Temporary fix to handle "null" subject names in security analysis result

src/main/java/org/gridsuite/securityanalysis/server/entities/SecurityAnalysisResultEntity.java

@@ -94,9 +94,14 @@
         return Stream.concat(
                 securityAnalysisResult.getPostContingencyResults().stream().flatMap(pcr -> pcr.getLimitViolationsResult().getLimitViolations().stream()),
                 securityAnalysisResult.getPreContingencyResult().getLimitViolationsResult().getLimitViolations().stream())
-            .map(lm -> new Pair<>(lm.getSubjectId(), lm.getSubjectName()))
+            .map(lm -> new Pair<>(lm.getSubjectId(), normalizeSubjectName(lm.getSubjectName())))
             .distinct()
             .map(pair -> new SubjectLimitViolationEntity(pair.getFirst(), pair.getSecond()))
             .toList();
     }
+
+    // FIXME: powsybl limit violation detection may expose missing names as "null" instead of null. Method to remove when https://github.com/powsybl/powsybl-core/pull/3922 is merged
+    private static String normalizeSubjectName(String subjectName) {
+        return "null".equals(subjectName) ? null : subjectName;
+    }
 }

src/test/java/org/gridsuite/securityanalysis/server/SecurityAnalysisResultEntityTest.java

@@ -0,0 +1,49 @@
+/**
+ * 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/.
+ */
+package org.gridsuite.securityanalysis.server;
+
+import com.powsybl.contingency.violations.LimitViolation;
+import com.powsybl.contingency.violations.LimitViolationType;
+import com.powsybl.iidm.network.Network;
+import com.powsybl.iidm.network.TwoSides;
+import com.powsybl.iidm.network.test.EurostagTutorialExample1Factory;
+import com.powsybl.loadflow.LoadFlowResult;
+import com.powsybl.network.store.iidm.impl.NetworkFactoryImpl;
+import com.powsybl.security.LimitViolationsResult;
+import com.powsybl.security.SecurityAnalysisResult;
+import org.gridsuite.securityanalysis.server.dto.SecurityAnalysisStatus;
+import org.gridsuite.securityanalysis.server.entities.SecurityAnalysisResultEntity;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+import java.util.UUID;
+
+import static com.powsybl.iidm.network.test.EurostagTutorialExample1Factory.NHV1_NHV2_1;
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Antoine Bouhours <antoine.bouhours at rte-france.com>
+ */
+class SecurityAnalysisResultEntityTest {
+
+    @Test
+    void toEntityNormalizesStringNullSubjectNames() {
+        Network network = EurostagTutorialExample1Factory.create(new NetworkFactoryImpl());
+        SecurityAnalysisResult securityAnalysisResult = new SecurityAnalysisResult(
+            new LimitViolationsResult(List.of(
+                new LimitViolation(NHV1_NHV2_1, null, LimitViolationType.CURRENT, "10'", 600, 1000, 1, 1100, TwoSides.ONE),
+                new LimitViolation(NHV1_NHV2_1, "null", LimitViolationType.CURRENT, "10'", 600, 1000, 1, 1100, TwoSides.ONE)
+            )),
+            LoadFlowResult.ComponentResult.Status.CONVERGED,
+            List.of()
+        );
+
+        SecurityAnalysisResultEntity entity = SecurityAnalysisResultEntity.toEntity(network, UUID.randomUUID(), securityAnalysisResult, SecurityAnalysisStatus.CONVERGED);
+
+        assertThat(entity.getSubjectLimitViolations()).hasSize(1);
+    }
+}