add error

src/main/scala/com/snowflake/snowpark/DataFrame.scala

@@ -2012,7 +2012,8 @@ class DataFrame private[snowpark] (
         joinTableFunction(
           tableFunctions.flatten.call(Map("input" -> Column(expr), "mode" -> lit("object"))),
           partitionByOrderBy).select(columns ++ Seq(Column("KEY"), Column("VALUE")))
-      case _ => null
+      case otherType =>
+        throw ErrorMessage.MISC_INVALID_EXPLODE_ARGUMENT_TYPE(otherType.typeName)
     }
   }
 

src/test/scala/com/snowflake/snowpark_test/TableFunctionSuite.scala

@@ -400,10 +400,26 @@ class TableFunctionSuite extends TestData {
       parse_json(df("a"))
         .cast(types.MapType(types.StringType, types.IntegerType))
         .as("a"))
-    df1.select(tableFunctions.explode(df1("a"))).show()
     checkAnswer(
       df1.select(lit(1), tableFunctions.explode(df1("a")), df1("a")("a")),
       Seq(Row(1, "a", "1", "1"), Row(1, "b", "2", "1")))
   }
 
+  test("explode with other column") {
+    val df = Seq("""{"a":1, "b": 2}""").toDF("a")
+    val df1 = df.select(
+      parse_json(df("a"))
+        .as("a"))
+    val error = intercept[SnowparkClientException] {
+      df1.select(tableFunctions.explode(df1("a"))).show()
+    }
+    assert(
+      error.message.contains(
+        "the input argument type of Explode function should be either Map or Array types"))
+    assert(
+      error.message.contains(
+        "The input argument type: Variant"))
+  }
+
+
 }