mu4e: allow lisp expressions for bookmarks

based on an idea by davidcsterratt

mu4e/mu4e-utils.el

@@ -375,14 +375,19 @@ and offer to create it if it does not exist yet."
 (defun mu4e-get-bookmark-query (kar)
   "Get the corresponding bookmarked query for shortcut character
 KAR, or raise an error if none is found."
- (let ((chosen-bm
-	 (find-if
-	   (lambda (bm)
-	     (= kar (nth 2 bm)))
-	   mu4e-bookmarks)))
-   (if chosen-bm
-     (nth 0 chosen-bm)
-     (mu4e-warn "Unknown shortcut '%c'" kar))))
+  (let* ((chosen-bm
+	   (or (find-if
+		 (lambda (bm)
+		   (= kar (nth 2 bm)))
+		mu4e-bookmarks)
+	    (mu4e-warn "Unknown shortcut '%c'" kar)))
+	 (expr (nth 0 chosen-bm))
+	 (query (eval expr)))
+    (if (stringp query)
+      query
+      (mu4e-warn "Expression must evaluate to query string ('%S')" expr))))
+
+
 
 
 ;;; converting flags->string and vice-versa ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

mu4e/mu4e.texi

@@ -1862,6 +1862,23 @@ defined in the echo area, with the shortcut key highlighted. So, to invoke the
 bookmark we just defined (to get the list of "Big Messages"), all you need to
 type is @kbd{bb}.
 
+@subsection Lisp expressions as bookmarks
+
+Instead of using strings, it is also possible to use Lisp expressions as
+bookmarks. The only requirement is that they evaluate to a query string.
+
+For example, to get all the messages that are at least a week old in
+your inbox:
+
+@lisp
+(add-to-list 'mu4e-bookmarks '(
+   (concat "maildir:/inbox date:.."
+       (format-time-string "%Y%m%d"
+                 (subtract-time (current-time) (days-to-time 7))))
+    "Messages older than a week" ?O) t)
+@end lisp
+
+
 @subsection Editing bookmarks before searching
 
 There is also @kbd{M-x mu4e-headers-search-bookmark-edit} (key @key{B}), which