Enable the unnamed-libraries experiment by default in 2.19.0

TEST=tests/language/library/unnamed_library_test.dart

Bug: https://github.com/dart-lang/language/issues/1073
Change-Id: I1c7fa7b4ee4450e344a7613525765e4ab590cc8c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/265381
Reviewed-by: Alexander Aprelev <aam@google.com>
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Michael Thomsen <mit@google.com>
Reviewed-by: Leaf Petersen <leafp@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>

CHANGELOG.md

@@ -54,6 +54,13 @@
 [#49687]: https://github.com/dart-lang/sdk/issues/49687
 [#2020]: https://github.com/dart-lang/language/issues/2020
 
+- Add support for **unnamed libraries**. Dart language 2.19 allows a library
+  directive to be written without a name (`library;`). A library directive can
+  be used for library-level annotations (such as `@deprecated`) and for
+  library-level documentation comments, and with this new feature, you don't
+  have to provide a unique name for each library directive. Instead, a name can
+  simply be omitted.
+
 ### Libraries
 
 #### `dart:core`

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

@@ -85,7 +85,7 @@ import 'package:analyzer/src/util/performance/operation_performance.dart';
 /// TODO(scheglov) Clean up the list of implicitly analyzed files.
 class AnalysisDriver implements AnalysisDriverGeneric {
   /// The version of data format, should be incremented on every format change.
-  static const int DATA_VERSION = 243;
+  static const int DATA_VERSION = 244;
 
   /// The number of exception contexts allowed to write. Once this field is
   /// zero, we stop writing any new exception contexts in this process.

pkg/analyzer/lib/src/dart/analysis/experiments.g.dart

@@ -344,7 +344,7 @@ class ExperimentalFeatures {
     isExpired: IsExpired.unnamed_libraries,
     documentation: 'Unnamed libraries',
     experimentalReleaseVersion: null,
-    releaseVersion: null,
+    releaseVersion: Version.parse('2.19.0'),
   );
 
   static final value_class = ExperimentalFeature(
@@ -435,7 +435,7 @@ class IsEnabledByDefault {
   static const bool triple_shift = true;
 
   /// Default state of the experiment "unnamed-libraries"
-  static const bool unnamed_libraries = false;
+  static const bool unnamed_libraries = true;
 
   /// Default state of the experiment "value-class"
   static const bool value_class = false;

pkg/analyzer/test/generated/error_parser_test.dart

@@ -2833,13 +2833,13 @@ main() {
 
   void test_unnamedLibraryDirective() {
     CompilationUnit unit = parseCompilationUnit("library;",
+        featureSet: FeatureSets.language_2_18,
         errors: [expectedError(ParserErrorCode.EXPERIMENT_NOT_ENABLED, 0, 7)]);
     expect(unit, isNotNull);
   }
 
   void test_unnamedLibraryDirective_enabled() {
-    CompilationUnit unit = parseCompilationUnit("library;",
-        featureSet: FeatureSets.latestWithExperiments);
+    CompilationUnit unit = parseCompilationUnit("library;");
     expect(unit, isNotNull);
   }
 

pkg/analyzer/test/util/feature_sets.dart

@@ -32,6 +32,11 @@ class FeatureSets {
     flags: [],
   );
 
+  static final FeatureSet language_2_18 = FeatureSet.fromEnableFlags2(
+    sdkLanguageVersion: Version.parse('2.18.0'),
+    flags: [],
+  );
+
   static final FeatureSet language_2_19 = FeatureSet.fromEnableFlags2(
     sdkLanguageVersion: Version.parse('2.19.0'),
     flags: [],

pkg/front_end/lib/src/api_prototype/experimental_flags_generated.dart

@@ -229,7 +229,7 @@ class ExperimentalFlag {
 
   static const ExperimentalFlag unnamedLibraries = const ExperimentalFlag(
       name: 'unnamed-libraries',
-      isEnabledByDefault: false,
+      isEnabledByDefault: true,
       isExpired: false,
       enabledVersion: const Version(2, 19),
       experimentEnabledVersion: const Version(2, 19),

runtime/vm/experimental_features.cc

@@ -18,7 +18,7 @@ namespace dart {
 
 bool GetExperimentalFeatureDefault(ExperimentalFeature feature) {
   constexpr bool kFeatureValues[] = {
-      true, true, true, true, true, true, true,
+      true, true, true, true, true, true, true, true,
       true, true, true, true, true, true, true,
   };
   ASSERT(static_cast<size_t>(feature) < ARRAY_SIZE(kFeatureValues));
@@ -27,6 +27,7 @@ bool GetExperimentalFeatureDefault(ExperimentalFeature feature) {
 
 const char* GetExperimentalFeatureName(ExperimentalFeature feature) {
   constexpr const char* kFeatureNames[] = {
+      "unnamed-libraries",
       "nonfunction-type-aliases",
       "non-nullable",
       "extension-methods",

runtime/vm/experimental_features.h

@@ -14,6 +14,7 @@
 namespace dart {
 
 enum class ExperimentalFeature {
+  unnamed_libraries,
   nonfunction_type_aliases,
   non_nullable,
   extension_methods,

tests/language/library/unnamed_library_test.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code as governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// SharedOptions=--enable-experiment=unnamed-libraries
-
 /// Doc comment.
 @deprecated
 library;

tools/experimental_features.yaml

@@ -135,9 +135,6 @@ features:
   patterns:
     help: "Patterns"
 
-  unnamed-libraries:
-    help: "Unnamed libraries"
-
 # Experiment flag only used for testing.
   test-experiment:
     help: >-
@@ -296,3 +293,10 @@ features:
       void main() {
         test([1, 2, 3]);
       }
+
+  unnamed-libraries:
+    help: "Unnamed libraries"
+    enabledIn: '2.19.0'
+    validation: |
+      library;
+      void main() => print('feature enabled');