Turn attribute_writing_ranks into global option

New concept: global options with backend-specific implementation

src/IO/ADIOS/ADIOS2IOHandler.cpp

@@ -90,7 +90,7 @@ ADIOS2IOHandlerImpl::ADIOS2IOHandlerImpl(
             MPI_Comm_rank(communicator, &rank);
             auto throw_error = []() {
                 throw error::BackendConfigSchema(
-                    {"adios2", "attribute_writing_ranks"},
+                    {"attribute_writing_ranks"},
                     "Type must be either an integer or an array of integers.");
             };
             if (attribute_writing_ranks.is_array())
@@ -178,6 +178,8 @@ template <typename Callback>
 void ADIOS2IOHandlerImpl::init(
     json::TracingJSON cfg, Callback &&callbackWriteAttributesFromRank)
 {
+    std::cout << "Initializing ADIOS2 with config:\n"
+              << cfg.json() << std::endl;
     // allow overriding through environment variable
     m_engineType =
         auxiliary::getEnvString("OPENPMD_ADIOS2_ENGINE", m_engineType);
@@ -196,6 +198,12 @@ void ADIOS2IOHandlerImpl::init(
             groupTableViaEnv == 0 ? UseGroupTable::No : UseGroupTable::Yes;
     }
 
+    // Backend-independent options with backend-dependent implementations
+    if (cfg.json().contains("attribute_writing_ranks"))
+    {
+        callbackWriteAttributesFromRank(cfg["attribute_writing_ranks"].json());
+    }
+
     if (cfg.json().contains("adios2"))
     {
         m_config = cfg["adios2"];

src/Series.cpp

@@ -2175,6 +2175,21 @@ namespace
 template <typename TracingJSON>
 void Series::parseJsonOptions(TracingJSON &options, ParsedInput &input)
 {
+    constexpr std::array
+        backend_independent_options_with_backend_specific_implementation = {
+            "attribute_writing_ranks"};
+
+    for (auto const &opt :
+         backend_independent_options_with_backend_specific_implementation)
+    {
+        // Suppress warnings for these options: The backends might or might not
+        // take those hints
+        if (options.json().contains(opt))
+        {
+            options[opt];
+        }
+    }
+
     auto &series = get();
     getJsonOption<bool>(
         options, "defer_iteration_parsing", series.m_parseLazily);

test/ParallelIOTest.cpp

@@ -1173,9 +1173,10 @@ doshuffle = "BLOSC_BITSHUFFLE"
 
     std::string writeConfigBP4 =
         R"END(
+attribute_writing_ranks = 0
+
 [adios2]
 unused = "parameter"
-attribute_writing_ranks = 0
 )END"
 #if openPMD_HAS_ADIOS_2_9
         "use_group_table = true"