Add docstring to with-env

1 files changed, 10 insertions, 1 deletions

diff --git a/hyperquirks.lisp b/hyperquirks.lisp
index 70584a5..8fdbe54 100644
--- a/hyperquirks.lisp
+++ b/hyperquirks.lisp
@@ -5,11 +5,20 @@
 ;;; MACROS
 
 (defmacro with-env ((&rest bindings) &body body)
+  "Execute BODY in context where environment variables are bound to
+particular values.  When BODY finishes executing, or exits early, the
+environment variables are restored to their original values.
+
+EXAMPLE:
+
+(with-env ((\"VAR1\" (get-value-for-var))
+           (\"VAR2\" \"SOME_VAL\"))
+  (do-stuff-with-environment))"
   (let ((bindings
           (loop :for binding :in bindings
                 :collect (list* (gensym "VAR") (gensym "VAL") binding))))
     `(let* ,(loop :for (oldval cacheval envvar newval) :in bindings
-                  :collect `(,oldval (uiop:getenv ,envvar))
+                  :collect `(,oldval (or (uiop:getenv ,envvar) ""))
                   :collect `(,cacheval ,newval))
        (setf ,@(loop :for (oldval cacheval envvar newval) :in bindings
                      :collect `(uiop:getenv ,envvar)