How to generate dynamic “Reply-To:” based on “Message-ID:”? [+detail]

问题

How can you generate a dynamic "Reply-To:" (and "From:") header in emacs/gnus based on Message-ID of the created message? I would like to use external (perl) script to generate a dynamic +detail part based on the "Messaged-ID:" header.

user+detail@example.net

I have managed to create a header with content generated by my external script. The script gets usenet group name as command line parameter. I would like to pass it the message-id value too.

My current code
~/.emacs :

'(gnus-posting-styles ("^pl\\.test$" ("Reply-To" message-make-reply-to)))

~/.gnus

(defun message-make-reply-to()
  (my-script ".../reply-to.pl" (message-fetch-field "Message-Id")))

(defun my-script(path &optional param) ....

The problem: the script does not receive message-id as its parameter (my-script gets correctly explicitly set parameter)

回答1:

;; Make sure the Message-ID header is present in newly created messages
(setq message-generate-headers-first '(Message-ID))

;; Prevent emacs from resetting the Message-ID before the message is sent.
(setq message-deletable-headers
      (remove 'Message-ID message-deletable-headers))

(setq gnus-posting-styles
      '(("^pl\\.test$"
         ("Reply-To" '(message-make-reply-to)))))

Note the additional quote and parentheses around message-make-reply-to. The explanation for this is that the function is run at different times, depending on whether it's given as a symbol or as a quoted s-expression.

If given as symbol, it is run when a lambda function is added to message-setup-hook. That happens in a message-mode-hook, i.e. right after the new buffer is created and switched into message-mode. The cause for this is some wild quoting/unquoting of values during creation of the lambda function.
If given as a quoted sexpr, evaluation is delayed until after the buffer is filled with initial values. It is close to the last code which is run on message setup.

Alternative Solution (without `gnus-posting-styles`)

In cases where the new header should be added to every new message, the Reply-To header can also be set using the message-header-setup-hook. A custom hook needs to be defined to add the header for each new message.

(defun reply-to-message-header-setup-hook ()
  (let* ((msg-id (message-fetch-field "Message-ID"))
         (reply-to (my-script ".../reply-to-pl" msg-id)))
    (message-add-header (concat "Reply-To: " reply-to))))

;; Call the hook every time a new message is created
(add-hook 'message-header-setup-hook 'reply-to-message-header-setup-hook)

;; Make sure the Message-ID header is present in newly created messages
(setq message-generate-headers-first '(Message-ID))

来源：https://stackoverflow.com/questions/15310574/how-to-generate-dynamic-reply-to-based-on-message-id-detail

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