feat: add protected API to regenerate data in viewport (#23043) (#23045)

The PR adds a protected `refreshViewport` method to both DataCommunicator and HierarchicalDataCommunicator. This method regenerates and resends data for items that are currently visible in the viewport.

Co-authored-by: Sergey Vinogradov <mr.vursen@gmail.com>

Author: vaadin-bot

flow-data/src/main/java/com/vaadin/flow/data/provider/DataCommunicator.java

@@ -435,6 +435,14 @@ public void refresh(T data) {
         requestFlushUpdatedData();
     }
 
+    /**
+     * Regenerates and resends data for all items in the current viewport.
+     */
+    protected void refreshViewport() {
+        resendEntireRange = true;
+        requestFlush();
+    }
+
     /**
      * Confirm update with the given {@code updateId}.
      *

flow-data/src/main/java/com/vaadin/flow/data/provider/hierarchy/HierarchicalDataCommunicator.java

@@ -256,6 +256,11 @@ public void refresh(T item, boolean refreshChildren) {
         requestFlush().invalidateItem(item);
     }
 
+    @Override
+    protected void refreshViewport() {
+        requestFlush().invalidateViewport();
+    }
+
     @Override
     public Stream<T> fetchFromProvider(int offset, int limit) {
         return fetchDataProviderChildren(null, Range.withLength(offset, limit))

flow-data/src/test/java/com/vaadin/flow/data/provider/DataCommunicatorTest.java

@@ -41,6 +41,7 @@
 import org.mockito.Mockito;
 import org.mockito.MockitoAnnotations;
 import tools.jackson.databind.JsonNode;
+import tools.jackson.databind.node.ObjectNode;
 
 import com.vaadin.flow.component.Component;
 import com.vaadin.flow.component.ComponentEventListener;
@@ -246,6 +247,33 @@ public void reattach_same_roundtrip_refresh_nothing() {
         Assert.assertNull("Expected no communication after reattach", lastSet);
     }
 
+    @Test
+    public void refreshViewport_updatedRangeSent() {
+        var compositeDataGenerator = new CompositeDataGenerator<Item>();
+        dataCommunicator = new DataCommunicator<>(compositeDataGenerator,
+                arrayUpdater, data -> {
+                }, element.getNode()) {
+        };
+        dataCommunicator.setDataProvider(createDataProvider(), null);
+        dataCommunicator.setViewportRange(0, 6);
+
+        var count = new AtomicInteger(0);
+        compositeDataGenerator.addDataGenerator(new DataGenerator<Item>() {
+            @Override
+            public void generateData(Item item, ObjectNode json) {
+                json.put("count", String.valueOf(count.get()));
+            }
+        });
+
+        fakeClientCommunication();
+        Assert.assertEquals(Range.withLength(0, 6), lastSet);
+        lastSet = null;
+
+        dataCommunicator.refreshViewport();
+        fakeClientCommunication();
+        Assert.assertEquals(Range.withLength(0, 6), lastSet);
+    }
+
     @Test
     public void setFlushRequest_remove_setFlushRequest_reattach_noEndlessFlushLoop() {
         AtomicInteger listenerInvocationCounter = new AtomicInteger(0);

flow-data/src/test/java/com/vaadin/flow/data/provider/hierarchy/HierarchicalDataCommunicatorDataRefreshTest.java

@@ -17,6 +17,7 @@
 
 import java.util.Arrays;
 import java.util.Map;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import org.junit.Assert;
 import org.junit.Before;
@@ -362,4 +363,30 @@ public void refreshAllItems_allItemsRemovedFromKeyMapper() {
         Assert.assertFalse(keyMapper.has(new Item("Item 0-0")));
         Assert.assertFalse(keyMapper.has(new Item("Item 0-0-0")));
     }
+
+    @Test
+    public void refreshViewport_updatedRangeSent() {
+        populateTreeData(treeData, 6, 1, 1);
+        dataCommunicator.expand(
+                Arrays.asList(new Item("Item 1"), new Item("Item 1-0")));
+        dataCommunicator.setViewportRange(0, 6);
+
+        var count = new AtomicInteger(0);
+        compositeDataGenerator.addDataGenerator(new DataGenerator<Item>() {
+            @Override
+            public void generateData(Item item, ObjectNode json) {
+                json.put("count", String.valueOf(count.get()));
+            }
+        });
+
+        fakeClientCommunication();
+        assertArrayUpdateItems("count", "0", "0", "0", "0", "0", "0");
+
+        Mockito.clearInvocations(arrayUpdater, arrayUpdate);
+
+        count.incrementAndGet();
+        dataCommunicator.refreshViewport();
+        fakeClientCommunication();
+        assertArrayUpdateItems("count", "1", "1", "1", "1", "1", "1");
+    }
 }