utf-7 and utf-7-imap are not ASCII-compatible (bug#40407)

* lisp/international/mule-conf.el (utf-7, utf-7-imap):
Add expedient to disable the :ascii-compatible-p property set
automatically by define-coding-system.
* test/lisp/international/mule-tests.el (mule-utf-7): New test.

2 files changed, 23 insertions, 0 deletions

diff --git a/lisp/international/mule-conf.el b/lisp/international/mule-conf.el
index e6e6135243f..e5ea491a373 100644
--- a/lisp/international/mule-conf.el
+++ b/lisp/international/mule-conf.el
@@ -1517,6 +1517,9 @@ for decoding and encoding files, process I/O, etc."
   :charset-list '(unicode)
   :pre-write-conversion 'utf-7-pre-write-conversion
   :post-read-conversion 'utf-7-post-read-conversion)
+;; FIXME: `define-coding-system' automatically sets :ascii-compatible-p,
+;; but UTF-7 is not ASCII compatible; disable (bug#40407).
+(coding-system-put 'utf-7 :ascii-compatible-p nil)
 
 (define-coding-system 'utf-7-imap
   "UTF-7 encoding of Unicode, IMAP version (RFC 2060)"
@@ -1525,6 +1528,8 @@ for decoding and encoding files, process I/O, etc."
   :charset-list '(unicode)
   :pre-write-conversion 'utf-7-imap-pre-write-conversion
   :post-read-conversion 'utf-7-imap-post-read-conversion)
+;; See comment for utf-7 above.
+(coding-system-put 'utf-7-imap :ascii-compatible-p nil)
 
 ;; Use us-ascii for terminal output if some other coding system is not
 ;; specified explicitly.
diff --git a/test/lisp/international/mule-tests.el b/test/lisp/international/mule-tests.el
index 91e3c2279f0..bb96943888f 100644
--- a/test/lisp/international/mule-tests.el
+++ b/test/lisp/international/mule-tests.el
@@ -48,6 +48,24 @@
                         (append (kbd "C-x RET c u t f - 8 RET C-u C-u c a b RET") nil)))
                    (read-string "prompt:")))))
 
+(ert-deftest mule-utf-7 ()
+  ;; utf-7 and utf-7-imap are not ASCII-compatible.
+  (should-not (coding-system-get 'utf-7 :ascii-compatible-p))
+  (should-not (coding-system-get 'utf-7-imap :ascii-compatible-p))
+  ;; Invariant ASCII subset.
+  (let ((s (apply #'string (append (number-sequence #x20 #x25)
+                                   (number-sequence #x27 #x7e)))))
+    (should (equal (encode-coding-string s 'utf-7-imap) s))
+    (should (equal (decode-coding-string s 'utf-7-imap) s)))
+  ;; Escaped ampersand.
+  (should (equal (encode-coding-string "a&bcd" 'utf-7-imap) "a&-bcd"))
+  (should (equal (decode-coding-string "a&-bcd" 'utf-7-imap) "a&bcd"))
+  ;; Ability to encode Unicode.
+  (should (equal (check-coding-systems-region "あ" nil '(utf-7-imap)) nil))
+  (should (equal (encode-coding-string "あ" 'utf-7-imap) "&MEI-"))
+  (should (equal (decode-coding-string "&MEI-" 'utf-7-imap) "あ")))
+
+
 ;; Stop "Local Variables" above causing confusion when visiting this file.