From a3a16b319faa413a2b8767fb155c014d2be83a0d Mon Sep 17 00:00:00 2001
From: 10sr <8.slashes@gmail.com>
Date: Mon, 7 Oct 2019 22:34:03 +0900
Subject: [PATCH 1/3] Disallow setting mode when it is not listed in whitelist

---
 editorconfig.el | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/editorconfig.el b/editorconfig.el
index 6b966223..17bca3ef 100644
--- a/editorconfig.el
+++ b/editorconfig.el
@@ -488,6 +488,10 @@ to non-nil when FINAL-NEWLINE is true."
              (> (string-to-number length) 0))
     (setq fill-column (string-to-number length))))
 
+(defvar editorconfig-file-type-emacs-whitelist
+  '()
+  "List of known `major-mode' that can be used for file_type_emacs value.")
+
 (defun editorconfig-set-major-mode-from-name (filetype)
   "Set buffer `major-mode' by FILETYPE.
 
@@ -499,7 +503,12 @@ FILETYPE should be s string like `\"ini\"`, if not nil or empty string."
                                    "-mode")))))
     (when mode
       (if (fboundp mode)
-          (editorconfig-apply-major-mode-safely mode)
+          (if (apply 'provided-mode-derived-p mode
+                     editorconfig-file-type-emacs-whitelist)
+              (editorconfig-apply-major-mode-safely mode)
+            (display-warning :error (format "Major-mode `%S' is not listed in `%S'"
+                                            mode
+                                            'editorconfig-file-type-emacs-whitelist)))
         (display-warning :error (format "Major-mode `%S' not found"
                                         mode))
         nil))))

From c9de2a46979102e3cc21d2d63619b088bacd2a5c Mon Sep 17 00:00:00 2001
From: 10sr <8.slashes@gmail.com>
Date: Tue, 8 Oct 2019 13:40:49 +0900
Subject: [PATCH 2/3] Add editorconfig-file-type-emacs-whitelist value

---
 editorconfig.el | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/editorconfig.el b/editorconfig.el
index 17bca3ef..64ab20e2 100644
--- a/editorconfig.el
+++ b/editorconfig.el
@@ -489,7 +489,9 @@ to non-nil when FINAL-NEWLINE is true."
     (setq fill-column (string-to-number length))))
 
 (defvar editorconfig-file-type-emacs-whitelist
-  '()
+  (append (mapcar 'car
+                  editorconfig-indentation-alist)
+          '(conf-mode))
   "List of known `major-mode' that can be used for file_type_emacs value.")
 
 (defun editorconfig-set-major-mode-from-name (filetype)

From aefcc0be4189c500570043569c142b096d9eef9d Mon Sep 17 00:00:00 2001
From: 10sr <8.slashes@gmail.com>
Date: Tue, 8 Oct 2019 13:55:05 +0900
Subject: [PATCH 3/3] Fix support for Emacs<26

---
 editorconfig.el | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/editorconfig.el b/editorconfig.el
index 64ab20e2..b38a3aa8 100644
--- a/editorconfig.el
+++ b/editorconfig.el
@@ -494,6 +494,18 @@ to non-nil when FINAL-NEWLINE is true."
           '(conf-mode))
   "List of known `major-mode' that can be used for file_type_emacs value.")
 
+;; Emacs<26 does not have provided-mode-derived-p
+(defun editorconfig--provided-mode-derived-p (mode &rest modes)
+  "Non-nil if MODE is derived from one of MODES.
+Uses the `derived-mode-parent' property of the symbol to trace backwards.
+If you just want to check `major-mode', use `derived-mode-p'."
+  (if (fboundp 'provided-mode-derived-p)
+      (apply 'provided-mode-derived-p mode modes)
+    (while (and (not (memq mode modes))
+                (setq mode (get mode 'derived-mode-parent))))
+    mode))
+
+
 (defun editorconfig-set-major-mode-from-name (filetype)
   "Set buffer `major-mode' by FILETYPE.
 
@@ -505,7 +517,7 @@ FILETYPE should be s string like `\"ini\"`, if not nil or empty string."
                                    "-mode")))))
     (when mode
       (if (fboundp mode)
-          (if (apply 'provided-mode-derived-p mode
+          (if (apply 'editorconfig--provided-mode-derived-p mode
                      editorconfig-file-type-emacs-whitelist)
               (editorconfig-apply-major-mode-safely mode)
             (display-warning :error (format "Major-mode `%S' is not listed in `%S'"