From 2674b6a08a90b9a97d3adf2b3e4497b61880e173 Mon Sep 17 00:00:00 2001
From: dickmao <none>
Date: Fri, 7 Feb 2020 19:33:13 -0500
Subject: [PATCH] Question assumption that mm source buffer is unibyte

In my Gnus experience, the source buffer that mm-shr acts upon can be
multibyte.

* lisp/gnus/mm-decode.el (mm-with-part): propagate multibyte/unibyte setting
from source buffer to target.
* test/lisp/gnus/mm-decode-tests.el (test-mm-decode-multibyte): add test
---
 lisp/gnus/mm-decode.el            |  8 ++-----
 test/lisp/gnus/mm-decode-tests.el | 39 +++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 6 deletions(-)
 create mode 100644 test/lisp/gnus/mm-decode-tests.el

diff --git a/lisp/gnus/mm-decode.el b/lisp/gnus/mm-decode.el
index d33bb56dc9..19a18b4f45 100644
--- a/lisp/gnus/mm-decode.el
+++ b/lisp/gnus/mm-decode.el
@@ -1255,16 +1255,12 @@ mm-handle-displayed-p
 
 (defmacro mm-with-part (handle &rest forms)
   "Run FORMS in the temp buffer containing the contents of HANDLE."
-  ;; The handle-buffer's content is a sequence of bytes, not a sequence of
-  ;; chars, so the buffer should be unibyte.  It may happen that the
-  ;; handle-buffer is multibyte for some reason, in which case now is a good
-  ;; time to adjust it, since we know at this point that it should
-  ;; be unibyte.
   `(let* ((handle ,handle))
      (when (and (mm-handle-buffer handle)
 		(buffer-name (mm-handle-buffer handle)))
        (with-temp-buffer
-	 (mm-disable-multibyte)
+         (set-buffer-multibyte (buffer-local-value 'enable-multibyte-characters
+                                                   (mm-handle-buffer handle)))
 	 (insert-buffer-substring (mm-handle-buffer handle))
 	 (mm-decode-content-transfer-encoding
 	  (mm-handle-encoding handle)
diff --git a/test/lisp/gnus/mm-decode-tests.el b/test/lisp/gnus/mm-decode-tests.el
new file mode 100644
index 0000000000..8a9d471b74
--- /dev/null
+++ b/test/lisp/gnus/mm-decode-tests.el
@@ -0,0 +1,39 @@
+;;; mm-decode-tests.el --- tests for gnus/mm-decode.el    -*- lexical-binding:t -*-
+
+;; Copyright (C) 2019-2020 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 'mm-decode)
+
+(ert-deftest test-mm-decode-multibyte ()
+  (should
+   (or (not (fboundp 'libxml-parse-html-region))
+       (with-temp-buffer
+         (set-buffer-multibyte t)
+         (save-excursion
+           (insert "<p>最近也想尝试,但是感觉蛮难的,比如不知道如何在"))
+         (let ((handle (mm-make-handle
+                        (current-buffer)
+                        (rfc2231-parse-qp-string
+                         "Content-Type: text/html; charset=UTF-8"))))
+           (not (zerop (length (with-temp-buffer (mm-shr handle)
+                                                 (buffer-string))))))))))
+
+;;; mm-decode-tests.el ends here
-- 
2.24.1