netrc parser revamp (was: gmail and pop3)

[Ted Zlatanov <tzz@lifelogs.com>]

On Thu, 06 Jun 2013 14:06:35 -0400 Ted Zlatanov <tzz@lifelogs.com> wrote: 

TZ> After sending this, I saw bug#12097 which has some background on this.

TZ> So definitely a TODO for me is to rewrite that parser.  Sorry for the
TZ> trouble.

Take a look at the following.  It implements a parser that will go
through the current buffer and extract all the netrc entries, respecting
multiline entries and other weird things.  Also, netrc used single
quotes (double quotes are a Gnusism apparently), so this supports both
single and double quotes.  Entries must start with "machine" which is
required in the netrc format.

It doesn't treat "macdef" entries especially because I have never seen
them used by anyone and didn't want the extra complexity.  If you feel
they must be supported, speak up.

e.g. try it on this netrc content:

#+begin_src text
machine A login tzz@lifelogs.com password "A lovely A"
# test again
machine B login tzz@lifelogs.com
 password 'B single quotes B'
default other info goes here
#+end_src

If this works as expected I'll put it into auth-source.el.  So please
try it on your weird wacky netrc files :)

Thanks
Ted

#+begin_src lisp
(defun auth-source-netrc-parse-next-interesting ()
  "Advance to the next interesting position in the current buffer."
  ;; If we're looking at a comment or are at the end of the line, move forward
  (while (or (looking-at "#")
             (and (eolp)
                  (not (eobp))))
    (forward-line 1))
  (skip-chars-forward "\t "))

(defun auth-source-netrc-parse-one ()
  "Read one thing from the current buffer."
  (auth-source-netrc-parse-next-interesting)

  (when (or (looking-at "'\\([^']+\\)'")
            (looking-at "\"\\([^\"]+\\)\"")
            (looking-at "\\([^ \t\n]+\\)"))
    (forward-char (length (match-string 0)))
    (auth-source-netrc-parse-next-interesting)
    (match-string-no-properties 1)))

(defun auth-source-netrc-parse-entries ()
  "Parse all the netrc entries from the current buffer."
  (let (item item2 all alist default)
    (while (setq item (auth-source-netrc-parse-one))

      (setq default (equal item "default"))
      ;; We're starting a new machine.  Save the old one.
      (when (or default
                (equal item "machine"))
        (when alist
          (push alist all))
        (setq alist nil))

      ;; In default entries, we don't have a next token.
      ;; We store them as ("machine" . t)
      (if default
          (push (cons "machine" t) alist)
        ;; Not a default entry.  Grab the next item.
        (when (setq item2 (auth-source-netrc-parse-one))
          (push (cons item item2) alist))))
    (when alist
      (push alist all))
    (nreverse all)))

#+end_src