Build output wrapping strangely on nix 1.12

[catern]

This happens for any builds at all. Here is an example:

*** Downloading ‘http://cache.nixos.org/nar/0rg7ay0gq47g51fbvmrvm75dddg1nps3h3s3sw4s1gbg77rhlzpy.nar.xz’ to ‘/nix/store/vg0i8d25492xgighz1njszhlyxhrvns7-perl-libwww-perl-6.15’...
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                              D
load
Uploa
d   T
otal
   S
pent    Left  Speed
0     0
0
 0
  0
   0
      0

0 --
:--:
-- --:--:
-- -
-:-
-:--
    0
100 75184  100 75184    0     0   554k      0 --:--:--
--:--:-- --:--:--  560k

[dtzWill]

I've seen this as well, upon occasion.

I think this can be refined a bit in the following two ways, at least from what I can tell. Does this match your experiences, @catern ?

1) Using 1.12 with 1.11 daemon (1.12 daemon reports to the progress bar thing) 2) Only curl progress output does this, not output from build itself

I'm not sure if it's wrapping--offhand it looks more like it expects to be able to read a full line at a time or something, but instead gets partial lines? Mostly I mean that it doesn't exactly look like any "wrapping" behavior that would be intentionally created by curl :).

[catern]

I am using 1.12 with a 1.11 daemon, that's correct.

But I also see this with build output as well. Only when there is a delay between printing the start of a line and the rest of it, though. (I haven't tested this, I just noticed it happening on ./configure runs, where the configure test result gets put on the next line).

I think your guess is correct, I think this is due to Nix expecting to read a full line and only getting partial lines. Most build tools write line-at-a-time, and small writes are atomic, so that's usually fine, but I guess curl does not write line-at-a-time.

[copumpkin]

Happening to me too

[catern]

In case anyone wants to debug this, here's something I noticed in an unrelated investigation of nix-daemon (writing a protocol dissector for its protocol). It looks the stderr messages are already mangled when they come from nix-daemon:

< Container: 
    type = STDERR_NEXT
    data = Dloa (total 4)
< Container: 
    type = STDERR_NEXT
    data = d  Up (total 5)
< Container: 
    type = STDERR_NEXT
    data = load (total 4)
< Container: 
    type = STDERR_NEXT
    data =    T (total 4)
< Container: 
    type = STDERR_NEXT
    data = otal (total 4)
< Container: 
    type = STDERR_NEXT
    data =    S (total 4)
< Container: 
    type = STDERR_NEXT
    data = pent (total 4)

This is printed by Nix 1.11 as one STDERR_NEXT per line. I believe Nix 1.12 also prints one per line. Somewhat confusing...

[stale[bot]]

I marked this as stale due to inactivity. → More info

[catern]

I never figured out what was causing this, but I think it was just an issue with having a nix-daemon and nix client tools with different versions. 1.12 is now long out of date anyway.