Re: [Buildroot] [PATCH 1/1] support/testing/infra/emulator.py: prevent the commands from wrapping

["Yann E. MORIN" <yann.morin.1998@free.fr>]

Edgar, All,

On 2021-10-05 19:17 +0200, Edgar Bonet spake thusly:
> Traditional VT-10x terminals (and their emulators) have a "magic

I've added a reference to https://vt100.net/docs/vt100-ug/chapter3.html,
and...

> margins" feature that enables the last character position to be updated
> without scrolling the screen: whenever a character is printed on the
> last column, the cursor stays over the character, instead of moving to
> the next line.
> 
> The Busybox shell, ash, attempts to defeat this feature by printing
> CF,LF right after echoing a character to the last column.[1] This

... I fixed s/CF/CR/ here, then applied to master, thanks.

Regards,
Yann E. MORIN.

> doesn't play well with emulator.py. The run() method of the Emulator
> class captures the output of the emulated system and assumes the first
> line it reads is the echo of the command, and all subsequent lines are
> the command's output. If the line made by the command + shell prompt is
> longer than 80 characters, then it is echoed as two or more lines, and
> all but the first one are mistaken for the command's output.
> 
> We fix this by telling the emulated system that we are using an
> ultra-wide terminal with 29999 columns. Larger values would be ignored
> and replaced by the default, namely 80 columns.[2]
> 
> [1] https://git.busybox.net/busybox/tree/libbb/lineedit.c?h=1_34_0#n412
> [2] https://git.busybox.net/busybox/tree/libbb/xfuncs.c?h=1_34_0#n258
> 
> Signed-off-by: Edgar Bonet <bonet@grenoble.cnrs.fr>
> Reported-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
> Co-authored-by: Yann E. MORIN <yann.morin.1998@free.fr>
> ---
>  support/testing/infra/emulator.py | 2 ++
>  1 file changed, 2 insertions(+)
> 
> Note that I tested that the command
> 
>     stty columns 29999
> 
> does fix the wrapping behavior on an actual board, while using a serial
> connection. I did not test the script emulator.py, as I am unfamiliar
> with the testing infrastructure. Would someone volunteer to do that
> test?
> 
> diff --git a/support/testing/infra/emulator.py b/support/testing/infra/emulator.py
> index 0a77eb80fc..f1f5eac3a8 100644
> --- a/support/testing/infra/emulator.py
> +++ b/support/testing/infra/emulator.py
> @@ -100,6 +100,8 @@ class Emulator(object):
>          if index != 0:
>              raise SystemError("Cannot login")
>          self.run("dmesg -n 1")
> +        # Prevent the shell from wrapping the commands at 80 columns.
> +        self.run("stty columns 29999")
>  
>      # Run the given 'cmd' with a 'timeout' on the target
>      # return a tuple (output, exit_code)
> -- 
> 2.25.1
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