bug#56025: [WIP PATCH] 29.0.50; em-extpipe-test-2 times out on EMBA and Cygwin

[Ken Brown]

On 7/16/2022 10:35 PM, Jim Porter wrote:
> Ok, attached is a WIP patch to do this. It seems to work for me under Cygwin, 
> although I've only lightly tested it in that environment. If this works for you 
> too, I'll finish cleaning this up and add tests/documentation for it.

It does work for me too.  Thanks!

> Note that in my patch, I temporarily undid my previous patch to send EOF 
> multiple times. This is just for testing purposes, but since we're using a pipe 
> for this connection now, a single call to `process-send-eof' should be 
> sufficient.

There shouldn't be a need for any calls to process-send-eof.  This is a noop 
anyway when writing to a pipe, as it should be.  A process reading from a pipe 
automatically recognizes EOF when a read returns 0 bytes, which is supposed to 
happen when no process has the pipe open for writing.

> (There are some obscure cases where we might want to keep the 
> current behavior, like redirecting to a process created some other way, so I 
> think it makes sense to keep that code. Probably...)

Ideally, Eshell should know whether it's writing to a pipe or a pty.  It should 
send up to 3 EOFs in the latter case and 0 in the former case.  If it's too hard 
to arrange that, then it's probably harmless to send up to 3 EOFs in the pipe 
case too.  But then maybe a comment in the code would be useful, so that readers 
don't wonder why you're sending EOF to a pipe.

Thanks again for your work.

Ken