Fix test failure

Signed-off-by: Tomoyuki Morita <moritato@amazon.com>

Author: ykmr1224

core/src/main/java/org/opensearch/sql/calcite/rel/RelFieldBuilder.java

@@ -125,7 +125,7 @@ public RexNode dynamicField(int inputCount, int inputOrdinal, String fieldName)
         relBuilder.field(inputCount, inputOrdinal, DYNAMIC_FIELDS_MAP), fieldName);
   }
 
-  public RexNode createItemAccess(RexNode field, String itemName) {
+  private RexNode createItemAccess(RexNode field, String itemName) {
     return PPLFuncImpTable.INSTANCE.resolve(
         rexBuilder, BuiltinFunctionName.INTERNAL_ITEM, field, rexBuilder.makeLiteral(itemName));
   }

ppl/src/main/java/org/opensearch/sql/ppl/parser/AstBuilder.java

@@ -764,6 +764,10 @@ public UnresolvedPlan visitSpathCommand(OpenSearchPPLParser.SpathCommandContext
     if (inField == null) {
       throw new IllegalArgumentException("`input` parameter is required for `spath`");
     }
+    if (outField != null && path == null) {
+      throw new IllegalArgumentException(
+          "`path` parameter is required when `output` is specified for `spath`");
+    }
 
     return new SPath(inField, outField, path);
   }

ppl/src/test/java/org/opensearch/sql/ppl/calcite/CalcitePPLSpathTest.java

@@ -47,12 +47,12 @@ public void testEvalWithOutput() {
   }
 
   @Test
-  public void testSpathWithoutOutput() {
+  public void testSpathWithoutPath() {
     String ppl = "source=EMP | fields ENAME | spath input=ENAME";
     RelNode root = getRelNode(ppl);
 
     String expectedSparkSql =
-        "SELECT `append`(`ENAME`, `JSON_EXTRACT_ALL`(`ENAME`)['ENAME']) `ENAME`,"
+        "SELECT `APPEND`(`ENAME`, `JSON_EXTRACT_ALL`(`ENAME`)['ENAME']) `ENAME`,"
             + " `MAP_REMOVE`(`JSON_EXTRACT_ALL`(`ENAME`), ARRAY ('ENAME')) `_MAP`\n"
             + "FROM `scott`.`EMP`";
     verifyPPLToSparkSQL(root, expectedSparkSql);

ppl/src/test/java/org/opensearch/sql/ppl/utils/SPathRewriteTest.java

@@ -55,6 +55,11 @@ public void testSpathMissingInputArgumentHandling() {
     plan("source = t | spath path=a output=a");
   }
 
+  @Test(expected = IllegalArgumentException.class)
+  public void testSpathMissingPathArgumentHandling() {
+    plan("source = t | spath input=a output=a");
+  }
+
   @Test
   public void testSpathArgumentDeshuffle() {
     assertEquals(plan("source = t | spath path=a input=a"), plan("source = t | spath input=a a"));