Fix infinite loop in data communication (#8927)

* Fix infinite loop in data communication

* Switch to less aggressive reset when data communication is out of sync

* Remove triggering of reset if reset is already being performed

* Avoid redundant collection of streams in DataCommunicator

2 files changed, 78 insertions, 0 deletions

diff --git a/uitest/src/main/java/com/vaadin/tests/components/grid/DataCommunicatorInfiniteLoop.java b/uitest/src/main/java/com/vaadin/tests/components/grid/DataCommunicatorInfiniteLoop.java
new file mode 100644
index 0000000000..385a8ef09e
--- /dev/null
+++ b/uitest/src/main/java/com/vaadin/tests/components/grid/DataCommunicatorInfiniteLoop.java
@@ -0,0 +1,62 @@
+package com.vaadin.tests.components.grid;
+
+import java.util.stream.Stream;
+
+import com.vaadin.data.provider.DataProvider;
+import com.vaadin.data.provider.DataProviderListener;
+import com.vaadin.data.provider.Query;
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.shared.Registration;
+import com.vaadin.tests.components.AbstractTestUI;
+import com.vaadin.ui.Grid;
+
+public class DataCommunicatorInfiniteLoop extends AbstractTestUI {
+
+    private static class CustomDataProvider
+            implements DataProvider<String, Void> {
+
+        private boolean sendRealCount = false;
+
+        @Override
+        public boolean isInMemory() {
+            return false;
+        }
+
+        @Override
+        public int size(Query<String, Void> query) {
+            if (sendRealCount) {
+                return 1;
+            } else {
+                sendRealCount = true;
+                return 2;
+            }
+        }
+
+        @Override
+        public Stream<String> fetch(Query<String, Void> query) {
+            return Stream.of("one item").skip(query.getOffset());
+        }
+
+        @Override
+        public void refreshItem(String item) {
+        }
+
+        @Override
+        public void refreshAll() {
+        }
+
+        @Override
+        public Registration addDataProviderListener(
+                DataProviderListener<String> listener) {
+            return () -> {
+            };
+        }
+    }
+
+    @Override
+    protected void setup(VaadinRequest request) {
+        Grid<String> grid = new Grid<>(new CustomDataProvider());
+        grid.addColumn(string -> string);
+        addComponent(grid);
+    }
+}
diff --git a/uitest/src/test/java/com/vaadin/tests/components/grid/DataCommunicatorInfiniteLoopTest.java b/uitest/src/test/java/com/vaadin/tests/components/grid/DataCommunicatorInfiniteLoopTest.java
new file mode 100644
index 0000000000..b911ad27f9
--- /dev/null
+++ b/uitest/src/test/java/com/vaadin/tests/components/grid/DataCommunicatorInfiniteLoopTest.java
@@ -0,0 +1,16 @@
+package com.vaadin.tests.components.grid;
+
+import org.junit.Test;
+
+import com.vaadin.testbench.By;
+import com.vaadin.tests.tb3.SingleBrowserTest;
+
+public class DataCommunicatorInfiniteLoopTest extends SingleBrowserTest {
+
+    @Test
+    public void grid_does_not_get_stuck_in_infinite_loop() {
+        openTestURL();
+        waitUntil(driver -> driver.findElement(By.className("v-grid-body"))
+                .findElements(By.className("v-grid-row")).size() == 1);
+    }
+}