uiop:ensure-pathname

(uiop:ensure-pathname pathname &key on-error defaults type dot-dot empty-is-nil want-pathname want-relative want-absolute ensure-absolute ensure-subpath want-file want-directory ensure-directory want-non-wild want-wild wilden want-existing ensure-directories-exist truename &allow-other-keys)

The constraint machine the rest of uiop routes through: coerces a designator (a string goes through uiop:parse-unix-namestring), then applies the :want-* checks and :ensure-* transforms in upstream's order. A failed check signals an error naming the pathname and the constraint, or calls a custom :on-error function.

Lite next to upstream, deliberately: the report is Invalid pathname ~S: ~A, :want-logical always fails (no logical pathname exists), :resolve-symlinks / :truenamize are accepted and ignored, and :truename answers what probe-file answers.

Backend support

Works on all four backends (Lisp source, uiop-pathname.lisp).