Add null-arg-name guard and make storage engine test less brittle

- validateNamedArgs() now rejects null/empty arg names defensively,
  closing a potential NPE if the shared table-function path is later
  wired into PPL
- OpenSearchStorageEngineTest uses contains-check instead of exact
  collection size assertion
- Add testNullArgNameThrows test

Signed-off-by: Eric Wei <mengwei.eric@gmail.com>

Author: mengweieric

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/VectorSearchTableFunctionImplementation.java

@@ -146,7 +146,7 @@ static Map<String, String> parseOptions(String optionStr) {
     return options;
   }
 
-  /** Reject non-named arguments early. vectorSearch() requires named args (key=value). */
+  /** Reject non-named arguments and null arg names early. */
   private void validateNamedArgs() {
     for (Expression arg : arguments) {
       if (!(arg instanceof NamedArgumentExpression)) {
@@ -155,6 +155,12 @@ private void validateNamedArgs() {
                 + "but received: "
                 + arg.getClass().getSimpleName());
       }
+      String name = ((NamedArgumentExpression) arg).getArgName();
+      if (name == null || name.isEmpty()) {
+        throw new ExpressionEvaluationException(
+            "vectorSearch() requires named arguments (e.g., table='index'), "
+                + "but received an argument with no name");
+      }
     }
   }
 

opensearch/src/test/java/org/opensearch/sql/opensearch/storage/OpenSearchStorageEngineTest.java

@@ -6,7 +6,6 @@
 package org.opensearch.sql.opensearch.storage;
 
 import static org.junit.jupiter.api.Assertions.assertAll;
-import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.opensearch.sql.analysis.DataSourceSchemaIdentifierNameResolver.DEFAULT_DATASOURCE_NAME;
@@ -43,8 +42,9 @@ public void getTable() {
   public void getFunctionsReturnsVectorSearchResolver() {
     OpenSearchStorageEngine engine = new OpenSearchStorageEngine(client, settings);
     Collection<FunctionResolver> functions = engine.getFunctions();
-    assertEquals(1, functions.size());
-    assertTrue(functions.iterator().next() instanceof VectorSearchTableFunctionResolver);
+    assertTrue(
+        functions.stream().anyMatch(f -> f instanceof VectorSearchTableFunctionResolver),
+        "getFunctions() should contain a VectorSearchTableFunctionResolver");
   }
 
   @Test

opensearch/src/test/java/org/opensearch/sql/opensearch/storage/VectorSearchTableFunctionImplementationTest.java

@@ -235,6 +235,22 @@ void testNonNamedArgThrows() {
     assertTrue(ex.getMessage().contains("requires named arguments"));
   }
 
+  @Test
+  void testNullArgNameThrows() {
+    FunctionName functionName = FunctionName.of("vectorsearch");
+    List<Expression> args =
+        List.of(
+            DSL.namedArgument(null, DSL.literal("my-index")),
+            DSL.namedArgument("field", DSL.literal("embedding")),
+            DSL.namedArgument("vector", DSL.literal("[1.0, 2.0]")),
+            DSL.namedArgument("option", DSL.literal("k=5")));
+    VectorSearchTableFunctionImplementation impl =
+        new VectorSearchTableFunctionImplementation(functionName, args, client, settings);
+    ExpressionEvaluationException ex =
+        assertThrows(ExpressionEvaluationException.class, () -> impl.applyArguments());
+    assertTrue(ex.getMessage().contains("requires named arguments"));
+  }
+
   private VectorSearchTableFunctionImplementation createImpl() {
     return createImplWithArgs("my-index", "embedding", "[1.0, 2.0, 3.0]", "k=5");
   }