[PATCH 5 of 9 v2] stdio: catch StdioError in dispatch.run and clean up appropriately

[Yuya Nishihara]

On Thu, 13 Apr 2017 21:29:43 -0700, Bryan O'Sullivan wrote:
> # HG changeset patch
> # User Bryan O'Sullivan <bryano at fb.com>
> # Date 1491947652 25200
> #      Tue Apr 11 14:54:12 2017 -0700
> # Node ID 942022da49166766fe4a7967b71411879221c197
> # Parent  a5aa1dfd9afed15c0cd762c4a72e5e0082ac074c
> stdio: catch StdioError in dispatch.run and clean up appropriately
> 
> We attempt to report what went wrong, and more importantly exit the
> program with an error code.
> 
> (The exception we catch is not yet raised anywhere in the code.)
> 
> diff --git a/mercurial/dispatch.py b/mercurial/dispatch.py
> --- a/mercurial/dispatch.py
> +++ b/mercurial/dispatch.py
> @@ -77,7 +77,22 @@ class request(object):
>  
>  def run():
>      "run the command in sys.argv"
> -    sys.exit((dispatch(request(pycompat.sysargv[1:])) or 0) & 255)
> +    req = request(pycompat.sysargv[1:])
> +    err = None
> +    try:
> +        status = (dispatch(req) or 0) & 255
> +    except error.StdioError as err:
> +        status = -1
> +    if util.safehasattr(req.ui, 'fout'):
> +        try:
> +            req.ui.fout.close()
> +        except IOError as err:
> +            status = -1
> +    if util.safehasattr(req.ui, 'ferr'):
> +        if err is not None and err.errno != errno.EPIPE:
> +            req.ui.ferr.write('abort: %s\n' % err.strerror)
> +        req.ui.ferr.close()
> +    sys.exit(status & 255)

Can't we change .close() to .flush() ?

As I said before, req.ui.fout != sys.__stdout__ but they share the same fd.
If we had an extension that registers Python atexit handler to print something,
the Python process would crash on Windows.