Make getValueProvider return ValueProvider (#8983)

* Make getValueProvider return ValueProvider

The instance can only be a ValueProvider, but the getter previously
returned a less specific type. Making the getter return ValueProvider
makes it easier to reuse the provider in other contexts that require
ValueProvider, e.g. when adding filters to a ListDataProvider.

1 files changed, 29 insertions, 0 deletions

diff --git a/server/src/test/java/com/vaadin/tests/components/grid/GridValueProvider.java b/server/src/test/java/com/vaadin/tests/components/grid/GridValueProvider.java
index 09108b6746..27ba971127 100644
--- a/server/src/test/java/com/vaadin/tests/components/grid/GridValueProvider.java
+++ b/server/src/test/java/com/vaadin/tests/components/grid/GridValueProvider.java
@@ -15,9 +15,16 @@
  */
 package com.vaadin.tests.components.grid;
 
+import java.util.List;
+import java.util.Locale;
+import java.util.stream.Collectors;
+
 import org.junit.Assert;
 import org.junit.Test;
 
+import com.vaadin.data.provider.DataProvider;
+import com.vaadin.data.provider.ListDataProvider;
+import com.vaadin.data.provider.Query;
 import com.vaadin.tests.data.bean.Person;
 import com.vaadin.tests.data.bean.Sex;
 import com.vaadin.ui.Grid;
@@ -45,4 +52,26 @@ public class GridValueProvider {
         Assert.assertEquals("eeemaaail", col.getValueProvider().apply(person));
 
     }
+
+    @Test
+    public void reuseValueProviderForFilter() {
+        Grid<Person> grid = new Grid<>(Person.class);
+        Column<Person, String> col = (Column<Person, String>) grid
+                .getColumn("email");
+
+        Person lowerCasePerson = new Person("first", "last", "email", 123,
+                Sex.UNKNOWN, null);
+        Person upperCasePerson = new Person("FIRST", "LAST", "EMAIL", 123,
+                Sex.UNKNOWN, null);
+        ListDataProvider<Person> persons = DataProvider.ofItems(lowerCasePerson,
+                upperCasePerson);
+
+        persons.addFilter(col.getValueProvider(),
+                value -> value.toUpperCase(Locale.ENGLISH).equals(value));
+
+        List<Person> queryPersons = persons.fetch(new Query<>())
+                .collect(Collectors.toList());
+        Assert.assertEquals(1, queryPersons.size());
+        Assert.assertSame(upperCasePerson, queryPersons.get(0));
+    }
 }