Add feature to hack properties before applying

README.md

@@ -108,6 +108,26 @@ only blocks of `web-mode`: it can be achieved by adding following to your init.e
 
 You can also define your own custom properties and enable them here.
 
+### `editorconfig-hack-properties-functions`
+
+A list of function to alter property values before applying them.
+
+These functions will be run after loading \".editorconfig\" files and before
+applying them to current buffer, so that you can alter some properties from
+\".editorconfig\" before they take effect.
+
+For example, Makefiles always use tab characters for indentation: you can
+overwrite \"indent_style\" property when current `major-mode` is a
+`makefile-mode` with following code:
+
+``` emacs-lisp
+(add-hook 'editorconfig-hack-properties-functions
+          '(lambda (props)
+             (when (derived-mode-p makefile-mode)
+               (puthash 'indent_style \"tab\" props))))
+
+```
+
 ### `editorconfig-indentation-alist`
 
 Alist of indentation setting methods by modes.

doc/editorconfig.texi

@@ -130,6 +130,7 @@ precedence.
 @anchor{#customize}
 @menu
 * editorconfig-after-apply-functions::
+* editorconfig-hack-properties-functions::
 * editorconfig-indentation-alist::
 * editorconfig-exec-path::
 * editorconfig-get-properties-function::
@@ -155,6 +156,26 @@ achieved by adding following to your init.el:
 
 You can also define your own custom properties and enable them here.
 
+@node editorconfig-hack-properties-functions
+@subsection @code{editorconfig-hack-properties-functions}
+@anchor{#editorconfig-hack-properties-functions}
+A list of function to alter property values before applying them.
+
+These functions will be run after loading ".editorconfig" files and
+before applying them to current buffer, so that you can alter some
+properties from ".editorconfig" before they take effect.
+
+For example, Makefiles always use tab characters for indentation: you
+can overwrite "indent_style" property when current @code{major-mode} is
+a @code{makefile-mode} with following code:
+
+@verbatim
+(add-hook 'editorconfig-hack-properties-functions
+          '(lambda (props)
+             (when (derived-mode-p makefile-mode)
+               (puthash 'indent_style \"tab\" props))))
+@end verbatim
+
 @node editorconfig-indentation-alist
 @subsection @code{editorconfig-indentation-alist}
 @anchor{#editorconfig-indentation-alist}

editorconfig.el

@@ -120,6 +120,24 @@ show line numbers on the left:
   'editorconfig-after-apply-functions
   "0.7.14")
 
+(defcustom editorconfig-hack-properties-functions ()
+  "A list of function to alter property values before applying them.
+
+These functions will be run after loading \".editorconfig\" files and before
+applying them to current buffer, so that you can alter some properties from
+\".editorconfig\" before they take effect.
+
+For example, Makefiles always use tab characters for indentation: you can
+overwrite \"indent_style\" property when current `major-mode' is a
+`makefile-mode' with following code:
+
+  (add-hook 'editorconfig-hack-properties-functions
+            '(lambda (props)
+               (when (derived-mode-p makefile-mode)
+                 (puthash 'indent_style \"tab\" props))))"
+  :type 'hook
+  :group 'editorconfig)
+
 (defcustom editorconfig-indentation-alist
   ;; For contributors: Sort modes in alphabetical order, please :)
   '((apache-mode apache-indent-level)
@@ -588,6 +606,13 @@ applies available properties."
             (error "Invalid editorconfig-get-properties-function value"))
           (let ((props (funcall editorconfig-get-properties-function)))
             (progn
+              (condition-case err
+                  (run-hook-with-args 'editorconfig-hack-properties-functions props)
+                (error
+                 (display-warning 'editorconfig-hack-properties-functions
+                                  (concat (error-message-string err)
+                                          ". Abort running hook.")
+                                  :warning)))
               (setq editorconfig-properties-hash props)
               (editorconfig-set-indentation (gethash 'indent_style props)
                                             (gethash 'indent_size props)

ert-tests/editorconfig.el

@@ -57,22 +57,22 @@
   (editorconfig-mode 1)
 
   (with-visit-file (concat editorconfig-secondary-ert-dir
-                     "2_space.el")
+                           "2_space.el")
     (should (eq lisp-indent-offset 2)))
 
   (let ((editorconfig-lisp-use-default-indent t))
     (with-visit-file (concat editorconfig-secondary-ert-dir
-                       "2_space.el")
+                             "2_space.el")
       (should (eq lisp-indent-offset nil))))
 
   (let ((editorconfig-lisp-use-default-indent 2))
     (with-visit-file (concat editorconfig-secondary-ert-dir
-                       "2_space.el")
+                             "2_space.el")
       (should (eq lisp-indent-offset nil))))
 
   (let ((editorconfig-lisp-use-default-indent 4))
     (with-visit-file (concat editorconfig-secondary-ert-dir
-                       "2_space.el")
+                             "2_space.el")
       (should (eq lisp-indent-offset 2))))
   (editorconfig-mode -1))
 
@@ -107,3 +107,14 @@
     (should (eq major-mode 'perl-mode))
     (should (eq perl-indent-level 5)))
   (editorconfig-mode -1))
+
+(ert-deftest test-hack-properties-functions nil
+  (editorconfig-mode 1)
+  (add-hook 'editorconfig-hack-properties-functions
+            (lambda (props)
+              (puthash 'indent_size "5" props)))
+  (with-visit-file (concat editorconfig-ert-dir
+                           "4_space.py")
+    (should (eq python-indent-offset 5)))
+  (setq editorconfig-hack-properties-functions nil)
+  (editorconfig-mode -1))