Notify the user a bit more before clicking IDNA links

* lisp/net/shr.el (shr-urlify): Show the puny-encoded domain name
in the mouseover string (bug#25600).

1 files changed, 18 insertions, 6 deletions

diff --git a/lisp/net/shr.el b/lisp/net/shr.el
index 2dc1036e412..aa62e724636 100644
--- a/lisp/net/shr.el
+++ b/lisp/net/shr.el
@@ -38,6 +38,7 @@
 (require 'seq)
 (require 'svg)
 (require 'image)
+(require 'puny)
 
 (defgroup shr nil
   "Simple HTML Renderer"
@@ -1209,12 +1210,23 @@ START, and END.  Note that START and END should be markers."
   (add-text-properties
    start (point)
    (list 'shr-url url
-         'help-echo (let ((iri (or (ignore-errors
-                                     (decode-coding-string
-                                      (url-unhex-string url)
-                                      'utf-8 t))
-                                   url)))
-                      (if title (format "%s (%s)" iri title) iri))
+         'help-echo (let ((parsed (url-generic-parse-url
+                                   (or (ignore-errors
+                                         (decode-coding-string
+                                          (url-unhex-string url)
+                                          'utf-8 t))
+                                       url)))
+                          iri)
+                      ;; If we have an IDNA domain, then show the
+                      ;; decoded version in the mouseover to let the
+                      ;; user know that there's something possibly
+                      ;; fishy.
+                      (setf (url-host parsed)
+                            (puny-encode-domain (url-host parsed)))
+                      (setq iri (url-recreate-url parsed))
+                      (if title
+                          (format "%s (%s)" iri title)
+                        iri))
          'follow-link t
          'mouse-face 'highlight))
   ;; Don't overwrite any keymaps that are already in the buffer (i.e.,