fix: restore support for falsy wait values and callable + strategy

[jd]

Three runtime regressions from the mypy-strictness stack (#679, #677), all
A/B verified against a2af454. None were caught by the test suite, and all
three only fire once a retry actually happens, so happy-path callers see
nothing until production.

1. Retrying(wait=None), wait=0 and wait=sum([]) now raise
   TypeError: 'NoneType' object is not callable from inside iter().
   refactor: drop always-true truthiness checks and enable truthy-bool #679 removed the if self.wait: guard on the grounds that truthy-bool
   proved it always true -- but that only holds for the declared type.
   Untyped callers pass None/0 to mean "no wait", and sum([]) over an
   empty strategy list returns the int 0. The TypeError is raised outside
   the attempt's try/except, so it escapes uncaught and destroys the caller's
   real exception. Restore the guard with a local truthy-bool suppression
   explaining why the "impossible" branch is reachable. before, after,
   before_sleep and retry_error_callback all kept their is not None
   guards; wait was the only one dropped.

2. plain_callable + wait_strategy now raises TypeError. WaitBaseT
   admits plain callables, and a function has no __add__, so this went
   through wait_base.__radd__ -- which fix: annotate wait_base.__radd__ as taking the int seed from sum() #677 narrowed to int. Widen it to
   WaitBaseT | int and build the wait_combine again. 5 + strategy is
   still rejected, now via NotImplemented rather than a combination that
   fails later. The parameter stays int rather than Literal[0] because
   typeshed's sum() protocol requires __radd__(x: int); narrowing it
   would make every sum() over strategies need a type: ignore.

3. wait_combine.__call__ passed the state as retry_state=, which crashes
   on any WaitBaseT callable whose parameter has another name. Pass it
   positionally, as BaseRetrying._run_wait already does.

Adds regression tests for all three plus the async path -- the original
change shipped with no test covering any of them.

[jd]

This pull request is part of a Mergify stack:

#	Pull Request	Link
1	fix: restore support for falsy wait values and callable + strategy	#694	👈
2	fix: read the tornado global live instead of an import-time snapshot	#695

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-08-06 06:44 UTC · Rule: default · triggered by rule autoqueue
• ✅ Checks skipped · PR is already up-to-date
• ✅ Merged — 2026-08-06 06:44 UTC · at 6e425f390dc7dfa1f3e83e7ab9fc44b4618d2bb7 · squash

This pull request spent 7 seconds in the queue, including 1 second running CI.

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• github-review-approved [🛡 GitHub branch protection]
  • fix: restore support for falsy wait values and callable + strategy #694