Separate out the holiday lists into its own function

* lisp/calendar/holidays.el (holiday-lists): Separated out into
its own function so that it can be altered (bug#55140).
(list-holidays): Use it.

1 files changed, 36 insertions, 25 deletions

diff --git a/lisp/calendar/holidays.el b/lisp/calendar/holidays.el
index 2afa667a56c..ca7166c371a 100644
--- a/lisp/calendar/holidays.el
+++ b/lisp/calendar/holidays.el
@@ -400,6 +400,36 @@ This function is suitable for execution in an init file."
            (displayed-year (calendar-extract-year date)))
       (calendar-list-holidays))))
 
+(defun holiday-lists ()
+  "Return a list of all holiday lists.
+This is used by `list-holidays', and you can customize the return
+value by using `add-function'."
+  (delq
+   nil
+   (list
+    (cons "All" calendar-holidays)
+    (cons "Equinoxes/Solstices"
+          (list (list 'solar-equinoxes-solstices)))
+    (if holiday-general-holidays
+        (cons "General" holiday-general-holidays))
+    (if holiday-local-holidays
+        (cons "Local" holiday-local-holidays))
+    (if holiday-other-holidays
+        (cons "Other" holiday-other-holidays))
+    (if holiday-christian-holidays
+        (cons "Christian" holiday-christian-holidays))
+    (if holiday-hebrew-holidays
+        (cons "Hebrew" holiday-hebrew-holidays))
+    (if holiday-islamic-holidays
+        (cons "Islamic" holiday-islamic-holidays))
+    (if holiday-bahai-holidays
+        (cons "Bahá’í" holiday-bahai-holidays))
+    (if holiday-oriental-holidays
+        (cons "Oriental" holiday-oriental-holidays))
+    (if holiday-solar-holidays
+        (cons "Solar" holiday-solar-holidays))
+    (cons "Ask" nil))))
+
 ;; rms: "Emacs commands to display a list of something generally start
 ;; with `list-'.  Please make `list-holidays' the principal name."
 ;;;###autoload
@@ -421,7 +451,11 @@ documentation of `calendar-holidays' for a list of the variables
 that control the choices, as well as a description of the format
 of a holiday list.
 
-The optional LABEL is used to label the buffer created."
+The optional LABEL is used to label the buffer created.
+
+The list of holiday lists is computed by the `holiday-lists', and
+you can alter the results by redefining that function, or use
+`add-function' to all values."
   (interactive
    (let* ((start-year (calendar-read-sexp
                        "Starting year of holidays (>0)"
@@ -433,30 +467,7 @@ The optional LABEL is used to label the buffer created."
                      start-year
                      start-year))
           (completion-ignore-case t)
-          (lists
-           (list
-            (cons "All" calendar-holidays)
-            (cons "Equinoxes/Solstices"
-                  (list (list 'solar-equinoxes-solstices)))
-            (if holiday-general-holidays
-                (cons "General" holiday-general-holidays))
-            (if holiday-local-holidays
-                (cons "Local" holiday-local-holidays))
-            (if holiday-other-holidays
-                (cons "Other" holiday-other-holidays))
-            (if holiday-christian-holidays
-                (cons "Christian" holiday-christian-holidays))
-            (if holiday-hebrew-holidays
-                (cons "Hebrew" holiday-hebrew-holidays))
-            (if holiday-islamic-holidays
-                (cons "Islamic" holiday-islamic-holidays))
-            (if holiday-bahai-holidays
-                (cons "Bahá’í" holiday-bahai-holidays))
-            (if holiday-oriental-holidays
-                (cons "Oriental" holiday-oriental-holidays))
-            (if holiday-solar-holidays
-                (cons "Solar" holiday-solar-holidays))
-            (cons "Ask" nil)))
+          (lists (holiday-lists))
           (choice (capitalize
                    (completing-read "List (TAB for choices): " lists nil t)))
           (which (if (string-equal choice "Ask")