(describe-function): If no fn specified, say so.

(variable-at-point): Return 0 if no variable there.
(describe-variable): If no variable specified, say so.
Don't use nil as the variable.

diff --git a/lisp/help.el b/lisp/help.el
index ba8664fc14b27e7e67cf6cea7d7cd9deaebced80..e775139ddb8d215ecabe8c09769711e5a87a4e7e 100644 (file)
--- a/lisp/help.el
+++ b/lisp/help.el
@@ -493,71 +493,74 @@ C-w print information on absence of warranty for GNU Emacs."
                                obarray 'fboundp t))
      (list (if (equal val "")
               fn (intern val)))))
-  (with-output-to-temp-buffer "*Help*"
-    (prin1 function)
-    (princ ": ")
-    (let* ((def (symbol-function function))
-          file-name
-          (beg (if (commandp def) "an interactive " "a ")))
-      (princ (cond ((or (stringp def)
-                       (vectorp def))
-                   "a keyboard macro")
-                  ((subrp def)
-                   (concat beg "built-in function"))
-                  ((byte-code-function-p def)
-                   (concat beg "compiled Lisp function"))
-                  ((symbolp def)
-                   (format "alias for `%s'" def))
-                  ((eq (car-safe def) 'lambda)
-                   (concat beg "Lisp function"))
-                  ((eq (car-safe def) 'macro)
-                   "a Lisp macro")
-                  ((eq (car-safe def) 'mocklisp)
-                   "a mocklisp function")
-                  ((eq (car-safe def) 'autoload)
-                   (setq file-name (nth 1 def))
-                   (format "%s autoloaded Lisp %s"
-                           (if (commandp def) "an interactive" "an")
-                           (if (nth 4 def) "macro" "function")
-                           ))
-                  (t "")))
-      (or file-name
-         (setq file-name (describe-function-find-file function)))
-      (if file-name
-         (progn
-           (princ " in `")
-           ;; We used to add .el to the file name,
-           ;; but that's completely wrong when the user used load-file.
-           (princ file-name)
-           (princ "'")))
-      (princ ".")
-      (terpri)
-      (let ((arglist (cond ((byte-code-function-p def)
-                           (car (append def nil)))
-                          ((eq (car-safe def) 'lambda)
-                           (nth 1 def))
-                          (t t))))
-       (if (listp arglist)
-           (progn
-             (princ (cons function
-                          (mapcar (lambda (arg)
-                                    (if (memq arg '(&optional &rest))
-                                        arg
-                                      (intern (upcase (symbol-name arg)))))
-                                  arglist)))
-             (terpri))))
-      (let ((doc (documentation function)))
-       (if doc
-           (progn (terpri)
-                  (princ doc))
-         (princ "not documented"))))
-    (print-help-return-message)
-    (save-excursion
-      (set-buffer standard-output)
-      (help-mode)
-      ;; Return the text we displayed.
-      (buffer-string))))
-
+  (if function
+      (with-output-to-temp-buffer "*Help*"
+       (prin1 function)
+       (princ ": ")
+       (let* ((def (symbol-function function))
+              file-name
+              (beg (if (commandp def) "an interactive " "a ")))
+         (princ (cond ((or (stringp def)
+                           (vectorp def))
+                       "a keyboard macro")
+                      ((subrp def)
+                       (concat beg "built-in function"))
+                      ((byte-code-function-p def)
+                       (concat beg "compiled Lisp function"))
+                      ((symbolp def)
+                       (format "alias for `%s'" def))
+                      ((eq (car-safe def) 'lambda)
+                       (concat beg "Lisp function"))
+                      ((eq (car-safe def) 'macro)
+                       "a Lisp macro")
+                      ((eq (car-safe def) 'mocklisp)
+                       "a mocklisp function")
+                      ((eq (car-safe def) 'autoload)
+                       (setq file-name (nth 1 def))
+                       (format "%s autoloaded Lisp %s"
+                               (if (commandp def) "an interactive" "an")
+                               (if (nth 4 def) "macro" "function")
+                               ))
+                      (t "")))
+         (or file-name
+             (setq file-name (describe-function-find-file function)))
+         (if file-name
+             (progn
+               (princ " in `")
+               ;; We used to add .el to the file name,
+               ;; but that's completely wrong when the user used load-file.
+               (princ file-name)
+               (princ "'")))
+         (princ ".")
+         (terpri)
+         (let ((arglist (cond ((byte-code-function-p def)
+                               (car (append def nil)))
+                              ((eq (car-safe def) 'lambda)
+                               (nth 1 def))
+                              (t t))))
+           (if (listp arglist)
+               (progn
+                 (princ (cons function
+                              (mapcar (lambda (arg)
+                                        (if (memq arg '(&optional &rest))
+                                            arg
+                                          (intern (upcase (symbol-name arg)))))
+                                      arglist)))
+                 (terpri))))
+         (let ((doc (documentation function)))
+           (if doc
+               (progn (terpri)
+                      (princ doc))
+             (princ "not documented"))))
+       (print-help-return-message)
+       (save-excursion
+         (set-buffer standard-output)
+         (help-mode)
+         ;; Return the text we displayed.
+         (buffer-string)))
+    (message "You didn't specify a function")))
+
+;; We return 0 if we can't find a variable to return.
 (defun variable-at-point ()
   (condition-case ()
       (let ((stab (syntax-table)))
@@ -570,9 +573,10 @@ C-w print information on absence of warranty for GNU Emacs."
                  (forward-sexp -1))
              (skip-chars-forward "'")
              (let ((obj (read (current-buffer))))
-               (and (symbolp obj) (boundp obj) obj)))
+               (or (and (symbolp obj) (boundp obj) obj)
+                   0)))
          (set-syntax-table stab)))
-    (error nil)))
+    (error 0)))
 
 (defun describe-variable (variable)
   "Display the full documentation of VARIABLE (a symbol).
@@ -581,38 +585,40 @@ Returns the documentation as a string, also."
    (let ((v (variable-at-point))
         (enable-recursive-minibuffers t)
         val)
-     (setq val (completing-read (if v
+     (setq val (completing-read (if (symbolp v)
                                    (format "Describe variable (default %s): " v)
                                  "Describe variable: ")
                                obarray 'boundp t))
      (list (if (equal val "")
               v (intern val)))))
-  (with-output-to-temp-buffer "*Help*"
-    (prin1 variable)
-    (if (not (boundp variable))
-        (princ " is void")
-      (princ "'s value is ")
-      (prin1 (symbol-value variable)))
-    (terpri)
-    (if (local-variable-p variable)
-       (progn
-         (princ (format "Local in buffer %s; " (buffer-name)))
-         (if (not (default-boundp variable))
-             (princ "globally void")
-           (princ "global value is ")
-           (prin1 (default-value variable)))
-         (terpri)))
-    (terpri)
-    (princ "Documentation:")
-    (terpri)
-    (let ((doc (documentation-property variable 'variable-documentation)))
-      (princ (or doc "not documented as a variable.")))
-    (print-help-return-message)
-    (save-excursion
-      (set-buffer standard-output)
-      (help-mode)
-      ;; Return the text we displayed.
-      (buffer-string))))
+  (if (symbolp variable)
+      (with-output-to-temp-buffer "*Help*"
+       (prin1 variable)
+       (if (not (boundp variable))
+           (princ " is void")
+         (princ "'s value is ")
+         (prin1 (symbol-value variable)))
+       (terpri)
+       (if (local-variable-p variable)
+           (progn
+             (princ (format "Local in buffer %s; " (buffer-name)))
+             (if (not (default-boundp variable))
+                 (princ "globally void")
+               (princ "global value is ")
+               (prin1 (default-value variable)))
+             (terpri)))
+       (terpri)
+       (princ "Documentation:")
+       (terpri)
+       (let ((doc (documentation-property variable 'variable-documentation)))
+         (princ (or doc "not documented as a variable.")))
+       (print-help-return-message)
+       (save-excursion
+         (set-buffer standard-output)
+         (help-mode)
+         ;; Return the text we displayed.
+         (buffer-string)))
+    (message "You did not specify a variable")))
 
 (defun where-is (definition)
   "Print message listing key sequences that invoke specified command.