[cdp][java] Allow filters to recover from failed requests in NetworkInterceptor

java/src/org/openqa/selenium/devtools/RequestFailedException.java

@@ -0,0 +1,29 @@
+// 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.devtools;
+
+import org.openqa.selenium.WebDriverException;
+import org.openqa.selenium.remote.http.Filter;
+import org.openqa.selenium.remote.http.HttpHandler;
+
+/**
+ * This exception is thrown by the final {@link HttpHandler} in a {@link Filter} chain when the
+ * browser fails to send a HTTP request. It can be caught in a {@link Filter} to handle the error
+ * by, for example, returning a custom HTTP response.
+ */
+public class RequestFailedException extends WebDriverException {}

java/src/org/openqa/selenium/devtools/idealized/Network.java

@@ -45,6 +45,7 @@
 import org.openqa.selenium.devtools.DevToolsException;
 import org.openqa.selenium.devtools.Event;
 import org.openqa.selenium.devtools.NetworkInterceptor;
+import org.openqa.selenium.devtools.RequestFailedException;
 import org.openqa.selenium.internal.Either;
 import org.openqa.selenium.internal.Require;
 import org.openqa.selenium.remote.http.Contents;
@@ -202,8 +203,12 @@ public void prepareToInterceptTraffic() {
             String id = getRequestId(pausedRequest);
 
             if (hasErrorResponse(pausedRequest)) {
-              pendingResponses.remove(id);
-              devTools.send(continueWithoutModification(pausedRequest));
+              CompletableFuture<HttpResponse> future = pendingResponses.remove(id);
+              if (future == null) {
+                devTools.send(continueWithoutModification(pausedRequest));
+              } else {
+                future.completeExceptionally(new RequestFailedException());
+              }
               return;
             }
 
@@ -244,6 +249,11 @@ public void prepareToInterceptTraffic() {
                             pendingResponses.remove(id);
                             return STOP_PROCESSING;
                           } catch (ExecutionException e) {
+                            if (e.getCause() instanceof RequestFailedException) {
+                              // Throwing here will give the user's filter a chance to intercept
+                              // the failure and handle it.
+                              throw (RequestFailedException) e.getCause();
+                            }
                             if (fetchEnabled.get()) {
                               LOG.log(WARNING, e, () -> "Unable to process request");
                             }
@@ -261,6 +271,10 @@ public void prepareToInterceptTraffic() {
             }
 
             devTools.send(fulfillRequest(pausedRequest, forBrowser));
+          } catch (RequestFailedException e) {
+            // If the exception reaches here, we know the user's filter has not handled it and the
+            // browser should continue its normal error handling.
+            devTools.send(continueWithoutModification(pausedRequest));
           } catch (TimeoutException e) {
             if (fetchEnabled.get()) {
               throw e;

java/test/org/openqa/selenium/devtools/NetworkInterceptorTest.java

@@ -254,11 +254,32 @@ void shouldHandleRedirects() {
 
   @Test
   @NoDriverBeforeTest
-  void shouldProceedAsNormalIfRequestResultInAnKnownError() {
+  void shouldProceedAsNormalIfRequestResultInAnKnownErrorAndExceptionNotCaughtByFilter() {
     Filter filter = next -> next;
     try (NetworkInterceptor ignored = new NetworkInterceptor(driver, filter)) {
       assertThatExceptionOfType(WebDriverException.class)
           .isThrownBy(() -> driver.get("http://localhost:" + PortProber.findFreePort()));
     }
   }
+
+  @Test
+  @NoDriverBeforeTest
+  void shouldPassResponseBackToBrowserIfRequestResultsInAnKnownErrorAndExceptionCaughtByFilter() {
+    Filter filter =
+        next ->
+            req -> {
+              try {
+                return next.execute(req);
+              } catch (RequestFailedException e) {
+                return new HttpResponse()
+                    .setStatus(200)
+                    .setContent(Contents.utf8String("Hello, World!"));
+              }
+            };
+    try (NetworkInterceptor ignored = new NetworkInterceptor(driver, filter)) {
+      driver.get("http://localhost:" + PortProber.findFreePort());
+      String body = driver.findElement(By.tagName("body")).getText();
+      assertThat(body).contains("Hello, World!");
+    }
+  }
 }