[vm] Get experimental flag default values from YAML

Bug: https://github.com/dart-lang/sdk/issues/44053
Change-Id: Ia7ee5fe212cf0f5c619026d967e5747d71bf31ec
Fixes: https://github.com/dart-lang/sdk/issues/44053
TEST=No behavior change, so just running existing tests.
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/171663
Commit-Queue: Liam Appelbe <liama@google.com>
Reviewed-by: Alexander Markov <alexmarkov@google.com>

runtime/vm/dart.cc

@@ -806,7 +806,7 @@ bool Dart::DetectNullSafety(const char* script_uri,
   }
 
   // If we are loading from source, figure out the mode from the source.
-  if (!KernelIsolate::GetExperimentalFlag("no-non-nullable")) {
+  if (KernelIsolate::GetExperimentalFlag(ExperimentalFeature::non_nullable)) {
     return KernelIsolate::DetectNullSafety(script_uri, package_config,
                                            original_working_directory);
   }

runtime/vm/experimental_features.cc

@@ -0,0 +1,45 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+// NOTE: THIS FILE IS GENERATED. DO NOT EDIT.
+//
+// Instead modify 'tools/experimental_features.yaml' and run
+// 'dart tools/generate_experimental_flags.dart' to update.
+//
+// Current version: 2.12.0
+
+#include "vm/experimental_features.h"
+
+#include <cstring>
+#include "platform/assert.h"
+#include "vm/globals.h"
+
+namespace dart {
+
+bool GetExperimentalFeatureDefault(ExperimentalFeature feature) {
+  constexpr bool kFeatureValues[] = {
+    true,
+    true,
+    true,
+    true,
+    true,
+    true,
+  };
+  ASSERT(static_cast<size_t>(feature) < ARRAY_SIZE(kFeatureValues));
+  return kFeatureValues[static_cast<int>(feature)];
+}
+
+const char* GetExperimentalFeatureName(ExperimentalFeature feature) {
+  constexpr const char* kFeatureNames[] = {
+    "non-nullable",
+    "extension-methods",
+    "constant-update-2018",
+    "control-flow-collections",
+    "set-literals",
+    "spread-collections",
+  };
+  ASSERT(static_cast<size_t>(feature) < ARRAY_SIZE(kFeatureNames));
+  return kFeatureNames[static_cast<int>(feature)];
+}
+
+}  // namespace dart

runtime/vm/experimental_features.h

@@ -0,0 +1,30 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+// NOTE: THIS FILE IS GENERATED. DO NOT EDIT.
+//
+// Instead modify 'tools/experimental_features.yaml' and run
+// 'dart tools/generate_experimental_flags.dart' to update.
+//
+// Current version: 2.12.0
+
+#ifndef RUNTIME_VM_EXPERIMENTAL_FEATURES_H_
+#define RUNTIME_VM_EXPERIMENTAL_FEATURES_H_
+
+namespace dart {
+
+enum class ExperimentalFeature {
+  non_nullable,
+  extension_methods,
+  constant_update_2018,
+  control_flow_collections,
+  set_literals,
+  spread_collections,
+};
+
+bool GetExperimentalFeatureDefault(ExperimentalFeature feature);
+const char* GetExperimentalFeatureName(ExperimentalFeature feature);
+
+}  // namespace dart
+
+#endif  // RUNTIME_VM_EXPERIMENTAL_FEATURES_H_

runtime/vm/kernel_isolate.cc

@@ -417,13 +417,16 @@ void KernelIsolate::AddExperimentalFlag(const char* value) {
   free(temp);
 }
 
-bool KernelIsolate::GetExperimentalFlag(const char* value) {
+bool KernelIsolate::GetExperimentalFlag(ExperimentalFeature feature) {
+  const char* value = GetExperimentalFeatureName(feature);
   for (const char* str : *experimental_flags_) {
     if (strcmp(str, value) == 0) {
       return true;
+    } else if (strstr(str, "no-") == str && strcmp(str + 3, value) == 0) {
+      return false;
     }
   }
-  return false;
+  return GetExperimentalFeatureDefault(feature);
 }
 
 DEFINE_OPTION_HANDLER(KernelIsolate::AddExperimentalFlag,

runtime/vm/kernel_isolate.h

@@ -12,6 +12,7 @@
 
 #include "vm/allocation.h"
 #include "vm/dart.h"
+#include "vm/experimental_features.h"
 #include "vm/os_thread.h"
 
 namespace dart {
@@ -78,7 +79,7 @@ class KernelIsolate : public AllStatic {
   static void NotifyAboutIsolateShutdown(const Isolate* isolate);
 
   static void AddExperimentalFlag(const char* value);
-  static bool GetExperimentalFlag(const char* value);
+  static bool GetExperimentalFlag(ExperimentalFeature feature);
 
  protected:
   static void InitCallback(Isolate* I);

runtime/vm/unit_test.cc

@@ -220,7 +220,7 @@ const char* TestCase::GetTestLib(const char* url) {
 }
 
 bool TestCase::IsNNBD() {
-  return !KernelIsolate::GetExperimentalFlag("no-non-nullable");
+  return KernelIsolate::GetExperimentalFlag(ExperimentalFeature::non_nullable);
 }
 
 #ifndef PRODUCT

runtime/vm/vm_sources.gni

@@ -98,6 +98,8 @@ vm_sources = [
   "elf.h",
   "exceptions.cc",
   "exceptions.h",
+  "experimental_features.cc",
+  "experimental_features.h",
   "ffi_callback_trampolines.cc",
   "ffi_callback_trampolines.h",
   "field_table.cc",

tools/experimental_features.yaml

@@ -10,7 +10,8 @@
 #
 # ### Code Generation
 #
-# When you change this file, run the following to update analyzer and kernel:
+# When you change this file, run the following to update analyzer, kernel, and
+# vm:
 #
 # analyzer:
 #   dart pkg/analyzer/tool/experiments/generate.dart
@@ -18,6 +19,9 @@
 # kernel:
 #   pkg/front_end/tool/fasta generate-experimental-flags
 #
+# vm:
+#   dart tools/generate_experimental_flags.dart
+#
 # ### Overview
 #
 # This document consists mostly of a map called "features".

tools/generate_experimental_flags.dart

@@ -0,0 +1,125 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// @dart = 2.9
+
+import 'dart:io' show File, Platform;
+import 'package:yaml/yaml.dart' show YamlMap, loadYaml;
+
+void main() {
+  YamlMap yaml =
+      loadYaml(new File.fromUri(computeYamlFile()).readAsStringSync());
+  final currentVersion = getAsVersionNumber(yaml['current-version']);
+  final enumNames = new StringBuffer();
+  final featureValues = new StringBuffer();
+  final featureNames = new StringBuffer();
+
+  YamlMap features = yaml['features'];
+  for (var entry in features.entries) {
+    final category = (entry.value as YamlMap)['category'];
+    if (category == null || category == "vm" || category == "language") {
+      final version = getAsVersionNumber((entry.value as YamlMap)['enabledIn']);
+      if (version != null) {
+        final value = isGreaterOrEqualVersion(currentVersion, version);
+        final name = entry.key.replaceAll('-', '_');
+        enumNames.write('  $name,\n');
+        featureValues.write('    $value,\n');
+        featureNames.write('    "${entry.key}",\n');
+      }
+    }
+  }
+
+  final h = '''
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+// NOTE: THIS FILE IS GENERATED. DO NOT EDIT.
+//
+// Instead modify 'tools/experimental_features.yaml' and run
+// 'dart tools/generate_experimental_flags.dart' to update.
+//
+// Current version: ${currentVersion.join('.')}
+
+#ifndef RUNTIME_VM_EXPERIMENTAL_FEATURES_H_
+#define RUNTIME_VM_EXPERIMENTAL_FEATURES_H_
+
+namespace dart {
+
+enum class ExperimentalFeature {
+$enumNames};
+
+bool GetExperimentalFeatureDefault(ExperimentalFeature feature);
+const char* GetExperimentalFeatureName(ExperimentalFeature feature);
+
+}  // namespace dart
+
+#endif  // RUNTIME_VM_EXPERIMENTAL_FEATURES_H_
+''';
+
+  final cc = '''
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+// NOTE: THIS FILE IS GENERATED. DO NOT EDIT.
+//
+// Instead modify 'tools/experimental_features.yaml' and run
+// 'dart tools/generate_experimental_flags.dart' to update.
+//
+// Current version: ${currentVersion.join('.')}
+
+#include "vm/experimental_features.h"
+
+#include <cstring>
+#include "platform/assert.h"
+#include "vm/globals.h"
+
+namespace dart {
+
+bool GetExperimentalFeatureDefault(ExperimentalFeature feature) {
+  constexpr bool kFeatureValues[] = {
+$featureValues  };
+  ASSERT(static_cast<size_t>(feature) < ARRAY_SIZE(kFeatureValues));
+  return kFeatureValues[static_cast<int>(feature)];
+}
+
+const char* GetExperimentalFeatureName(ExperimentalFeature feature) {
+  constexpr const char* kFeatureNames[] = {
+$featureNames  };
+  ASSERT(static_cast<size_t>(feature) < ARRAY_SIZE(kFeatureNames));
+  return kFeatureNames[static_cast<int>(feature)];
+}
+
+}  // namespace dart
+''';
+
+  File.fromUri(computeHFile()).writeAsStringSync(h);
+  File.fromUri(computeCcFile()).writeAsStringSync(cc);
+}
+
+Uri computeYamlFile() {
+  return Platform.script.resolve("experimental_features.yaml");
+}
+
+Uri computeCcFile() {
+  return Platform.script.resolve("../runtime/vm/experimental_features.cc");
+}
+
+Uri computeHFile() {
+  return Platform.script.resolve("../runtime/vm/experimental_features.h");
+}
+
+List<num> getAsVersionNumber(dynamic value) {
+  if (value == null) return null;
+  final version = List.of("$value".split(".").map(int.parse));
+  while (version.length < 3) version.add(0);
+  return version;
+}
+
+bool isGreaterOrEqualVersion(List<num> left, List<num> right) {
+  assert(left.length == right.length);
+  for (var i = 0; i < left.length; ++i) {
+    if (left[i] != right[i]) return left[i] > right[i];
+  }
+  return true;
+}