fix sql results mixed array and scalar values

sql/src/main/java/org/apache/druid/sql/calcite/run/SqlResults.java

@@ -41,6 +41,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
 import java.util.stream.Collectors;
@@ -70,7 +71,7 @@ public static Object coerce(
       } else if (value instanceof Boolean) {
         coercedValue = String.valueOf(value);
       } else {
-        final Object maybeList = maybeCoerceArrayToList(value, false);
+        final Object maybeList = coerceArrayToList(value, false);
 
         // Check if "maybeList" was originally a Collection of some kind, or was able to be coerced to one.
         // Then Iterate through the collection, coercing each value. Useful for handling multi-value dimensions.
@@ -152,10 +153,7 @@ public static Object coerce(
         // the protobuf jdbc handler prefers lists (it actually can't handle java arrays as sql arrays, only java lists)
         // the json handler could handle this just fine, but it handles lists as sql arrays as well so just convert
         // here if needed
-        coercedValue = maybeCoerceArrayToList(value, true);
-        if (coercedValue == null) {
-          throw cannotCoerce(value, sqlTypeName, fieldName);
-        }
+        coercedValue = coerceArrayToList(value, true);
       }
     } else {
       throw cannotCoerce(value, sqlTypeName, fieldName);
@@ -166,11 +164,11 @@ public static Object coerce(
 
   /**
    * Attempt to coerce a value to {@link List}. If it cannot be coerced, either return the original value (if mustCoerce
-   * is false) or return null (if mustCoerce is true).
+   * is false) or return the value as a single element list (if mustCoerce is true).
    */
   @VisibleForTesting
   @Nullable
-  static Object maybeCoerceArrayToList(Object value, boolean mustCoerce)
+  static Object coerceArrayToList(Object value, boolean mustCoerce)
   {
     if (value instanceof List) {
       return value;
@@ -184,7 +182,7 @@ static Object maybeCoerceArrayToList(Object value, boolean mustCoerce)
       final Object[] array = (Object[]) value;
       final ArrayList<Object> lst = new ArrayList<>(array.length);
       for (Object o : array) {
-        lst.add(maybeCoerceArrayToList(o, false));
+        lst.add(coerceArrayToList(o, false));
       }
       return lst;
     } else if (value instanceof long[]) {
@@ -199,7 +197,7 @@ static Object maybeCoerceArrayToList(Object value, boolean mustCoerce)
       }
       return lst;
     } else if (mustCoerce) {
-      return null;
+      return Collections.singletonList(value);
     }
     return value;
   }

sql/src/test/java/org/apache/druid/sql/calcite/run/SqlResultsTest.java

@@ -62,6 +62,8 @@ public void testCoerceStringArrays()
     assertCoerceArrayToList(stringList, stringList);
     assertCoerceArrayToList(stringList, stringArray);
     assertCoerceArrayToList(stringList, stringArray2);
+    assertCoerceArrayToList(null, null);
+    assertCoerceArrayToList(Collections.singletonList("a"), "a");
   }
 
   @Test
@@ -76,6 +78,8 @@ public void testCoerceLongArrays()
     assertCoerceArrayToList(listWithNull, arrayWithNull);
     assertCoerceArrayToList(list, list);
     assertCoerceArrayToList(list, array);
+    assertCoerceArrayToList(null, null);
+    assertCoerceArrayToList(Collections.singletonList(1L), 1L);
   }
 
   @Test
@@ -90,6 +94,8 @@ public void testCoerceDoubleArrays()
     assertCoerceArrayToList(listWithNull, arrayWithNull);
     assertCoerceArrayToList(list, list);
     assertCoerceArrayToList(list, array);
+    assertCoerceArrayToList(null, null);
+    assertCoerceArrayToList(Collections.singletonList(1.1), 1.1);
   }
 
   @Test
@@ -104,6 +110,8 @@ public void testCoerceFloatArrays()
     assertCoerceArrayToList(listWithNull, arrayWithNull);
     assertCoerceArrayToList(list, list);
     assertCoerceArrayToList(list, array);
+    assertCoerceArrayToList(null, null);
+    assertCoerceArrayToList(Collections.singletonList(1.1f), 1.1f);
   }
 
   @Test
@@ -225,11 +233,6 @@ public void testCoerceOfArrayOfPrimitives()
       Assert.assertEquals("Cannot coerce field [fieldName] from type [Byte Array] to type [BIGINT]", e.getMessage());
     }
   }
-  @Test
-  public void testCoerceArrayFails()
-  {
-    assertCannotCoerce("xyz", SqlTypeName.ARRAY);
-  }
 
   @Test
   public void testCoerceUnsupportedType()
@@ -238,15 +241,9 @@ public void testCoerceUnsupportedType()
   }
 
   @Test
-  public void testMustCoerce()
-  {
-    Assert.assertNull(SqlResults.maybeCoerceArrayToList("hello", true));
-  }
-
-  @Test
-  public void testMayNotCoerce()
+  public void testMayNotCoerceList()
   {
-    Assert.assertEquals("hello", SqlResults.maybeCoerceArrayToList("hello", false));
+    Assert.assertEquals("hello", SqlResults.coerceArrayToList("hello", false));
   }
 
   private void assertCoerce(Object expected, Object toCoerce, SqlTypeName typeName)
@@ -269,9 +266,9 @@ private void assertCannotCoerce(Object toCoerce, SqlTypeName typeName)
     MatcherAssert.assertThat(e, ThrowableMessageMatcher.hasMessage(CoreMatchers.containsString("Cannot coerce")));
   }
 
-  private static void assertCoerceArrayToList(Object expected, Object toCoerce)
+  private void assertCoerceArrayToList(Object expected, Object toCoerce)
   {
-    Object coerced = SqlResults.maybeCoerceArrayToList(toCoerce, true);
+    Object coerced = SqlResults.coerce(jsonMapper, DEFAULT_CONTEXT, toCoerce, SqlTypeName.ARRAY, "");
     Assert.assertEquals(expected, coerced);
   }
 }