tenacity 9.1.4: Control Tenacity 9.1.4 exhaustion for result-based and exception-based retries without sleeping

# Notes

The network reference sample covered exception filtering and bounded attempts.
This contract adds result-predicate exhaustion, callback fallback semantics, and
the difference between default `RetryError` wrapping and `reraise=True`.

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tenacity==9.1.4

from tenacity import RetryError, retry, retry_if_exception_type, retry_if_result, stop_after_attempt, wait_none


result_calls = 0


@retry(
    retry=retry_if_result(lambda value: value is None),
    stop=stop_after_attempt(3),
    wait=wait_none(),
)
def exhausted_result():
    global result_calls
    result_calls += 1
    return None


try:
    exhausted_result()
except RetryError as exc:
    assert result_calls == 3
    assert exc.last_attempt.failed is False
    assert exc.last_attempt.result() is None
else:
    raise AssertionError("result-based exhaustion must raise RetryError without a callback")


fallback_calls = 0


def fallback(retry_state):
    assert retry_state.attempt_number == 3
    assert retry_state.outcome.failed is False
    return ("fallback", retry_state.outcome.result())


@retry(
    retry=retry_if_result(lambda value: value is None),
    stop=stop_after_attempt(3),
    wait=wait_none(),
    retry_error_callback=fallback,
)
def exhausted_result_with_fallback():
    global fallback_calls
    fallback_calls += 1
    return None


assert exhausted_result_with_fallback() == ("fallback", None)
assert fallback_calls == 3


default_error_calls = 0


@retry(
    retry=retry_if_exception_type(ValueError),
    stop=stop_after_attempt(2),
    wait=wait_none(),
)
def default_error():
    global default_error_calls
    default_error_calls += 1
    raise ValueError("measured failure")


try:
    default_error()
except RetryError as exc:
    assert default_error_calls == 2
    assert isinstance(exc.last_attempt.exception(), ValueError)
else:
    raise AssertionError("default exception exhaustion must raise RetryError")


reraise_calls = 0


@retry(
    retry=retry_if_exception_type(ValueError),
    stop=stop_after_attempt(2),
    wait=wait_none(),
    reraise=True,
)
def reraised_error():
    global reraise_calls
    reraise_calls += 1
    raise ValueError("measured failure")


try:
    reraised_error()
except ValueError as exc:
    assert str(exc) == "measured failure"
    assert reraise_calls == 2
else:
    raise AssertionError("reraise=True must expose the final ValueError")