Subject: Test suite

From: Kévin Le Gouguec <[email-masked]>
Date: Tue, 30 Apr 2019 08:08:33 +0200

As part of the discussion on help-gnu-emacs[1], Stefan applied a simpler
patch in commit f478082f9f, only for font-lock-prepend-text-property
though.  Does it make sense to do the same in
font-lock-append-text-property?

As a learning experience with ERT, I wrote the attached test suite; with
the current master branch, only the prepend test passes, the other
fails.  Applying the same change in font-lock-append-text-property lets
both tests pass.

>From 7bd1a551de8cef452a7ade7eaa055d38bf3a0800 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?K=C3=A9vin=20Le=20Gouguec?= <[email-masked]>
Date: Tue, 30 Apr 2019 08:00:34 +0200
Subject: [PATCH] Add a test suite for anonymous face handling in text
 properties

* test/lisp/font-lock-tests.el: New test suite.  Only
font-lock-test-prepend-anonymous-face passes as of f478082f9f.
---
 test/lisp/font-lock-tests.el | 43 ++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 test/lisp/font-lock-tests.el

diff --git a/test/lisp/font-lock-tests.el b/test/lisp/font-lock-tests.el
new file mode 100644
index 0000000000..ad282f6cad
--- /dev/null
+++ b/test/lisp/font-lock-tests.el
@@ -0,0 +1,43 @@
+;;; 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)))))
+
+(provide 'font-lock-tests)
+
+;; font-lock-tests.el ends here
-- 
2.21.0

Apologies for posting all over the place.

[1]: http://lists.gnu.org/archive/html/help-gnu-emacs/2019-04/msg00289.html