register-read-with-preview: Quit if user input C-g or ESC

* lisp/register.el (register-read-with-preview):
Quit if user input C-g or ESC (bug#27634).
* doc/emacs/regs.texi (Registers): Update manual.
* test/lisp/register-tests.el (register-test-bug27634): Add test.

3 files changed, 51 insertions, 1 deletions

diff --git a/doc/emacs/regs.texi b/doc/emacs/regs.texi
index 7369f6b05b6..40e3e2c1c31 100644
--- a/doc/emacs/regs.texi
+++ b/doc/emacs/regs.texi
@@ -15,7 +15,10 @@ jump back to that position once, or many times.
   Each register has a name that consists of a single character, which
 we will denote by @var{r}; @var{r} can be a letter (such as @samp{a})
 or a number (such as @samp{1}); case matters, so register @samp{a} is
-not the same as register @samp{A}.
+not the same as register @samp{A}.  You can also set a register in
+non-alphanumeric characters, for instance @samp{*} or @samp{C-d}.
+Note, it's not possible to set a register in @samp{C-g} or @samp{ESC},
+because these keys are reserved to terminate interactive commands.
 
 @findex view-register
   A register can store a position, a piece of text, a rectangle, a
diff --git a/lisp/register.el b/lisp/register.el
index 7cc3ccd870c..e395963f56a 100644
--- a/lisp/register.el
+++ b/lisp/register.el
@@ -164,6 +164,10 @@ display such a window regardless."
 		       help-chars)
 	    (unless (get-buffer-window buffer)
 	      (register-preview buffer 'show-empty)))
+          (when (or (eq ?\C-g last-input-event)
+                    (eq 'escape last-input-event)
+                    (eq ?\C-\[ last-input-event))
+            (keyboard-quit))
 	  (if (characterp last-input-event) last-input-event
 	    (error "Non-character input-event")))
       (and (timerp timer) (cancel-timer timer))
diff --git a/test/lisp/register-tests.el b/test/lisp/register-tests.el
new file mode 100644
index 00000000000..0425bc0e0f4
--- /dev/null
+++ b/test/lisp/register-tests.el
@@ -0,0 +1,43 @@
+;;; register-tests.el --- tests for register.el  -*- lexical-binding: t-*-
+
+;; Copyright (C) 2017 Free Software Foundation, Inc.
+
+;; Author: Tino Calacha <tino.calancha@gmail.com>
+;; Keywords:
+
+;; 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 <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+
+;;; Code:
+(require 'ert)
+(require 'cl-lib)
+
+(ert-deftest register-test-bug27634 ()
+  "Test for http://debbugs.gnu.org/27634 ."
+  (dolist (event (list ?\C-g 'escape ?\C-\[))
+    (cl-letf (((symbol-function 'read-key) #'ignore)
+              (last-input-event event)
+              (register-alist nil))
+      (should (equal 'quit
+                     (condition-case err
+                         (call-interactively 'point-to-register)
+                       (quit (car err)))))
+      (should-not register-alist))))
+
+(provide 'register-tests)
+;;; register-tests.el ends here