Correctly test for mutually comparable types (#8598)

2 files changed, 9 insertions, 2 deletions

diff --git a/server/src/main/java/com/vaadin/ui/Grid.java b/server/src/main/java/com/vaadin/ui/Grid.java
index b11bef7eed..186be328f4 100644
--- a/server/src/main/java/com/vaadin/ui/Grid.java
+++ b/server/src/main/java/com/vaadin/ui/Grid.java
@@ -902,8 +902,8 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
 
                 Class<?> baseType = ReflectTools.findCommonBaseType(aClass,
                         bClass);
-                if (!baseType.isAssignableFrom(Comparable.class)) {
-                    return false;
+                if (Comparable.class.isAssignableFrom(baseType)) {
+                    return true;
                 }
             }
 
diff --git a/server/src/test/java/com/vaadin/tests/server/component/grid/GridTest.java b/server/src/test/java/com/vaadin/tests/server/component/grid/GridTest.java
index 397bc27b82..40c753943e 100644
--- a/server/src/test/java/com/vaadin/tests/server/component/grid/GridTest.java
+++ b/server/src/test/java/com/vaadin/tests/server/component/grid/GridTest.java
@@ -9,6 +9,7 @@ import java.text.DecimalFormatSymbols;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.Date;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
@@ -487,6 +488,12 @@ public class GridTest {
         testValueProviderSorting(10.1, 200, 3000.1, 4000);
     }
 
+    @Test
+    public void defaultSorting_mutuallyComparableTypes() {
+        testValueProviderSorting(new Date(10), new java.sql.Date(1000000),
+                new Date(100000000));
+    }
+
     private static void testValueProviderSorting(Object... expectedOrder) {
         SerializableComparator<Object> comparator = new Grid<>()
                 .addColumn(ValueProvider.identity())