Fix when_all hang when some children complete before construction

[passuied]

Fixes #1149

Description

WhenAllTask.__init__ was resetting _completed_tasks / _failed_tasks after CompositeTask.__init__ had already counted children that were complete at construction time. That drops early completions, so deferred when_all(children) hangs forever when some but not all children finished before when_all was built.

Changes

• Stop resetting counters in WhenAllTask.__init__ (keep empty-list fast path)
• Add unit tests for partial pre-completion, all pre-completion, and when_any([when_all, timeout])

Test plan

• uv run pytest tests/ext/workflow/durabletask/test_task.py
• CI green

RELEASE NOTE: FIX Bug causing when_all to hang when some child tasks complete before when_all is constructed

Made with Cursor

[Copilot]

Pull request overview

This PR fixes a durabletask when_all(children) hang that occurs when some (but not all) child tasks complete before the WhenAllTask is constructed (deferred fan-in). It aligns WhenAllTask’s construction behavior with CompositeTask’s existing “count pre-completed children” initialization logic and adds regression coverage to prevent reintroduction.

Changes:

• Stop resetting WhenAllTask’s _completed_tasks / _failed_tasks after CompositeTask.__init__ has already accounted for pre-completed children.
• Add unit tests covering partial pre-completion, full pre-completion, and when_any([when_all(children), timeout]) interaction.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
dapr/ext/workflow/_durabletask/task.py	Removes the counter reset in WhenAllTask.__init__ so pre-completed children are retained and when_all can complete correctly.
tests/ext/workflow/durabletask/test_task.py	Adds regression tests for deferred when_all with pre-completed children and composition with when_any.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.84%. Comparing base (34136f2) to head (0de8299).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1150      +/-   ##
==========================================
+ Coverage   82.76%   82.84%   +0.08%     
==========================================
  Files         123      123              
  Lines       10123    10121       -2     
==========================================
+ Hits         8378     8385       +7     
+ Misses       1745     1736       -9     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.