[Fuchsia] Switch DCHECK to WARNING when service directory not connected.

Since it is possible for a parent process to exit without waiting for
its children to teardown, child processes may attempt to open /svc only
after it has been torn-down, causing no Directory handle to be returned.

ServiceDirectoryClient::ForCurrentProcess() now returns an instance not
connected to any actual directory, rather than crashing, if it is unable
to open "/svc".

Bug: 950672
Change-Id: I6f4acfa1c325d7831a3d5bf28cf04a8d1a3d66dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1560376
Commit-Queue: Wez <wez@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#650579}

base/fuchsia/service_directory_client.cc

@@ -10,23 +10,12 @@
 #include "base/fuchsia/file_utils.h"
 #include "base/fuchsia/fuchsia_logging.h"
 #include "base/logging.h"
+#include "base/memory/ptr_util.h"
 #include "base/no_destructor.h"
 
 namespace base {
 namespace fuchsia {
 
-namespace {
-
-// Singleton container for the process-global ServiceDirectoryClient instance.
-std::unique_ptr<ServiceDirectoryClient>* ProcessServiceDirectoryClient() {
-  static base::NoDestructor<std::unique_ptr<ServiceDirectoryClient>>
-      service_directory_client_ptr(std::make_unique<ServiceDirectoryClient>(
-          OpenDirectory(base::FilePath(kServiceDirectoryPath))));
-  return service_directory_client_ptr.get();
-}
-
-}  // namespace
-
 ServiceDirectoryClient::ServiceDirectoryClient(
     fidl::InterfaceHandle<::fuchsia::io::Directory> directory)
     : directory_(std::move(directory)) {
@@ -37,7 +26,7 @@ ServiceDirectoryClient::~ServiceDirectoryClient() = default;
 
 // static
 const ServiceDirectoryClient* ServiceDirectoryClient::ForCurrentProcess() {
-  return ProcessServiceDirectoryClient()->get();
+  return ServiceDirectoryClient::ProcessInstance()->get();
 }
 
 zx_status_t ServiceDirectoryClient::ConnectToServiceUnsafe(
@@ -48,19 +37,40 @@ zx_status_t ServiceDirectoryClient::ConnectToServiceUnsafe(
                                  request.release());
 }
 
+ServiceDirectoryClient::ServiceDirectoryClient() {}
+
+// static
+std::unique_ptr<ServiceDirectoryClient>
+ServiceDirectoryClient::CreateForProcess() {
+  fidl::InterfaceHandle<::fuchsia::io::Directory> directory =
+      OpenDirectory(base::FilePath(kServiceDirectoryPath));
+  if (directory)
+    return std::make_unique<ServiceDirectoryClient>(std::move(directory));
+  LOG(WARNING) << "/svc is not available.";
+  return base::WrapUnique(new ServiceDirectoryClient);
+}
+
+// static
+std::unique_ptr<ServiceDirectoryClient>*
+ServiceDirectoryClient::ProcessInstance() {
+  static base::NoDestructor<std::unique_ptr<ServiceDirectoryClient>>
+      service_directory_client_ptr(CreateForProcess());
+  return service_directory_client_ptr.get();
+}
+
 ScopedServiceDirectoryClientForCurrentProcessForTest::
     ScopedServiceDirectoryClientForCurrentProcessForTest(
         fidl::InterfaceHandle<::fuchsia::io::Directory> directory)
-    : old_client_(std::move(*ProcessServiceDirectoryClient())) {
-  *ProcessServiceDirectoryClient() =
+    : old_client_(std::move(*ServiceDirectoryClient::ProcessInstance())) {
+  *ServiceDirectoryClient::ProcessInstance() =
       std::make_unique<ServiceDirectoryClient>(std::move(directory));
-  client_ = ProcessServiceDirectoryClient()->get();
+  client_ = ServiceDirectoryClient::ProcessInstance()->get();
 }
 
 ScopedServiceDirectoryClientForCurrentProcessForTest::
     ~ScopedServiceDirectoryClientForCurrentProcessForTest() {
-  DCHECK_EQ(ProcessServiceDirectoryClient()->get(), client_);
-  *ProcessServiceDirectoryClient() = std::move(old_client_);
+  DCHECK_EQ(ServiceDirectoryClient::ProcessInstance()->get(), client_);
+  *ServiceDirectoryClient::ProcessInstance() = std::move(old_client_);
 }
 
 }  // namespace fuchsia

base/fuchsia/service_directory_client.h

@@ -25,6 +25,8 @@ class SynchronousInterfacePtr;
 namespace base {
 namespace fuchsia {
 
+class ScopedServiceDirectoryClientForCurrentProcessForTest;
+
 // Helper for connecting to services from a supplied fuchsia.io.Directory.
 class BASE_EXPORT ServiceDirectoryClient {
  public:
@@ -69,6 +71,18 @@ class BASE_EXPORT ServiceDirectoryClient {
                                      zx::channel request) const;
 
  private:
+  friend class ScopedServiceDirectoryClientForCurrentProcessForTest;
+  ServiceDirectoryClient();
+
+  // Creates a ServiceDirectoryClient connected to the process' "/svc"
+  // directory, or a dummy instance if the "/svc" directory is not available.
+  static std::unique_ptr<ServiceDirectoryClient> CreateForProcess();
+
+  // Returns the container holding the ForCurrentProcess() instance. The
+  // default ServiceDirectoryClient is created the first time this function is
+  // called.
+  static std::unique_ptr<ServiceDirectoryClient>* ProcessInstance();
+
   const fidl::InterfaceHandle<::fuchsia::io::Directory> directory_;
 
   DISALLOW_COPY_AND_ASSIGN(ServiceDirectoryClient);