more-docstrings: fix when symbol has no docstring (loop)

ciel.asd

@@ -122,7 +122,7 @@
   :description "CIEL Is an Extended Lisp.")
 
 (asdf:defsystem "ciel/repl"
-  :depends-on (;; :ciel  ;; don't, it will re-load its components files and re-apply their side effects (docstrings.lisp).
+  :depends-on (;; :ciel  ;; let's avoid, it could run side effects twice (like a defparameter set then reset).
                ;; deps
                :cl-readline
                :cffi  ;; "tmp", for cl-readline add history

src/more-docstrings/README.md

@@ -35,9 +35,6 @@ https://lispcookbook.github.io/cl-cookbook/iteration.html
 
 and that's it. To be continued.
 
-A couple gotchas though:
+A gotcha though:
 
-- if we quickload the package twice, the docstrings
-are appended twice too :S The hash-table cache doesn't help in that
-case.
-- we are modifying the symbols in the :cl package.
+- we are modifying the symbols in the :cl package, there is currently no way to "undo" these additions.

src/more-docstrings/docstrings.lisp

@@ -37,7 +37,8 @@ case.
 
         (let ((doc (documentation symbol doc-type)))
           (setf (gethash symbol *docstrings-cache*)
-                doc)
+                ;; don't store a NIL docstring.
+                (or doc ""))
           doc))))
 
 (defun docstring-append (symbol s &optional (doc-type 'function))