emacs: Observe the charset of MIME parts when reading them.

`notmuch--get-bodypart-raw' previously assumed that all non-binary MIME
parts could be successfully read by assuming that they were UTF-8
encoded. This was demonstrated to be wrong, specifically when a part was
marked as ISO8859-1 and included accented characters (which were
incorrectly rendered as a result).

Rather than assuming UTF-8, attempt to use the part's declared charset
when reading it, falling back to US-ASCII if the declared charset is
unknown, unsupported or invalid.

diff --git a/emacs/notmuch-lib.el b/emacs/notmuch-lib.el
index 78978ee34c9b806438c3fd9c497a11c11f9eb41c..f05ded6f36df7941a9dea189382bdd250ff5e14d 100644 (file)
--- a/emacs/notmuch-lib.el
+++ b/emacs/notmuch-lib.el
@@ -23,6 +23,7 @@
 
 ;;; Code:
 
+(require 'mm-util)
 (require 'mm-view)
 (require 'mm-decode)
 (require 'cl)
@@ -572,7 +573,20 @@ the given type."
                                   ,@(when process-crypto '("--decrypt"))
                                   ,(notmuch-id-to-query (plist-get msg :id))))
                           (coding-system-for-read
-                           (if binaryp 'no-conversion 'utf-8)))
+                           (if binaryp 'no-conversion
+                             (let ((coding-system (mm-charset-to-coding-system
+                                                   (plist-get part :content-charset))))
+                               ;; Sadly,
+                               ;; `mm-charset-to-coding-system' seems
+                               ;; to return things that are not
+                               ;; considered acceptable values for
+                               ;; `coding-system-for-read'.
+                               (if (coding-system-p coding-system)
+                                   coding-system
+                                 ;; RFC 2047 says that the default
+                                 ;; charset is US-ASCII. RFC6657
+                                 ;; complicates this somewhat.
+                                 'us-ascii)))))
                       (apply #'call-process notmuch-command nil '(t nil) nil args)
                       (buffer-string))))))
     (when (and cache data)