pkg/front_end/tool/_fasta/generate_experimental_flags.dart - sdk.git - Git at Google

 // Copyright (c) 2019, 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.

 import 'dart:io' show File;

 import 'package:_fe_analyzer_shared/src/scanner/characters.dart'
     show $A, $MINUS, $a, $z;

 import 'package:_fe_analyzer_shared/src/sdk/allowed_experiments.dart';

 import 'package:dart_style/dart_style.dart' show DartFormatter;

 import 'package:yaml/yaml.dart' show YamlMap, loadYaml;

 import '../../test/utils/io_utils.dart' show computeRepoDirUri;

 void main(List<String> arguments) {
   final Uri repoDir = computeRepoDirUri();
   new File.fromUri(computeCfeGeneratedFile(repoDir))
       .writeAsStringSync(generateCfeFile(repoDir), flush: true);
   new File.fromUri(computeKernelGeneratedFile(repoDir))
       .writeAsStringSync(generateKernelFile(repoDir), flush: true);
 }

 Uri computeCfeGeneratedFile(Uri repoDir) {
   return repoDir.resolve(
       "pkg/front_end/lib/src/api_prototype/experimental_flags_generated.dart");
 }

 Uri computeKernelGeneratedFile(Uri repoDir) {
   return repoDir.resolve("pkg/kernel/lib/default_language_version.dart");
 }

 Uri computeYamlFile(Uri repoDir) {
   return repoDir.resolve("tools/experimental_features.yaml");
 }

 Uri computeAllowListFile(Uri repoDir) {
   return repoDir.resolve("sdk/lib/_internal/allowed_experiments.json");
 }

 String generateKernelFile(Uri repoDir) {
   Uri yamlFile = computeYamlFile(repoDir);
   Map<dynamic, dynamic> yaml =
       loadYaml(new File.fromUri(yamlFile).readAsStringSync());

   int currentVersionMajor;
   int currentVersionMinor;
   {
     String currentVersion = getAsVersionNumberString(yaml['current-version'])!;
     List<String> split = currentVersion.split(".");
     currentVersionMajor = int.parse(split[0]);
     currentVersionMinor = int.parse(split[1]);
   }

   StringBuffer sb = new StringBuffer();

   sb.write('''
 // Copyright (c) 2021, 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 pkg/front_end/tool/fasta.dart generate-experimental-flags' to update.

 import "ast.dart";

 Version defaultLanguageVersion = const Version($currentVersionMajor, $currentVersionMinor);
 ''');

   return new DartFormatter().format("$sb");
 }

 String generateCfeFile(Uri repoDir) {
   Uri yamlFile = computeYamlFile(repoDir);
   Map<dynamic, dynamic> yaml =
       loadYaml(new File.fromUri(yamlFile).readAsStringSync());

   int currentVersionMajor;
   int currentVersionMinor;
   {
     String currentVersion = getAsVersionNumberString(yaml['current-version'])!;
     List<String> split = currentVersion.split(".");
     currentVersionMajor = int.parse(split[0]);
     currentVersionMinor = int.parse(split[1]);
   }

   StringBuffer sb = new StringBuffer();

   sb.write('''
 // Copyright (c) 2021, 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 pkg/front_end/tool/fasta.dart generate-experimental-flags' to update.

 part of 'experimental_flags.dart';
 ''');

   Map<String, dynamic> features = {};
   Map<dynamic, dynamic> yamlFeatures = yaml['features'];
   for (MapEntry<dynamic, dynamic> entry in yamlFeatures.entries) {
     String category = entry.value["category"] ?? "language";
     if (category != "language" && category != "CFE") {
       // Skip a feature with a category that's not language or CFE.
       // In the future we might want to generate different code for different
       // things.
       continue;
     }
     features[entry.key] = entry.value;
   }

   List<String> keys = features.keys.toList()..sort();

   sb.write('''

 /// An experiment flag including its fixed properties.
 class ExperimentalFlag {
   /// The name of this flag as used in the --enable-experiment option.
   final String name;

   /// `true` if this experimental feature is enabled by default.
   ///
   /// When `true`, the feature can still be disabled in individual libraries
   /// with a language version below the [experimentEnabledVersion], and if not
   /// [isExpired], the feature can also be disabled by using a 'no-' prefix
   /// in the --enable-experiment option.
   final bool isEnabledByDefault;

   /// `true` if this feature can no longer be changed using the
   /// --enable-experiment option.
   ///
   /// Libraries can still opt out of the feature by using a language version
   /// below the [experimentEnabledVersion].
   final bool isExpired;
   final Version enabledVersion;

   /// The minimum version that supports this feature.
   ///
   /// If the feature is not enabled by default, this is the current language
   /// version.
   final Version experimentEnabledVersion;

   /// The minimum version that supports this feature in allowed libraries.
   ///
   /// Allowed libraries are specified in
   ///
   ///    sdk/lib/_internal/allowed_experiments.json
   final Version experimentReleasedVersion;

   const ExperimentalFlag(
       {required this.name,
       required this.isEnabledByDefault,
       required this.isExpired,
       required this.enabledVersion,
       required this.experimentEnabledVersion,
       required this.experimentReleasedVersion});
 ''');
   for (String key in keys) {
     String identifier = keyToIdentifier(key);
     int enabledInMajor;
     int enabledInMinor;
     String? enabledIn =
         getAsVersionNumberString((features[key] as YamlMap)['enabledIn']);
     if (enabledIn == null) {
       enabledInMajor = currentVersionMajor;
       enabledInMinor = currentVersionMinor;
     } else {
       List<String> split = enabledIn.split(".");
       enabledInMajor = int.parse(split[0]);
       enabledInMinor = int.parse(split[1]);
     }
     bool? expired = (features[key] as YamlMap)['expired'];
     bool shipped = (features[key] as YamlMap)['enabledIn'] != null;
     if (shipped) {
       if (expired == false) {
         throw 'Cannot mark shipped feature "$key" as "expired: false"';
       }
     }
     int releaseMajor;
     int releaseMinor;
     String? experimentalReleaseVersion = getAsVersionNumberString(
         (features[key] as YamlMap)['experimentalReleaseVersion']);
     if (experimentalReleaseVersion != null) {
       List<String> split = experimentalReleaseVersion.split(".");
       releaseMajor = int.parse(split[0]);
       releaseMinor = int.parse(split[1]);
     } else if (enabledIn != null) {
       List<String> split = enabledIn.split(".");
       releaseMajor = int.parse(split[0]);
       releaseMinor = int.parse(split[1]);
     } else {
       releaseMajor = currentVersionMajor;
       releaseMinor = currentVersionMinor;
     }

     sb.writeln('''
   static const ExperimentalFlag ${identifier} =
     const ExperimentalFlag(
       name: '$key',
       isEnabledByDefault: $shipped,
       isExpired: ${expired == true},
       enabledVersion: const Version($enabledInMajor, $enabledInMinor),
       experimentEnabledVersion: const Version($enabledInMajor, $enabledInMinor),
       experimentReleasedVersion: const Version($releaseMajor, $releaseMinor));
 ''');
   }
   sb.write('''
 }
 ''');

   sb.write('''
 /// Interface for accessing the global state of experimental features.
 class GlobalFeatures {
   final Map<ExperimentalFlag, bool> explicitExperimentalFlags;
   final AllowedExperimentalFlags? allowedExperimentalFlags;
   final Map<ExperimentalFlag, bool>? defaultExperimentFlagsForTesting;
   final Map<ExperimentalFlag, Version>? experimentEnabledVersionForTesting;
   final Map<ExperimentalFlag, Version>? experimentReleasedVersionForTesting;

   GlobalFeatures(this.explicitExperimentalFlags,
       {this.allowedExperimentalFlags,
       this.defaultExperimentFlagsForTesting,
       this.experimentEnabledVersionForTesting,
       this.experimentReleasedVersionForTesting});

   GlobalFeature _computeGlobalFeature(ExperimentalFlag flag) {
     return new GlobalFeature(
         flag,
         isExperimentEnabled(flag,
             defaultExperimentFlagsForTesting: defaultExperimentFlagsForTesting,
             explicitExperimentalFlags: explicitExperimentalFlags));
   }

   LibraryFeature _computeLibraryFeature(
       ExperimentalFlag flag, Uri canonicalUri, Version libraryVersion) {
     return new LibraryFeature(
         flag,
         isExperimentEnabledInLibrary(flag, canonicalUri,
             defaultExperimentFlagsForTesting: defaultExperimentFlagsForTesting,
             explicitExperimentalFlags: explicitExperimentalFlags,
             allowedExperimentalFlags: allowedExperimentalFlags),
         getExperimentEnabledVersionInLibrary(
             flag, canonicalUri, explicitExperimentalFlags,
             allowedExperimentalFlags: allowedExperimentalFlags,
             defaultExperimentFlagsForTesting: defaultExperimentFlagsForTesting,
             experimentEnabledVersionForTesting:
                 experimentEnabledVersionForTesting,
             experimentReleasedVersionForTesting:
                 experimentReleasedVersionForTesting),
         isExperimentEnabledInLibraryByVersion(
             flag, canonicalUri, libraryVersion,
             defaultExperimentFlagsForTesting: defaultExperimentFlagsForTesting,
             explicitExperimentalFlags: explicitExperimentalFlags,
             allowedExperimentalFlags: allowedExperimentalFlags));
   }
 ''');
   for (String key in keys) {
     String identifier = keyToIdentifier(key);
     sb.write('''

   GlobalFeature? _${identifier};
   GlobalFeature get ${identifier} =>
       _${identifier} ??= _computeGlobalFeature(ExperimentalFlag.${identifier});
 ''');
   }
   sb.write('''
 }

 /// Interface for accessing the state of experimental features within a
 /// specific library.
 class LibraryFeatures {
   final GlobalFeatures globalFeatures;
   final Uri canonicalUri;
   final Version libraryVersion;

   LibraryFeatures(this.globalFeatures, this.canonicalUri, this.libraryVersion);
 ''');
   for (String key in keys) {
     String identifier = keyToIdentifier(key);
     sb.write('''

   LibraryFeature? _${identifier};
   LibraryFeature get ${identifier} => _${identifier} ??= globalFeatures
       ._computeLibraryFeature(
           ExperimentalFlag.${identifier},
           canonicalUri,
           libraryVersion);
 ''');
   }
   sb.write('''
 }
 ''');

   sb.write('''
 ExperimentalFlag? parseExperimentalFlag(String flag) {
   switch (flag) {
 ''');
   for (String key in keys) {
     sb.writeln('    case "$key":');
     sb.writeln('     return ExperimentalFlag.${keyToIdentifier(key)};');
   }
   sb.write('''  }
   return null;
 }

 final Map<ExperimentalFlag, bool> defaultExperimentalFlags = {
 ''');
   for (String key in keys) {
     sb.writeln('''
   ExperimentalFlag.${keyToIdentifier(key)}:
       ExperimentalFlag.${keyToIdentifier(key)}.isEnabledByDefault,''');
   }
   sb.write('''
 };
 ''');

   Uri allowListFile = computeAllowListFile(repoDir);
   AllowedExperiments allowedExperiments = parseAllowedExperiments(
       new File.fromUri(allowListFile).readAsStringSync());

   sb.write('''
 const AllowedExperimentalFlags defaultAllowedExperimentalFlags =
     const AllowedExperimentalFlags(
 ''');
   sb.writeln('sdkDefaultExperiments: {');
   for (String sdkDefaultExperiment
       in allowedExperiments.sdkDefaultExperiments) {
     sb.writeln('ExperimentalFlag.${keyToIdentifier(sdkDefaultExperiment)},');
   }
   sb.writeln('},');
   sb.writeln('sdkLibraryExperiments: {');
   allowedExperiments.sdkLibraryExperiments
       .forEach((String library, List<String> experiments) {
     sb.writeln('"$library": {');
     for (String experiment in experiments) {
       sb.writeln('ExperimentalFlag.${keyToIdentifier(experiment)},');
     }
     sb.writeln('},');
   });
   sb.writeln('},');
   sb.writeln('packageExperiments: {');
   allowedExperiments.packageExperiments
       .forEach((String package, List<String> experiments) {
     sb.writeln('"$package": {');
     for (String experiment in experiments) {
       sb.writeln('ExperimentalFlag.${keyToIdentifier(experiment)},');
     }
     sb.writeln('},');
   });
   sb.writeln('});');

   return new DartFormatter().format("$sb");
 }

 String keyToIdentifier(String key, {bool upperCaseFirst = false}) {
   StringBuffer identifier = StringBuffer();
   bool first = true;
   for (int index = 0; index < key.length; ++index) {
     int code = key.codeUnitAt(index);
     if (code == $MINUS) {
       ++index;
       code = key.codeUnitAt(index);
       if ($a <= code && code <= $z) {
         code = code - $a + $A;
       }
     }
     if (first && upperCaseFirst && $a <= code && code <= $z) {
       code = code - $a + $A;
     }
     first = false;
     identifier.writeCharCode(code);
   }
   return identifier.toString();
 }

 String? getAsVersionNumberString(dynamic value) {
   if (value == null) return null;
   if (value is String) return value;
   if (value is double) return "$value";
   throw "Unexpected value: $value (${value.runtimeType})";
 }
	// Copyright (c) 2019, 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.

	import 'dart:io' show File;

	import 'package:_fe_analyzer_shared/src/scanner/characters.dart'
	show $A, $MINUS, $a, $z;

	import 'package:_fe_analyzer_shared/src/sdk/allowed_experiments.dart';

	import 'package:dart_style/dart_style.dart' show DartFormatter;

	import 'package:yaml/yaml.dart' show YamlMap, loadYaml;

	import '../../test/utils/io_utils.dart' show computeRepoDirUri;

	void main(List<String> arguments) {
	final Uri repoDir = computeRepoDirUri();
	new File.fromUri(computeCfeGeneratedFile(repoDir))
	.writeAsStringSync(generateCfeFile(repoDir), flush: true);
	new File.fromUri(computeKernelGeneratedFile(repoDir))
	.writeAsStringSync(generateKernelFile(repoDir), flush: true);
	}

	Uri computeCfeGeneratedFile(Uri repoDir) {
	return repoDir.resolve(
	"pkg/front_end/lib/src/api_prototype/experimental_flags_generated.dart");
	}

	Uri computeKernelGeneratedFile(Uri repoDir) {
	return repoDir.resolve("pkg/kernel/lib/default_language_version.dart");
	}

	Uri computeYamlFile(Uri repoDir) {
	return repoDir.resolve("tools/experimental_features.yaml");
	}

	Uri computeAllowListFile(Uri repoDir) {
	return repoDir.resolve("sdk/lib/_internal/allowed_experiments.json");
	}

	String generateKernelFile(Uri repoDir) {
	Uri yamlFile = computeYamlFile(repoDir);
	Map<dynamic, dynamic> yaml =
	loadYaml(new File.fromUri(yamlFile).readAsStringSync());

	int currentVersionMajor;
	int currentVersionMinor;
	{
	String currentVersion = getAsVersionNumberString(yaml['current-version'])!;
	List<String> split = currentVersion.split(".");
	currentVersionMajor = int.parse(split[0]);
	currentVersionMinor = int.parse(split[1]);
	}

	StringBuffer sb = new StringBuffer();

	sb.write('''
	// Copyright (c) 2021, 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 pkg/front_end/tool/fasta.dart generate-experimental-flags' to update.

	import "ast.dart";

	Version defaultLanguageVersion = const Version($currentVersionMajor, $currentVersionMinor);
	''');

	return new DartFormatter().format("$sb");
	}

	String generateCfeFile(Uri repoDir) {
	Uri yamlFile = computeYamlFile(repoDir);
	Map<dynamic, dynamic> yaml =
	loadYaml(new File.fromUri(yamlFile).readAsStringSync());

	int currentVersionMajor;
	int currentVersionMinor;
	{
	String currentVersion = getAsVersionNumberString(yaml['current-version'])!;
	List<String> split = currentVersion.split(".");
	currentVersionMajor = int.parse(split[0]);
	currentVersionMinor = int.parse(split[1]);
	}

	StringBuffer sb = new StringBuffer();

	sb.write('''
	// Copyright (c) 2021, 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 pkg/front_end/tool/fasta.dart generate-experimental-flags' to update.

	part of 'experimental_flags.dart';
	''');

	Map<String, dynamic> features = {};
	Map<dynamic, dynamic> yamlFeatures = yaml['features'];
	for (MapEntry<dynamic, dynamic> entry in yamlFeatures.entries) {
	String category = entry.value["category"] ?? "language";
	if (category != "language" && category != "CFE") {
	// Skip a feature with a category that's not language or CFE.
	// In the future we might want to generate different code for different
	// things.
	continue;
	}
	features[entry.key] = entry.value;
	}

	List<String> keys = features.keys.toList()..sort();

	sb.write('''

	/// An experiment flag including its fixed properties.
	class ExperimentalFlag {
	/// The name of this flag as used in the --enable-experiment option.
	final String name;

	/// `true` if this experimental feature is enabled by default.
	///
	/// When `true`, the feature can still be disabled in individual libraries
	/// with a language version below the [experimentEnabledVersion], and if not
	/// [isExpired], the feature can also be disabled by using a 'no-' prefix
	/// in the --enable-experiment option.
	final bool isEnabledByDefault;

	/// `true` if this feature can no longer be changed using the
	/// --enable-experiment option.
	///
	/// Libraries can still opt out of the feature by using a language version
	/// below the [experimentEnabledVersion].
	final bool isExpired;
	final Version enabledVersion;

	/// The minimum version that supports this feature.
	///
	/// If the feature is not enabled by default, this is the current language
	/// version.
	final Version experimentEnabledVersion;

	/// The minimum version that supports this feature in allowed libraries.
	///
	/// Allowed libraries are specified in
	///
	/// sdk/lib/_internal/allowed_experiments.json
	final Version experimentReleasedVersion;

	const ExperimentalFlag(
	{required this.name,
	required this.isEnabledByDefault,
	required this.isExpired,
	required this.enabledVersion,
	required this.experimentEnabledVersion,
	required this.experimentReleasedVersion});
	''');
	for (String key in keys) {
	String identifier = keyToIdentifier(key);
	int enabledInMajor;
	int enabledInMinor;
	String? enabledIn =
	getAsVersionNumberString((features[key] as YamlMap)['enabledIn']);
	if (enabledIn == null) {
	enabledInMajor = currentVersionMajor;
	enabledInMinor = currentVersionMinor;
	} else {
	List<String> split = enabledIn.split(".");
	enabledInMajor = int.parse(split[0]);
	enabledInMinor = int.parse(split[1]);
	}
	bool? expired = (features[key] as YamlMap)['expired'];
	bool shipped = (features[key] as YamlMap)['enabledIn'] != null;
	if (shipped) {
	if (expired == false) {
	throw 'Cannot mark shipped feature "$key" as "expired: false"';
	}
	}
	int releaseMajor;
	int releaseMinor;
	String? experimentalReleaseVersion = getAsVersionNumberString(
	(features[key] as YamlMap)['experimentalReleaseVersion']);
	if (experimentalReleaseVersion != null) {
	List<String> split = experimentalReleaseVersion.split(".");
	releaseMajor = int.parse(split[0]);
	releaseMinor = int.parse(split[1]);
	} else if (enabledIn != null) {
	List<String> split = enabledIn.split(".");
	releaseMajor = int.parse(split[0]);
	releaseMinor = int.parse(split[1]);
	} else {
	releaseMajor = currentVersionMajor;
	releaseMinor = currentVersionMinor;
	}

	sb.writeln('''
	static const ExperimentalFlag ${identifier} =
	const ExperimentalFlag(
	name: '$key',
	isEnabledByDefault: $shipped,
	isExpired: ${expired == true},
	enabledVersion: const Version($enabledInMajor, $enabledInMinor),
	experimentEnabledVersion: const Version($enabledInMajor, $enabledInMinor),
	experimentReleasedVersion: const Version($releaseMajor, $releaseMinor));
	''');
	}
	sb.write('''
	}
	''');

	sb.write('''
	/// Interface for accessing the global state of experimental features.
	class GlobalFeatures {
	final Map<ExperimentalFlag, bool> explicitExperimentalFlags;
	final AllowedExperimentalFlags? allowedExperimentalFlags;
	final Map<ExperimentalFlag, bool>? defaultExperimentFlagsForTesting;
	final Map<ExperimentalFlag, Version>? experimentEnabledVersionForTesting;
	final Map<ExperimentalFlag, Version>? experimentReleasedVersionForTesting;

	GlobalFeatures(this.explicitExperimentalFlags,
	{this.allowedExperimentalFlags,
	this.defaultExperimentFlagsForTesting,
	this.experimentEnabledVersionForTesting,
	this.experimentReleasedVersionForTesting});

	GlobalFeature _computeGlobalFeature(ExperimentalFlag flag) {
	return new GlobalFeature(
	flag,
	isExperimentEnabled(flag,
	defaultExperimentFlagsForTesting: defaultExperimentFlagsForTesting,
	explicitExperimentalFlags: explicitExperimentalFlags));
	}

	LibraryFeature _computeLibraryFeature(
	ExperimentalFlag flag, Uri canonicalUri, Version libraryVersion) {
	return new LibraryFeature(
	flag,
	isExperimentEnabledInLibrary(flag, canonicalUri,
	defaultExperimentFlagsForTesting: defaultExperimentFlagsForTesting,
	explicitExperimentalFlags: explicitExperimentalFlags,
	allowedExperimentalFlags: allowedExperimentalFlags),
	getExperimentEnabledVersionInLibrary(
	flag, canonicalUri, explicitExperimentalFlags,
	allowedExperimentalFlags: allowedExperimentalFlags,
	defaultExperimentFlagsForTesting: defaultExperimentFlagsForTesting,
	experimentEnabledVersionForTesting:
	experimentEnabledVersionForTesting,
	experimentReleasedVersionForTesting:
	experimentReleasedVersionForTesting),
	isExperimentEnabledInLibraryByVersion(
	flag, canonicalUri, libraryVersion,
	defaultExperimentFlagsForTesting: defaultExperimentFlagsForTesting,
	explicitExperimentalFlags: explicitExperimentalFlags,
	allowedExperimentalFlags: allowedExperimentalFlags));
	}
	''');
	for (String key in keys) {
	String identifier = keyToIdentifier(key);
	sb.write('''

	GlobalFeature? _${identifier};
	GlobalFeature get ${identifier} =>
	_${identifier} ??= _computeGlobalFeature(ExperimentalFlag.${identifier});
	''');
	}
	sb.write('''
	}

	/// Interface for accessing the state of experimental features within a
	/// specific library.
	class LibraryFeatures {
	final GlobalFeatures globalFeatures;
	final Uri canonicalUri;
	final Version libraryVersion;

	LibraryFeatures(this.globalFeatures, this.canonicalUri, this.libraryVersion);
	''');
	for (String key in keys) {
	String identifier = keyToIdentifier(key);
	sb.write('''

	LibraryFeature? _${identifier};
	LibraryFeature get ${identifier} => _${identifier} ??= globalFeatures
	._computeLibraryFeature(
	ExperimentalFlag.${identifier},
	canonicalUri,
	libraryVersion);
	''');
	}
	sb.write('''
	}
	''');

	sb.write('''
	ExperimentalFlag? parseExperimentalFlag(String flag) {
	switch (flag) {
	''');
	for (String key in keys) {
	sb.writeln(' case "$key":');
	sb.writeln(' return ExperimentalFlag.${keyToIdentifier(key)};');
	}
	sb.write(''' }
	return null;
	}

	final Map<ExperimentalFlag, bool> defaultExperimentalFlags = {
	''');
	for (String key in keys) {
	sb.writeln('''
	ExperimentalFlag.${keyToIdentifier(key)}:
	ExperimentalFlag.${keyToIdentifier(key)}.isEnabledByDefault,''');
	}
	sb.write('''
	};
	''');

	Uri allowListFile = computeAllowListFile(repoDir);
	AllowedExperiments allowedExperiments = parseAllowedExperiments(
	new File.fromUri(allowListFile).readAsStringSync());

	sb.write('''
	const AllowedExperimentalFlags defaultAllowedExperimentalFlags =
	const AllowedExperimentalFlags(
	''');
	sb.writeln('sdkDefaultExperiments: {');
	for (String sdkDefaultExperiment
	in allowedExperiments.sdkDefaultExperiments) {
	sb.writeln('ExperimentalFlag.${keyToIdentifier(sdkDefaultExperiment)},');
	}
	sb.writeln('},');
	sb.writeln('sdkLibraryExperiments: {');
	allowedExperiments.sdkLibraryExperiments
	.forEach((String library, List<String> experiments) {
	sb.writeln('"$library": {');
	for (String experiment in experiments) {
	sb.writeln('ExperimentalFlag.${keyToIdentifier(experiment)},');
	}
	sb.writeln('},');
	});
	sb.writeln('},');
	sb.writeln('packageExperiments: {');
	allowedExperiments.packageExperiments
	.forEach((String package, List<String> experiments) {
	sb.writeln('"$package": {');
	for (String experiment in experiments) {
	sb.writeln('ExperimentalFlag.${keyToIdentifier(experiment)},');
	}
	sb.writeln('},');
	});
	sb.writeln('});');

	return new DartFormatter().format("$sb");
	}

	String keyToIdentifier(String key, {bool upperCaseFirst = false}) {
	StringBuffer identifier = StringBuffer();
	bool first = true;
	for (int index = 0; index < key.length; ++index) {
	int code = key.codeUnitAt(index);
	if (code == $MINUS) {
	++index;
	code = key.codeUnitAt(index);
	if ($a <= code && code <= $z) {
	code = code - $a + $A;
	}
	}
	if (first && upperCaseFirst && $a <= code && code <= $z) {
	code = code - $a + $A;
	}
	first = false;
	identifier.writeCharCode(code);
	}
	return identifier.toString();
	}

	String? getAsVersionNumberString(dynamic value) {
	if (value == null) return null;
	if (value is String) return value;
	if (value is double) return "$value";
	throw "Unexpected value: $value (${value.runtimeType})";
	}