Handle case-insensitive filenames for load-path shadows (Bug#5845)

* lisp/emacs-lisp/shadow.el (load-path-shadows-find): Check for
shadowing with case-insensitive matching for files of case-insensitive
directories (as determined by `file-name-case-insensitive-p').
* test/lisp/emacs-lisp/shadow-tests.el: New test.
* test/lisp/emacs-lisp/shadow-resources/p1/foo.el:
* test/lisp/emacs-lisp/shadow-resources/p2/FOO.el: New test files.

3 files changed, 51 insertions, 0 deletions

diff --git a/test/lisp/emacs-lisp/shadow-resources/p1/foo.el b/test/lisp/emacs-lisp/shadow-resources/p1/foo.el
new file mode 100644
index 00000000000..465038bee5e
--- /dev/null
+++ b/test/lisp/emacs-lisp/shadow-resources/p1/foo.el
@@ -0,0 +1 @@
+;;; This file intentionally left blank.
diff --git a/test/lisp/emacs-lisp/shadow-resources/p2/FOO.el b/test/lisp/emacs-lisp/shadow-resources/p2/FOO.el
new file mode 100644
index 00000000000..465038bee5e
--- /dev/null
+++ b/test/lisp/emacs-lisp/shadow-resources/p2/FOO.el
@@ -0,0 +1 @@
+;;; This file intentionally left blank.
diff --git a/test/lisp/emacs-lisp/shadow-tests.el b/test/lisp/emacs-lisp/shadow-tests.el
new file mode 100644
index 00000000000..9d4969fe8bb
--- /dev/null
+++ b/test/lisp/emacs-lisp/shadow-tests.el
@@ -0,0 +1,49 @@
+;;; shadow-tests.el --- Test suite for shadow.  -*- lexical-binding: t -*-
+
+;; Copyright (C) 2018 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)
+(require 'shadow)
+(eval-when-compile (require 'cl-lib))
+
+(defconst shadow-tests-data-directory
+  (expand-file-name "lisp/emacs-lisp/shadow-resources"
+                    (or (getenv "EMACS_TEST_DIRECTORY")
+                        (expand-file-name "../../.."
+                                          (or load-file-name
+                                              buffer-file-name))))
+  "Directory for shadow test files.")
+
+(ert-deftest shadow-case-insensitive ()
+  "Test shadowing for case insensitive filenames."
+  ;; Override `file-name-case-insentive-p' so we test the same thing
+  ;; regardless of what file system we're running on.
+  (cl-letf (((symbol-function 'file-name-case-insensitive-p) (lambda (_f) t)))
+    (should (equal (list (expand-file-name "p1/foo" shadow-tests-data-directory)
+                         (expand-file-name "p2/FOO" shadow-tests-data-directory))
+                   (load-path-shadows-find
+                    (list (expand-file-name "p1/" shadow-tests-data-directory)
+                          (expand-file-name "p2/" shadow-tests-data-directory))))))
+  (cl-letf (((symbol-function 'file-name-case-insensitive-p) (lambda (_f) nil)))
+    (should-not (load-path-shadows-find
+                 (list (expand-file-name "p1/" shadow-tests-data-directory)
+                       (expand-file-name "p2/" shadow-tests-data-directory))))))
+
+;;; shadow-tests.el ends here.