Improve/simplify filetype handling for buffers (#745)

* Improve/simplify filetype handling for buffers

There is no need to have a FileType autocmd anymore, which for some odd
reason even had to be in "ftdetect"?!

Now it will just use the `&filetype` property from buffers, instead of
updating it on FileType events.

This allows for easier lazy-loading of UltiSnips; without this patch it
would not have updated the list of filetypes for the buffer after just
being triggered (e.g. through NeoBundle's lazy-loading).
I am using the following currently:

    NeoBundleLazy 'SirVer/ultisnips', {
      \ 'on_funcs': ['UltiSnips#ExpandSnippetOrJump']}
    inoremap <silent> <c-j> <C-R>=UltiSnips#ExpandSnippetOrJump()<cr>

By manually defining the mapping for the trigger, I can invoke it and
NeoBundle will trigger the loading of the plugin.

autoload/UltiSnips.vim

@@ -1,11 +1,4 @@
 if exists("b:did_autoload_ultisnips") || !exists("g:_uspy")
-    " Define no-op function, called via ftdetect/UltiSnips.vim.
-    " TODO(sirver): Add a test for that using a bad g:UltiSnipsPythonVersion
-    " setting. Without this fix moving the cursor will spam errors, with this
-    " it should not.
-    function! UltiSnips#FileTypeChanged(...)
-    endfunction
-
     finish
 endif
 let b:did_autoload_ultisnips = 1
@@ -53,7 +46,7 @@ function! UltiSnips#Edit(bang, ...)
 endfunction
 
 function! UltiSnips#AddFiletypes(filetypes)
-    exec g:_uspy "UltiSnips_Manager.add_buffer_filetypes('" . a:filetypes . ".all')"
+    exec g:_uspy "UltiSnips_Manager.add_buffer_filetypes('" . a:filetypes . "')"
     return ""
 endfunction
 
@@ -116,13 +109,6 @@ function! UltiSnips#JumpForwards()
     return ""
 endfunction
 
-function! UltiSnips#FileTypeChanged(...)
-    exec g:_uspy "UltiSnips_Manager.reset_buffer_filetypes()"
-    exec g:_uspy "UltiSnips_Manager.add_buffer_filetypes('" . (a:0 ? a:1 : &ft) . "')"
-    return ""
-endfunction
-
-
 function! UltiSnips#AddSnippetWithPriority(trigger, value, description, options, filetype, priority)
     exec g:_uspy "trigger = vim.eval(\"a:trigger\")"
     exec g:_uspy "value = vim.eval(\"a:value\")"

pythonx/UltiSnips/_vim.py

@@ -51,6 +51,10 @@ def number(self):  # pylint:disable=no-self-use
         """The bufnr() of the current buffer."""
         return vim.current.buffer.number
 
+    @property
+    def filetypes(self):
+        return [ft for ft in vim.eval('&filetype').split('.') if ft]
+
     @property
     def cursor(self):  # pylint:disable=no-self-use
         """The current windows cursor.

pythonx/UltiSnips/snippet_manager.py

@@ -71,7 +71,7 @@ def __init__(self, expand_trigger, forward_trigger, backward_trigger):
         self._supertab_keys = None
 
         self._csnippets = []
-        self._buffer_filetypes = defaultdict(lambda: ['all'])
+        self._added_buffer_filetypes = defaultdict(lambda: [])
 
         self._vstate = VimState()
         self._visual_content = VisualContentPreserver()
@@ -255,15 +255,12 @@ def unregister_snippet_source(self, name):
                     self._snippet_sources[index + 1:]
                 break
 
-    def reset_buffer_filetypes(self):
-        """Reset the filetypes for the current buffer."""
-        if _vim.buf.number in self._buffer_filetypes:
-            del self._buffer_filetypes[_vim.buf.number]
+    def get_buffer_filetypes(self):
+        return (self._added_buffer_filetypes[_vim.buf.number] +
+                _vim.buf.filetypes + ['all'])
 
     def add_buffer_filetypes(self, ft):
-        """Checks for changes in the list of snippet files or the contents of
-        the snippet files and reloads them if necessary."""
-        buf_fts = self._buffer_filetypes[_vim.buf.number]
+        buf_fts = self._added_buffer_filetypes[_vim.buf.number]
         idx = -1
         for ft in ft.split('.'):
             ft = ft.strip()
@@ -272,7 +269,7 @@ def add_buffer_filetypes(self, ft):
             try:
                 idx = buf_fts.index(ft)
             except ValueError:
-                self._buffer_filetypes[_vim.buf.number].insert(idx + 1, ft)
+                self._added_buffer_filetypes[_vim.buf.number].insert(idx + 1, ft)
                 idx += 1
 
     @err_to_scratch_buffer.wrap
@@ -570,7 +567,7 @@ def _snips(self, before, partial, autotrigger_only=False):
         If partial is True, then get also return partial matches.
 
         """
-        filetypes = self._buffer_filetypes[_vim.buf.number][::-1]
+        filetypes = self.get_buffer_filetypes()[::-1]
         matching_snippets = defaultdict(list)
         clear_priority = None
         cleared = {}
@@ -792,9 +789,9 @@ def _get_file_to_edit(self, snippet_dir, requested_ft, bang,
             filetypes.append(requested_ft)
         else:
             if bang:
-                filetypes.extend(self._buffer_filetypes[_vim.buf.number])
+                filetypes.extend(self.get_buffer_filetypes())
             else:
-                filetypes.append(self._buffer_filetypes[_vim.buf.number][0])
+                filetypes.append(self.get_buffer_filetypes()[0])
 
         for ft in filetypes:
             potentials.update(find_snippet_files(ft, snippet_dir))