[dartdev] add --enable-experiment support to 'dart test'

Bug: #42339
Change-Id: Ic50493b1e9af5ae626358bee1c0c145f58bb7c2c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/153323
Auto-Submit: Devon Carew <devoncarew@google.com>
Commit-Queue: Jaime Wren <jwren@google.com>
Reviewed-by: Jaime Wren <jwren@google.com>

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

@@ -8,6 +8,7 @@ import 'dart:io';
 import 'package:args/args.dart';
 
 import '../core.dart';
+import '../experiments.dart';
 import '../sdk.dart';
 
 class TestCommand extends DartdevCommand<int> {
@@ -42,9 +43,15 @@ class TestCommand extends DartdevCommand<int> {
   @override
   FutureOr<int> run() async {
     final command = sdk.pub;
-    final args = argResults.arguments.toList();
-
-    args.insertAll(0, ['run', 'test']);
+    final testArgs = argResults.arguments.toList();
+
+    final args = [
+      'run',
+      if (wereExperimentsSpecified)
+        '--$experimentFlagName=${specifiedExperiments.join(',')}',
+      'test',
+      ...testArgs,
+    ];
 
     log.trace('$command ${args.join(' ')}');
 

pkg/dartdev/test/commands/test_test.dart

@@ -65,4 +65,26 @@ void main() {
     expect(result.stdout, contains('All tests passed!'));
     expect(result.stderr, isEmpty);
   }, skip: 'https://github.com/dart-lang/sdk/issues/40854');
+
+  test('--enable-experiment', () {
+    p = project(mainSrc: 'int get foo => 1;\n');
+    p.file('test/foo_test.dart', '''
+import 'package:test/test.dart';
+
+void main() {
+  test('', () {
+    int a;
+    a = null;
+    print('a is \$a.');
+  });
+}
+''');
+
+    var result = p.runSync('pub', ['get', '--offline']);
+    expect(result.exitCode, 0);
+
+    result = p.runSync('--enable-experiment=non-nullable',
+        ['test', '--no-color', '--reporter', 'expanded']);
+    expect(result.exitCode, 1);
+  }, skip: 'https://github.com/dart-lang/sdk/issues/40854');
 }