Add the enable-experiment flag back to DAS

Bug: https://github.com/dart-lang/sdk/issues/48960
Change-Id: I6576f45e63e28902986db844df49a06a71385704
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/245202
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>

pkg/analysis_server/lib/src/analysis_server.dart

@@ -874,6 +874,10 @@ class AnalysisServerOptions {
 
   /// If set, this string will be reported as the protocol version.
   String? reportProtocolVersion;
+
+  /// Experiments which have been enabled (or disabled) via the
+  /// `--enable-experiment` command-line option.
+  List<String> enabledExperiments = [];
 }
 
 class ServerContextManagerCallbacks extends ContextManagerCallbacks {

pkg/analysis_server/lib/src/analysis_server_abstract.dart

@@ -228,6 +228,7 @@ abstract class AbstractAnalysisServer {
       resourceProvider,
       sdkManager,
       options.packagesFile,
+      options.enabledExperiments,
       byteStore,
       fileContentCache,
       analysisPerformanceLogger,

pkg/analysis_server/lib/src/context_manager.dart

@@ -7,6 +7,7 @@ import 'dart:collection';
 
 import 'package:analysis_server/src/lsp/handlers/handlers.dart';
 import 'package:analysis_server/src/services/correction/fix/data_driven/transform_set_parser.dart';
+import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/instrumentation/instrumentation.dart';
@@ -206,6 +207,10 @@ class ContextManagerImpl implements ContextManager {
   /// clean up when we destroy a context.
   final bazelWatchedPathsPerFolder = <Folder, _BazelWatchedFiles>{};
 
+  /// Experiments which have been enabled (or disabled) via the
+  /// `--enable-experiment` command-line option.
+  final List<String> _enabledExperiments;
+
   /// Information about the current/last queued context rebuild.
   ///
   /// This is used when a new build is requested to cancel any in-progress
@@ -216,6 +221,7 @@ class ContextManagerImpl implements ContextManager {
       this.resourceProvider,
       this.sdkManager,
       this.packagesFile,
+      this._enabledExperiments,
       this._byteStore,
       this._fileContentCache,
       this._performanceLog,
@@ -456,6 +462,18 @@ class ContextManagerImpl implements ContextManager {
           sdkPath: sdkManager.defaultSdkDirectory,
           packagesFile: packagesFile,
           fileContentCache: _fileContentCache,
+          updateAnalysisOptions2: ({
+            required analysisOptions,
+            required contextRoot,
+            required sdk,
+          }) {
+            if (_enabledExperiments.isNotEmpty) {
+              analysisOptions.contextFeatures = FeatureSet.fromEnableFlags2(
+                sdkLanguageVersion: sdk.languageVersion,
+                flags: _enabledExperiments,
+              );
+            }
+          },
         );
 
         for (var analysisContext in collection.contexts) {

pkg/analysis_server/lib/src/server/driver.dart

@@ -65,6 +65,9 @@ class Driver implements ServerStarter {
   static const String DISABLE_SERVER_FEATURE_SEARCH =
       'disable-server-feature-search';
 
+  /// The name of the multi-option to enable one or more experiments.
+  static const String ENABLE_EXPERIMENT = 'enable-experiment';
+
   /// The name of the option used to print usage information.
   static const String HELP_OPTION = 'help';
 
@@ -170,6 +173,11 @@ class Driver implements ServerStarter {
     analysisServerOptions.reportProtocolVersion =
         results[REPORT_PROTOCOL_VERSION] as String?;
 
+    analysisServerOptions.enabledExperiments =
+        results.wasParsed(ENABLE_EXPERIMENT)
+            ? results[ENABLE_EXPERIMENT] as List<String>
+            : <String>[];
+
     // Read in any per-SDK overrides specified in <sdk>/config/settings.json.
     var sdkConfig = SdkConfiguration.readFromSdk();
     analysisServerOptions.configurationOverrides = sdkConfig;
@@ -689,6 +697,13 @@ class Driver implements ServerStarter {
       help: 'The path to the package resolution configuration file, which '
           'supplies a mapping of package names\ninto paths.',
     );
+    parser.addMultiOption(
+      ENABLE_EXPERIMENT,
+      valueHelp: 'experiment',
+      help: 'Enable one or more experimental features '
+          '(see dart.dev/go/experiments).',
+      hide: true,
+    );
 
     parser.addOption(
       SERVER_PROTOCOL,
@@ -784,8 +799,6 @@ class Driver implements ServerStarter {
     parser.addFlag('dartpad', hide: true);
     // Removed 11/15/2020.
     parser.addFlag('enable-completion-model', hide: true);
-    // Removed 10/30/2020.
-    parser.addMultiOption('enable-experiment', hide: true);
     // Removed 9/23/2020.
     parser.addFlag('enable-instrumentation', hide: true);
     // Removed 11/12/2020.

pkg/analyzer/lib/src/dart/analysis/analysis_context_collection.dart

@@ -6,6 +6,7 @@ import 'package:_fe_analyzer_shared/src/macros/executor/multi_executor.dart'
     as macro;
 import 'package:analyzer/dart/analysis/analysis_context_collection.dart';
 import 'package:analyzer/dart/analysis/context_locator.dart';
+import 'package:analyzer/dart/analysis/context_root.dart';
 import 'package:analyzer/dart/analysis/declared_variables.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/physical_file_system.dart';
@@ -16,6 +17,7 @@ import 'package:analyzer/src/dart/analysis/driver_based_analysis_context.dart';
 import 'package:analyzer/src/dart/analysis/file_content_cache.dart';
 import 'package:analyzer/src/dart/analysis/performance_logger.dart';
 import 'package:analyzer/src/generated/engine.dart' show AnalysisOptionsImpl;
+import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/summary2/kernel_compilation_service.dart';
 import 'package:analyzer/src/summary2/macro.dart';
 import 'package:analyzer/src/util/sdk.dart';
@@ -53,7 +55,15 @@ class AnalysisContextCollectionImpl implements AnalysisContextCollection {
     String? sdkSummaryPath,
     AnalysisDriverScheduler? scheduler,
     FileContentCache? fileContentCache,
-    void Function(AnalysisOptionsImpl)? updateAnalysisOptions,
+    @Deprecated('Use updateAnalysisOptions2, which must be a function that '
+        'accepts a second parameter')
+        void Function(AnalysisOptionsImpl)? updateAnalysisOptions,
+    void Function({
+      required AnalysisOptionsImpl analysisOptions,
+      required ContextRoot contextRoot,
+      required DartSdk sdk,
+    })?
+        updateAnalysisOptions2,
   }) : resourceProvider =
             resourceProvider ?? PhysicalResourceProvider.INSTANCE {
     sdkPath ??= getSdkPath();
@@ -61,6 +71,12 @@ class AnalysisContextCollectionImpl implements AnalysisContextCollection {
     _throwIfAnyNotAbsoluteNormalizedPath(includedPaths);
     _throwIfNotAbsoluteNormalizedPath(sdkPath);
 
+    if (updateAnalysisOptions != null && updateAnalysisOptions2 != null) {
+      throw ArgumentError(
+          'Either updateAnalysisOptions or updateAnalysisOptions2 must be '
+          'given, but not both.');
+    }
+
     var contextLocator = ContextLocator(
       resourceProvider: this.resourceProvider,
     );
@@ -86,7 +102,9 @@ class AnalysisContextCollectionImpl implements AnalysisContextCollection {
         sdkPath: sdkPath,
         sdkSummaryPath: sdkSummaryPath,
         scheduler: scheduler,
+        // ignore: deprecated_member_use_from_same_package
         updateAnalysisOptions: updateAnalysisOptions,
+        updateAnalysisOptions2: updateAnalysisOptions2,
         fileContentCache: fileContentCache,
         macroKernelBuilder: macroKernelBuilder,
         macroExecutor: macroExecutor,

pkg/analyzer/lib/src/dart/analysis/context_builder.dart

@@ -59,7 +59,14 @@ class ContextBuilderImpl implements ContextBuilder {
     AnalysisDriverScheduler? scheduler,
     String? sdkPath,
     String? sdkSummaryPath,
-    void Function(AnalysisOptionsImpl)? updateAnalysisOptions,
+    @Deprecated('Use updateAnalysisOptions2')
+        void Function(AnalysisOptionsImpl)? updateAnalysisOptions,
+    void Function({
+      required AnalysisOptionsImpl analysisOptions,
+      required ContextRoot contextRoot,
+      required DartSdk sdk,
+    })?
+        updateAnalysisOptions2,
     FileContentCache? fileContentCache,
     MacroKernelBuilder? macroKernelBuilder,
     macro.MultiMacroExecutor? macroExecutor,
@@ -67,6 +74,11 @@ class ContextBuilderImpl implements ContextBuilder {
     // TODO(scheglov) Remove this, and make `sdkPath` required.
     sdkPath ??= getSdkPath();
     ArgumentError.checkNotNull(sdkPath, 'sdkPath');
+    if (updateAnalysisOptions != null && updateAnalysisOptions2 != null) {
+      throw ArgumentError(
+          'Either updateAnalysisOptions or updateAnalysisOptions2 must be '
+          'given, but not both.');
+    }
 
     byteStore ??= MemoryByteStore();
     performanceLog ??= PerformanceLog(StringBuffer());
@@ -104,6 +116,12 @@ class ContextBuilderImpl implements ContextBuilder {
     var options = _getAnalysisOptions(contextRoot, sourceFactory);
     if (updateAnalysisOptions != null) {
       updateAnalysisOptions(options);
+    } else if (updateAnalysisOptions2 != null) {
+      updateAnalysisOptions2(
+        analysisOptions: options,
+        contextRoot: contextRoot,
+        sdk: sdk,
+      );
     }
 
     final analysisContext =

pkg/analyzer/lib/src/lint/analysis.dart

@@ -116,7 +116,11 @@ class LintDriver {
       sdkPath: options.dartSdkPath,
       includedPaths:
           files.map((file) => _absoluteNormalizedPath(file.path)).toList(),
-      updateAnalysisOptions: (analysisOptions) {
+      updateAnalysisOptions2: ({
+        required analysisOptions,
+        required contextRoot,
+        required sdk,
+      }) {
         _updateAnalyzerOptions(analysisOptions, options);
       },
     );

pkg/analyzer/test/src/dart/resolution/context_collection_resolution.dart

@@ -4,6 +4,7 @@
 
 import 'package:analyzer/dart/analysis/analysis_context.dart';
 import 'package:analyzer/dart/analysis/analysis_context_collection.dart';
+import 'package:analyzer/dart/analysis/context_root.dart';
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/dart/analysis/analysis_context_collection.dart';
@@ -12,6 +13,7 @@ import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer/src/dart/analysis/driver_based_analysis_context.dart';
 import 'package:analyzer/src/dart/analysis/experiments.dart';
 import 'package:analyzer/src/generated/engine.dart' show AnalysisOptionsImpl;
+import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/summary2/kernel_compilation_service.dart';
 import 'package:analyzer/src/test_utilities/mock_packages.dart';
 import 'package:analyzer/src/test_utilities/mock_sdk.dart';
@@ -234,7 +236,11 @@ abstract class ContextResolutionTest
 
   /// Override this method to update [analysisOptions] for every context root,
   /// the default or already updated with `analysis_options.yaml` file.
-  void updateAnalysisOptions(AnalysisOptionsImpl analysisOptions) {}
+  void updateAnalysisOptions({
+    required AnalysisOptionsImpl analysisOptions,
+    required ContextRoot contextRoot,
+    required DartSdk sdk,
+  }) {}
 
   /// Call this method if the test needs to use the empty byte store, without
   /// any information cached.
@@ -267,7 +273,7 @@ abstract class ContextResolutionTest
       sdkPath: sdkRoot.path,
       sdkSummaryPath: sdkSummaryFile?.path,
       librarySummaryPaths: librarySummaryFiles?.map((e) => e.path).toList(),
-      updateAnalysisOptions: updateAnalysisOptions,
+      updateAnalysisOptions2: updateAnalysisOptions,
     );
 
     verifyCreatedCollection();

pkg/analyzer/test/src/diagnostics/illegal_language_version_override_test.dart

@@ -2,8 +2,10 @@
 // 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 'package:analyzer/dart/analysis/context_root.dart';
 import 'package:analyzer/src/error/codes.dart';
 import 'package:analyzer/src/generated/engine.dart';
+import 'package:analyzer/src/generated/sdk.dart';
 import 'package:pub_semver/src/version_constraint.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ -72,7 +74,11 @@ void f() {}
   }
 
   @override
-  void updateAnalysisOptions(AnalysisOptionsImpl analysisOptions) {
+  void updateAnalysisOptions({
+    required AnalysisOptionsImpl analysisOptions,
+    required ContextRoot contextRoot,
+    required DartSdk sdk,
+  }) {
     analysisOptions.sourceLanguageConstraint =
         VersionConstraint.parse('>= 2.12.0');
   }

pkg/analyzer_cli/lib/src/driver.dart

@@ -4,6 +4,7 @@
 
 import 'dart:io' as io;
 
+import 'package:analyzer/dart/analysis/context_root.dart';
 import 'package:analyzer/dart/sdk/build_sdk_summary.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/error/listener.dart';
@@ -17,6 +18,7 @@ import 'package:analyzer/src/dart/analysis/file_content_cache.dart';
 import 'package:analyzer/src/dart/analysis/file_state.dart';
 import 'package:analyzer/src/dart/analysis/results.dart';
 import 'package:analyzer/src/generated/engine.dart';
+import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/lint/linter.dart';
 import 'package:analyzer/src/lint/pub.dart';
@@ -553,7 +555,7 @@ class _AnalysisContextProvider {
       packagesFile: _commandLineOptions!.defaultPackagesPath,
       resourceProvider: _resourceProvider,
       sdkPath: _commandLineOptions!.dartSdkPath,
-      updateAnalysisOptions: _updateAnalysisOptions,
+      updateAnalysisOptions2: _updateAnalysisOptions,
       fileContentCache: _fileContentCache,
     );
 
@@ -578,7 +580,11 @@ class _AnalysisContextProvider {
     _analysisContext = _collection!.contextFor(path);
   }
 
-  void _updateAnalysisOptions(AnalysisOptionsImpl analysisOptions) {
+  void _updateAnalysisOptions({
+    required AnalysisOptionsImpl analysisOptions,
+    required ContextRoot contextRoot,
+    required DartSdk sdk,
+  }) {
     _commandLineOptions!.updateAnalysisOptions(analysisOptions);
   }
 }

pkg/dartdev/lib/src/analysis_server.dart

@@ -17,6 +17,7 @@ import 'package:args/args.dart';
 import 'package:path/path.dart' as path;
 
 import 'core.dart';
+import 'experiments.dart';
 import 'sdk.dart';
 import 'utils.dart';
 
@@ -33,6 +34,7 @@ class AnalysisServer {
     this.cacheDirectoryPath,
     required this.commandName,
     required this.argResults,
+    this.enabledExperiments = const [],
   });
 
   final String? cacheDirectoryPath;
@@ -41,6 +43,7 @@ class AnalysisServer {
   final List<FileSystemEntity> analysisRoots;
   final String commandName;
   final ArgResults? argResults;
+  final List<String> enabledExperiments;
 
   Process? _process;
 
@@ -103,6 +106,8 @@ class AnalysisServer {
       sdkPath.path,
       if (cacheDirectoryPath != null) '--cache=$cacheDirectoryPath',
       if (packagesFile != null) '--packages=${packagesFile!.path}',
+      if (enabledExperiments.isNotEmpty)
+        '--$experimentFlagName=${enabledExperiments.join(',')}'
     ];
 
     final process = await startDartProcess(sdk, command);

pkg/dartdev/lib/src/commands/analyze.dart

@@ -6,12 +6,14 @@ import 'dart:async';
 import 'dart:convert';
 import 'dart:io' as io;
 
+import 'package:analyzer/src/dart/analysis/experiments.dart';
 import 'package:cli_util/cli_logging.dart';
 import 'package:meta/meta.dart';
 import 'package:path/path.dart' as path;
 
 import '../analysis_server.dart';
 import '../core.dart';
+import '../experiments.dart';
 import '../sdk.dart';
 import '../utils.dart';
 
@@ -80,7 +82,8 @@ class AnalyzeCommand extends DartdevCommand {
         valueHelp: 'path',
         help: 'The path to the Dart SDK.',
         hide: !verbose,
-      );
+      )
+      ..addExperimentalFlags();
   }
 
   @override
@@ -110,12 +113,6 @@ class AnalyzeCommand extends DartdevCommand {
     final machineFormat = args['format'] == 'machine';
     final jsonFormat = args['format'] == 'json';
 
-    final targetsNames =
-        targets.map((entity) => path.basename(entity.path)).join(', ');
-
-    var progress =
-        machineFormat ? null : log.progress('Analyzing $targetsNames');
-
     io.Directory sdkPath;
     if (args.wasParsed('sdk-path')) {
       sdkPath = io.Directory(args['sdk-path'] as String);
@@ -137,6 +134,26 @@ class AnalyzeCommand extends DartdevCommand {
       sdkPath = io.Directory(sdk.sdkPath);
     }
 
+    final experimentNames = {
+      for (var experiment in args.enabledExperiments)
+        if (experiment.startsWith('no-'))
+          experiment.substring(3)
+        else
+          experiment
+    };
+    final unknownExperiments =
+        experimentNames.difference(ExperimentStatus.knownFeatures.keys.toSet());
+    if (unknownExperiments.isNotEmpty) {
+      final unknownExperimentsText =
+          unknownExperiments.map((e) => "'$e'").join(', ');
+      usageException('Unknown experiment(s): $unknownExperimentsText');
+    }
+
+    final targetsNames =
+        targets.map((entity) => path.basename(entity.path)).join(', ');
+    final progress =
+        machineFormat ? null : log.progress('Analyzing $targetsNames');
+
     final AnalysisServer server = AnalysisServer(
       _packagesFile(),
       sdkPath,
@@ -144,6 +161,7 @@ class AnalyzeCommand extends DartdevCommand {
       cacheDirectoryPath: args['cache'],
       commandName: 'analyze',
       argResults: args,
+      enabledExperiments: args.enabledExperiments,
     );
 
     server.onErrors.listen((FileAnalysisErrors fileErrors) {

pkg/dartdev/lib/src/commands/compile.dart

@@ -123,8 +123,8 @@ class CompileSnapshotCommand extends CompileSubcommandCommand {
         help: defineOption.help,
         abbr: defineOption.abbr,
         valueHelp: defineOption.valueHelp,
-      );
-    addExperimentalFlags(argParser, verbose);
+      )
+      ..addExperimentalFlags(verbose: verbose);
   }
 
   @override
@@ -255,9 +255,8 @@ Remove debugging information from the output and save it separately to the speci
         help: 'Pass additional options to gen_snapshot.',
         hide: true,
         valueHelp: 'opt1,opt2,...',
-      );
-
-    addExperimentalFlags(argParser, verbose);
+      )
+      ..addExperimentalFlags(verbose: verbose);
   }
 
   @override

pkg/dartdev/lib/src/commands/run.dart

@@ -179,15 +179,15 @@ class RunCommand extends DartdevCommand {
             hide: !verbose,
             help:
                 'Use the Dart Development Service (DDS) for enhanced debugging '
-                'functionality. Note: Disabling DDS may break some functionality '
-                'in IDEs and other tooling.',
+                'functionality. Note: Disabling DDS may break some '
+                'functionality in IDEs and other tooling.',
             defaultsTo: true)
         ..addFlag(
           'debug-dds',
           hide: true,
         );
     }
-    addExperimentalFlags(argParser, verbose);
+    argParser.addExperimentalFlags(verbose: verbose);
   }
 
   @override

pkg/dartdev/lib/src/experiments.dart

@@ -9,53 +9,53 @@ import 'package:collection/collection.dart' show IterableExtension;
 const experimentFlagName = 'enable-experiment';
 
 /// Return a list of all the non-expired Dart experiments.
-List<ExperimentalFeature> get experimentalFeatures {
-  List<ExperimentalFeature> features = ExperimentStatus.knownFeatures.values
-      .where((feature) => !feature.isExpired)
-      .toList();
-  features.sort((a, b) => a.enableString.compareTo(b.enableString));
-  return features;
-}
+List<ExperimentalFeature> get experimentalFeatures =>
+    ExperimentStatus.knownFeatures.values
+        .where((feature) => !feature.isExpired)
+        .toList()
+      ..sort((a, b) => a.enableString.compareTo(b.enableString));
 
-void addExperimentalFlags(ArgParser argParser, bool verbose) {
-  List<ExperimentalFeature> features = experimentalFeatures;
+extension ArgParserExtensions on ArgParser {
+  void addExperimentalFlags({bool verbose = false}) {
+    List<ExperimentalFeature> features = experimentalFeatures;
 
-  Map<String, String> allowedHelp = {};
-  for (ExperimentalFeature feature in features) {
-    String suffix =
-        feature.isEnabledByDefault ? ' (no-op - enabled by default)' : '';
-    allowedHelp[feature.enableString] = '${feature.documentation}$suffix';
+    Map<String, String> allowedHelp = {};
+    for (ExperimentalFeature feature in features) {
+      String suffix =
+          feature.isEnabledByDefault ? ' (no-op - enabled by default)' : '';
+      allowedHelp[feature.enableString] = '${feature.documentation}$suffix';
+    }
+
+    addMultiOption(
+      experimentFlagName,
+      valueHelp: 'experiment',
+      allowedHelp: verbose ? allowedHelp : null,
+      help: 'Enable one or more experimental features '
+          '(see dart.dev/go/experiments).',
+      hide: !verbose,
+    );
   }
-
-  argParser.addMultiOption(
-    experimentFlagName,
-    valueHelp: 'experiment',
-    allowedHelp: verbose ? allowedHelp : null,
-    help: 'Enable one or more experimental features '
-        '(see dart.dev/go/experiments).',
-    hide: !verbose,
-  );
 }
 
-extension EnabledExperimentsArg on ArgResults {
+extension ArgResultsExtensions on ArgResults {
   List<String> get enabledExperiments {
     List<String> enabledExperiments = [];
     // Check to see if the ArgParser which generated this result accepts
-    // --enable-experiment as an option. If so, return the result if it was
+    // `--enable-experiment` as an option. If so, return the result if it was
     // provided.
     if (options.contains(experimentFlagName)) {
       if (wasParsed(experimentFlagName)) {
-        enabledExperiments = this[experimentFlagName];
+        enabledExperiments = this[experimentFlagName] as List<String>;
       }
     } else {
-      // In the case where a command uses ArgParser.allowAnything() as its
-      // parser the valid set of options for the command isn't specified and
+      // In the case where a command uses `ArgParser.allowAnything()` as its
+      // parser, the valid set of options for the command isn't specified and
       // isn't enforced. Instead, we have to manually parse the arguments to
-      // look for --enable-experiment=. Currently, this path is only taken for
-      // the pub and test commands, as well as when we are trying to send
+      // look for `--enable-experiment=`. Currently, this path is only taken for
+      // the `pub` and `test` commands, as well as when we are trying to send
       // analytics.
-      final String? experiments = arguments.firstWhereOrNull(
-        (e) => e.startsWith('--enable-experiment='),
+      final experiments = arguments.firstWhereOrNull(
+        (e) => e.startsWith('--$experimentFlagName='),
       );
       if (experiments == null) {
         return [];
@@ -63,7 +63,7 @@ extension EnabledExperimentsArg on ArgResults {
       enabledExperiments = experiments.split('=')[1].split(',');
     }
 
-    for (ExperimentalFeature feature in experimentalFeatures) {
+    for (final feature in experimentalFeatures) {
       // We allow default true flags, but complain when they are passed in.
       if (feature.isEnabledByDefault &&
           enabledExperiments.contains(feature.enableString)) {

pkg/dartdev/test/commands/analyze_test.dart

@@ -421,6 +421,26 @@ void defineAnalyze() {
     expect(result.stderr, isEmpty);
   });
 
+  test('--enable-experiment', () async {
+    p = project(mainSrc: 'final x = List.filled(growable: true, 7, "");');
+    var result = await p
+        .run(['analyze', '--enable-experiment=no-named-arguments-anywhere']);
+
+    expect(result.exitCode, 3);
+    expect(result.stdout,
+        contains('Positional arguments must occur before named arguments.'));
+    expect(result.stderr, isEmpty);
+  });
+
+  test('--enable-experiment with a bad experiment', () async {
+    p = project();
+    var result = await p.run(['analyze', '--enable-experiment=bad']);
+
+    expect(result.exitCode, 64);
+    expect(result.stdout, isEmpty);
+    expect(result.stderr, contains("Unknown experiment(s): 'bad'"));
+  });
+
   test('--verbose', () async {
     p = project(mainSrc: '''
 int f() {