(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.

1 files changed, 100 insertions, 94 deletions

diff --git a/lisp/help.el b/lisp/help.el
index ba8664fc14b..e775139ddb8 100644
--- 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.