Neovim, cwd, NERDTree and CtrlP

A follow-up to my latest article where I explain how I made further changes to make things work with NERDTree and CtrlP

Previously on this blog #

I like the idea of having one tab per project, and one working directory per tab.

In a way, you could say I like managing my working directory myself, like using a manual transmission instead of an automatic car.

Thus I’ve added several shortcuts like:

• <leader>cd, or <leader>ew to go to the parent directory of the file being edited, using :lcd instead of :cd so that I do not change the working directory on every tab and window.

• <leader>ew, to edit the file next to the one I’m currently editing, without to temporary change the working directory.

I also used the new TabNewEntered event from Neovim to change working directory upon tab creation:

function! OnTabEnter(path)
  if isdirectory(a:path)
    let dirname = a:path
  else
    let dirname = fnamemodify(a:path, ":h")
  endif
  execute "tcd ". dirname
endfunction()

autocmd TabNewEntered * call OnTabEnter(expand("<amatch>"))

This worked great until I realized NERDTree was messing things up.

NERDTree and events #

For some reason¹, when NERDTree is installed, the event does not get triggered with the correct path.

When going from ~/src/blog to ~/src/foo, the OnTabEnter function gets called with the old path, even though NERDTree shows ~/src/foo instead.

The culprit seems to be those lines:

if g:NERDTreeHijackNetrw
  augroup NERDTreeHijackNetrw
    autocmd VimEnter * silent! autocmd! FileExplorer
    au BufEnter,VimEnter * call nerdtree#checkForBrowse(expand("<amatch>"))
  augroup END
endif

Fortunately, there’s a way to disable NERDTree behavior:

let g:NERDTreeHijackNetrw = 0

Opening NERDTree #

But now NERDTree no longer opens by default when I edit a directory.

There’s a :NERDTree command, but it opens in a split window and I don’t want that: I want the NERDTree window to replace the window of the file I’m currently editing.

Why?

Because for me, vim is all about doing several things without moving your eyes or your hands to much.

Let’s say I’m in a middle of editing foo.py and I need to open a file for some reason (realized I need to patch an other file, or look for the implementation of a function I’m using), I will use :e or <leader>b so that the old buffer contents gets replaced by the new, and then I can come back to foo.py without loosing focus.

For me browsing the file system looking for things, or creating a directory in the correct place for a new file I want to write is not worth breaking the flow.

If I’m okay with breaking the flow, I’ll consider using a split (for fixing a test …), or a tab if I’m doing something completely different (a new feature, patching the changelog …), or even closing vim and re-open it from an other terminal window.

Thus I patched² NERDTree so that it would not try to create a split:

diff --git a/lib/nerdtree/creator.vim b/lib/nerdtree/creator.vim
index 89f03a3..cd67cfd 100644
--- a/lib/nerdtree/creator.vim
+++ b/lib/nerdtree/creator.vim
@@ -194,14 +194,11 @@ function! s:Creator._createTreeWin()

     if !exists('t:NERDTreeBufName')
         let t:NERDTreeBufName = self._nextBufferName()
-        silent! exec splitLocation . 'vertical ' . splitSize . ' new'
         silent! exec "edit " . t:NERDTreeBufName
     else
-        silent! exec splitLocation . 'vertical ' . splitSize . ' split'
         silent! exec "buffer " . t:NERDTreeBufName
     endif

-    setlocal winfixwidth
     call self._setCommonBufOptions()
 endfunction

After that, I wrote a new function and a defined a mapping to call it:

function! NerdTreeInPlace(path)
  :execute "NERDTree " . a:path
endfunction

nnoremap <leader>r :call NerdTreeInPlace(getcwd())<cr>

Closing NERDTree #

I now had a binding for opening NERDTree but then it’s complicated to close the NERDTree window: since no other buffer is open, using q does not work.

So I had to make sure I could go to the previous buffer, using the same key strokes: toggling is fun and only requires me to remember one shortcut :)

But how to make sure I could get back where I came from?

Easy, use marks!

In vim, you can set marks in command mode by using m followed by a letter. To get back to the previous mark, use a back tick:

ma
`a

This works across files providing the letter is uppercase.

So that’s what the function looks like now:

function! ToggleNerdTreeInPlace(path)
  if bufname("%") =~ "NERD_tree_"
    :normal! `N
  else
    :nomal! mN
    :execute "NERDTree " . a:path
    :only
  endif
endfunction

nnoremap <leader>r :call ToggleNerdTreeInPlace(getcwd())<cr>

(I use the letter N so that I can still use global marks from A to M if I want to)

An other annoying thing for me is that by default NERDTree will open files in a new window, keeping the directory view opened.³

You can also fix that by using:

let g:NERDTreeQuitOnOpen = 1

There! Now if you type o or enter when browsing files, the NERDTree window will close.

Fixing CtrlP #

By default CtrlP tries to guess the “project root dir”, by looking for directories like .git, .bzr and such in the upper directories.

So if my working directory is src/foo/doc and I want to look for a documentation file, CtrlP will show me all the files in src/foo, which again, is not what I want. (Remember, I prefer manual transmission to automatic).

You can prevent CtrlP from being too smart by disabling this feature completely:

let g:ctrlp_working_path_mode = ""

And, if you do need to get back to the root of your git project, you can use:

function! CdTop()
  let topdir=system("git rev-parse --show-toplevel")
  :execute ":lcd " . topdir
endfunction

command! CdTop call CdTop()

Or, if you use vim-fugitive, you can use :Gcd or :Glcd

By the way, I have the same kind of function in my zshrc:

function gcd() {
  topdir=$(git rev-parse --show-toplevel)
  if [[ $? -ne 0 ]]; then
    return 1
  fi
  cd "${topdir}/${1}"
}

Coincidence? I think not!