Run ScopedTaskScheduler tasks synchronously.

base/test/scoped_task_scheduler.cc

 // Copyright 2016 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 "base/test/scoped_task_scheduler.h"
 
+#include <memory>
+#include <utility>
 #include <vector>
 
 #include "base/bind.h"
-#include "base/task_scheduler/scheduler_worker_pool_params.h"
+#include "base/logging.h"
+#include "base/memory/ptr_util.h"
+#include "base/memory/ref_counted.h"
+#include "base/message_loop/message_loop.h"
+#include "base/metrics/histogram_base.h"
+#include "base/run_loop.h"
+#include "base/sequence_token.h"
+#include "base/sequenced_task_runner.h"
+#include "base/single_thread_task_runner.h"
+#include "base/task_runner.h"
+#include "base/task_scheduler/task.h"
 #include "base/task_scheduler/task_scheduler.h"
-#include "base/threading/platform_thread.h"
-#include "base/time/time.h"
+#include "base/task_scheduler/task_tracker.h"
+#include "base/threading/thread_task_runner_handle.h"
 
 namespace base {
 namespace test {
 
-ScopedTaskScheduler::ScopedTaskScheduler() {
+namespace {
+
+enum class ExecutionMode { PARALLEL, SEQUENCED, SINGLE_THREADED };
+
+class TestTaskScheduler : public TaskScheduler {
+ public:
+  // |external_message_loop| is an externally provided MessageLoop on which to
+  // run tasks. A MessageLoop will be created by TestTaskScheduler if
+  // |external_message_loop| is nullptr.
+  explicit TestTaskScheduler(MessageLoop* external_message_loop);
+  ~TestTaskScheduler() override;
+
+  // TaskScheduler:
+  void PostTaskWithTraits(const tracked_objects::Location& from_here,
+                          const TaskTraits& traits,
+                          const Closure& task) override;
+  scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits(
+      const TaskTraits& traits) override;
+  scoped_refptr<SequencedTaskRunner> CreateSequencedTaskRunnerWithTraits(
+      const TaskTraits& traits) override;
+  scoped_refptr<SingleThreadTaskRunner> CreateSingleThreadTaskRunnerWithTraits(
+      const TaskTraits& traits) override;
+  std::vector<const HistogramBase*> GetHistograms() const override;
+  void Shutdown() override;
+  void FlushForTesting() override;
+
+  // Posts |task| to this TaskScheduler with |sequence_token|. Returns true on
+  // success.
+  bool PostTask(std::unique_ptr<internal::Task> task,
+                const SequenceToken& sequence_token);
+
+  // Runs |task| with |sequence_token| using this TaskScheduler's TaskTracker.
+  void RunTask(std::unique_ptr<internal::Task> task,
+               const SequenceToken& sequence_token);
+
+  // Returns true if this TaskScheduler runs its tasks on the current thread.
+  bool RunsTasksOnCurrentThread() const;
+
+ private:
+  // |message_loop_owned_| will be non-null if this TestTaskScheduler owns the
+  // MessageLoop (wasn't provided an external one at construction).
+  // |message_loop_| will always be set and is used by this TestTaskScheduler to
+  // run tasks.
+  std::unique_ptr<MessageLoop> message_loop_owned_;
+  MessageLoop* message_loop_;
+
+  // The SingleThreadTaskRunner associated with |message_loop_|.
+  const scoped_refptr<SingleThreadTaskRunner> message_loop_task_runner_ =
+      message_loop_->task_runner();
+
+  // Handles shutdown behaviors and sets up the environment to run a task.
+  internal::TaskTracker task_tracker_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestTaskScheduler);
+};
+
+class TestTaskSchedulerTaskRunner : public SingleThreadTaskRunner {
+ public:
+  TestTaskSchedulerTaskRunner(TestTaskScheduler* task_scheduler,
+                              ExecutionMode execution_mode,
+                              TaskTraits traits);
+
+  // SingleThreadTaskRunner:
+  bool PostDelayedTask(const tracked_objects::Location& from_here,
+                       const Closure& closure,
+                       TimeDelta delay) override;
+  bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
+                                  const Closure& closure,
+                                  TimeDelta delay) override;
+  bool RunsTasksOnCurrentThread() const override;
+
+ private:
+  ~TestTaskSchedulerTaskRunner() override;
+
+  TestTaskScheduler* const task_scheduler_;
+  const ExecutionMode execution_mode_;
+  const SequenceToken sequence_token_;
+  const TaskTraits traits_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestTaskSchedulerTaskRunner);
+};
+
+TestTaskScheduler::TestTaskScheduler(MessageLoop* external_message_loop)
+    : message_loop_owned_(external_message_loop ? nullptr
+                                                : MakeUnique<MessageLoop>()),
+      message_loop_(message_loop_owned_ ? message_loop_owned_.get()
+                                        : external_message_loop) {}
+
+TestTaskScheduler::~TestTaskScheduler() {
+  // Prevent the RunUntilIdle() call below from running SKIP_ON_SHUTDOWN and
+  // CONTINUE_ON_SHUTDOWN tasks.
+  task_tracker_.SetHasShutdownStartedForTesting();
+
+  // Run pending BLOCK_SHUTDOWN tasks.
+  RunLoop().RunUntilIdle();
+}
+
+void TestTaskScheduler::PostTaskWithTraits(
+    const tracked_objects::Location& from_here,
+    const TaskTraits& traits,
+    const Closure& task) {
+  CreateTaskRunnerWithTraits(traits)->PostTask(from_here, task);
+}
+
+scoped_refptr<TaskRunner> TestTaskScheduler::CreateTaskRunnerWithTraits(
+    const TaskTraits& traits) {
+  return make_scoped_refptr(
+      new TestTaskSchedulerTaskRunner(this, ExecutionMode::PARALLEL, traits));
+}
+
+scoped_refptr<SequencedTaskRunner>
+TestTaskScheduler::CreateSequencedTaskRunnerWithTraits(
+    const TaskTraits& traits) {
+  return make_scoped_refptr(
+      new TestTaskSchedulerTaskRunner(this, ExecutionMode::SEQUENCED, traits));
+}
+
+scoped_refptr<SingleThreadTaskRunner>
+TestTaskScheduler::CreateSingleThreadTaskRunnerWithTraits(
+    const TaskTraits& traits) {
+  return make_scoped_refptr(new TestTaskSchedulerTaskRunner(
+      this, ExecutionMode::SINGLE_THREADED, traits));
+}
+
+std::vector<const HistogramBase*> TestTaskScheduler::GetHistograms() const {
+  NOTREACHED();
+  return std::vector<const HistogramBase*>();

[dcheng, 2016/12/15 06:47:36]

Alternatively, {} suffices. I don't feel strongly though, and I have to admit,
I'm a bit curious if this will be optimized to the same thing.

[fdoray, 2016/12/15 16:39:32]

Done.

[fdoray, 2016/12/15 20:49:33]

Breaks   linux_chromium_compile_dbg_ng and  linux_chromium_rel_ng  .

+}
+
+void TestTaskScheduler::Shutdown() {
+  NOTREACHED();
+}
+
+void TestTaskScheduler::FlushForTesting() {
+  NOTREACHED();
+}
+
+bool TestTaskScheduler::PostTask(std::unique_ptr<internal::Task> task,
+                                 const SequenceToken& sequence_token) {
+  DCHECK(task);
+  if (!task_tracker_.WillPostTask(task.get()))
+    return false;
+  internal::Task* const task_ptr = task.get();
+  return message_loop_task_runner_->PostDelayedTask(
+      task_ptr->posted_from, Bind(&TestTaskScheduler::RunTask, Unretained(this),
+                                  Passed(std::move(task)), sequence_token),

[dcheng, 2016/12/15 06:47:36]

I'd prefer to just write this as Passed(&task) to remain consistent with other
code.

[fdoray, 2016/12/15 16:39:32]

Done.

[gab, 2016/12/15 17:56:29]

I thought
https://groups.google.com/a/chromium.org/forum/#!msg/cxx/KXWZtoP5HJ4/5TRPU81Z...
had settled on a preference for explicit std::move?

+      task_ptr->delay);
+}
+
+void TestTaskScheduler::RunTask(std::unique_ptr<internal::Task> task,
+                                const SequenceToken& sequence_token) {
+  // Clear the MessageLoop TaskRunner to allow TaskTracker to register a
+  // Thread/SequencedTaskRunnerHandle as appropriate.
+  MessageLoop::current()->SetTaskRunner(nullptr);
+
+  // Run the task.
+  task_tracker_.RunTask(std::move(task), sequence_token.IsValid()
+                                             ? sequence_token
+                                             : SequenceToken::Create());
+
+  // Restore the MessageLoop TaskRunner.
+  MessageLoop::current()->SetTaskRunner(message_loop_task_runner_);
+}
+
+bool TestTaskScheduler::RunsTasksOnCurrentThread() const {
+  return message_loop_task_runner_->RunsTasksOnCurrentThread();
+}
+
+TestTaskSchedulerTaskRunner::TestTaskSchedulerTaskRunner(
+    TestTaskScheduler* task_scheduler,
+    ExecutionMode execution_mode,
+    TaskTraits traits)
+    : task_scheduler_(task_scheduler),
+      execution_mode_(execution_mode),
+      sequence_token_(execution_mode == ExecutionMode::PARALLEL
+                          ? SequenceToken()
+                          : SequenceToken::Create()),
+      traits_(traits) {}
+
+bool TestTaskSchedulerTaskRunner::PostDelayedTask(
+    const tracked_objects::Location& from_here,
+    const Closure& closure,
+    TimeDelta delay) {
+  auto task = MakeUnique<internal::Task>(from_here, closure, traits_, delay);
+  if (execution_mode_ == ExecutionMode::SEQUENCED)
+    task->sequenced_task_runner_ref = make_scoped_refptr(this);
+  else if (execution_mode_ == ExecutionMode::SINGLE_THREADED)
+    task->single_thread_task_runner_ref = make_scoped_refptr(this);
+  return task_scheduler_->PostTask(std::move(task), sequence_token_);
+}
+
+bool TestTaskSchedulerTaskRunner::PostNonNestableDelayedTask(
+    const tracked_objects::Location& from_here,
+    const Closure& closure,
+    TimeDelta delay) {
+  // Tasks are never nested within the task scheduler.
+  return PostDelayedTask(from_here, closure, delay);
+}
+
+bool TestTaskSchedulerTaskRunner::RunsTasksOnCurrentThread() const {
+  if (execution_mode_ == ExecutionMode::PARALLEL)
+    return task_scheduler_->RunsTasksOnCurrentThread();
+  return sequence_token_ == SequenceToken::GetForCurrentThread();
+}
+
+TestTaskSchedulerTaskRunner::~TestTaskSchedulerTaskRunner() = default;
+
+}  // namespace
+
+ScopedTaskScheduler::ScopedTaskScheduler() : ScopedTaskScheduler(nullptr) {}
+
+ScopedTaskScheduler::ScopedTaskScheduler(MessageLoop* external_message_loop) {
   DCHECK(!TaskScheduler::GetInstance());
-
-  // Create a TaskScheduler with a single thread to make tests deterministic.
-  constexpr int kMaxThreads = 1;
-  std::vector<SchedulerWorkerPoolParams> worker_pool_params_vector;
-  worker_pool_params_vector.emplace_back(
-      "Simple", ThreadPriority::NORMAL,
-      SchedulerWorkerPoolParams::StandbyThreadPolicy::LAZY, kMaxThreads,
-      TimeDelta::Max());
-  TaskScheduler::CreateAndSetDefaultTaskScheduler(
-      worker_pool_params_vector,
-      Bind([](const TaskTraits&) -> size_t { return 0; }));
+  TaskScheduler::SetInstance(
+      MakeUnique<TestTaskScheduler>(external_message_loop));
   task_scheduler_ = TaskScheduler::GetInstance();
 }
 
 ScopedTaskScheduler::~ScopedTaskScheduler() {
+  DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK_EQ(task_scheduler_, TaskScheduler::GetInstance());
-  TaskScheduler::GetInstance()->Shutdown();
-  TaskScheduler::GetInstance()->JoinForTesting();
   TaskScheduler::SetInstance(nullptr);
 }
 
 }  // namespace test
 }  // namespace base