Syncing pwd with Fern root dir

[iamvoidcoder]

Hi

Is there an easy way to somehow auto-sync pwd with Fern's root dir? Via a custom Fern autocmd event perhaps? So that if you drill in/out in the Fern's file system tree whenever the root dir changes to automatically perform :cd <current_fern_root>?

The reason is quite simple. It is sort of hard to manually keep these two in sync. It would be much easier if e.g. after drilling in into a folder in Fern (Enter) or moving up a level (Backspace) it also changed pwd so that any relative path commands or plugins that rely on pwd (such as e.g. FZF) would work relative to the current Fern root dir.

If there is a way to somehow hook a custom script handler for the Fern root change events and obtain the current root path I can see this sorting both the pwd syncing and my other question about preserving drawer state.

Thanks

[lambdalisue]

Maybe https://github.com/lambdalisue/fern.vim/wiki/Tips#perform-tcd-on-the-root-node-after-enter-or-leave-action would help you.

[iamvoidcoder]

This is Neovim 0.4.4 on MacOS 11.2.3

Latest Fern installed via vim-plug:

call plug#begin('~/.config/nvim/autoload/plugged')
Plug 'lambdalisue/fern.vim'
call plug#end()

Here is a simple test:

1. Starting nvim, new empty editing buffer:

:ls!
  2 %a   "[No Name]"                    line 1

2. Opening an instance of Fern drawer:

:Fern . -drawer
:ls!
  2  a   "[No Name]"                    line 0
  3u%a-  "fern://drawer:1/file:///Users/Vcd;$" line 1

3. In the Fern drawer I'm entering directory "Temp" by pressing <CR>

:ls!
  2  a   "[No Name]"                    line 0
  3u# -  "fern://drawer:1/file:///Users/Vcd;$" line 13
  4u%a-  "fern://drawer:1/file:///Users/Vcd/Temp$" line 1

As you can see the previous fern buffer remained opened. Now if I do :b3 it will correctly show the previous buffer. I can jump between these fern buffers and the buffers themselves are fully functional. However every time I do "enter" or "leave" command it will leave on of these unlisted buffers behind.

[lambdalisue]

Well, that's expected behavior. It should be OK.

the amount of RAM used by nvim is starting to grow up a lot.

I'd love to ask the memory usage. How much

[iamvoidcoder]

Ah this is expected then? How strange. So these hidden unlisted buffers, when are they going be freed? Is there a memory usage threshold or some automated garbage collector in vim to automatically free them? Sorry, I know nothing about the internals.

I haven't attempted any precise measurements. After starting nvim, with a single empty editing buffer open it is taking like 17MB. After opening Fern drawer and moving back and forth through the file system without opening any files I can see it jumping to about 40MB or so.

This is not causing any issues really. I just wanted to understand why every leave/enter command is leaving an unneeded hidden buffer behind. Are these going to be freed eventually?

Thanks

[lambdalisue]

All I know is https://github.com/vim/vim/blob/dad4473f02e1fec86d43a2fc094536a4b27d3b25/runtime/doc/options.txt#L1343

If you care, use setlocal bufhidden=wipe would solve the issue but then you cannot get back with <C-o> or whatever.

[iamvoidcoder]

Thanks. This is sorting it. I think I'll go with an autocmd.

autocmd FileType fern setl bufhidden=wipe

[oredaze]

I have a related question and it doesn't seem worth it to open a new topic.
I want to change the cwd once, only if I start vim with a directory (and thus start with fern).
Lets say I do nvim ~/myproject/mydir after that I always have to do :cd ~/myproject/mydir. I want to skip the second, but don't want any automatic cd-ing after that.

[lambdalisue]

Fern itself doesn't provide exact feature so you need to write some Vim script. See :help VimEnter for detail.