Don't print empty keymaps in `C-h b'

* lisp/help.el (describe-map-tree): Don't print the heading if the
keymap is empty (bug#22334).  Tweak the look to compress it more
vertically.

lisp/help.el

@@ -1275,17 +1275,8 @@ Any inserted text ends in two newlines (used by
                             result))
                       amaps))
          (maps orig-maps)
-         (print-title (or maps always-title)))
+         (print-title (or maps always-title))
-    ;; Print title.
+         (start-point (point)))
-    (when print-title
-      (insert (concat (if title
-                          (concat title
-                                  (if prefix
-                                      (concat " Starting With "
-                                              (help--key-description-fontified prefix)))
-                                  ":\n"))
-                      "key             binding\n"
-                      "---             -------\n")))
     ;; Describe key bindings.
     (setq help--keymaps-seen nil)
     (while (consp maps)
@@ -1310,8 +1301,24 @@ Any inserted text ends in two newlines (used by
           (describe-map (cdr elt) elt-prefix transl partial
                         sub-shadows no-menu mention-shadow)))
       (setq maps (cdr maps)))
-    (when print-title
+    ;; Print title...
-      (insert "\n"))))
+    (when (and print-title
+               ;; ... unless the keymap was empty.
+               (/= (point) start-point))
+      (save-excursion
+        (goto-char start-point)
+        (when (eolp)
+          (delete-region (point) (1+ (point))))
+        (insert
+         (concat
+          (if title
+              (concat title
+                      (if prefix
+                          (concat " Starting With "
+                                  (help--key-description-fontified prefix)))
+                      ":\n"))
+          "\nkey             binding\n"
+          (make-separator-line)))))))
 
 (defun help--shadow-lookup (keymap key accept-default remap)
   "Like `lookup-key', but with command remapping.

test/lisp/help-tests.el

@@ -91,10 +91,9 @@
 (ert-deftest help-tests-substitute-command-keys/keymaps ()
   (with-substitute-command-keys-test
    (test "\\{minibuffer-local-must-match-map}"
-         "\
+         "
 key             binding
----             -------
+-------------------------------------------------------------------------------
-
 C-g		abort-minibuffers
 TAB		minibuffer-complete
 C-j		minibuffer-complete-and-exit
@@ -122,7 +121,6 @@ M-r		previous-matching-history-element
 M-s		next-matching-history-element
 
 M-g M-c		switch-to-completions
-
 ")))
 
 (ert-deftest help-tests-substitute-command-keys/keymap-change ()
@@ -250,10 +248,9 @@ M-g M-c		switch-to-completions
    (with-temp-buffer
      (help-tests-major-mode)
      (test "\\{help-tests-major-mode-map}"
-           "\
+           "
 key             binding
----             -------
+-------------------------------------------------------------------------------
-
 ( .. )		short-range
 1 .. 4		foo-range
 a .. c		foo-other-range
@@ -261,7 +258,6 @@ a .. c		foo-other-range
 C-e		foo-something
 x		foo-original
 <F1>		foo-function-key1
-
 "))))
 
 (ert-deftest help-tests-substitute-command-keys/shadow ()
@@ -270,10 +266,9 @@ x		foo-original
      (help-tests-major-mode)
      (help-tests-minor-mode)
      (test "\\{help-tests-major-mode-map}"
-           "\
+           "
 key             binding
----             -------
+-------------------------------------------------------------------------------
-
 ( .. )		short-range
 1 .. 4		foo-range
 a .. c		foo-other-range
@@ -283,7 +278,6 @@ C-e		foo-something
 x		foo-original
   (this binding is currently shadowed)
 <F1>		foo-function-key1
-
 "))))
 
 (ert-deftest help-tests-substitute-command-keys/command-remap ()
@@ -293,14 +287,12 @@ x		foo-original
       (help-tests-major-mode)
       (define-key help-tests-major-mode-map [remap foo] 'bar)
       (test "\\{help-tests-major-mode-map}"
-            "\
+            "
 key             binding
----             -------
+-------------------------------------------------------------------------------
-
 <remap>		Prefix Command
 
 <remap> <foo>	bar
-
 ")))))
 
 (ert-deftest help-tests-describe-map-tree/no-menu-t ()
@@ -312,11 +304,10 @@ key             binding
                                           :enable mark-active
                                           :help "Help text"))))))
       (describe-map-tree map nil nil nil nil t nil nil nil)
-      (should (equal (buffer-string) "key             binding
+      (should (equal (buffer-string) "
----             -------
+key             binding
-
+-------------------------------------------------------------------------------
 C-a		foo
-
 ")))))
 
 (ert-deftest help-tests-describe-map-tree/no-menu-nil ()
@@ -328,14 +319,13 @@ C-a		foo
                                           :enable mark-active
                                           :help "Help text"))))))
       (describe-map-tree map nil nil nil nil nil nil nil nil)
-      (should (equal (buffer-string) "key             binding
+      (should (equal (buffer-string) "
----             -------
+key             binding
-
+-------------------------------------------------------------------------------
 C-a		foo
 <menu-bar>	Prefix Command
 
 <menu-bar> <foo>		foo
-
 ")))))
 
 (ert-deftest help-tests-describe-map-tree/mention-shadow-t ()
@@ -345,13 +335,12 @@ C-a		foo
                            (2 . bar))))
           (shadow-maps '((keymap . ((1 . baz))))))
       (describe-map-tree map t shadow-maps nil nil t nil nil t)
-      (should (equal (buffer-string) "key             binding
+      (should (equal (buffer-string) "
----             -------
+key             binding
-
+-------------------------------------------------------------------------------
 C-a		foo
   (this binding is currently shadowed)
 C-b		bar
-
 ")))))
 
 (ert-deftest help-tests-describe-map-tree/mention-shadow-nil ()
@@ -361,11 +350,10 @@ C-b		bar
                            (2 . bar))))
           (shadow-maps '((keymap . ((1 . baz))))))
       (describe-map-tree map t shadow-maps nil nil t nil nil nil)
-      (should (equal (buffer-string) "key             binding
+      (should (equal (buffer-string) "
----             -------
+key             binding
-
+-------------------------------------------------------------------------------
 C-b		bar
-
 ")))))
 
 (ert-deftest help-tests-describe-map-tree/partial-t ()
@@ -374,11 +362,10 @@ C-b		bar
           (map '(keymap . ((1 . foo)
                            (2 . undefined)))))
       (describe-map-tree map t nil nil nil nil nil nil nil)
-      (should (equal (buffer-string) "key             binding
+      (should (equal (buffer-string) "
----             -------
+key             binding
-
+-------------------------------------------------------------------------------
 C-a		foo
-
 ")))))
 
 (ert-deftest help-tests-describe-map-tree/partial-nil ()
@@ -387,12 +374,11 @@ C-a		foo
           (map '(keymap . ((1 . foo)
                            (2 . undefined)))))
       (describe-map-tree map nil nil nil nil nil nil nil nil)
-      (should (equal (buffer-string) "key             binding
+      (should (equal (buffer-string) "
----             -------
+key             binding
-
+-------------------------------------------------------------------------------
 C-a		foo
 C-b		undefined
-
 ")))))
 
 (defvar help-tests--was-in-buffer nil)