[java] Handling a special case of a driver returning null as a result…

… of findElement command. Fixes #5809

java/client/src/org/openqa/selenium/remote/RemoteWebDriver.java

@@ -36,6 +36,7 @@
 import org.openqa.selenium.ImmutableCapabilities;
 import org.openqa.selenium.JavascriptExecutor;
 import org.openqa.selenium.MutableCapabilities;
+import org.openqa.selenium.NoSuchElementException;
 import org.openqa.selenium.NoSuchFrameException;
 import org.openqa.selenium.NoSuchWindowException;
 import org.openqa.selenium.OutputType;
@@ -322,6 +323,9 @@ protected WebElement findElement(String by, String using) {
     Response response = execute(DriverCommand.FIND_ELEMENT,
         ImmutableMap.of("using", by, "value", using));
     Object value = response.getValue();
+    if (value == null) { // see https://github.com/SeleniumHQ/selenium/issues/5809
+      throw new NoSuchElementException(String.format("Cannot locate an element using %s=%s", by, using));
+    }
     WebElement element;
     try {
       element = (WebElement) value;

java/client/src/org/openqa/selenium/remote/RemoteWebElement.java

@@ -22,6 +22,7 @@
 import org.openqa.selenium.Beta;
 import org.openqa.selenium.By;
 import org.openqa.selenium.Dimension;
+import org.openqa.selenium.NoSuchElementException;
 import org.openqa.selenium.OutputType;
 import org.openqa.selenium.Point;
 import org.openqa.selenium.Rectangle;
@@ -185,6 +186,9 @@ protected WebElement findElement(String using, String value) {
                                 ImmutableMap.of("id", id, "using", using, "value", value));
 
     Object responseValue = response.getValue();
+    if (responseValue == null) { // see https://github.com/SeleniumHQ/selenium/issues/5809
+      throw new NoSuchElementException(String.format("Cannot locate an element using %s=%s", using, value));
+    }
     WebElement element;
     try {
       element = (WebElement) responseValue;
@@ -346,6 +350,7 @@ public Dimension getSize() {
     return new Dimension(width, height);
   }
 
+  @SuppressWarnings({"unchecked"})
   public Rectangle getRect() {
     Response response = execute(DriverCommand.GET_ELEMENT_RECT, ImmutableMap.of("id", id));
     Map<String, Object> rawRect = (Map<String, Object>) response.getValue();

java/client/test/org/openqa/selenium/remote/BUCK

@@ -30,6 +30,7 @@ java_test(name = 'client-tests',
     'RemoteClientTests.java',
     'RemoteLogsTest.java',
     'RemoteWebDriverInitializationTest.java',
+    'RemoteWebDriverUnitTest.java',
     'W3CHandshakeResponseTest.java',
     'W3CRemoteDriverTest.java',
     'internal/ApacheHttpClientTest.java',

java/client/test/org/openqa/selenium/remote/RemoteClientTests.java

@@ -30,6 +30,7 @@
     ProtocolHandshakeTest.class,
     RemoteLogsTest.class,
     RemoteWebDriverInitializationTest.class,
+    RemoteWebDriverUnitTest.class,
     W3CHandshakeResponseTest.class
 })
 public class RemoteClientTests {

java/client/test/org/openqa/selenium/remote/RemoteWebDriverUnitTest.java

@@ -0,0 +1,98 @@
+// Licensed to the Software Freedom Conservancy (SFC) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The SFC licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package org.openqa.selenium.remote;
+
+import static java.util.Collections.EMPTY_MAP;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import org.junit.Test;
+import org.openqa.selenium.By;
+import org.openqa.selenium.ImmutableCapabilities;
+import org.openqa.selenium.NoSuchElementException;
+import org.openqa.selenium.WebElement;
+
+import java.io.IOException;
+import java.util.List;
+
+public class RemoteWebDriverUnitTest {
+
+  @Test
+  public void returnsEmptyListIfRemoteEndReturnsNullFromFindElements() throws IOException {
+    CommandExecutor executor = prepareExecutorMock();
+
+    RemoteWebDriver driver = new RemoteWebDriver(executor, new ImmutableCapabilities());
+    List<WebElement> result = driver.findElements(By.id("id"));
+    assertThat(result).isNotNull().isEmpty();
+  }
+
+  @Test
+  public void returnsEmptyListIfRemoteEndReturnsNullFromFindChildren() throws IOException {
+    CommandExecutor executor = prepareExecutorMock();
+
+    RemoteWebDriver driver = new RemoteWebDriver(executor, new ImmutableCapabilities());
+    RemoteWebElement element = new RemoteWebElement();
+    element.setParent(driver);
+    element.setId("unique");
+
+    List<WebElement> result = element.findElements(By.id("id"));
+    assertThat(result).isNotNull().isEmpty();
+  }
+
+  @Test
+  public void throwsIfRemoteEndReturnsNullFromFindElement() throws IOException {
+    CommandExecutor executor = prepareExecutorMock();
+
+    RemoteWebDriver driver = new RemoteWebDriver(executor, new ImmutableCapabilities());
+    assertThatExceptionOfType(NoSuchElementException.class)
+        .isThrownBy(() -> driver.findElement(By.id("id")));
+  }
+
+  @Test
+  public void throwIfRemoteEndReturnsNullFromFindChild() throws IOException {
+    CommandExecutor executor = prepareExecutorMock();
+
+    RemoteWebDriver driver = new RemoteWebDriver(executor, new ImmutableCapabilities());
+    RemoteWebElement element = new RemoteWebElement();
+    element.setParent(driver);
+    element.setId("unique");
+
+    assertThatExceptionOfType(NoSuchElementException.class)
+        .isThrownBy(() -> element.findElement(By.id("id")));
+  }
+
+  private CommandExecutor prepareExecutorMock() throws IOException {
+    CommandExecutor executor = mock(CommandExecutor.class);
+    when(executor.execute(any())).thenAnswer(invocation -> {
+      if (invocation.<Command>getArgument(0).getName().equals(DriverCommand.NEW_SESSION)) {
+        Response newSessionResponse = new Response();
+        newSessionResponse.setValue(EMPTY_MAP);
+        return newSessionResponse;
+      } else {
+        Response nullResponse = new Response();
+        nullResponse.setValue(null);
+        return nullResponse;
+      }
+    });
+    return executor;
+  }
+
+}