Revert "Use Feature to specify experiments."

This reverts commit fce81082c0.

Reason for revert: I changed my mind, specifically about using something else than `String` in `AnalysisOptionsFileConfig`.

Original change's description:
> Use Feature to specify experiments.
>
> Change-Id: Ide1a58c93cfc4920dff3ab2f52113434de93fff0
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/288162
> Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
> Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

Change-Id: Ib6eb1c04c099e318e935e9761f12bf35f561389f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/288260
Auto-Submit: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>

pkg/analysis_server/test/abstract_context.dart

@@ -3,7 +3,6 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/dart/analysis/analysis_context.dart';
-import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/dart/analysis/session.dart';
 import 'package:analyzer/file_system/file_system.dart';
@@ -45,12 +44,12 @@ class AbstractContextTest with ResourceProviderMixin {
 
   /// Return a list of the experiments that are to be enabled for tests in this
   /// class, an empty list if there are no experiments that should be enabled.
-  List<Feature> get experiments => [
-        Feature.class_modifiers,
-        Feature.macros,
-        Feature.patterns,
-        Feature.records,
-        Feature.sealed_class,
+  List<String> get experiments => [
+        EnableString.class_modifiers,
+        EnableString.macros,
+        EnableString.patterns,
+        EnableString.records,
+        EnableString.sealed_class,
       ];
 
   String get latestLanguageVersion =>
@@ -106,7 +105,7 @@ class AbstractContextTest with ResourceProviderMixin {
 
   /// Create an analysis options file based on the given arguments.
   void createAnalysisOptionsFile({
-    List<Feature>? experiments,
+    List<String>? experiments,
     List<String>? cannotIgnore,
     bool? implicitCasts,
     List<String>? lints,
@@ -120,12 +119,7 @@ class AbstractContextTest with ResourceProviderMixin {
     if (experiments != null) {
       buffer.writeln('  enable-experiment:');
       for (var experiment in experiments) {
-        final experimentalFlag = experiment.experimentalFlag;
-        if (experimentalFlag != null) {
-          buffer.writeln('    - ${experiment.experimentalFlag}');
-        } else {
-          throw ArgumentError('Not experimental: $experiment');
-        }
+        buffer.writeln('    - $experiment');
       }
     }
 

pkg/analysis_server/test/analysis/notification_highlights2_test.dart

@@ -7,6 +7,7 @@ import 'dart:async';
 import 'package:analysis_server/protocol/protocol.dart';
 import 'package:analysis_server/protocol/protocol_constants.dart';
 import 'package:analysis_server/protocol/protocol_generated.dart';
+import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/source/source_range.dart';
 import 'package:analyzer/src/test_utilities/test_code_format.dart';
 import 'package:analyzer_plugin/protocol/protocol_common.dart';
@@ -25,6 +26,12 @@ void main() {
 
 @reflectiveTest
 class AnalysisNotificationHighlightsTest extends HighlightsTestSupport {
+  @override
+  List<String> get experiments => [
+        Feature.inline_class.enableString,
+        ...super.experiments,
+      ];
+
   void assertHighlightText(TestCode testCode, int index, String expected) {
     var actual = _getHighlightText(testCode, index);
     if (actual != expected) {

pkg/analysis_server/test/analysis_server_base.dart

@@ -27,7 +27,7 @@ import 'src/utilities/mock_packages.dart';
 
 /// TODO(scheglov) this is duplicate
 class AnalysisOptionsFileConfig {
-  final List<Feature> experiments;
+  final List<String> experiments;
   final bool implicitCasts;
   final bool implicitDynamic;
   final List<String> lints;
@@ -52,12 +52,7 @@ class AnalysisOptionsFileConfig {
     if (experiments.isNotEmpty) {
       buffer.writeln('  enable-experiment:');
       for (var experiment in experiments) {
-        final experimentalFlag = experiment.experimentalFlag;
-        if (experimentalFlag != null) {
-          buffer.writeln('    - ${experiment.experimentalFlag}');
-        } else {
-          throw ArgumentError('Not experimental: $experiment');
-        }
+        buffer.writeln('    - $experiment');
       }
     }
     buffer.writeln('  language:');
@@ -219,13 +214,15 @@ class ContextResolutionTest with ResourceProviderMixin {
 }
 
 class PubPackageAnalysisServerTest extends ContextResolutionTest {
-  List<Feature> get experiments => [
-        Feature.class_modifiers,
-        Feature.inline_class,
-        Feature.macros,
-        Feature.patterns,
-        Feature.records,
-        Feature.sealed_class,
+  // If experiments are needed,
+  // add `import 'package:analyzer/dart/analysis/features.dart';`
+  // and list the necessary experiments here.
+  List<String> get experiments => [
+        Feature.class_modifiers.enableString,
+        Feature.macros.enableString,
+        Feature.patterns.enableString,
+        Feature.records.enableString,
+        Feature.sealed_class.enableString,
       ];
 
   /// The path that is not in [workspaceRootPath], contains external packages.

pkg/analysis_server/test/services/completion/dart/imported_reference_contributor_test.dart

@@ -11,6 +11,7 @@ import 'package:analysis_server/src/provisional/completion/dart/completion_dart.
 import 'package:analysis_server/src/services/completion/dart/completion_manager.dart';
 import 'package:analysis_server/src/services/completion/dart/imported_reference_contributor.dart';
 import 'package:analysis_server/src/services/completion/dart/suggestion_builder.dart';
+import 'package:analyzer/src/dart/analysis/experiments.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ -2393,6 +2394,7 @@ class B extends A {
   }
 
   Future<void> test_function_parameters_nnbd_required() async {
+    createAnalysisOptionsFile(experiments: [EnableString.non_nullable]);
     resolveSource('$testPackageLibPath/a.dart', '''
 void m(int? nullable, int nonNullable) {}
 ''');
@@ -2415,6 +2417,7 @@ void f() {^}
   }
 
   Future<void> test_function_parameters_nnbd_required_into_legacy() async {
+    createAnalysisOptionsFile(experiments: [EnableString.non_nullable]);
     resolveSource('$testPackageLibPath/a.dart', '''
 void m(int? nullable, int nonNullable) {}
 ''');
@@ -2438,6 +2441,7 @@ void f() {^}
   }
 
   Future<void> test_function_parameters_nnbd_required_legacy() async {
+    createAnalysisOptionsFile(experiments: [EnableString.non_nullable]);
     resolveSource('$testPackageLibPath/a.dart', '''
 // @dart = 2.8
 void m(int param) {}

pkg/analysis_server/test/src/services/correction/fix/fix_processor.dart

@@ -7,7 +7,6 @@ import 'package:analysis_server/src/services/correction/bulk_fix_processor.dart'
 import 'package:analysis_server/src/services/correction/change_workspace.dart';
 import 'package:analysis_server/src/services/correction/fix.dart';
 import 'package:analysis_server/src/services/correction/fix_internal.dart';
-import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/src/dart/analysis/byte_store.dart';
 import 'package:analyzer/src/dart/error/lint_codes.dart';
@@ -88,7 +87,7 @@ abstract class BulkFixProcessorTest extends AbstractSingleUnitTest {
   late BulkFixProcessor processor;
 
   @override
-  List<Feature> get experiments => const [];
+  List<String> get experiments => const [];
 
   /// Return the lint code being tested.
   String? get lintCode => null;

pkg/analysis_server/test/src/services/correction/fix/remove_break_test.dart

@@ -4,7 +4,6 @@
 
 import 'package:analysis_server/src/services/correction/fix.dart';
 import 'package:analysis_server/src/services/linter/lint_names.dart';
-import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ -20,7 +19,7 @@ void main() {
 @reflectiveTest
 class RemoveBreakBulkTest extends BulkFixProcessorTest {
   @override
-  List<Feature> get experiments => [Feature.patterns, Feature.records];
+  List<String> get experiments => ['patterns', 'records'];
 
   @override
   String get lintCode => LintNames.unnecessary_breaks;
@@ -54,7 +53,7 @@ f() {
 @reflectiveTest
 class RemoveBreakTest extends FixProcessorLintTest {
   @override
-  List<Feature> get experiments => [Feature.patterns, Feature.records];
+  List<String> get experiments => ['patterns', 'records'];
 
   @override
   FixKind get kind => DartFixKind.REMOVE_BREAK;

pkg/analysis_server/test/src/services/correction/fix/update_sdk_constraints_test.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analysis_server/src/services/correction/fix.dart';
+import 'package:analyzer/src/dart/analysis/experiments.dart';
 import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ -63,6 +64,8 @@ const c = a == null;
   }
 
   Future<void> test_gtGtGtOperator() async {
+    writeTestPackageConfig(languageVersion: latestLanguageVersion);
+    createAnalysisOptionsFile(experiments: [EnableString.triple_shift]);
     await testUpdate(content: '''
 class C {
   C operator >>>(C other) => this;

pkg/analysis_server/test/src/utilities/selection_test.dart

@@ -5,6 +5,7 @@
 import 'package:analysis_server/src/utilities/selection.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/source/source_range.dart';
+import 'package:analyzer/src/dart/analysis/experiments.dart';
 import 'package:analyzer/src/test_utilities/test_code_format.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
@@ -20,6 +21,12 @@ void main() {
 
 @reflectiveTest
 class SelectionTest extends AbstractSingleUnitTest {
+  @override
+  List<String> get experiments => [
+        ...super.experiments,
+        EnableString.patterns,
+      ];
+
   Future<void> assertMembers(
       {String prefix = '', required String postfix}) async {
     var nodes = await nodesInRange('''