Extinct extensions serialization

iidm/iidm-serde/src/main/java/com/powsybl/iidm/serde/AbstractIdentifiableSerDe.java

@@ -24,6 +24,9 @@ protected boolean isValid(T identifiable, P parent) {
 
     protected abstract void writeRootElementAttributes(T identifiable, P parent, NetworkSerializerContext context);
 
+    protected void addExtinctExtensions(T identifiable, NetworkSerializerContext context) {
+    }
+
     protected void writeSubElements(T identifiable, P parent, NetworkSerializerContext context) {
     }
 
@@ -38,6 +41,7 @@ public final void write(T identifiable, P parent, NetworkSerializerContext conte
         IidmSerDeUtil.runFromMinimumVersion(IidmVersion.V_1_2, context, () -> context.getWriter().writeBooleanAttribute("fictitious", identifiable.isFictitious(), false));
 
         writeRootElementAttributes(identifiable, parent, context);
+        addExtinctExtensions(identifiable, context);
 
         IidmSerDeUtil.runFromMinimumVersion(IidmVersion.V_1_3, context, () -> AliasesSerDe.write(identifiable, getRootElementName(), context));
 

iidm/iidm-serde/src/main/java/com/powsybl/iidm/serde/BatterySerDe.java

@@ -10,6 +10,8 @@
 import com.powsybl.iidm.network.Battery;
 import com.powsybl.iidm.network.BatteryAdder;
 import com.powsybl.iidm.network.VoltageLevel;
+import com.powsybl.iidm.network.extensions.removed.VoltageRegulationExtension;
+import com.powsybl.iidm.network.regulation.RegulationMode;
 import com.powsybl.iidm.serde.util.IidmSerDeUtil;
 
 import static com.powsybl.iidm.serde.ConnectableSerDeUtil.*;
@@ -43,6 +45,17 @@ protected void writeRootElementAttributes(Battery b, VoltageLevel vl, NetworkSer
         writePQ(null, b.getTerminal(), context.getWriter());
     }
 
+    @Override
+    protected void addExtinctExtensions(Battery b, NetworkSerializerContext context) {
+        if (com.powsybl.iidm.serde.extensions.VoltageRegulationSerDe.isExtensionNeededAndExportable(b, context)) {
+            VoltageRegulationExtension extension = new VoltageRegulationExtension(b,
+                    b.getVoltageRegulation().getTerminal(),
+                    b.getVoltageRegulation().getMode() == RegulationMode.VOLTAGE,
+                    b.getVoltageRegulation().getTargetValue());
+            context.addExtinctExtensionsToSerialize(b.getId(), extension);
+        }
+    }
+
     @Override
     protected void writeSubElements(Battery b, VoltageLevel vl, NetworkSerializerContext context) {
         ReactiveLimitsSerDe.INSTANCE.write(b, context);

iidm/iidm-serde/src/main/java/com/powsybl/iidm/serde/GeneratorSerDe.java

@@ -8,7 +8,9 @@
 package com.powsybl.iidm.serde;
 
 import com.powsybl.iidm.network.*;
+import com.powsybl.iidm.network.extensions.removed.RemoteReactivePowerControl;
 import com.powsybl.iidm.network.regulation.RegulationMode;
+import com.powsybl.iidm.serde.extensions.RemoteReactivePowerControlSerDe;
 import com.powsybl.iidm.serde.util.IidmSerDeUtil;
 
 import java.util.concurrent.atomic.AtomicReference;
@@ -90,6 +92,17 @@ private static void writeTargetQByVersion(Generator g, NetworkSerializerContext
             context.getWriter().writeDoubleAttribute("targetQ", g.getTargetQ()));
     }
 
+    @Override
+    protected void addExtinctExtensions(Generator g, NetworkSerializerContext context) {
+        if (RemoteReactivePowerControlSerDe.isExtensionNeededAndExportable(g, context)) {
+            RemoteReactivePowerControl extension = new RemoteReactivePowerControl(g,
+                    g.getVoltageRegulation().getTargetValue(),
+                    g.getVoltageRegulation().getTerminal(),
+                    g.getVoltageRegulation().isRegulating());
+            context.addExtinctExtensionsToSerialize(g.getId(), extension);
+        }
+    }
+
     @Override
     protected void writeSubElements(Generator g, VoltageLevel vl, NetworkSerializerContext context) {
         IidmSerDeUtil.runUntilMaximumVersion(IidmVersion.V_1_15, context, () -> {

iidm/iidm-serde/src/main/java/com/powsybl/iidm/serde/NetworkSerializerContext.java

@@ -7,13 +7,15 @@
  */
 package com.powsybl.iidm.serde;
 
+import com.powsybl.commons.extensions.Extension;
 import com.powsybl.commons.io.SerializerContext;
 import com.powsybl.commons.io.TreeDataWriter;
 import com.powsybl.iidm.network.Identifiable;
 import com.powsybl.iidm.network.TopologyLevel;
 import com.powsybl.iidm.serde.anonymizer.Anonymizer;
 
 import java.util.*;
+import java.util.stream.Stream;
 
 /**
  * @author Geoffroy Jamgotchian {@literal <geoffroy.jamgotchian at rte-france.com>}
@@ -26,6 +28,7 @@ public class NetworkSerializerContext extends AbstractNetworkSerDeContext<Export
     private final boolean valid;
     private final Set<Identifiable> exportedEquipments;
     private final Map<String, TopologyLevel> voltageLevelExportTopologyLevel;
+    private final Map<String, List<Extension<? extends Identifiable<?>>>> extinctExtensionsToSerializeByIdentifiable;
 
     NetworkSerializerContext(Anonymizer anonymizer, TreeDataWriter writer, ExportOptions options, BusFilter filter, IidmVersion version, boolean valid) {
         super(anonymizer, version);
@@ -35,6 +38,7 @@ public class NetworkSerializerContext extends AbstractNetworkSerDeContext<Export
         this.valid = valid;
         this.exportedEquipments = new HashSet<>();
         this.voltageLevelExportTopologyLevel = new HashMap<>();
+        this.extinctExtensionsToSerializeByIdentifiable = new HashMap<>();
     }
 
     @Override
@@ -84,4 +88,14 @@ public void addVoltageLevelExportTopologyLevel(String voltageLevelId, TopologyLe
     public TopologyLevel getVoltageLevelExportTopologyLevel(String voltageLevelId) {
         return voltageLevelExportTopologyLevel.get(voltageLevelId);
     }
+
+    public void addExtinctExtensionsToSerialize(String identifiableId, Extension<? extends Identifiable<?>> extension) {
+        extinctExtensionsToSerializeByIdentifiable.computeIfAbsent(identifiableId, k -> new ArrayList<>()).add(extension);
+    }
+
+    public Stream<Extension<Identifiable<?>>> getExtinctExtensionsToSerialize(String identifiableId) {
+        return extinctExtensionsToSerializeByIdentifiable.containsKey(identifiableId) ?
+            extinctExtensionsToSerializeByIdentifiable.get(identifiableId).stream()
+                    .map(e -> (Extension<Identifiable<?>>) e) : Stream.empty();
+    }
 }

iidm/iidm-serde/src/main/java/com/powsybl/iidm/serde/extensions/ExtinctExtensionSerDe.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2026, RTE (http://www.rte-france.com)
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ * SPDX-License-Identifier: MPL-2.0
+ */
+package com.powsybl.iidm.serde.extensions;
+
+import com.powsybl.commons.extensions.Extendable;
+import com.powsybl.commons.extensions.Extension;
+import com.powsybl.commons.extensions.ExtensionSerDe;
+import com.powsybl.iidm.network.Network;
+import com.powsybl.iidm.serde.ExportOptions;
+import com.powsybl.iidm.serde.IidmVersion;
+
+/**
+ * <p>Interface for the (de)serialization of extensions that no longer exists.</p>
+ * <p>It is useful for backward compatibility purposes.</p>
+ *
+ * @author Olivier Perrin {@literal <olivier.perrin at rte-france.com>}
+ */
+public interface ExtinctExtensionSerDe<T extends Extendable, E extends Extension<T>> extends ExtensionSerDe<T, E> {
+
+    default boolean isExtensionNeededAndExportable(Network network, ExportOptions options) {
+        return isExtensionExportable(options) && isExtensionNeeded(network);
+    }
+
+    private boolean isExtensionExportable(ExportOptions options) {
+        return isExtensionExportable(options, getName(), getLastSupportedVersion());
+    }
+
+    static boolean isExtensionExportable(ExportOptions options, String extensionName, IidmVersion lastSupportedVersion) {
+        return options.withExtension(extensionName) && options.getVersion().compareTo(lastSupportedVersion) <= 0;
+    }
+
+    IidmVersion getLastSupportedVersion();
+
+    boolean isExtensionNeeded(Network network);
+}

iidm/iidm-serde/src/main/java/com/powsybl/iidm/serde/extensions/ExtinctExtensionSerDeService.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2026, RTE (http://www.rte-france.com)
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ * SPDX-License-Identifier: MPL-2.0
+ */
+package com.powsybl.iidm.serde.extensions;
+
+import com.powsybl.commons.util.ServiceLoaderCache;
+
+import java.util.List;
+
+/**
+ * @author Olivier Perrin {@literal <olivier.perrin at rte-france.com>}
+ */
+public final class ExtinctExtensionSerDeService {
+
+    private static final ServiceLoaderCache<ExtinctExtensionSerDe> EXTINCT_SERDE_SERVICE = new ServiceLoaderCache<>(ExtinctExtensionSerDe.class);
+
+    private ExtinctExtensionSerDeService() {
+    }
+
+    public static List<ExtinctExtensionSerDe> findAll() {
+        return EXTINCT_SERDE_SERVICE.getServices();
+    }
+
+}

iidm/iidm-serde/src/main/java/com/powsybl/iidm/serde/extensions/RemoteReactivePowerControlSerDe.java

@@ -13,6 +13,7 @@
 import com.powsybl.commons.io.DeserializerContext;
 import com.powsybl.commons.io.SerializerContext;
 import com.powsybl.iidm.network.Generator;
+import com.powsybl.iidm.network.Network;
 import com.powsybl.iidm.network.Terminal;
 import com.powsybl.iidm.network.extensions.removed.RemoteReactivePowerControl;
 import com.powsybl.iidm.network.regulation.RegulationMode;
@@ -25,8 +26,11 @@
 /**
  * @author Damien Jeandemange {@literal <damien.jeandemange at artelys.com>}
  */
-@AutoService(ExtensionSerDe.class)
-public class RemoteReactivePowerControlSerDe extends AbstractExtensionSerDe<Generator, RemoteReactivePowerControl> {
+@AutoService({ExtensionSerDe.class, ExtinctExtensionSerDe.class})
+public class RemoteReactivePowerControlSerDe extends AbstractExtensionSerDe<Generator, RemoteReactivePowerControl>
+        implements ExtinctExtensionSerDe<Generator, RemoteReactivePowerControl> {
+
+    public static final IidmVersion LAST_SUPPORTED_VERSION = IidmVersion.V_1_15;
 
     public RemoteReactivePowerControlSerDe() {
         super(RemoteReactivePowerControl.NAME, "network", RemoteReactivePowerControl.class,
@@ -62,4 +66,25 @@ public RemoteReactivePowerControl read(Generator extendable, DeserializerContext
         }
         return null;
     }
+
+    @Override
+    public IidmVersion getLastSupportedVersion() {
+        return LAST_SUPPORTED_VERSION;
+    }
+
+    @Override
+    public boolean isExtensionNeeded(Network n) {
+        return n.getGeneratorStream().anyMatch(RemoteReactivePowerControlSerDe::isExtensionNeeded);
+    }
+
+    private static boolean isExtensionNeeded(Generator g) {
+        return g.getVoltageRegulation() != null
+                && g.getVoltageRegulation().getTerminal() != null
+                && g.getVoltageRegulation().getMode() == RegulationMode.REACTIVE_POWER;
+    }
+
+    public static boolean isExtensionNeededAndExportable(Generator g, NetworkSerializerContext context) {
+        return ExtinctExtensionSerDe.isExtensionExportable(context.getOptions(), RemoteReactivePowerControl.NAME, LAST_SUPPORTED_VERSION)
+                && isExtensionNeeded(g);
+    }
 }

iidm/iidm-serde/src/main/java/com/powsybl/iidm/serde/extensions/VoltageRegulationSerDe.java

@@ -12,6 +12,7 @@
 import com.powsybl.commons.io.DeserializerContext;
 import com.powsybl.commons.io.SerializerContext;
 import com.powsybl.iidm.network.Battery;
+import com.powsybl.iidm.network.Network;
 import com.powsybl.iidm.network.extensions.removed.VoltageRegulationExtension;
 import com.powsybl.iidm.network.regulation.RegulationMode;
 import com.powsybl.iidm.network.regulation.VoltageRegulation;
@@ -24,8 +25,11 @@
 /**
  * @author Coline Piloquet {@literal <coline.piloquet@rte-france.fr>}
  */
-@AutoService(ExtensionSerDe.class)
-public class VoltageRegulationSerDe extends AbstractVersionableNetworkExtensionSerDe<Battery, VoltageRegulationExtension, VoltageRegulationSerDe.Version> {
+@AutoService({ExtensionSerDe.class, ExtinctExtensionSerDe.class})
+public class VoltageRegulationSerDe extends AbstractVersionableNetworkExtensionSerDe<Battery, VoltageRegulationExtension, VoltageRegulationSerDe.Version>
+    implements ExtinctExtensionSerDe<Battery, VoltageRegulationExtension> {
+
+    public static final IidmVersion LAST_SUPPORTED_VERSION = IidmVersion.V_1_15;
 
     public enum Version implements SerDeVersion<Version> {
         V_1_0_LEGACY("/xsd/voltageRegulation_V1_0_legacy.xsd", "http://www.itesla_project.eu/schema/iidm/ext/voltageregulation/1_0",
@@ -117,4 +121,23 @@ protected Version getDefaultVersion() {
         // Default version is v1.1, the subsequent ones have been added without any change
         return Version.V_1_1;
     }
+
+    @Override
+    public IidmVersion getLastSupportedVersion() {
+        return LAST_SUPPORTED_VERSION;
+    }
+
+    @Override
+    public boolean isExtensionNeeded(Network n) {
+        return n.getBatteryStream().anyMatch(VoltageRegulationSerDe::isExtensionNeeded);
+    }
+
+    private static boolean isExtensionNeeded(Battery b) {
+        return b.getVoltageRegulation() != null;
+    }
+
+    public static boolean isExtensionNeededAndExportable(Battery b, NetworkSerializerContext context) {
+        return ExtinctExtensionSerDe.isExtensionExportable(context.getOptions(), VoltageRegulationExtension.NAME, LAST_SUPPORTED_VERSION)
+                && isExtensionNeeded(b);
+    }
 }