invalidate_cache() no-op for async functions in L1-only mode

[27Bslash6]

Problem

invalidate_cache() called with no arguments on an async-decorated function does not clear the L1 cache in backend=None (L1-only) mode.

Reproduction

from cachekit import cache
import asyncio

call_count = 0

@cache(backend=None, ttl=300)
async def fn(x):
    global call_count
    call_count += 1
    return x * 2

async def test():
    global call_count

    await fn(5)
    print(f"After call 1: computed={call_count}")  # 1

    await fn(5)
    print(f"After call 2: computed={call_count}")  # 1 (cached)

    # Per-key invalidation works:
    await fn.invalidate_cache(5)
    await fn(5)
    print(f"After invalidate(5), call 3: computed={call_count}")  # 2 (recomputed) OK

    # No-arg bulk invalidation does NOT work:
    await fn.invalidate_cache()
    await fn(5)
    print(f"After invalidate(), call 4: computed={call_count}")  # 2 (still cached!) BUG

asyncio.run(test())

Expected

Call 4 should recompute (computed=3) because invalidate_cache() with no args should clear ALL cached entries for the function.

Actual

Call 4 returns the cached value (computed=2). The no-arg bulk invalidation is a no-op.

Analysis

The no-arg path in the wrapper checks _func_has_params and iterates _cached_keys, but the L1-only mode code path may not be populating _cached_keys correctly, so the snapshot is empty and no entries are invalidated.

Additional issue

cache_clear() raises TypeError for async functions:

TypeError: cache_clear() cannot clear cache for async functions. Use 'await fn.ainvalidate_cache()' instead.

But ainvalidate_cache() (which invalidate_cache aliases to for async functions) doesn't work either, as shown above.

Environment

• cachekit 0.4.0
• Python 3.13
• @cache(backend=None) (L1-only mode)

[27Bslash6]

Fixed in v0.6.1 via PR #108. The no-arg invalidation path now tracks cache keys per decorated function and clears them all. The exact repro (async + backend=None + no-arg invalidation) is covered by test_async_invalidate_no_args_clears_all_entries and passes.