Renaming a file open in a hidden buffer blanks the buffer

[ealang]

Hi, thanks for the great plugin!

I came across one issue with renames and hidden buffers. If you rename a file open in a hidden buffer, then navigate back to the buffer, the buffer is now empty until you reload it (e.g. with ":e"). Runs the risk of accidentally writing the empty buffer to disk. The buffer appears to get renamed correctly, but the contents are gone. No issue with visible buffers.

[lambdalisue]

Please write a step by step procedure to reproduce your situation.

[ealang]

Vanilla Neovim v0.5.0 + latest Fern

1. echo hello > hello.md
2. nvim hello.md
3. :Fern .
4. Rename to hello2.md
5. Still in Fern, open hello2.md
6. Note buffer is blank
7. :e to restore contents

[lambdalisue]

Thanks for the procedure. Unfortunately, I could not reproduce your situation with that procedure.

Kapture.2021-10-09.at.17.51.18.mp4

Please provide me a minimal vimrc to reproduce the situation. Please make it minimal

[ealang]

Oh, that is puzzling. Thanks for looking into this. I ran my test with neovim + Fern (ed2e422) with an empty init.vim and no other plugins installed. I also tried vim with the same result.

I started digging into this a bit last week. ealang@1e20482

I noticed removing set hidden makes the problem go away. Maybe worth noting that if set hidden is already present in vimrc, the issue disappears.

My thinking was that with nohidden by default, the hello.md buffer gets unloaded, then with hidden turned on vim might assume the buffer still has content. I didn't know what purposes set hidden serves in that function. My commit definitely breaks a case where nohidden is on, but you :hide a buffer with modifications (results in Fern getting an E37 when trying to switch away from the buffer after running file).

I hit the same issue with these steps (mimics what Fern is doing):

1. echo hello > hello.md
2. nvim hello.md
3. Switch to a new buffer and close buffer 1
4. :!mv hello.md hello2.md
5. :set hidden
6. :1buffer
7. Note buffer is blank
8. :file hello2.md
9. :2buffer
10. :set nohidden
11. :1buffer
12. Buffer is still blank, get E13

[lambdalisue]

Reproduced. I'll investigate.

[lambdalisue]

My thinking was that with nohidden by default, the hello.md buffer gets unloaded, then with hidden turned on vim might assume the buffer still has content. I didn't know what purposes set hidden serves in that function. My commit definitely breaks a case where nohidden is on, but you :hide a buffer with modifications (results in Fern getting an E37 when trying to switch away from the buffer after running file).

Your change (set bufhidden=hide) seems ok. How do you get E37 if you applied that change?

[ealang]

If I make some changes (again with nohidden in vimrc) in a buffer without saving, and run:hide, then when Fern later tries to leave the buffer it gets E37. Using buffer! seems to keep the modifications and allow the buffer switch.

Opened #373

[lambdalisue]

If I make some changes (again with nohidden in vimrc) in a buffer without saving, and run:hide, then when Fern later tries to leave the buffer it gets E37. Using buffer! seems to keep the modifications and allow the buffer switch.

I'm sorry I don't get it. Could you write step by step procedure to reproduce E37? I'd love to know if that's normal situation or so on.

[ealang]

Getting an E37 without the buffer! in my pr:

1. Open two buffers
2. Make some changes in one of them (don't save)
3. :hide the buffer with changes
4. Rename the file that has the changes

Fern will fail to run keepjumps keepalt %dbuffer due to the E37, can see it in :messages.

It doesn't seem like a normal situation, but idk. I didn't know it was possible until I read the :help buffer entry:

The commands that move through the buffer list sometimes make a
buffer hidden although the 'hidden' option is off ...

[lambdalisue]

I actually hadn't really understood the behavior of :hide command. Now I got the situation thanks 👍

Well, I think it's a kind of situation that we should care... I'll think about workarounds (or anybody?)

[lambdalisue]

Getting an E37 without the buffer! in my pr:

Oops. So buffer! doesn't throw E37 right? Do you know any drawback for using buffer! there?

[ealang]

Oops. So buffer! doesn't throw E37 right? Do you know any drawback for using buffer! there?

Correct, with the buffer! I don't get a E37. I can't find any drawbacks based on some testing. My interpretation of the buffer-! help entry is that it will hide the buffer regardless of no/hidden option.