CGMES: Deterministic CGM subnetworks import order

cgmes/cgmes-conversion/src/main/java/com/powsybl/cgmes/conversion/CgmesImport.java

@@ -55,13 +55,15 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.Comparator;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Properties;
 import java.util.Set;
+import java.util.TreeSet;
 import java.util.UUID;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
@@ -211,13 +213,20 @@ public void update(Network network, ReadOnlyDataSource ds, Properties p, ReportN
 
     static class FilteredReadOnlyDataSource implements ReadOnlyDataSource {
         private final ReadOnlyDataSource ds;
+        // The modeling authority or IGM name that this subnetwork was separated by, used to sort subnetworks deterministically.
+        private final String key;
         private final Predicate<String> filter;
 
-        FilteredReadOnlyDataSource(ReadOnlyDataSource ds, Predicate<String> filter) {
+        FilteredReadOnlyDataSource(ReadOnlyDataSource ds, String key, Predicate<String> filter) {
             this.ds = ds;
+            this.key = key;
             this.filter = filter;
         }
 
+        String getKey() {
+            return key;
+        }
+
         @Override
         public String getBaseName() {
             return ds.getBaseName();
@@ -261,6 +270,11 @@ public Set<String> listNames(String regex) throws IOException {
     }
 
     static class MultipleGridModelChecker {
+        // Subnetworks are sorted by their key (modeling authority or IGM name) so that import order,
+        // and the resulting report, are deterministic and do not depend on hash-based Set iteration order.
+        private static final Comparator<ReadOnlyDataSource> SUBNETWORK_ORDER =
+                Comparator.comparing(ds -> ((FilteredReadOnlyDataSource) ds).getKey());
+
         private final ReadOnlyDataSource dataSource;
         private XMLInputFactory xmlInputFactory;
 
@@ -335,9 +349,9 @@ private Set<ReadOnlyDataSource> separateByModelingAuthority() {
                 }
             }
             return igmNames.keySet().stream()
-                    .map(ma -> new FilteredReadOnlyDataSource(dataSource,
+                    .<ReadOnlyDataSource>map(ma -> new FilteredReadOnlyDataSource(dataSource, ma,
                             name -> isBoundary(name) || igmNames.get(ma).contains(name) || shared.contains(name)))
-                    .collect(Collectors.toSet());
+                    .collect(Collectors.toCollection(() -> new TreeSet<>(SUBNETWORK_ORDER)));
         }
 
         private Optional<String> readModelingAuthority(String name) {
@@ -426,10 +440,10 @@ private Set<ReadOnlyDataSource> separateByIgmName() {
                     .map(name -> name.split("_")[2])
                     .collect(Collectors.toSet());
             return igmNames.stream()
-                    .map(igmName -> new FilteredReadOnlyDataSource(dataSource, name -> name.contains(igmName)
+                    .<ReadOnlyDataSource>map(igmName -> new FilteredReadOnlyDataSource(dataSource, igmName, name -> name.contains(igmName)
                             || isBoundary(name)
                             || isShared(name, igmNames)))
-                    .collect(Collectors.toSet());
+                    .collect(Collectors.toCollection(() -> new TreeSet<>(SUBNETWORK_ORDER)));
         }
 
         private static boolean isBoundary(String name) {

cgmes/cgmes-conversion/src/test/java/com/powsybl/cgmes/conversion/test/conformity/CgmesConformity3ConversionTest.java

@@ -81,11 +81,8 @@ void microGridBaseCaseAssembledSeparatingByFilename() {
         params.put(CgmesImport.IMPORT_CGM_WITH_SUBNETWORKS_DEFINED_BY, CgmesImport.SubnetworkDefinedBy.FILENAME.name());
         Network n = Network.read(CgmesConformity3Catalog.microGridBaseCaseAssembled().dataSource(), params);
         assertEquals(2, n.getSubnetworks().size());
-        assertEquals(List.of("BE", "NL"),
-                n.getSubnetworks().stream()
-                        .map(n1 -> n1.getSubstations().iterator().next().getCountry().map(Objects::toString).orElse(""))
-                        .sorted()
-                        .toList());
+        // Subnetworks are sorted by IGM name ("BE" < "NL")
+        assertEquals(List.of("BE", "NL"), subnetworksCountries(n));
         checkExportSvTerminals(n);
     }
 
@@ -96,14 +93,17 @@ void microGridBaseCaseAssembledSeparatingByModelingAuthority() {
         params.put(CgmesImport.IMPORT_CGM_WITH_SUBNETWORKS_DEFINED_BY, CgmesImport.SubnetworkDefinedBy.MODELING_AUTHORITY.name());
         Network n = Network.read(CgmesConformity3Catalog.microGridBaseCaseAssembled().dataSource(), params);
         assertEquals(2, n.getSubnetworks().size());
-        assertEquals(List.of("BE", "NL"),
-                n.getSubnetworks().stream()
-                        .map(n1 -> n1.getSubstations().iterator().next().getCountry().map(Objects::toString).orElse(""))
-                        .sorted()
-                        .toList());
+        // Subnetworks are sorted by modeling authority ("http://elia.be/CGMES" < "http://tennet.nl/CGMES")
+        assertEquals(List.of("BE", "NL"), subnetworksCountries(n));
         checkExportSvTerminals(n);
     }
 
+    private List<String> subnetworksCountries(Network n) {
+        return n.getSubnetworks().stream()
+                .map(n1 -> n1.getSubstations().iterator().next().getCountry().map(Objects::toString).orElse(""))
+                .toList();
+    }
+
     private void checkExportSvTerminals(Network network) {
         CgmesExportContext context = new CgmesExportContext(network);
         context.setExportBoundaryPowerFlows(true);