No new line at file end

[mironnn]

Add a new line at the end of python file or not to remove it

Currently black removes extra blank line after python code at the end of file.
Tested inside the docker build from the repository.

root@8c79a371a51b:/# black test.py --check --diff --verbose
--- test.py	2021-06-11 09:53:10.665099 +0000
+++ test.py	2021-06-11 09:53:15.809714 +0000
@@ -1,6 +1,5 @@
 def main():
     print(11)


 main()
-
would reformat test.py
Oh no! 💥 💔 💥
1 file would be reformatted.
root@8c79a371a51b:/#

Desired style

Add a new line at the end of the file.

Flake8 example
https://www.flake8rules.com/rules/W292.html

[felix-hilden]

Hi, thanks for reporting! However, I can't reproduce this on the playground. I'm not familiar with the docker build though. Do you have the latest version?

[mironnn]

@felix-hilden thank you for the quick response!

Steps for reproduce:

1. git clone https://github.com/psf/black.git
2. cd black
3. docker build -t test_black .
4. docker run -it black_test bash
5. apt update
6. apt install vim
7. make any python file and check with black

Could you please check with such steps?

I checked with docker, that builds and installs inside latest black.
Also tested with 21.6b0 from pypi

[mironnn]

Or use old true python venv module

Steps:

1. python3 -m venv .venv
2. source .venv/bin/activate
3. pip install black
4. make a python code example with a blank line at the end
5. run black to this file. The file will be modified and a blank line at the end of the file will be removed.

[felix-hilden]

Given that you are able to reproduce it with an ordinary virtual environment, I think we have something weird going on here. I have the current main (which is equivalent to the latest release) pulled and I created a file like you described:

def main():
    print(11)


main()

It does have the line ending despite what GitHub shows 😅 Both black test.py and black test.py --check --diff --verbose produce no modifications on the file. The same thing happens in a virtual environment with no configuration and a fresh install of Black.

---

I'm not trying to discredit your finding or say that it's invalid by the way, I hope we can figure out what's going on 😄

[ichard26]

I cannot reproduce using the docker container from main (aa31a11). After format, vim doesn't tell give me the noeol indicator as your bug report would suggest. There was a bug with the diff output not adding a missing terminating newline: #1662, but that was fixed a long time ago.

[mironnn]

Please advise, what I'm doing wrong?

black_last_line.mp4

[TomFryers]

It looks to me like your file ends with two new‐line characters, and Black is removing the extra one.

[felix-hilden]

Indeed, could you verify @mironnn by perhaps reading the file in Python or using some other editor?

[ichard26]

Given no one else has reported this bug and we haven't heard anything from the OP in nearly a year, I'm closing this. I'd be happy to reopen this if someone (else) could provide reproduction steps that work.

[mironnn]

@ichard26 you're kidding

[TomFryers]

@mironnn I'm not quite sure what you're getting at. It seems to me like Black is functioning as intended.

[itsdani]

I have came across the same thing and I also thought black was removing the new line, but it isn't.
The explanation is that vim/neovim doesn't show the empty line at EOF, and always appends it by default. For more details check out this question and :h eol in vim