If different clients does it differently, you have incompatibilies. This punishes everybody. Since normalizing // to / removes information which may be significant, the obviously correct choice is folllowing the spec.
replyif it is significant, you coded your app wrong, plain and simple
replyOf course not. It's an explicit feature part of every specification.
replyPlenty of websites rewrite paths like /a/b/c/d into a backend service call like /?w=a&x=b&y=c&z=d. In that scheme, /a//c/d would rewrite to /?w=a&x=&y=c&z=d, something entirely distinct from /a/c/d working out to /?w=a&x=b&y=c
It's not the application's fault that the people attempting to configure web server URLs don't know how web server URLs work.
Why?
replyNot sure I agree. The correct thing is to not mess with the URL at all if you're unsure about what to be doing to it. Doing nothing is the easiest thing of them all, why not do that?
replybecause the you need some consistency or normalisation before applying ACL or do routing?
replyURL normalization is defined and it doesn't include collapsing slashes.
replyNot that you can include custom normalization rules (like collapsing slashes, tolower()ing the entire path, removing the query part of the URL), but that's not part of the standard. If you're doing anything extra, the risk of breaking stuff is on you.