Make elfeed-protocol Nextcloud password fetch retriable

A failed pass/gpg fetch (e.g. YubiKey not plugged in yet) used to pass
process output straight to string-trim, which signals instead of
returning nil on empty output, aborting the sentinel before
elfeed-feeds or elfeed-protocol-enable ran. That left elfeed-feeds nil
for the rest of the session with no visible error beyond a *Messages*
line, and every later elfeed-update silently had nothing to fetch.

Wrap the fetch in azos/elfeed-protocol-init-feeds so a failed attempt
can be retried interactively instead of requiring a full reload of the
elfeed-protocol feature.

features/lauretta/emacs/config.org

@@ -207,12 +207,9 @@ deprecation warning, and =elfeed-feeds= ends up with the bare URL
 and no =:password=, so requests silently authenticate with an empty
 password and nothing ever lands in the db.
 
-This =:config= block runs synchronously the first time =elfeed= is
-loaded (i.e. the first =M-x elfeed= of the session), with no user
-keypress behind it the way =azos/caldav-sync= has. Fetching the
-password with =shell-command-to-string= there used to deadlock
-Emacs whenever the GPG PIN cache had expired: that call blocks
-Emacs's single thread on the =pass|gpg= subprocess, but
+Fetching the password with =shell-command-to-string= used to
+deadlock Emacs whenever the GPG PIN cache had expired: that call
+blocks Emacs's single thread on the =pass|gpg= subprocess, but
 =pinentry-emacs= (see the GPG Pinentry section above) needs Emacs's
 command loop running to answer its loopback prompt — so Emacs waits
 on gpg-agent while gpg-agent waits on Emacs. Fetching the password
@@ -222,11 +219,27 @@ with =make-process= instead keeps the command loop alive, so
 fires. Same stderr-redirect reasoning as before, to keep a stray
 gpg/pass warning off the captured password.
 
+The fetch is wrapped in a named, interactive function rather than
+inlined in =:config= so a failed attempt (e.g. =pass= produced no
+output because the YubiKey wasn't plugged in yet) can be retried
+with =M-x azos/elfeed-protocol-init-feeds= — re-running =:config=
+itself would require reloading the =elfeed-protocol= feature
+entirely. An earlier version passed =(process-get proc 'output)=
+straight to =string-trim=, which signals (not just returns nil) when
+no output was ever read, aborting the sentinel before =elfeed-feeds=
+or =elfeed-protocol-enable= ran — so a failed first attempt left
+=elfeed-feeds= permanently =nil= for the rest of the session with no
+visible error beyond a =*Messages*= line, and every subsequent
+=elfeed-update= silently had nothing to fetch.
+
 #+begin_src emacs-lisp
-(use-package elfeed-protocol
-  :after elfeed
-  :config
-  (setq elfeed-protocol-enabled-protocols '(owncloud))
+(defun azos/elfeed-protocol-init-feeds ()
+  "Fetch the Nextcloud password and (re)enable elfeed-protocol sync.
+Unlike the one-shot `use-package' :config form this is called from,
+safe to call again (e.g. via \\[azos/elfeed-protocol-init-feeds]) if
+a previous attempt failed, such as the YubiKey not being plugged in
+yet — it re-spawns the `pass' process and re-prompts for the PIN."
+  (interactive)
   (make-process
    :name "elfeed-protocol-pass"
    :command '("sh" "-c" "pass zakobar.com 2>/dev/null | head -1")
@@ -234,10 +247,20 @@ gpg/pass warning off the captured password.
    :filter (lambda (proc chunk)
              (process-put proc 'output (concat (or (process-get proc 'output) "") chunk)))
    :sentinel (lambda (proc _event)
-               (setq elfeed-feeds
-                     `(("owncloud+https://aner@nextcloud.zakobar.com"
-                        :password ,(string-trim (process-get proc 'output)))))
-               (elfeed-protocol-enable))))
+               (let ((password (string-trim (or (process-get proc 'output) ""))))
+                 (if (string-empty-p password)
+                     (message "elfeed-protocol: `pass zakobar.com' produced no output; retry with M-x azos/elfeed-protocol-init-feeds")
+                   (setq elfeed-feeds
+                         `(("owncloud+https://aner@nextcloud.zakobar.com"
+                            :password ,password)))
+                   (elfeed-protocol-enable)
+                   (elfeed-update))))))
+
+(use-package elfeed-protocol
+  :after elfeed
+  :config
+  (setq elfeed-protocol-enabled-protocols '(owncloud))
+  (azos/elfeed-protocol-init-feeds))
 #+end_src
 
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