email: Quote display names when serializing email addresses.

* email/email.scm (interpret-address): Quote display names when they
have illegal characters.
* tests/email.scm ("quote display-name when serializing email
addresses with illegal characters", "do not quote display-name when
serializing email addresses without illegal characters"): New tests.

1 files changed, 15 insertions, 1 deletions

diff --git a/email/email.scm b/email/email.scm
index ff0f5e9..22d9739 100644
--- a/email/email.scm
+++ b/email/email.scm
@@ -957,7 +957,21 @@ For example,
   (match-lambda
     ((('name . name)
       ('address . address))
-     (format #f "~a <~a>" name address))
+     (string-append
+      ;; Quote display names with illegal characters.
+      (let ((char-set:atext (char-set-intersection
+                             char-set:ascii
+                             (char-set-union char-set:letter
+                                             char-set:digit
+                                             (char-set #\! #\# #\$ #\%
+                                                       #\& #\' #\* #\+
+                                                       #\- #\/ #\= #\?
+                                                       #\^ #\_ #\` #\{
+                                                       #\| #\} #\~)))))
+        (if (string-every char-set:atext name)
+            name
+            (string-append "\"" name "\"")))
+      " <" address ">"))
     ((('address . address)) address)))
 
 (define (parse-email-body headers body)