fix: allow refresh-token auth without userName

- DataCloudConnection.of() accepts null userName (optional for refresh-token auth)
- DataCloudDatabaseMetadata.getUserName() throws SQLException with state 28000 when userName is null
- DataCloudDatasource normalizes null userName to empty string for connect path

Fixes regression where driver required userName for refresh-token auth (e.g. 'userName is marked non-null but is null').

Author: KaviarasuSakthivadivel

jdbc-core/src/main/java/com/salesforce/datacloud/jdbc/core/DataCloudConnection.java

@@ -110,7 +110,7 @@ public static DataCloudConnection of(
             @NonNull HyperGrpcStubProvider stubProvider,
             @NonNull ConnectionProperties properties,
             JdbcURL jdbcUrl,
-            @NonNull String userName,
+            String userName,
             @NonNull ThrowingJdbcSupplier<String> lakehouseSupplier,
             @NonNull ThrowingJdbcSupplier<List<String>> dataspacesSupplier)
             throws SQLException {

jdbc-core/src/main/java/com/salesforce/datacloud/jdbc/core/DataCloudDatabaseMetadata.java

@@ -42,9 +42,16 @@ public class DataCloudDatabaseMetadata implements DatabaseMetaData {
 
     private final ThrowingJdbcSupplier<List<String>> dataspacesSupplier;
 
-    @Getter
     private final String userName;
 
+    @Override
+    public String getUserName() throws SQLException {
+        if (userName == null) {
+            throw new SQLException("userName is not available for this connection", "28000");
+        }
+        return userName;
+    }
+
     @Override
     public boolean allProceduresAreCallable() {
         return false;

jdbc-core/src/test/java/com/salesforce/datacloud/jdbc/core/DataCloudConnectionTest.java

@@ -4,6 +4,7 @@
  */
 package com.salesforce.datacloud.jdbc.core;
 
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.mockito.ArgumentMatchers.any;
@@ -13,6 +14,7 @@
 import io.grpc.ClientInterceptor;
 import java.sql.Connection;
 import java.sql.SQLException;
+import java.util.Collections;
 import lombok.Getter;
 import lombok.SneakyThrows;
 import lombok.val;
@@ -105,4 +107,28 @@ void testDriverInterceptorsAreAddedWhenStubProviderIsUsed() {
         verify(stubProvider.stub).withInterceptors(any(ClientInterceptor[].class));
         connection.close();
     }
+
+    /**
+     * The driver must not require userName for refresh-token auth; connection creation succeeds with null userName,
+     * and getMetaData().getUserName() throws SQLException when userName was not provided.
+     */
+    @Test
+    void connectionWithNullUserName_succeeds_refreshTokenAuth() throws SQLException {
+        val stubProvider = new TestStubProvider();
+        try (DataCloudConnection conn = DataCloudConnection.of(
+                stubProvider,
+                ConnectionProperties.defaultProperties(),
+                null,
+                null, // userName optional for refresh-token auth
+                () -> "",
+                Collections::emptyList)) {
+            assertThat(conn).isNotNull();
+            assertThat(conn.isClosed()).isFalse();
+            assertThat(conn.getMetaData()).isNotNull();
+            assertThatThrownBy(() -> conn.getMetaData().getUserName())
+                    .isInstanceOf(SQLException.class)
+                    .hasMessageContaining("userName is not available for this connection")
+                    .satisfies(e -> assertThat(((SQLException) e).getSQLState()).isEqualTo("28000"));
+        }
+    }
 }

jdbc-core/src/test/java/com/salesforce/datacloud/jdbc/core/DataCloudDatabaseMetadataTest.java

@@ -5,6 +5,7 @@
 package com.salesforce.datacloud.jdbc.core;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.assertj.core.api.Assertions.fail;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertThrows;
@@ -71,10 +72,23 @@ public void testAllTablesAreSelectable() {
     }
 
     @Test
-    public void testGetUserName() {
+    public void testGetUserName() throws SQLException {
         assertThat(dataCloudDatabaseMetadata.getUserName()).isEqualTo("userName");
     }
 
+    /**
+     * When userName is null (e.g. refresh-token auth without userName), getUserName() throws SQLException.
+     */
+    @Test
+    public void testGetUserName_throwsWhenNull() throws SQLException {
+        DataCloudDatabaseMetadata metadataWithNullUser = new DataCloudDatabaseMetadata(
+                connection, JdbcURL.of("jdbc:salesforce-datacloud://login.salesforce.com"), null, null, null);
+        assertThatThrownBy(metadataWithNullUser::getUserName)
+                .isInstanceOf(SQLException.class)
+                .hasMessageContaining("userName is not available for this connection")
+                .satisfies(e -> assertThat(((SQLException) e).getSQLState()).isEqualTo("28000"));
+    }
+
     @Test
     public void testIsReadOnly() {
         assertThat(dataCloudDatabaseMetadata.isReadOnly()).isTrue();

jdbc/src/main/java/com/salesforce/datacloud/jdbc/DataCloudDatasource.java

@@ -156,7 +156,7 @@ private static DataCloudConnection createConnection(
                 stubProvider,
                 connectionProperties,
                 jdbcUrl,
-                authProperties.getUserName(),
+                authProperties.getUserName() != null ? authProperties.getUserName() : "",
                 tokenProvider::getLakehouseName,
                 dataspaceClient);
     }