Nixpkgs: zsh-5.4.2 eats unterminated line in command output

[pvgoran]

Issue description

Here is what I get with zsh-5.4.2:

root@nixos> echo -n "abc\ndef"
abc

It's very confusing, if a program outputs a single unterminated error message and then exits.

With zsh-5.3.1, everything is fine:

root@nixos> echo -n "abc\ndef"
abc
def%

Steps to reproduce

Install zsh in nixos, run zsh, execute a command that outputs an unterminated line.

Technical details

• System: 17.09.1502.19879836d1 (Hummingbird)
• Nix version: nix-env (Nix) 1.11.15
• Nixpkgs version: 17.09.1502.19879836d1
• Sandboxing enabled: no

[nico202]

I can reproduce it

[vyp]

I can reproduce. Could this possibly be a zsh issue?

[pvgoran]

Most probably it is. Or it can be a problem of the prompt (I don't think Nixos uses the default zsh prompt).

[7c6f434c]

5.4.2 from Nixpkgs, non-NixOS prompt, works fine/could not reproduce issue.

[nico202]

edit: ignore the following, it's just because the default prompt is on a single line

Wait, it might be our zshrc?
I exaplain:
zsh prompt: run zsh (uses zshrc) -> echo -n "hi" -> nothing
zsh prompt: run zsh -f -d ( no zshrc) -> echo -n "hi" -> hi%

[AndersonTorres]

Yes, I can reproduce it here, too.

Another strange thing:

$> echo -n"abc\ndef"
-nabc
def
$> echo "abc\ndef" 
abc
def
$> echo -E "abc\ndef" 
abc\ndef

Maybe things of echo builtin?

[pvgoran]

Maybe things of echo builtin?

No. I originally encountered it with my own Perl program.

[nico202]

bash: echo = "\n\n"
bash: echo -n = "\n"

zsh: echo = "\n"
zsh: echo -n ""

Yeah it's eating the last newline

[nico202]

@7c6f434c can you test if you get this output?

[AndersonTorres]

/nix/store/<hash>-coreutils-8.28/bin/echo -e '1\n1'       
1
1
/nix/store/<hash>-coreutils-8.28/bin/echo -ne '1\n11\n111\n1111\na'
1
11
111
1111

And in fish it runs OK!

[nico202]

@AndersonTorres it does not depend on echo. both builtin and coretuils echo have the same (wrong) output on zsh and the same (right) output on bash

[7c6f434c]

@nico202 technically, I get colour-inverted version of same, but yes, that's how I have tested the issue in the first place and that's what I get.

[vyp]

For reference, I am not using the default NixOS prompt.

[vyp]

With zsh -d -f for me it works:

nixos% echo -n "abc\ndef"
abc
def%
nixos%

@nico202 not sure if this is expected?

[dtzWill]

More investigation needed but after stumbling on this:

https://www.bountysource.com/issues/48757141-failure-to-output-content-without-newline

I added setopt prompt_sp to my ~/.zshrc (well I added it to the list) and this seems to work now.

Inclined to say "working as expected" but I'm not sure if there are things to patch up re:themes and such.

[pvgoran]

It's an upstream problem. They changed interaction of the prompt_sp option with prompt_opts (https://github.com/zsh-users/zsh/commit/43e55a9bcd2c90124a751f2597d2f33cb6e3c042), but forgot to update the built-in prompts - at least, the "walters" prompt that Nixos uses by default.

[LnL7]

Is this resolved now?

[dtzWill]

Well the behavior is still present, but since it's an upstream problem and one everyone has (AFAIK?) I think we can go ahead and close this.

[pvgoran]

Not sure it can be closed like this. For upstream, this is a problem with one of their many prompts, but for Nixos, it's a problem that occurs in default configuration.

[dtzWill]

Thanks for speaking up and clarifying. Reopening, sorry :).

[MarcWeber]

I hit this issue, too. It took a lot of my time understanding that zsh's configuration was the problem, not my program.

autoload -U promptinit && promptinit && prompt walters

the last 'promp walters' is causing it.

It could be fixed by setopt prompt_sp
If you added this to promptInit after walter I think people (me ?) would be happy :)

[matthewbauer]

Done in #66992

[takeda]

@LnL7 looks like this should also be updated on darwin-nix, actually if one uses oh-my-zsh with themes like agnoster, setting promptInit to empty is better, otherwise one can see CWD on left and the right side of the terminal.