Re: automatically changing FCC when From changes (or fill FCC only when sending)

[David Pinto <carandraug@gmail.com>]

On Fri, 22 Sept 2023 at 10:25, David Bremner <david@tethera.net> wrote:
> David Pinto <carandraug@gmail.com> writes:
> > [...]
> > You mention updating the "From" when the "To" changes with the
> > notmuch-address-post-completion-functions hook.  Could there be a hook
> > for when the "From" changes which I could use to change the FCC?
>
> My partial-solution relies on using completion to change To. If you are
> OK with that (i.e. manual editing without completion would not update
> Fcc), then the same scheme could work.
>
> Another option that seems technically feasible, but would involve some
> elisp programming, would be to write a command that re-applies the
> calculation of Fcc from From that already exists, and run that manually
> or perhaps opt-in to running it automatically on send.

Thank you for the hints.  I followed your hint and read the code for
notmuch-fcc-header-setup.  Then I wrote a function that updates the
FCC header and I hooked it to the address-post-completion:

    (defun update-fcc-header (addr)
      "Replace FCC header appropriate for given address"
      (let ((subdir (cdr (assoc addr notmuch-fcc-dirs 'string-match-p))))
        (when subdir
          (save-excursion
            (message-goto-fcc)
            (delete-region (line-beginning-position) (point))
            (insert "Fcc: " subdir)))))

    (defun update-fcc-header-when-from-address-completion (addr)
      "To hook on notmuch-address-post-completion-functions"
      (let ((cline (thing-at-point 'line)))
        (when (or (string-prefix-p "From:" cline)
                  (string-prefix-p "Resent-From:" cline))
          (update-fcc-header addr))))

    (setq notmuch-address-post-completion-functions
          '(update-fcc-header-when-from-address-completion))

It's here for anyone interested on the same functionality in the
future.

Do you think this is an interesting feature to be part of notmuch?  If
so, I could improve it and add some checks to cover for the different
notmuch-fcc-dirs types of values.

Best wishes
David