fix: hand redis.asyncio.Redis the async Retry, not the sync one

[AlexeyShalaev]

build_redis_retry built redis.retry.Retry for both factories, and create_async_redis_client handed that to redis.asyncio.Redis. The sync class's call_with_retry is a plain function: it calls do() once and returns the coroutine it got, so the client awaited that coroutine outside the retry loop, and retry.enabled=True, max_attempts=N never retried on an async client — single node on every redis-py in the range, and the async cluster's pipeline path with it. The zero-retry object from #27 was the same class, which happened not to matter: no retries need no loop.

What changed

build_redis_retry(settings, *, asyncio=False) and build_base_redis_kwargs(settings, *, asyncio=False) build redis.retry.Retry by default, exactly as before, and redis.asyncio.retry.Retry with asyncio=True — the exponential object and the zero-retry one alike. The async factory passes asyncio=True for single and cluster; the sync factory is untouched. build_redis_retry carries Literal overloads, so a sync caller still sees redis.retry.Retry from the type checker and an async caller sees the async class, with a bool overload for code that passes the flag through.

The two API rows, rule 5 and a "common mistakes" block on the agents page, and the retry section of the configuration guide say what the code does.

What I checked in redis-py

One venv per version, the same ten as for #25, reading the classes off the source. redis.asyncio.retry.Retry is there from 4.5.0 through 8.1.0, never a subclass of redis.retry.Retry, always with async def call_with_retry and the same (backoff, retries, supported_errors) constructor. On every one of those versions the async Connection.connect and Redis.execute_command both await ...retry.call_with_retry(...), so the fix behaves the same across the range and moves no floor.

What I rejected

Swapping the class inside the async factory alone. build_base_redis_kwargs and build_redis_retry are exported from the root, and anyone building a redis.asyncio.Redis from them by hand would keep the trap — the reason #27 put the zero-retry object in the helper rather than in the factory.

A second pair of helpers for the async side, mirroring the aio/sync split. Two more root exports and two more rows on the agents page for one bit of information, and build_base_redis_kwargs would either be duplicated or wrap the sync one and patch retry, which is the rejected shape one level down.

Tests

Unit: the async factory's retry, single and cluster, is redis.asyncio.retry.Retry with retries enabled (test_resilience.py, now parametrized over cluster) and with retries off (test_client.py); both helpers build the async class with asyncio=True and the sync class by default (test_utils.py). Integration: an async client with max_attempts=3, backoff_base=0.1, backoff_cap=1.0 and socket_timeout=0.5 against a paused redis:7-alpine raises TimeoutError after 3.0 to 6.0 s — four attempts plus 0.2 + 0.4 + 0.8 s of backoff — with a sync twin. The sync unit tests are unchanged and still pin redis.retry.Retry.

With master's utils.py and aio/factory.py swapped back in under the new tests, those eight fail — the three helper tests, the two enabled and two disabled async factory tests, and the async integration test at 0.50 s — and the ten sync and retries-off ones pass.

Before and after

One GET per kit-built client, retries enabled as above, socket_timeout=0.5, against the paused container, redis-py 8.1.0.

master:

  kit async, enabled max_attempts=3        retry handed to redis-py: redis.retry.Retry retries=3 backoff=ExponentialBackoff
  kit sync,  enabled max_attempts=3        retry handed to redis-py: redis.retry.Retry retries=3 backoff=ExponentialBackoff
--- Redis paused: one GET per client ---
  kit async, enabled max_attempts=3        -> TimeoutError      0.50 s
  kit sync,  enabled max_attempts=3        -> TimeoutError      3.42 s

this branch:

  kit async, enabled max_attempts=3        retry handed to redis-py: redis.asyncio.retry.Retry retries=3 backoff=ExponentialBackoff
  kit sync,  enabled max_attempts=3        retry handed to redis-py: redis.retry.Retry retries=3 backoff=ExponentialBackoff
--- Redis paused: one GET per client ---
  kit async, enabled max_attempts=3        -> TimeoutError      3.41 s
  kit sync,  enabled max_attempts=3        -> TimeoutError      3.42 s

Gate

make check: ruff check All checks passed!, ruff format 54 files already formatted, mypy Success: no issues found in 25 source files. make test: 144 passed, coverage 99.64% against the 90% floor. uv.lock untouched. CHANGELOG.md is release-please's.

Closes #26