1 files changed, 19 insertions, 0 deletions
diff --git a/lisp/net/tramp-crypt.el b/lisp/net/tramp-crypt.el
index f8de7085e25..278fb9d8732 100644
--- a/lisp/net/tramp-crypt.el
+++ b/lisp/net/tramp-crypt.el
@@ -112,6 +112,14 @@ initializing a new crypted remote directory."
   "Non-nil when encryption support is available.")
 (setq tramp-crypt-enabled (executable-find tramp-crypt-encfs-program))
 
+;; This function takes action since Emacs 28.1, when
+;; `read-extended-command-predicate' is set to
+;; `command-completion-default-include-p'.
+(defun tramp-crypt-enabled-p (_symbol _buffer)
+  "A predicate for Tramp interactive commands.
+They are completed by \"M-x TAB\" only when encryption support is enabled."
+  tramp-crypt-enabled)
+
 ;;;###tramp-autoload
 (defconst tramp-crypt-encfs-config ".encfs6.xml"
   "Encfs configuration file name.")
@@ -469,6 +477,7 @@ See `tramp-crypt-do-encrypt-or-decrypt-file'."
 Files in that directory and all subdirectories will be encrypted
 before copying to, and decrypted after copying from that
 directory.  File names will be also encrypted."
+  ;; (declare (completion tramp-crypt-enabled-p))
   (interactive "DRemote directory name: ")
   (unless tramp-crypt-enabled
     (tramp-user-error nil "Feature is not enabled."))
@@ -481,10 +490,16 @@ directory.  File names will be also encrypted."
     (setq tramp-crypt-directories (cons name tramp-crypt-directories)))
   (tramp-register-file-name-handlers))
 
+;; Starting with Emacs 28.1, this can be replaced by the "(declare ...)" form.
+;;;###tramp-autoload
+(function-put
+ #'tramp-crypt-add-directory 'completion-predicate #'tramp-crypt-enabled-p)
+
 (defun tramp-crypt-remove-directory (name)
   "Unmark remote directory NAME for encryption.
 Existing files in that directory and its subdirectories will be
 kept in their encrypted form."
+  ;; (declare (completion tramp-crypt-enabled-p))
   (interactive "DRemote directory name: ")
   (unless tramp-crypt-enabled
     (tramp-user-error nil "Feature is not enabled."))
@@ -498,6 +513,10 @@ kept in their encrypted form."
     (setq tramp-crypt-directories (delete name tramp-crypt-directories))
     (tramp-register-file-name-handlers)))
 
+;; Starting with Emacs 28.1, this can be replaced by the "(declare ...)" form.
+(function-put
+ #'tramp-crypt-remove-directory 'completion-predicate #'tramp-crypt-enabled-p)
+
 ;; `auth-source' requires a user.
 (defun tramp-crypt-dissect-file-name (name)
   "Return a `tramp-file-name' structure for NAME.