scoped_feature_list.h | Explore in Territory

// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_TEST_SCOPED_FEATURE_LIST_H_
#define BASE_TEST_SCOPED_FEATURE_LIST_H_

#include <memory>
#include <string>
#include <vector>

#include "base/containers/flat_map.h"
#include "base/feature_list.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/raw_ref.h"
#include "base/metrics/field_trial.h"
#include "base/metrics/field_trial_params.h"
#include "base/types/pass_key.h"
#include "third_party/abseil-cpp/absl/base/attributes.h"

namespace base::test {

// A reference to a base::Feature and field trial params that should be force
// enabled and overwritten for test purposes.
struct FeatureRefAndParams { … };

// A lightweight wrapper for a reference to a base::Feature. Allows lists of
// features to be enabled/disabled to be easily passed without actually copying
// the underlying base::Feature. Actual C++ references do not work well for this
// purpose, as vectors of references are disallowed.
class FeatureRef { … };

// ScopedFeatureList resets the global FeatureList instance to a new instance
// and restores the original instance upon destruction. Whether the existing
// FeatureList state is kept or discarded depends on the `Init` method called.
// When using the non-deprecated APIs, a corresponding FieldTrialList is also
// created.
//
// Note: Re-using the same object is allowed. To reset the feature list and
// initialize it anew, call `Reset` and then one of the `Init` methods.
//
// If multiple instances of this class are used in a nested fashion, they
// should be destroyed in the opposite order of their Init*() methods being
// called.
//
// ScopedFeatureList needs to be initialized on the main thread (via one of
// Init*() methods) before running code that inspects the state of features,
// such as in the constructor of the test harness.
//
// WARNING: To be clear, in multithreaded test environments (such as browser
// tests) there may background threads using FeatureList before the test body is
// even entered. In these cases it is imperative that ScopedFeatureList be
// initialized BEFORE those threads are started, hence the recommendation to do
// initialization in the test harness's constructor.
class ScopedFeatureList final { … };

}  // namespace base::test

#endif  // BASE_TEST_SCOPED_FEATURE_LIST_H_
chromium/base/test/scoped_feature_list.h
