[13.x] Implement CanFlushLocks on FailoverStore

[sumaiazaman]

Summary

• FailoverStore now implements CanFlushLocks and the flushLocks() / hasSeparateLockStore() methods
• Cache::flushLocks() now works when the failover cache driver is in use

Context

Every cache store that ships with Laravel implements CanFlushLocks:

Store	CanFlushLocks before	CanFlushLocks after
ArrayStore	✅	✅
DatabaseStore	✅	✅
FileStore	✅	✅
RedisStore	✅	✅
FailoverStore	❌	✅

FailoverStore already implements LockProvider (for acquiring locks), but calling Cache::flushLocks() with the failover driver threw "This cache store does not support flushing locks." because the store didn't implement CanFlushLocks.

Solution

Added CanFlushLocks to the class declaration and implemented two methods:

flushLocks(): bool — iterates through every backing store and calls flushLocks() on those that implement CanFlushLocks. Unlike attemptOnAllStores() (which returns on the first success), this flushes all stores, because locks may have been acquired on any of them during failover.

hasSeparateLockStore(): bool — returns true. The failover store delegates entirely to its backing stores, each of which manages lock storage independently.

Example

Before:

// config/cache.php: 'default' => 'failover'
Cache::flushLocks(); // throws BadMethodCallException: "This cache store does not support flushing locks."

After:

Cache::flushLocks(); // true — flushes locks on all backing stores

Why no breaking changes

This is a purely additive change. No existing method signatures are modified, and no existing callers are affected.

Changes

• src/Illuminate/Cache/FailoverStore.php — added CanFlushLocks import, added to class declaration, implemented flushLocks() and hasSeparateLockStore()
• tests/Cache/CacheFailoverStoreTest.php — new unit test file

Test Plan

• php83 vendor/bin/phpunit tests/Cache/CacheFailoverStoreTest.php — all 3 tests pass