Fix StreamGroup.broadcast() close() not completing when streams close.

[suojae]

Fix StreamGroup.broadcast() close() not completing when streams close.

Description

This PR fixes issue #372 where StreamGroup.close() never completes when streams in the group close without being explicitly removed.

The documentation states:

[stream] won't close until [close] is called on the group and every stream in the group closes.

However, with the current implementation, when a broadcast StreamGroup is used and close() is called, it will never complete unless streams are explicitly removed from the group.

Changes

• Added a test case that demonstrates the issue: "completes close() when streams close without being removed"
• Fixed the implementation of close() in StreamGroup to properly detect and handle broadcast streams closing
• The fix ensures that when all streams in a group close, the group's close() method completes as documented

Testing

The added test case now passes, and all existing tests continue to pass.

[github-actions]

PR Health

Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?
async	None	2.13.0	2.13.1-wip	2.13.0	✔️

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Package	Changed Files

Changes to files need to be accounted for in their respective changelogs.

Coverage ⚠️

File	Coverage
pkgs/async/lib/src/stream_group.dart	💔 93 % ⬇️ 2 %

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API leaks ✔️

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License Headers ✔️

// Copyright (c) 2025, 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.

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[lrhn]

Since a listen throwing is likely rare, I'd prefer to not allocate this list unless it's actually needed.
It's wasteful to allocate a list that won't be used in 99.9% of cases.

So

  List<Stream<T>>? streamsToRemove;
  ... updateAll...
    on Object {
      (streamsToRemove ??= []).add(stream);
      return null;
    }
...
  if (streamsToRemove != null) {
    for (final stream in streamsToRemove) {
      ...
   }
  }

[suojae]

Thanks! I've implemented the suggested optimization to avoid unnecessary list allocation.
Changed the code to use a nullable list that's only initialized when needed and the null-safe call to forEach ensures we only iterate when a list was actually created.

commit log: cd2faf2

[lrhn]

Move this to a

## 2.14.0-wip

entry, and update the pubspec.yaml version to match.
The 2.13.0 version has been released, so this fix won't be in it.
Can probably be a 2.13.1-wip "bugfix". @natebosch WDYT?

[suojae]

Moved it to 2.13.1-wip, Let me know if there are any other changes needed. Thanks! ☺️

commit log: 032a24b

[lrhn]

I think it's looking good. It needs a second reviewer, so we can have a second opinion.

[lrhn]

Pubspec version and changelog version do not agree. Both should be 2.13.1-wip.

[suojae]

Pubspec version and changelog version do not agree. Both should be 2.13.1-wip.

Fix version mismatch - update pubspec to 2.13.1-wip to match changelog. Thanks!

commit log: ef32af5

[lrhn]

Landed. Thank you for all the work!