trogau on "[Plugin: WP Super Cache] Can't cache 404s without trailing slash"

Was trying to resolve an issue with WP Super Cache seemingly not caching 404 pages correctly today, after adding.

I'd set it up to activate the filter via wpsupercache_404, but wasn't seeing caching working as expected. The pages would have comment text like "Cached page generated by WP-Super-Cache on 2014-10-03 06:03:50" embedded, but every page load would trigger an updated timestamp. Running in debug mode also showed "No wp-cache file exists. Must generate a new one." on each load.

After poking through the code I realised it seemed to be due to the 404 test URLs I was using not having a trailing slash. That is:

http://example.com/missing

... does not get served from cache, but

http://example.com/missing/

... operates as expected.

Had a quick search and I can see a lot of stuff about trailing slashes in WordPress/WP Super Cache from the past, but couldn't see anything relating to 404s so thought this might be of interest to anyone else having similar issues.

https://wordpress.org/plugins/wp-super-cache/