Stop passing experiment flags to parser for features that have shipped.

CHANGELOG.md

@@ -1,7 +1,9 @@
 ## 2.3.3-dev
 
-* Remove support for `inline class` since that syntax has changed.
 * Fix regression in splitting type annotations with library prefixes (#1249).
+* Remove support for `inline class` since that syntax has changed.
+* Add `--enable-experiment` command-line option to enable language experiments.
+  The library API also supports this with `DartFormatter.experimentFlags`.
 
 ## 2.3.2
 

lib/src/cli/format_command.dart

@@ -122,6 +122,8 @@ class FormatCommand extends Command<int> {
     var followLinks = argResults['follow-links'];
     var setExitIfChanged = argResults['set-exit-if-changed'] as bool;
 
+    var experimentFlags = argResults['enable-experiment'] as List<String>;
+
     // If stdin isn't connected to a pipe, then the user is not passing
     // anything to stdin, so let them know they made a mistake.
     if (argResults.rest.isEmpty && stdin.hasTerminal) {
@@ -145,7 +147,8 @@ class FormatCommand extends Command<int> {
         show: show,
         output: output,
         summary: summary,
-        setExitIfChanged: setExitIfChanged);
+        setExitIfChanged: setExitIfChanged,
+        experimentFlags: experimentFlags);
 
     if (argResults.rest.isEmpty) {
       await formatStdin(options, selection, stdinName);

lib/src/cli/formatter_options.dart

@@ -39,6 +39,11 @@ class FormatterOptions {
   /// Sets the exit code to 1 if any changes are made.
   final bool setExitIfChanged;
 
+  /// Flags to enable experimental language features.
+  ///
+  /// See dart.dev/go/experiments for details.
+  final List<String> experimentFlags;
+
   FormatterOptions(
       {this.indent = 0,
       this.pageWidth = 80,
@@ -47,8 +52,10 @@ class FormatterOptions {
       this.show = Show.changed,
       this.output = Output.write,
       this.summary = Summary.none,
-      this.setExitIfChanged = false})
-      : fixes = [...?fixes];
+      this.setExitIfChanged = false,
+      List<String>? experimentFlags})
+      : fixes = [...?fixes],
+        experimentFlags = [...?experimentFlags];
 
   /// Called when [file] is about to be formatted.
   ///

lib/src/cli/options.dart

@@ -101,13 +101,18 @@ void defineOptions(ArgParser parser,
         help: 'Produce machine-readable JSON output.',
         hide: !verbose);
   }
+
   parser.addFlag('follow-links',
       negatable: false,
       help: 'Follow links to files and directories.\n'
           'If unset, links will be ignored.',
       hide: !verbose);
   parser.addFlag('version',
       negatable: false, help: 'Show dart_style version.', hide: !verbose);
+  parser.addMultiOption('enable-experiment',
+      help: 'Enable one or more experimental features.\n'
+          'See dart.dev/go/experiments.',
+      hide: !verbose);
 
   if (verbose) parser.addSeparator('Options when formatting from stdin:');
 

lib/src/dart_formatter.dart

@@ -38,6 +38,11 @@ class DartFormatter {
 
   final Set<StyleFix> fixes;
 
+  /// Flags to enable experimental language features.
+  ///
+  /// See dart.dev/go/experiments for details.
+  final List<String> experimentFlags;
+
   /// Creates a new formatter for Dart code.
   ///
   /// If [lineEnding] is given, that will be used for any newlines in the
@@ -49,10 +54,15 @@ class DartFormatter {
   ///
   /// While formatting, also applies any of the given [fixes].
   DartFormatter(
-      {this.lineEnding, int? pageWidth, int? indent, Iterable<StyleFix>? fixes})
+      {this.lineEnding,
+      int? pageWidth,
+      int? indent,
+      Iterable<StyleFix>? fixes,
+      List<String>? experimentFlags})
       : pageWidth = pageWidth ?? 80,
         indent = indent ?? 0,
-        fixes = {...?fixes};
+        fixes = {...?fixes},
+        experimentFlags = [...?experimentFlags];
 
   /// Formats the given [source] string containing an entire Dart compilation
   /// unit.
@@ -200,19 +210,9 @@ class DartFormatter {
   // happens to parse without error, then we use that result instead.
   ParseStringResult _parse(String source, String? uri,
       {required bool patterns}) {
-    // Enable all features that are enabled by default in the current analyzer
-    // version.
+    var version = patterns ? Version(3, 0, 0) : Version(2, 19, 0);
     var featureSet = FeatureSet.fromEnableFlags2(
-      sdkLanguageVersion: Version(2, 19, 0),
-      flags: [
-        'inline-class',
-        'class-modifiers',
-        if (patterns) 'patterns',
-        'records',
-        'sealed-class',
-        'unnamed-libraries',
-      ],
-    );
+        sdkLanguageVersion: version, flags: experimentFlags);
 
     return parseString(
       content: source,

lib/src/io.dart

@@ -29,7 +29,8 @@ Future<void> formatStdin(
     var formatter = DartFormatter(
         indent: options.indent,
         pageWidth: options.pageWidth,
-        fixes: options.fixes);
+        fixes: options.fixes,
+        experimentFlags: options.experimentFlags);
     try {
       options.beforeFile(null, name);
       var source = SourceCode(input.toString(),
@@ -138,7 +139,8 @@ bool processFile(FormatterOptions options, File file, {String? displayPath}) {
   var formatter = DartFormatter(
       indent: options.indent,
       pageWidth: options.pageWidth,
-      fixes: options.fixes);
+      fixes: options.fixes,
+      experimentFlags: options.experimentFlags);
   try {
     var source = SourceCode(file.readAsStringSync(), uri: file.path);
     options.beforeFile(file, displayPath);

pubspec.yaml

@@ -9,7 +9,7 @@ environment:
   sdk: "^3.0.0"
 
 dependencies:
-  analyzer: '>=5.12.0 <7.0.0'
+  analyzer: '^6.2.0'
   args: ">=1.0.0 <3.0.0"
   path: ^1.0.0
   pub_semver: ">=1.4.4 <3.0.0"
@@ -22,7 +22,7 @@ dev_dependencies:
   # and publishing to npm hasn't been used in a while.
   #  node_preamble: ^1.0.0
   lints: ^2.0.0
-  test: ^1.16.8
+  test: ^1.24.6
   test_descriptor: ^2.0.0
   test_process: ^2.0.0
   yaml: ">=2.0.0 <4.0.0"

test/command_test.dart

@@ -454,6 +454,31 @@ void main() {
     });
   });
 
+  group('--enable-experiment', () {
+    test('passes experiment flags to parser', () async {
+      var process =
+          await runCommand(['--enable-experiment=test-experiment,variance']);
+      process.stdin.writeln('class Writer<in T> {}');
+      await process.stdin.close();
+
+      // The formatter doesn't actually support formatting variance annotations,
+      // but we want to test that the experiment flags are passed all the way
+      // to the parser, so just test that it parses the variance annotation
+      // without errors and then fails to format.
+      expect(await process.stderr.next,
+          'Hit a bug in the formatter when formatting stdin.');
+      expect(await process.stderr.next,
+          'Please report at: github.com/dart-lang/dart_style/issues');
+      expect(await process.stderr.next,
+          'The formatter produced unexpected output. Input was:');
+      expect(await process.stderr.next, 'class Writer<in T> {}');
+      expect(await process.stderr.next, '');
+      expect(await process.stderr.next, 'Which formatted to:');
+      expect(await process.stderr.next, 'class Writer<T> {}');
+      await process.shouldExit(70);
+    });
+  });
+
   group('with no paths', () {
     test('errors on --output=write', () async {
       var process = await runCommand(['--output=write']);