Preserve face text properties in comint prompt.

Fixes: debbugs:20084

* lisp/font-lock.el (font-lock--remove-face-from-text-property): New
function.  Adapted from the previously commented out
remove-single-text-property.
Remove previously unused and commented out auxiliary function
remove-text-property and obsolete comment.
* lisp/comint.el (comint-output-filter): Use it to remove
comint-highlight-prompt.
(comint-snapshot-last-prompt, comint-output-filter): Use
font-lock-prepend-text-property for comint-highlight-prompt.
* test/automated/textprop-tests.el: New file.
(textprop-tests-font-lock--remove-face-from-text-property): New test.

Thus, the original face text property of a prompt "candidate" (the
last line of an output chunk not ending with a newline) is
preserved.  This amends the fix for bug#14744.

2 files changed, 62 insertions, 0 deletions

diff --git a/test/ChangeLog b/test/ChangeLog
index a9cad319ead..30b88412468 100644
--- a/test/ChangeLog
+++ b/test/ChangeLog
@@ -1,3 +1,8 @@
+2015-03-27  Wolfgang Jenkner  <wjenkner@inode.at>
+
+        * automated/textprop-tests.el: New file.
+        (textprop-tests-font-lock--remove-face-from-text-property): New test.
+
 2015-03-24  Michael Albinus  <michael.albinus@gmx.de>
 
         * automated/tramp-tests.el (tramp-test18-file-attributes)
diff --git a/test/automated/textprop-tests.el b/test/automated/textprop-tests.el
new file mode 100644
index 00000000000..310a7a0e976
--- /dev/null
+++ b/test/automated/textprop-tests.el
@@ -0,0 +1,57 @@
+;;; textprop-tests.el --- Test suite for text properties.
+
+;; Copyright (C) 2015 Free Software Foundation, Inc.
+
+;; Author: Wolfgang Jenkner <wjenkner@inode.at>
+;; Keywords: internal
+
+;; 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/>.
+
+;;; Code:
+
+(require 'ert)
+
+(ert-deftest textprop-tests-font-lock--remove-face-from-text-property ()
+  "Test `font-lock--remove-face-from-text-property'."
+  (let* ((string "foobar")
+         (stack (list string))
+         (faces '(bold (:foreground "red") underline)))
+    ;; Build each string in `stack' by adding a face to the previous
+    ;; string.
+    (let ((faces (reverse faces)))
+      (push (copy-sequence (car stack)) stack)
+      (put-text-property 0 3 'font-lock-face (pop faces) (car stack))
+      (push (copy-sequence (car stack)) stack)
+      (put-text-property 3 6 'font-lock-face (pop faces) (car stack))
+      (push (copy-sequence (car stack)) stack)
+      (font-lock-prepend-text-property 2 5
+                                       'font-lock-face (pop faces) (car stack)))
+    ;; Check that removing the corresponding face from each string
+    ;; yields the previous string in `stack'.
+    (while faces
+      ;; (message "%S" (car stack))
+      (should (equal-including-properties
+               (progn
+                 (font-lock--remove-face-from-text-property 0 6
+                                                            'font-lock-face
+                                                            (pop faces)
+                                                            (car stack))
+                 (pop stack))
+               (car stack))))
+    ;; Sanity check.
+    ;; (message "%S" (car stack))
+    (should (and (equal-including-properties (pop stack) string)
+                 (null stack)))))