Automatically detect whether .h file is C or C++

* lisp/progmodes/cc-mode.el (c-or-c++-mode): A new function which
analyses contents of the buffer to determine whether it looks like C++
source code and based on that enables c-mode or c++-mode.
(c-or-c++-mode--regexp): Regular expression which, when matches
a buffer, signals file is C++.

1 files changed, 65 insertions, 0 deletions

diff --git a/test/lisp/progmodes/cc-mode.el b/test/lisp/progmodes/cc-mode.el
new file mode 100644
index 00000000000..6cd9fa4bad5
--- /dev/null
+++ b/test/lisp/progmodes/cc-mode.el
@@ -0,0 +1,65 @@
+;;; cc-mode-tests.el --- Test suite for cc-mode.  -*- lexical-binning: t -*-
+
+;; Copyright (C) 2016 Free Software Foundation, Inc.
+
+;; Author: Michal Nazarewicz <mina86@mina86.com>
+;; Keywords:       internal
+;; Human-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)
+(require 'ert-x)
+(require 'cc-mode)
+
+(ert-deftest c-or-c++-mode ()
+  "Test c-or-c++-mode language detection."
+  (cl-letf* ((mode nil)
+             (do-test (lambda (content expected)
+                        (delete-region (point-min) (point-max))
+                        (insert content)
+                        (setq mode nil)
+                        (c-or-c++-mode)
+                        (unless(eq expected mode)
+                          (ert-fail
+                           (format "expected %s but got %s when testing '%s'"
+                                   expected mode content)))))
+             ((symbol-function 'c-mode) (lambda () (setq mode 'c-mode)))
+             ((symbol-function 'c++-mode) (lambda () (setq mode 'c++-mode))))
+    (with-temp-buffer
+      (mapc (lambda (content)
+              (funcall do-test content 'c++-mode)
+              (funcall do-test (concat "// " content) 'c-mode)
+              (funcall do-test (concat " * " content) 'c-mode))
+            '("using \t namespace \t std;"
+              "using \t std::string;"
+              "namespace \t {"
+              "namespace \t foo \t {"
+              "class \t Blah_42 \t {"
+              "class \t Blah_42 \t \n"
+              "class \t _42_Blah:public Foo {"
+              "template \t < class T >"
+              "template< class T >"
+              "#include <string>"
+              "#include<iostream>"
+              "#include \t <map>"))
+
+      (mapc (lambda (content) (funcall do-test content 'c-mode))
+            '("struct \t Blah_42 \t {"
+              "struct template {"
+              "#include <string.h>")))))