🐛 Side-by-side looking ugly on GitHub Actions log

[jpfeuffer]

see #1309 for the diff
https://github.com/OpenMS/pyopenms-docs/actions/runs/4234240051/jobs/7356257942#step:7:152

Am I missing a setting?

[dandavison]

If I save your diff from #1309 and then do

cat /tmp/z.diff | delta --no-gitconfig --side-by-side

it looks normal. It looks like you might be trying to use bat as delta's pager? Check the output of

env | grep PAGER

delta's pager should be less not bat.

[jpfeuffer]

So, I double-checked. The PAGER variable was not set at all.
But even if I set it to less it does not work.

It works on my local computer, too. But not on the GitHub Actions logs.

[dandavison]

Hm, my guess is the automatic terminal width detection. If you felt like more investigations (!) you could look into things like echo $COLUMNS and tput cols and see if they are something sane.

[jpfeuffer]

By default, the environment of a GitHub Actions step is almost completely empty. This means also COLUMNS is missing.
Also after setting COLUMNS to 150, trying with and without "--width 150", with --line-fill-method ansi|spaces.
Nothing works.
As soon as there is a plus or minus line in the git output, your tool just adds no padding at all between left and right panel.

Tput output:
tput: No value for $TERM and no -T specified

[jpfeuffer]

If you check the screenshot, you will see that it works for lines with no changes and lines that were completely added/removed.
So I am suspecting a bug in delta.

[jpfeuffer]

Hm, my guess is the automatic terminal width detection

Why would it need to do that in the fixed "--width 150" case?
EDIT: I guess for wrapping, hmm..

[jpfeuffer]

I just realized not only side-by-side is affected!

It does not print any leading whitespaces in added lines.

Note: I had to switch to git diff --diff-algorithm histogram | delta because of the problems in #1309

[jpfeuffer]

Setting:

env:
    COLUMNS: 150
    LINES: 10000
    TERM: xterm-256color

as expected, does not help either. It shows correctly with tput cols now, as 150.

[dandavison]

Hm, maybe a bug in ANSI sequence handling by the terminal emulator being used by the Github Actions log UI? If you can't reproduce this in a standard terminal emulator then it seems like there's no evidence of a delta bug here, right?