service worker: Wait for inflight requests before activating

content/browser/service_worker/service_worker_registration.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/service_worker/service_worker_registration.h"
 
 #include <vector>
 
 #include "content/browser/service_worker/embedded_worker_status.h"
 #include "content/browser/service_worker/service_worker_context_core.h"
@@ skipping 164 matching lines @@
   } else if (active_version_.get() == version) {
     active_version_->RemoveListener(this);
     active_version_ = NULL;
     mask->add(ChangedVersionAttributesMask::ACTIVE_VERSION);
   }
 }
 
 void ServiceWorkerRegistration::ActivateWaitingVersionWhenReady() {
   DCHECK(waiting_version());
   should_activate_when_ready_ = true;
-
-  if (!active_version() || !active_version()->HasControllee() ||
-      waiting_version()->skip_waiting()) {
+  if (IsReadyToActivate())
     ActivateWaitingVersion(false);
-  }
 }
 
 void ServiceWorkerRegistration::ClaimClients() {
   DCHECK(context_);
   DCHECK(active_version());
 
   for (std::unique_ptr<ServiceWorkerContextCore::ProviderHostIterator> it =
            context_->GetProviderHostIterator();
        !it->IsAtEnd(); it->Advance()) {
     ServiceWorkerProviderHost* host = it->GetProviderHost();
@@ skipping 46 matching lines @@
                  callback,
                  most_recent_version));
 }
 
 void ServiceWorkerRegistration::OnNoControllees(ServiceWorkerVersion* version) {
   if (!context_)
     return;
   DCHECK_EQ(active_version(), version);
   if (is_uninstalling_)
     Clear();
-  else if (should_activate_when_ready_)
-    ActivateWaitingVersion(true);
+  else if (IsReadyToActivate())
+    ActivateWaitingVersion(true /* delay */);
+}
+
+void ServiceWorkerRegistration::OnNoInflightRequests(
+    ServiceWorkerVersion* version) {
+  if (!context_)
+    return;
+  DCHECK_EQ(active_version(), version);
+  if (IsReadyToActivate())
+    ActivateWaitingVersion(false /* delay */);
+}
+
+bool ServiceWorkerRegistration::IsReadyToActivate() const {

[nhiroki, 2016/07/08 05:04:42]

DCHECK(waiting_version()) ?

[falken, 2016/07/08 07:06:45]

Hmm good catch. The code assumes should_activate_when_ready_ is only true if
there is a waiting_version, but I think thanks to DeleteVersion that's not true.
Updated.

+  if (!should_activate_when_ready_)
+    return false;
+
+  const ServiceWorkerVersion* active = active_version();
+  return !(active &&
+           (active->HasInflightRequests() ||
+            (active->HasControllee() && !waiting_version()->skip_waiting())));

[nhiroki, 2016/07/08 05:04:42]

Negating the whole complex expression would make it difficult to read. How about
deforming it with De Morgan's laws like this?

   !(active && (HasInflight || (HasControllee && !skip_waiting)))
-> !active || !(HasInflight || (HasControllee && !skip_waiting))
-> !active || (!HasInflight && !(HasControllee && !skip_waiting))
-> !active || (!HasInflight && (!HasControllee || skip_waiting))

if (!active)
  return true;
if (!active->HasInflightRequests() &&
    (!HasControllee || waiting_version()->skip_waiting()))
  return true;
return false;

[falken, 2016/07/08 07:06:45]

Done.

 }
 
 void ServiceWorkerRegistration::ActivateWaitingVersion(bool delay) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   DCHECK(context_);
   DCHECK(waiting_version());
   DCHECK(should_activate_when_ready_);

[nhiroki, 2016/07/08 05:04:42]

Can you replace this check with "DCHECK(IsReadyToActivate())" ?

[falken, 2016/07/08 07:06:45]

Good. Done.

   should_activate_when_ready_ = false;
   scoped_refptr<ServiceWorkerVersion> activating_version = waiting_version();
   scoped_refptr<ServiceWorkerVersion> exiting_version = active_version();
 
   if (activating_version->is_redundant())
     return;  // Activation is no longer relevant.
 
   // "5. If exitingWorker is not null,
   if (exiting_version.get()) {
-    // TODO(michaeln): should wait for events to be complete
+    // TODO(falken): Update the quoted spec comments once
+    // https://github.com/slightlyoff/ServiceWorker/issues/916 is codified in
+    // the spec.
     // "1. Wait for exitingWorker to finish handling any in-progress requests."
+    // This is already handled by IsReadyToActivate().
     // "2. Terminate exitingWorker."
     exiting_version->StopWorker(
         base::Bind(&ServiceWorkerUtils::NoOpStatusCallback));
     // "3. Run the [[UpdateState]] algorithm passing exitingWorker and
     // "redundant" as the arguments."
     exiting_version->SetStatus(ServiceWorkerVersion::REDUNDANT);
   }
 
   // "6. Set serviceWorkerRegistration.activeWorker to activatingWorker."
   // "7. Set serviceWorkerRegistration.waitingWorker to null."
@@ skipping 188 matching lines @@
   if (!context_) {
     callback.Run(SERVICE_WORKER_ERROR_ABORT);
     return;
   }
   context_->storage()->NotifyDoneInstallingRegistration(
       this, version.get(), status);
   callback.Run(status);
 }
 
 }  // namespace content