Make undigest work with multipart/mixed messages

* test/lisp/mail/undigest.el: New test file (bug#12873).
* lisp/mail/undigest.el (rmail-digest-methods): Install
rmail-digest-parse-mixed-mime.
(rmail-content-type-boundary): New function, to get a specific
Content-type boundary.
(rmail-digest-parse-mixed-mime): New function, to search for a
multipart/digest message inside a multipart/mixed message.

1 files changed, 354 insertions, 0 deletions

diff --git a/test/lisp/mail/undigest-tests.el b/test/lisp/mail/undigest-tests.el
new file mode 100644
index 00000000000..24059aa349a
--- /dev/null
+++ b/test/lisp/mail/undigest-tests.el
@@ -0,0 +1,354 @@
+;;; undigest.el --- Tests for undigest.el  -*- lexical-binding:t -*-
+
+;; Copyright (C) 2022 Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Code:
+
+(require 'ert)
+(require 'rmail)
+(require 'undigest)
+
+;;; Variables:
+;; Some digests for testing.
+(defvar rmail-rfc934-digest "From tester  Fri Jan 24 00:00:00 2022
+From: Digester <digester@digester.com>
+To: Undigester <undigester@undigester.com>
+Date: ddd, dd mmm yy hh:mm:ss zzz
+Subject: Testing you
+
+Testing the undigester.
+
+------- Message sep
+
+From: NN1 <nn1@nn1.com>
+To: Digester <digester@digester.com>
+Date: ddd, dd mmm yy hh:mm:ss zzz
+Subject: Message one
+
+This is message one.
+
+------- Message sep
+
+From: NN2 <nn2@nn2.com>
+To: Digester <digester@digester.com>
+Date: ddd, dd mmm yy hh:mm:ss zzz
+Subject: Message two
+
+This is message two.
+"
+
+  "RFC 934 digest.")
+
+(defvar rmail-rfc1153-digest-strict "From tester  Fri Jan 24 00:00:00 2022
+Date: ddd, dd mmm yy hh:mm:ss zzz
+From: Digester <digester@digester.com>
+To: Undigester <undigester@undigester.com>
+Date: ddd, dd mmm yy hh:mm:ss zzz
+Subject: Testing you
+
+Some mailing list information.
+
+Today's Topics:
+
+    1.  Message One Subject (Sender)
+    2.  Message Two Subject (Sender)
+
+----------------------------------------------------------------------
+
+Date: ddd, dd mmm yy hh:mm:ss zzz
+From: NN1 <nn1@nn1.com>
+Subject: Message One Subject
+
+This is message one.
+
+------------------------------
+
+Date: ddd, dd mmm yy hh:mm:ss zzz
+From: NN2 <nn2@nn2.com>
+Subject: Message Two Subject
+
+This is message two.
+
+------------------------------
+
+End of Digest.
+************************************
+"
+  "RFC 1153 strict style digest.")
+
+(defvar rmail-rfc1153-digest-less-strict "From tester  Fri Jan 24 00:00:00 2022
+From: Digester <digester@digester.com>
+To: Undigester <undigester@undigester.com>
+Date: ddd, dd mmm yy hh:mm:ss zzz
+Subject: Testing you
+
+Some mailing list information.
+
+Today's Topics:
+
+    1.  Message One Subject (Sender)
+    2.  Message Two Subject (Sender)
+
+----------------------------------------------------------------------
+
+Date: ddd, dd mmm yy hh:mm:ss zzz
+From: NN1 <nn1@nn1.com>
+Subject: Message One Subject
+
+This is message one.
+
+------------------------------
+
+Date: ddd, dd mmm yy hh:mm:ss zzz
+From: NN2 <nn2@nn2.com>
+Subject: Message Two Subject
+
+This is message two.
+
+------------------------------
+
+Subject: Digest Footer
+
+End of Sbcl-help Digest, Vol 158, Issue 4
+*****************************************
+"
+  "RFC 1153 style digest, with a Subject header.")
+
+(defvar rmail-rfc1153-digest-sloppy "From tester  Fri Jan 24 00:00:00 2022
+From: Digester <digester@digester.com>
+To: Undigester <undigester@undigester.com>
+Date: ddd, dd mmm yy hh:mm:ss zzz
+Subject: Testing you
+
+Some mailing list information.
+
+Today's Topics:
+
+    1.  Message One Subject (Sender)
+    2.  Message Two Subject (Sender)
+
+----------------------------------------------------------------------
+
+Date: ddd, dd mmm yy hh:mm:ss zzz
+From: NN1 <nn1@nn1.com>
+Subject: Message One Subject
+
+This is message one.
+
+------------------------------
+
+Date: ddd, dd mmm yy hh:mm:ss zzz
+From: NN2 <nn2@nn2.com>
+Subject: Message Two Subject
+
+This is message two.
+
+------------------------------
+
+Subject: Digest Footer
+
+______________________________________________
+Some blurb.
+
+End of Digest.
+************************************
+"
+  "RFC 1153 sloppy style digest.")
+
+(defvar rmail-rfc1521-mime-digest "From tester  Fri Jan 24 00:00:00 2022
+From: Digester <digester@digester.com>
+To: Undigester <undigester@undigester.com>
+Date: ddd, dd mmm yy hh:mm:ss zzz
+Subject: Test digest
+MIME-Version: 1.0
+Content-Type: multipart/digest; boundary=\"----- =_aaaaaaaaaa0\"
+
+------- =_aaaaaaaaaa0
+Content-Type: message/rfc822
+
+From: NN1 <nn1@nn1.com>
+To: Digester <digester@digester.com>
+Date: ddd, dd mmm yy hh:mm:ss zzz
+Subject: Message one
+
+Message one.
+
+------- =_aaaaaaaaaa0
+
+From: NN2 <nn2@nn2.com>
+To: Digester <digester@digester.com>
+Date: ddd, dd mmm yy hh:mm:ss zzz
+Subject: Message two
+
+Message two.
+
+------- =_aaaaaaaaaa0
+"
+  "RFC 1521 style MIME digest.")
+
+(defvar rmail-multipart-mixed-digest
+  "From tester  Fri Jan 24 00:00:00 2022
+From: Digester <digester@digester.com>
+To: Undigester <undigester@undigester.com>
+Date: ddd, dd mmm yy hh:mm:ss zzz
+Subject: Test digest
+Content-Type: multipart/mixed; boundary=\"===============2529375068597856000==\"
+MIME-Version: 1.0
+
+--===============2529375068597856000==
+Content-Type: text/plain;
+MIME-Version: 1.0
+Content-Description: Today's Topics
+
+Some message.
+
+--===============2529375068597856000==
+Content-Type: multipart/digest; boundary=\"===============6060050777038710134==\"
+MIME-Version: 1.0
+
+--===============6060050777038710134==
+Content-Type: message/rfc822
+MIME-Version: 1.0
+
+From: NN1 <nn1@nn1.com>
+To: Digester <digester@digester.com>
+Date: ddd, dd mmm yy hh:mm:ss zzz
+Subject: Message one
+
+Message one.
+
+--===============6060050777038710134==
+Content-Type: message/rfc822
+MIME-Version: 1.0
+
+From: NN2 <nn2@nn2.com>
+To: Digester <digester@digester.com>
+Date: ddd, dd mmm yy hh:mm:ss zzz
+Subject: Message two
+
+Message two.
+
+--===============6060050777038710134==--
+
+--===============2529375068597856000==
+Content-Type: text/plain;
+MIME-Version: 1.0
+Content-Description: Digest Footer
+
+The footer.
+
+--===============2529375068597856000==--"
+  "RFC 1521 digest inside a multipart/mixed message.")
+
+;;; Utils:
+(defun rmail-message-content (message)
+  "Return the content of the message numbered MESSAGE."
+  (rmail-show-message message)
+  (let ((beg (rmail-msgbeg rmail-current-message))
+        (end (rmail-msgend rmail-current-message)))
+    (with-current-buffer rmail-view-buffer
+      (save-excursion
+	(goto-char beg)
+	(search-forward "\n\n" end nil)
+	(buffer-substring-no-properties (match-end 0) end)))))
+
+;;; Tests:
+(ert-deftest rmail-undigest-test-rfc934-digest ()
+  "Test that we can undigest a RFC 934 digest."
+  (let ((file (make-temp-file "undigest-test-")))
+    (with-temp-file file
+      (insert rmail-rfc934-digest)
+      (write-region nil nil file)
+      (rmail file)
+      (undigestify-rmail-message)
+      (should (= rmail-total-messages 4))
+      (should (string= (rmail-message-content 2) "Testing the undigester.\n\n"))
+      (should (string= (rmail-message-content 3) "This is message one.\n\n"))
+      (should (string= (rmail-message-content 4) "This is message two.\n")))))
+
+(ert-deftest rmail-undigest-test-rfc1153-digest-strict ()
+  "Test that we can undigest a strict RFC 1153 digest."
+  :expected-result :failed
+  (let ((file (make-temp-file "undigest-test-")))
+    (with-temp-file file
+      (insert rmail-rfc1153-digest-strict)
+      (write-region nil nil file)
+      (rmail file)
+      (should
+       (condition-case nil
+           (progn
+             ;; This throws an error, because the Trailer is not recognized
+             ;; as a valid RFC 822 (or later) message.
+             (undigestify-rmail-message)
+             (should (string= (rmail-message-content 2) "Testing the undigester.\n\n"))
+             (should (string= (rmail-message-content 3) "This is message one.\n\n"))
+             (should (string= (rmail-message-content 4) "This is message two.\n"))
+             t)
+         (error nil))))))
+
+(ert-deftest rmail-undigest-test-rfc1153-less-strict-digest ()
+  "Test that we can undigest a RFC 1153 with a Subject header in its footer."
+  (let ((file (make-temp-file "undigest-test-")))
+    (with-temp-file file
+      (insert rmail-rfc1153-digest-less-strict)
+      (write-region nil nil file)
+      (rmail file)
+      (undigestify-rmail-message)
+      (should (= rmail-total-messages 5))
+      (should (string= (rmail-message-content 3) "This is message one.\n\n"))
+      (should (string= (rmail-message-content 4) "This is message two.\n\n")))))
+
+(ert-deftest rmail-undigest-test-rfc1153-sloppy-digest ()
+  "Test that we can undigest a sloppy RFC 1153 digest."
+  (let ((file (make-temp-file "undigest-test-")))
+    (with-temp-file file
+      (insert rmail-rfc1153-digest-sloppy)
+      (write-region nil nil file)
+      (rmail file)
+      (undigestify-rmail-message)
+      (should (= rmail-total-messages 5))
+      (should (string= (rmail-message-content 3) "This is message one.\n\n"))
+      (should (string= (rmail-message-content 4) "This is message two.\n\n")))))
+
+;; This fails because `rmail-digest-parse-mime' combines the preamble with the
+;; first message of the digest.  And then, it doesn't get rid of the last
+;; separator.
+(ert-deftest rmail-undigest-test-rfc1521-mime-digest ()
+  "Test that we can undigest a RFC 1521 MIME digest."
+  :expected-result :failed
+  (let ((file (make-temp-file "undigest-test-")))
+    (with-temp-file file
+      (insert rmail-rfc1521-mime-digest)
+      (write-region nil nil file)
+      (rmail file)
+      (undigestify-rmail-message)
+      (should (= rmail-total-messages 3))
+      (should (string= (rmail-message-content 2) "Message one.\n\n"))
+      (should (string= (rmail-message-content 3) "Message two.\n\n")))))
+
+(ert-deftest rmail-undigest-test-multipart-mixed-digest ()
+  "Test that we can undigest a digest inside a multipart/mixed digest."
+  (let ((file (make-temp-file "undigest-test-")))
+    (with-temp-file file
+      (insert rmail-multipart-mixed-digest)
+      (write-region nil nil file)
+      (rmail file)
+      (undigestify-rmail-message)
+      (should (= rmail-total-messages 4))
+      (should (string= (rmail-message-content 2) "Message one.\n\n"))
+      (should (string= (rmail-message-content 3) "Message two.\n\n")))))