Explicitly forbid StatelessSession.upsert

src/integrationTest/java/com/mongodb/hibernate/UpsertIntegrationTests.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2025-present MongoDB, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.mongodb.hibernate;
+
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import com.mongodb.hibernate.internal.FeatureNotSupportedException;
+import com.mongodb.hibernate.junit.MongoExtension;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.Table;
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.hibernate.testing.orm.junit.SessionFactoryScopeAware;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+@SessionFactory(exportSchema = false)
+@DomainModel(annotatedClasses = {UpsertIntegrationTests.Item.class})
+@ExtendWith(MongoExtension.class)
+class UpsertIntegrationTests implements SessionFactoryScopeAware {
+    private SessionFactoryScope sessionFactoryScope;
+
+    @Override
+    public void injectSessionFactoryScope(SessionFactoryScope sessionFactoryScope) {
+        this.sessionFactoryScope = sessionFactoryScope;
+    }
+
+    @Test
+    void unsupported() {
+        var item = new Item(1, 1);
+        sessionFactoryScope.inStatelessTransaction(session ->
+                assertThatThrownBy(() -> session.upsert(item)).isInstanceOf(FeatureNotSupportedException.class));
+    }
+
+    @Entity
+    @Table(name = Item.COLLECTION_NAME)
+    static class Item {
+        static final String COLLECTION_NAME = "items";
+
+        @Id
+        int id;
+        /**
+         * {@link org.hibernate.StatelessSession#upsert(Object)} results in no commands issued to the DBMS if {@link Id}
+         * is the only persistent attribute, which must be a bug.
+         */
+        int v;
+
+        Item() {}
+
+        Item(int id, int v) {
+            this.id = id;
+            v = 1;
+        }
+    }
+}

src/main/java/com/mongodb/hibernate/dialect/MongoDialect.java

@@ -19,6 +19,7 @@
 import static com.mongodb.hibernate.internal.MongoConstants.MONGO_DBMS_NAME;
 import static java.lang.String.format;
 
+import com.mongodb.hibernate.internal.FeatureNotSupportedException;
 import com.mongodb.hibernate.internal.dialect.function.array.MongoArrayConstructorFunction;
 import com.mongodb.hibernate.internal.dialect.function.array.MongoArrayContainsFunction;
 import com.mongodb.hibernate.internal.dialect.function.array.MongoArrayIncludesFunction;
@@ -35,8 +36,16 @@
 import org.hibernate.dialect.Dialect;
 import org.hibernate.dialect.aggregate.AggregateSupport;
 import org.hibernate.engine.jdbc.dialect.spi.DialectResolutionInfo;
+import org.hibernate.engine.jdbc.mutation.JdbcValueBindings;
+import org.hibernate.engine.spi.SessionFactoryImplementor;
+import org.hibernate.engine.spi.SharedSessionContractImplementor;
+import org.hibernate.persister.entity.mutation.EntityMutationTarget;
 import org.hibernate.service.ServiceRegistry;
 import org.hibernate.sql.ast.SqlAstTranslatorFactory;
+import org.hibernate.sql.model.MutationOperation;
+import org.hibernate.sql.model.ValuesAnalysis;
+import org.hibernate.sql.model.internal.OptionalTableUpdate;
+import org.hibernate.sql.model.jdbc.OptionalTableUpdateOperation;
 import org.hibernate.type.descriptor.sql.internal.DdlTypeImpl;
 import org.jspecify.annotations.Nullable;
 
@@ -237,4 +246,21 @@ public void initializeFunctionRegistry(FunctionContributions functionContributio
         functionRegistry.register("array_includes", new MongoArrayIncludesFunction(false, typeConfiguration));
         functionRegistry.register("array_includes_nullable", new MongoArrayIncludesFunction(true, typeConfiguration));
     }
+
+    @Override
+    public MutationOperation createOptionalTableUpdateOperation(
+            EntityMutationTarget mutationTarget,
+            OptionalTableUpdate optionalTableUpdate,
+            SessionFactoryImplementor factory) {
+        return new OptionalTableUpdateOperation(mutationTarget, optionalTableUpdate, factory) {
+            @Override
+            public void performMutation(
+                    JdbcValueBindings jdbcValueBindings,
+                    ValuesAnalysis valuesAnalysis,
+                    SharedSessionContractImplementor session) {
+                throw new FeatureNotSupportedException(
+                        "TODO-HIBERNATE-94 https://jira.mongodb.org/browse/HIBERNATE-94");
+            }
+        };
+    }
 }