Logging output and newlines

[andyneff]

There seems to have been and issue with newlines being translated by tty "magic" in the past.

In the past, having a tty on docker compose caused the error. But more recently, not having a tty causes the issue.

First tackled on 90f743f, it stated sources such as:

1. docker outputs to standard out with added carriage return character moby/moby#8513
2. https://unix.stackexchange.com/a/242814/332869
3. https://superuser.com/q/1326853/352118

Testing

A simple method to cause the issue is:

docker run -it --rm ubuntu:latest bash -c 'echo {\"a\":5}' | jq

If the error does not occur, you will see

{
  "a": 5
}

However, if it does occur you will see

{
   "a": 5
         }

The problem is able to be reproduced in windows, but only when using WSL as part of the experiment:

No error

Powershell: docker run -it --rm ubuntu:latest bash -c "echo -e '{\"a`":\n5}'" | jq
Command prompt: docker run -it --rm ubuntu:latest bash -c "echo '{"\""a"\"":5}'" | "c:\ProgramData\chocolatey\bin\jq.exe"
mingw: winpty bash; docker run -it --rm ubuntu:latest bash -c echo\ '{\"a\":5}' | jq
(Same results when using MS Terminal)

Error

WSL/Linux: docker run -it --rm ubuntu:latest bash -c echo\ '{\"a\":5}' | jq

Notes

It seems to have something to do with tty settings -opost or -onlcr sometimes, but the pattern is not clear, and sometimes doesn't involve them at all afaik. It's hard to tell for sure.