Launchpad bug-1179630 Autodetect path search order

plugin/UltiSnips/__init__.py

@@ -965,8 +965,7 @@ class SnippetManager(object):
 
         paths = _vim.eval("&runtimepath").split(',')
 
-        if _vim.eval("exists('g:UltiSnipsDontReverseSearchPath')") == "0" or \
-           _vim.eval("g:UltiSnipsDontReverseSearchPath") == "0":
+        if self._should_reverse_search_path():
             paths = paths[::-1]
 
         for rtp in paths:
@@ -984,6 +983,57 @@ class SnippetManager(object):
 
         return ret
 
+    def _plugin_dir(self):
+        def apply_n_times(f, x, n):
+            if n < 1:
+                return x
+            else:
+                return apply_n_times(f, f(x), n - 1)
+
+        return apply_n_times(os.path.dirname, __file__, 3)
+
+    def _snippets_dir_is_before_plugin_dir(self):
+        def no_slash(path):
+            path_dir, path_base = os.path.split(path)
+
+            if path_base == "":
+                return path_dir
+            else:
+                return path
+
+        paths = _vim.eval("&runtimepath").split(',')
+        paths = map(os.path.expanduser, paths)
+        paths = map(no_slash, paths)
+
+        home = _vim.eval("$HOME")
+
+        def path_index_of(p):
+            try:
+                return paths.index(p)
+            except ValueError:
+                return -1
+
+        def vim_path_index(suffix):
+            return path_index_of(no_slash(os.path.join(home, suffix)))
+
+        plugin_dir = self._plugin_dir()
+
+        try:
+            vim1 = vim_path_index(".vim")
+            vim2 = vim_path_index("vimfiles")
+            max_vim_dir_index = max(vim1, vim2)
+            plugin_dir_index = paths.index(plugin_dir)
+            return plugin_dir_index < max_vim_dir_index
+        except ValueError:
+            return False
+
+    def _should_reverse_search_path(self):
+        reverse_setting = \
+           _vim.eval("exists('g:UltiSnipsDontReverseSearchPath')") != "0" and \
+           _vim.eval("g:UltiSnipsDontReverseSearchPath") != "0"
+
+        return reverse_setting or not self._snippets_dir_is_before_plugin_dir()
+
     @property
     def primary_filetype(self):
         """ Property for the primary filetype. This filetype