[CMEMOIZE-3] snapshot assumes too much about a CacheProtocol implementation

Wed, 14 Dec 2011 07:29:00 -0600

I believe this line https://github.com/clojure/core.memoize/blob/9bdf608af8bbf4a753fc19758446dd821cb45979/src/main/clojure/clojure/core/memoize.clj#L72 assumes too much about implementations of CacheProtocol, namely that they have a field named 'cache'.

The first call to .cache makes sense, since PluggableMemoization has a 'cache' field, but the second call to .cache assumes that any implementation of CacheProtocol that PluggableMemoization wraps will have a 'cache' field.

I ran into this issue when I desired to have a cache that ignores nils, so I attempted to wrap the TTLCache with an implementation of CacheProtocol that would not cache nil values. Calls to snapshot failed since it was trying to access a 'cache' field on my NoNilCache.

I suspect that the outer call to .cache could be replaced with a call to seq, since defcache adds an implementation of seq to each cache implementation which should pull out the keys/values from the cache.

I'd be glad to work up a patch given that I'm not off base in my assumptions.

Clojure JIRA

[CMEMOIZE-3] snapshot assumes too much about a CacheProtocol implementation