[vm] Disable dart:cli waitFor by default

Per breaking change request we are now disabling
waitFor by default.

Users can still enable it by passing the flag:

     --enabled-deprecated-wait-for

Issue https://github.com/dart-lang/sdk/issues/52121

TEST=standalone/io/wait_for_deprecation_test

CoreLibraryReviewExempt: standalone VM only change
Change-Id: Ied78f91344d15cb77e932514e2b752bb6ac5dc5d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/326021
Commit-Queue: Slava Egorov <vegorov@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
Reviewed-by: Michael Thomsen <mit@google.com>

runtime/vm/dart_api_impl.cc

@@ -82,6 +82,12 @@ DEFINE_FLAG(bool,
             dump_tables,
             false,
             "Dump common hash tables before snapshotting.");
+DEFINE_FLAG(bool,
+            enable_deprecated_wait_for,
+            false,
+            "Enable deprecated dart:cli waitFor. "
+            "This feature will be fully removed in Dart 3.4 release. "
+            "See https://dartbug.com/52121.");
 
 #define CHECK_ERROR_HANDLE(error)                                              \
   {                                                                            \
@@ -2110,6 +2116,17 @@ DART_EXPORT Dart_Handle Dart_HandleMessage() {
 }
 
 DART_EXPORT Dart_Handle Dart_WaitForEvent(int64_t timeout_millis) {
+  if (!FLAG_enable_deprecated_wait_for) {
+    return Dart_NewUnhandledExceptionError(Dart_NewStringFromCString(
+        "Synchronous waiting using dart:cli waitFor "
+        "and C API Dart_WaitForEvent is deprecated and disabled by default. "
+        "This feature will be fully removed in Dart 3.4 release. "
+        "You can currently still enable it by passing "
+        "--enable_deprecated_wait_for "
+        "to the Dart VM. "
+        "See https://dartbug.com/52121."));
+  }
+
   Thread* T = Thread::Current();
   Isolate* I = T->isolate();
   CHECK_API_SCOPE(T);

sdk/lib/cli/wait_for.dart

@@ -71,29 +71,14 @@ class _WaitForUtils {
  *
  * ## Deprecation notice
  *
- * The `waitFor` feature is deprecated.
- * The feature was intended to solve a particular problem for existing code,
- * a problem introduced by a breaking change to the platform libraries.
- * The `waitFor` function is not suitable for general use.
- * The feature has shortcomings that can affect other code
- * running in the same isolate, including:
- *  * A function call that looks synchronous may cause other asynchronous
- *    events to run before it returns.
- *    This is something synchronous code can usually assume not to happen,
- *    and some code may have been written to take advantage of that
- *    assumed behavior. Such code can fail in unexpected ways.
- *  * Multiple nested calls to `waitFor` may block each other
- *    since the most recent call always needs to complete
- *    before any other call can complete.
- *    Judicious use of `waitFor` is necessary to avoid unexpected deadlocks
- *    which wouldn't happen if using `await` instead.
- *    If more than one library in the same program is using `waitFor`,
- *    then it's hard to avoid or control whether such blocking will happen.
+ * The `waitFor` feature is deprecated, disabled by default and slated for
+ * removal in Dart 3.4 release.
+ *
+ * See https://dartbug.com/52121
+ *
+ * During transitionary period you can still force enable this feature
+ * by passing --enable-deprecated-wait-for to Dart VM.
  *
- * The feature is not actively maintained.
- * It will remain as-is to support the original problem it was added to solve,
- * at least until that problem can be solved in some other way.
- * 
  * ## Call semantics
  *
  * This call does the following:
@@ -137,8 +122,7 @@ class _WaitForUtils {
  * subsequent calls block waiting for a condition that is only satisfied when
  * an earlier call returns.
  */
-@Deprecated(
-    "This functionality is incomplete and may be removed in a later version")
+@Deprecated("This functionality is deprecated and will be removed in Dart 3.4")
 T waitFor<T>(Future<T> future, {Duration? timeout}) {
   late T result;
   bool futureCompleted = false;

tests/standalone/io/issue_32052_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:cli';
 

tests/standalone/io/wait_for_deprecation_test.dart

@@ -0,0 +1,23 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+// This test verifies that attempting to use `waitFor` without enabling it
+// causes an exception.
+
+import 'dart:async';
+import 'dart:cli';
+
+import 'package:async_helper/async_helper.dart';
+import 'package:expect/expect.dart';
+
+main() {
+  asyncStart();
+  Expect.throws<String>(() {
+    waitFor(Future.delayed(Duration(milliseconds: 10)).whenComplete(asyncEnd));
+  }, (v) {
+    return v.contains('deprecated and disabled') &&
+        v.contains('dartbug.com/52121') &&
+        v.contains('enable_deprecated_wait_for');
+  });
+}

tests/standalone/io/wait_for_error_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:cli';
 

tests/standalone/io/wait_for_event_isolate_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:isolate';
 

tests/standalone/io/wait_for_event_microtask_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:cli';
 

tests/standalone/io/wait_for_event_nested_microtask_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:cli';
 

tests/standalone/io/wait_for_event_nested_timer_microtask_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:cli';
 

tests/standalone/io/wait_for_event_nested_timer_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:cli';
 

tests/standalone/io/wait_for_event_nested_waits_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:cli';
 

tests/standalone/io/wait_for_event_timer_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:cli';
 

tests/standalone/io/wait_for_event_zone_caught_error_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:cli';
 

tests/standalone/io/wait_for_event_zone_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:cli';
 

tests/standalone/io/wait_for_exception_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:cli';
 

tests/standalone/io/wait_for_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:mirrors';
 import 'dart:cli';

tests/standalone/io/wait_for_timeout_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 import 'dart:async';
 import 'dart:cli';
 

tests/standalone_2/io/issue_32052_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';

tests/standalone_2/io/wait_for_error_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';

tests/standalone_2/io/wait_for_event_isolate_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';

tests/standalone_2/io/wait_for_event_microtask_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';

tests/standalone_2/io/wait_for_event_nested_microtask_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';

tests/standalone_2/io/wait_for_event_nested_timer_microtask_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';

tests/standalone_2/io/wait_for_event_nested_timer_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';

tests/standalone_2/io/wait_for_event_nested_waits_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';

tests/standalone_2/io/wait_for_event_timer_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';

tests/standalone_2/io/wait_for_event_zone_caught_error_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';

tests/standalone_2/io/wait_for_event_zone_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';

tests/standalone_2/io/wait_for_exception_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';

tests/standalone_2/io/wait_for_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';

tests/standalone_2/io/wait_for_timeout_test.dart

@@ -2,6 +2,8 @@
 // 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.
 
+// VMOptions=--enable-deprecated-wait-for
+
 // @dart = 2.9
 
 import 'dart:async';