Stop splicing anonymous faces in font-lock-append-text-property

This is the same fix as 2019-04-29 "Refrain from splicing anonymous
faces in text properties", which was only applied to
font-lock-prepend-text-property.

* lisp/font-lock.el (font-lock-append-text-property): Distinguish list
of faces from property list.
* test/lisp/font-lock-tests.el: New test suite.

(Bug#35476)

1 files changed, 41 insertions, 0 deletions

diff --git a/test/lisp/font-lock-tests.el b/test/lisp/font-lock-tests.el
new file mode 100644
index 00000000000..5d127039ff9
--- /dev/null
+++ b/test/lisp/font-lock-tests.el
@@ -0,0 +1,41 @@
+;;; font-lock-tests.el --- Test suite for font-lock. -*- lexical-binding: t -*-
+
+;; Copyright (C) 2019 Free Software Foundation, Inc.
+
+;; 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 <https://www.gnu.org/licenses/>.
+
+;;; Code:
+(require 'ert)
+
+(ert-deftest font-lock-test-append-anonymous-face ()
+  "Ensure `font-lock-append-text-property' does not splice anonymous faces."
+  (with-temp-buffer
+    (insert "foo")
+    (add-text-properties 1 3 '(face italic))
+    (font-lock-append-text-property 1 3 'face '(:strike-through t))
+    (should (equal (get-text-property 1 'face (current-buffer))
+                   '(italic (:strike-through t))))))
+
+(ert-deftest font-lock-test-prepend-anonymous-face ()
+  "Ensure `font-lock-prepend-text-property' does not splice anonymous faces."
+  (with-temp-buffer
+    (insert "foo")
+    (add-text-properties 1 3 '(face italic))
+    (font-lock-prepend-text-property 1 3 'face '(:strike-through t))
+    (should (equal (get-text-property 1 'face (current-buffer))
+                   '((:strike-through t) italic)))))
+
+;; font-lock-tests.el ends here