpp"
 #include "openPMD/auxiliary/DerefDynamicCast.hpp"
 #include "openPMD/auxiliary/JSON.hpp"
-#include "openPMD/auxiliary/Option.hpp"
 #include "openPMD/auxiliary/OutOfRangeMsg.hpp"
 #include "openPMD/auxiliary/ShareRaw.hpp"
 #include "openPMD/auxiliary/StringManip.hpp"