diff --git a/base/BUILD.gn b/base/BUILD.gn
index 9b52a9bd084ff..8cf35e71cb94c 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -294,6 +294,7 @@ component("base") {
"export_template.h",
"feature_list.cc",
"feature_list.h",
+ "feature_visitor.h",
"features.cc",
"features.h",
"file_version_info.h",
@@ -1002,10 +1003,6 @@ component("base") {
]
}
- if (is_chromeos_ash) {
- sources += [ "feature_visitor.h" ]
- }
-
if (is_linux || is_chromeos || is_android) {
sources += [
"files/file_path_watcher_inotify.cc",
diff --git a/base/feature_list.cc b/base/feature_list.cc
index e981c80430d58..75dc0b1f1fc23 100644
--- a/base/feature_list.cc
+++ b/base/feature_list.cc
@@ -2,24 +2,27 @@
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
+#include "base/location.h"
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/40284755): Remove this and spanify to fix the errors.
#pragma allow_unsafe_buffers
#endif
-#include "base/feature_list.h"
-
#include <stddef.h>
+#include <algorithm>
#include <string>
#include <string_view>
#include <tuple>
#include "base/base_switches.h"
+#include "base/check_is_test.h"
#include "base/containers/contains.h"
#include "base/containers/span.h"
#include "base/debug/crash_logging.h"
#include "base/debug/dump_without_crashing.h"
+#include "base/feature_list.h"
+#include "base/feature_visitor.h"
#include "base/logging.h"
#include "base/memory/ptr_util.h"
#include "base/memory/raw_ptr.h"
@@ -37,10 +40,6 @@
#include "build/build_config.h"
#include "build/chromeos_buildflags.h"
-#if BUILDFLAG(IS_CHROMEOS_ASH)
-#include "base/feature_visitor.h"
-#endif // BUILDFLAG(IS_CHROMEOS_ASH)
-
namespace base {
namespace {
@@ -687,14 +686,39 @@ void FeatureList::AddEarlyAllowedFeatureForTesting(std::string feature_name) {
allowed_feature_names_.insert(std::move(feature_name));
}
-#if BUILDFLAG(IS_CHROMEOS_ASH)
// static
-void FeatureList::VisitFeaturesAndParams(FeatureVisitor& visitor) {
- CHECK(g_feature_list_instance);
+void FeatureList::VisitFeaturesAndParams(FeatureVisitor& visitor,
+ std::string_view filter_prefix) {
+ // If there is no feature list, there are no overrides. This should only happen
+ // in tests.
+ // TODO(leszeks): Add a CHECK_IS_TEST() to verify the above.
+ if (!g_feature_list_instance) {
+ return;
+ }
+
FieldTrialParamAssociator* params_associator =
FieldTrialParamAssociator::GetInstance();
- for (auto& feature_override : g_feature_list_instance->overrides_) {
+ using FeatureOverride = std::pair<std::string, OverrideEntry>;
+ base::span<FeatureOverride> filtered_overrides(
+ g_feature_list_instance->overrides_);
+ if (!filter_prefix.empty()) {
+ // If there is a filter prefix, then change the begin/end range to be the
+ // range where the values are prefixed with the given prefix (overrides are
+ // lexically sorted, so this will be a continuous range). This is
+ // implemented as a binary search of the upper and lower bounds of the
+ // override iterator, projecting each iterator value to just the
+ // key, trimmed to the length of the prefix.
+ DCHECK(std::ranges::is_sorted(
+ filtered_overrides, std::less<>(),
+ [](const FeatureOverride& entry) { return entry.first; }));
+ filtered_overrides = std::ranges::equal_range(
+ filtered_overrides, filter_prefix, std::less<>(),
+ [filter_prefix](const FeatureOverride& entry) {
+ return std::string_view(entry.first).substr(0, filter_prefix.size());
+ });
+ }
+ for (const FeatureOverride& feature_override : filtered_overrides) {
FieldTrial* field_trial = feature_override.second.field_trial;
std::string trial_name;
@@ -712,7 +736,6 @@ void FeatureList::VisitFeaturesAndParams(FeatureVisitor& visitor) {
group_name);
}
}
-#endif // BULDFLAG(IS_CHROMEOS_ASH)
void FeatureList::FinalizeInitialization() {
DCHECK(!initialized_);
diff --git a/base/feature_list.h b/base/feature_list.h
index 602fbce18fb81..8e595511eb398 100644
--- a/base/feature_list.h
+++ b/base/feature_list.h
@@ -26,17 +26,13 @@
#include "base/memory/raw_ptr.h"
#include "base/synchronization/lock.h"
#include "build/build_config.h"
-#include "build/chromeos_buildflags.h"
namespace base {
class FieldTrial;
class FieldTrialList;
class PersistentMemoryAllocator;
-
-#if BUILDFLAG(IS_CHROMEOS_ASH)
class FeatureVisitor;
-#endif // BUILDFLAG(IS_CHROMEOS_ASH)
// Specifies whether a given feature is enabled or disabled by default.
// NOTE: The actual runtime state may be different, due to a field trial or a
@@ -579,15 +575,15 @@ class BASE_EXPORT FeatureList {
// only be called on a FeatureList that was set with SetEarlyAccessInstance().
void AddEarlyAllowedFeatureForTesting(std::string feature_name);
-#if BUILDFLAG(IS_CHROMEOS_ASH)
// Allows a visitor to record override state, parameters, and field trial
- // associated with each feature.
+ // associated with each feature. Optionally, provide a prefix which filters
+ // the visited features.
//
// NOTE: This is intended only for the special case of needing to get all
- // overrides. This use case is specific to CrOS-Ash. Most users should call
- // IsEnabled() to query a feature's state.
- static void VisitFeaturesAndParams(FeatureVisitor& visitor);
-#endif // BULDFLAG(IS_CHROMEOS_ASH)
+ // overrides. This use case is specific to CrOS-Ash and V8. Most users should
+ // call IsEnabled() to query a feature's state.
+ static void VisitFeaturesAndParams(FeatureVisitor& visitor,
+ std::string_view filter_prefix = "");
private:
FRIEND_TEST_ALL_PREFIXES(FeatureListTest, CheckFeatureIdentity);
diff --git a/base/feature_list_unittest.cc b/base/feature_list_unittest.cc
index 2bb02ed75f11a..618078b3c9677 100644
--- a/base/feature_list_unittest.cc
+++ b/base/feature_list_unittest.cc
@@ -19,6 +19,7 @@
#include <vector>
#include "base/feature_list_buildflags.h"
+#include "base/feature_visitor.h"
#include "base/format_macros.h"
#include "base/memory/read_only_shared_memory_region.h"
#include "base/metrics/field_trial.h"
@@ -32,10 +33,6 @@
#include "build/chromeos_buildflags.h"
#include "testing/gtest/include/gtest/gtest.h"
-#if BUILDFLAG(IS_CHROMEOS_ASH)
-#include "base/feature_visitor.h"
-#endif // BUILDFLAG(IS_CHROMEOS_ASH)
-
namespace base {
namespace {
@@ -851,7 +848,6 @@ TEST(FeatureListAccessorTest, InitFromCommandLineWithFeatureParams) {
}
}
-#if BUILDFLAG(IS_CHROMEOS_ASH)
// Test only class to verify correctness of
// FeatureList::VisitFeaturesAndParams().
class TestFeatureVisitor : public FeatureVisitor {
@@ -979,6 +975,35 @@ TEST(TestFeatureVisitor, FeatureHasParams) {
EXPECT_EQ(actual_feature_state, expected_feature_state);
}
-#endif // BUILDFLAG(IS_CHROMEOS_ASH)
+
+TEST(TestFeatureVisitor, FeatureWithPrefix) {
+ base::test::ScopedFeatureList outer_scope;
+ outer_scope.InitWithEmptyFeatureAndFieldTrialLists();
+
+ base::test::ScopedFeatureList initialized_feature_list;
+
+ initialized_feature_list.InitFromCommandLine(
+ /*enable_features=*/
+ "AFeature,AnotherFeature,TestFeature,TestFeature2,PrefixedFeature,"
+ "PrefixedFeature2",
+ /*disable_features=*/"");
+
+ TestFeatureVisitor visitor;
+ base::FeatureList::VisitFeaturesAndParams(visitor, "Prefixed");
+ std::multiset<TestFeatureVisitor::VisitedFeatureState> actual_feature_state =
+ visitor.feature_state();
+
+ std::multiset<TestFeatureVisitor::VisitedFeatureState>
+ expected_feature_state = {
+ {"PrefixedFeature",
+ FeatureList::OverrideState::OVERRIDE_ENABLE_FEATURE,
+ FieldTrialParams{}, "", ""},
+ {"PrefixedFeature2",
+ FeatureList::OverrideState::OVERRIDE_ENABLE_FEATURE,
+ FieldTrialParams{}, "", ""},
+ };
+
+ EXPECT_EQ(actual_feature_state, expected_feature_state);
+}
} // namespace base
diff --git a/base/feature_visitor.h b/base/feature_visitor.h
index b85440d122147..47732397bfb5c 100644
--- a/base/feature_visitor.h
+++ b/base/feature_visitor.h
@@ -9,21 +9,21 @@
#include <string>
#include "base/feature_list.h"
-#include "build/chromeos_buildflags.h"
-
-static_assert(BUILDFLAG(IS_CHROMEOS_ASH), "For ChromeOS ash-chrome only");
namespace variations::cros_early_boot::evaluate_seed {
class EarlyBootFeatureVisitor;
}
+namespace gin {
+class V8FeatureVisitor;
+}
+
namespace base {
class TestFeatureVisitor;
-// An interface for EarlyBootFeatureVisitor that provides a method to
-// iterate over a feature's name, override state, parameters, and associated
-// field trial.
+// An interface for FeatureList that provides a method to iterate over a
+// feature's name, override state, parameters, and associated field trial.
//
// NOTE: This is intended only for the special case of needing to get all
// feature overrides. Most users should call FeatureList::IsEnabled() to query
@@ -45,6 +45,7 @@ class FeatureVisitor {
private:
friend variations::cros_early_boot::evaluate_seed::EarlyBootFeatureVisitor;
+ friend gin::V8FeatureVisitor;
friend TestFeatureVisitor;
// The constructor is private so only friend classes can inherit from this
diff --git a/gin/v8_initializer.cc b/gin/v8_initializer.cc
index b1237e4ee88e1..0894e32248a2f 100644
--- a/gin/v8_initializer.cc
+++ b/gin/v8_initializer.cc
@@ -22,6 +22,7 @@
#include "base/debug/alias.h"
#include "base/debug/crash_logging.h"
#include "base/feature_list.h"
+#include "base/feature_visitor.h"
#include "base/files/file.h"
#include "base/files/file_path.h"
#include "base/files/memory_mapped_file.h"
@@ -218,10 +219,77 @@ void SetV8FlagsIfOverridden(const base::Feature& feature,
}
}
+constexpr std::string_view kV8FlagFeaturePrefix = "V8Flag_";
+
+} // namespace
+
+class V8FeatureVisitor : public base::FeatureVisitor {
+ public:
+ void Visit(const std::string& feature_name,
+ base::FeatureList::OverrideState override_state,
+ const std::map<std::string, std::string>& params,
+ const std::string& trial_name,
+ const std::string& group_name) override {
+ std::string_view feature_name_view(feature_name);
+
+ // VisitFeaturesAndParams is called with kV8FlagFeaturePrefix as a filter
+ // prefix, so we expect all feature names to start with "V8Flag_". Strip
+ // this prefix off to get the corresponding V8 flag name.
+ DCHECK(feature_name_view.starts_with(kV8FlagFeaturePrefix));
+ std::string_view flag_name =
+ feature_name_view.substr(kV8FlagFeaturePrefix.size());
+
+ switch (override_state) {
+ case base::FeatureList::OverrideState::OVERRIDE_USE_DEFAULT:
+ return;
+
+ case base::FeatureList::OverrideState::OVERRIDE_DISABLE_FEATURE:
+ SetV8FlagsFormatted("--no-%s", flag_name);
+ // Do not set parameters for disabled features.
+ break;
+
+ case base::FeatureList::OverrideState::OVERRIDE_ENABLE_FEATURE:
+ SetV8FlagsFormatted("--%s", flag_name);
+ for (const auto& [param_name, param_value] : params) {
+ SetV8FlagsFormatted("--%s=%s", param_name.c_str(),
+ param_value.c_str());
+ }
+ break;
+ }
+ }
+};
+
+namespace {
+
void SetFlags(IsolateHolder::ScriptMode mode,
const std::string js_command_line_flags) {
- // We assume that all feature flag defaults correspond to the default
- // values of the corresponding V8 flags.
+ // Chromium features prefixed with "V8Flag_" are forwarded to V8 as V8 flags,
+ // with the "V8Flag_" prefix stripped off. For example, an enabled feature
+ // "V8Flag_foo_bar" will be passed to V8 as the flag `--foo_bar`. Similarly,
+ // if that feature is explicitly disabled, it will be passed to V8 as
+ // `--no-foo_bar`. No Chromium-side declaration of a V8Flag_foo_bar feature
+ // is necessary, the matching is done on strings.
+ //
+ // Parameters attached to features will also be passed through, with the same
+ // name as the parameter and the value passed by string, to be decoded by V8's
+ // flag parsing.
+ //
+ // Thus, running Chromium with:
+ //
+ // --enable-features=V8Flag_foo,V8Flag_bar:bar_param/20
+ // --disable-features=V8Flag_baz
+ //
+ // will be converted, on V8 initialization, to V8 flags:
+ //
+ // --foo --bar --bar_param=20 --no-baz
+ V8FeatureVisitor feature_visitor;
+ base::FeatureList::VisitFeaturesAndParams(feature_visitor,
+ kV8FlagFeaturePrefix);
+
+ // Otherwise, feature flags explicitly defined in Chromium are translated
+ // to V8 flags as follows. We ignore feature flag default values, instead
+ // using the corresponding V8 flags default values if there is no explicit
+ // feature override.
SetV8FlagsIfOverridden(features::kV8CompactCodeSpaceWithStack,
"--compact-code-space-with-stack",
"--no-compact-code-space-with-stack");
diff --git a/tools/v8_context_snapshot/v8_context_snapshot_generator.cc b/tools/v8_context_snapshot/v8_context_snapshot_generator.cc
index 472c6492a8e12..37ee2e0391301 100644
--- a/tools/v8_context_snapshot/v8_context_snapshot_generator.cc
+++ b/tools/v8_context_snapshot/v8_context_snapshot_generator.cc
@@ -35,6 +35,10 @@ class SnapshotPlatform final : public blink::Platform {
int main(int argc, char** argv) {
base::AtExitManager at_exit;
+ // Initialize an empty feature list for gin startup.
+ auto early_access_feature_list = std::make_unique<base::FeatureList>();
+ base::FeatureList::SetInstance(std::move(early_access_feature_list));
+
const bool kRemoveRecognizedFlags = true;
v8::V8::SetFlagsFromCommandLine(&argc, argv, kRemoveRecognizedFlags);
base::CommandLine::Init(argc, argv);