Funny control chars using stack + docker

[shanemikel]

I've been trying to figure out why stack w/ docker support doesn't work with interactive-haskell-mode for emacs. In short, output from the repl contains unexpected escape sequences meant for a terminal.

I've managed to attach to the stack relay process output, and it is printing these chars before emacs touches anything.

Any thoughts? Is stack making some invocation that assumes a full-featured terminal?

0000000    :   l   o   a   d       "   /   U   s   e   r   s   /   s   p
0000020    e   a   r   l   m   a   n   /   W   o   r   k   /   M   o   n
0000040    a   d   s   /   s   r   c   /   T   r   i   v   i   a   l   .
0000060    h   s   "  \r  \r  \n 033   [   ?   1   l 033   >   [   1
0000100    o   f       1   ]       C   o   m   p   i   l   i   n   g
0000120    T   r   i   v   i   a   l
0000140        (       /   U   s   e   r   s   /   s   p   e   a   r   l
0000160    m   a   n   /   W   o   r   k   /   M   o   n   a   d   s   /
0000200    s   r   c   /   T   r   i   v   i   a   l   .   h   s   ,
0000220    i   n   t   e   r   p   r   e   t   e   d       )  \r  \n   O
0000240    k   ,       m   o   d   u   l   e   s       l   o   a   d   e
0000260    d   :       T   r   i   v   i   a   l   .  \r  \n 033   [   ?
0000300    1   h 033   = 004   :   l   o   a   d       "   /   U   s   e
0000320    r   s   /   s   p   e   a   r   l   m   a   n   /   W   o   r
0000340    k   /   M   o   n   a   d   s   /   s   r   c   /   T   r   i
0000360    v   i   a   l   .   h   s   "  \r  \r  \n 033   [   ?   1   l
0000400  033   >   [   1       o   f       1   ]       C   o   m   p   i
0000420    l   i   n   g       T   r   i   v   i   a   l
0000440                            (       /   U   s   e   r   s   /   s
0000460    p   e   a   r   l   m   a   n   /   W   o   r   k   /   M   o
0000500    n   a   d   s   /   s   r   c   /   T   r   i   v   i   a   l
0000520    .   h   s   ,       i   n   t   e   r   p   r   e   t   e   d
0000540        )  \r  \n   O   k   ,       m   o   d   u   l   e   s
0000560    l   o   a   d   e   d   :       T   r   i   v   i   a   l   .
0000600   \r  \n 033   [   ?   1   h 033   = 004  \n  \n
0000614

haskell/haskell-mode#872

[shanemikel]

Okay, I've confirmed using haskell-mode and a script that execs cabal in my own rolled container, that these chars don't show up unless the --tty flag is passed. That is, same error with --tty and none without it.

Does stack check if we're on a tty before passing the flag to docker?