If the general change is too risky, I think there are still a few functions that

would benefit from being able to accept nils on a case-by-case basis.

Examples:

looking-at, string-match, search-forward-*

string-to-list, string-to-vector, (maybe) string-to-number

auto-save-file-name-p, backup-file-name-p

directory-file-name, expand-file-name, file-name-as-directory and their ilk (all of which handle "" gracefully)

rename-file, copy-file, delete-file ("no such file/dir" being more informative than "wrong type argument" here)

write-file (prompts on empty string; might as well prompt on nil)

There's a lot of code out there that's forced to do type assertions on string args

that could be simplified if these common functions could accept nils.

-steve