Check Redis server before hash field TTL

[sakshichitnis27]

Fixes #829

Summary

Check the connected Redis server version before using hash field expiration commands. This prevents HashModel.save() from calling HTTL on Redis versions older than 7.4.

Added regression tests for supported and unsupported server versions.

Testing

• Verified the fix against Redis 7.2.14
• pytest -q -n auto ./tests/ ./tests_sync/

Fixes #829

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Note

Medium Risk
Changes core HashModel save paths to call INFO once per client and alters the public async API of supports_hash_field_expiration; behavior on Redis < 7.4 is safer but callers must await the helper.

Overview
Hash field expiration (HTTL / HEXPIRE on HashModel.save() and related helpers) is now gated on the connected Redis server version, not only redis-py ≥ 5.1.0. That stops saves on servers like 7.2.x from issuing unsupported commands (fixes #829).

supports_hash_field_expiration is async, takes the Redis client, runs INFO server when the library looks capable, treats 7.4+ as supported, and caches the result per client in a weakref.WeakKeyDictionary. Failed INFO calls are not cached so a later retry can succeed. HashModel.save, expire_field, field_ttl, and persist_field all await this check before using field TTL APIs.

Tests cover version thresholds (7.2 vs 7.4+), per-connection caching, and recovery after a transient RedisError on INFO.

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[sakshichitnis27]

Hi maintainers,
I’ve opened PR #841 to address this issue. Please let me know if any changes or additional tests are needed. I’d be happy to update it. Thanks!

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