Implement "scratch" and "tempfile" proxy types

Thanks to @fewaffles for most of the implementation.

autoload/inline_edit/proxy.vim

@@ -12,13 +12,18 @@ function! inline_edit#proxy#New(controller, start_line, end_line, filetype, inde
         \ 'UpdateOtherProxies':   function('inline_edit#proxy#UpdateOtherProxies'),
         \ }
 
-  let [lines, position] = s:LoadContents(proxy)
-  call s:CreateBuffer(proxy, lines)
-  call s:UpdateBuffer(proxy)
+  let [lines, position] = s:LoadOriginalBufferContents(proxy)
+  call s:CreateProxyBuffer(proxy, lines)
+  call s:UpdateProxyBuffer(proxy)
+  call s:SetStatusline(proxy)
   call s:PositionCursor(proxy, position)
 
   " On writing proxy buffer, update original one
-  autocmd BufWritePost <buffer> silent call b:proxy.UpdateOriginalBuffer()
+  if g:inline_edit_proxy_type == 'scratch'
+    autocmd BufWriteCmd <buffer> silent call b:proxy.UpdateOriginalBuffer()
+  elseif g:inline_edit_proxy_type == 'tempfile'
+    autocmd BufWritePost <buffer> silent call b:proxy.UpdateOriginalBuffer()
+  endif
 
   return proxy
 endfunction
@@ -43,6 +48,7 @@ function! inline_edit#proxy#UpdateOriginalBuffer() dict
 
   " Switch to the original buffer, delete the relevant lines, add the new
   " ones, switch back to the diff buffer.
+  setlocal nomodified
   exe 'buffer ' . self.original_buffer
 
   call inline_edit#PushCursor()
@@ -63,15 +69,16 @@ function! inline_edit#proxy#UpdateOriginalBuffer() dict
   let new_line_count = len(new_lines)
 
   let self.end = self.start + new_line_count - 1
-  call s:UpdateBuffer(self)
+  call s:UpdateProxyBuffer(self)
 
   call inline_edit#PopCursor() " in proxy buffer
 
   call self.controller.SyncProxies(self, new_line_count - line_count)
 endfunction
 
-" Collect data from original buffer
-function! s:LoadContents(proxy)
+" Called once upon setup. Returns the lines from the original buffer and the
+" position of the cursor in that buffer.
+function! s:LoadOriginalBufferContents(proxy)
   let proxy    = a:proxy
   let position = getpos('.')
   let lines    = []
@@ -83,46 +90,70 @@ function! s:LoadContents(proxy)
   return [lines, position]
 endfunction
 
-" Create proxy buffer
-function! s:CreateBuffer(proxy, lines)
+" Called once upon setup. Creates the actual buffer and writes the given lines
+" to it.
+function! s:CreateProxyBuffer(proxy, lines)
   let proxy = a:proxy
   let lines = a:lines
 
-  exe 'silent split ' . tempname()
-
   " avoid warnings
   let saved_readonly = &readonly
   let &readonly = 0
 
-  call append(0, lines)
-  $delete _
-  write
+  if g:inline_edit_proxy_type == 'scratch'
+    exe 'silent new'
+    setlocal buftype=acwrite
+    setlocal bufhidden=hide
+    call append(0, lines)
+    $delete _
+    set nomodified
+
+    let original_bufname = bufname(proxy.original_buffer)
+    let filename = printf('[%s:%d-%d]', original_bufname, proxy.start, proxy.end)
+    silent exec 'keepalt file ' . filename
+  elseif g:inline_edit_proxy_type == 'tempfile'
+    exe 'silent split ' . tempname()
+    call append(0, lines)
+    $delete _
+    write
+  endif
+
+  let &readonly = saved_readonly
+
   set foldlevel=99
   let proxy.proxy_buffer = bufnr('%')
+endfunction
 
-  let &readonly = saved_readonly
+" Called once upon setup and then after every write. After the actual updating
+" logic is finished, this sets up some needed buffer properties.
+function! s:UpdateProxyBuffer(proxy)
+  let b:proxy = a:proxy
 
-  if proxy.filetype == ''
+  if a:proxy.filetype == ''
     " attempt autodetection
     filetype detect
-    let proxy.filetype = &filetype
+    let a:proxy.filetype = &filetype
   endif
-  let &filetype = proxy.filetype
-endfunction
 
-function! s:UpdateBuffer(proxy)
-  let b:proxy = a:proxy
   let &filetype = a:proxy.filetype
+endfunction
+
+" Called once upon setup. Manipulates the statusline to show information for
+" the proxy. Does nothing if the proxy type is not "tempfile"
+function! s:SetStatusline(proxy)
+  if g:inline_edit_proxy_type != 'tempfile'
+    return
+  endif
 
-  " TODO don't clobber the statusline after saving
-  let statusline = printf('[%s:%%{b:proxy.start}-%%{b:proxy.end}]', bufname(b:proxy.original_buffer))
+  let statusline = printf('[%s:%%{b:proxy.start}-%%{b:proxy.end}]', bufname(a:proxy.original_buffer))
   if &statusline =~ '%[fF]'
     let statusline = substitute(&statusline, '%[fF]', statusline, '')
   endif
   exe "setlocal statusline=" . escape(statusline, ' |')
 endfunction
 
-" Position cursor correctly
+" Called once upon setup. Positions the cursor where it was in the original
+" buffer, relative to the extracted contents.
 function! s:PositionCursor(proxy, position)
   let proxy       = a:proxy
   let position    = a:position

doc/inline_edit.txt

@@ -158,6 +158,27 @@ those as well.
 The reason for this is to be able to extend the plugin easier in this specific
 case (editing an html-like filetype).
 
+                                                 *b:inline_edit_proxy_type*
+>
+    let b:inline_proxy_type = 'tempfile'
+<
+
+Default value: "scratch"
+
+This variable can have one of two values, "scratch" or "tempfile".
+
+If it is set to "scratch" (the default), the created proxy buffer is not
+connected to any file. The benefit is that the filename can then be set to be
+an informative string instead of a weird temporary filename. The drawback is
+that you can't run some external commands on this buffer, since there is no
+real backing file.
+
+If it is set to "tempfile", the proxy buffer is actually a temporary file. The
+benefit is that you run external commands that expect an actual file (like
+executing |:make|). The drawback is that the only way to display information
+on the proxy is by hacking the statusline, which may cause issues and can't
+work reliably on all statuslines.
+
 
 ==============================================================================
 EXTENDING                                                *inline-edit-extending*

example/example.sh

@@ -6,6 +6,6 @@ RUBY
 
 cat <<PYTHON
   #! /usr/bin/env python3
-
+  
   print("OK")
 PYTHON

plugin/inline_edit.vim

@@ -18,6 +18,14 @@ if !exists('g:inline_edit_html_like_filetypes')
   let g:inline_edit_html_like_filetypes = []
 endif
 
+if !exists('g:inline_edit_proxy_type')
+  let g:inline_edit_proxy_type = 'scratch'
+endif
+
+if index(['scratch', 'tempfile'], g:inline_edit_proxy_type) < 0
+  echoerr 'Inline Edit: Proxy type can''t be "'.g:inline_edit_proxy_type.'". Needs to be one of: scratch, tempfile'
+endif
+
 " Default patterns
 call add(g:inline_edit_patterns, {
       \ 'main_filetype': 'markdown',