comint-password-prompt-regexp

[Stephen Berman <stephen.berman@gmx.net>]

On one of my systems, when using ssh in shell-mode (M-x shell), the
password prompt does not appear in the minibuffer but only in the
*shell* buffer directly under the ssh invocation, and the password is
not hidden when it's entered.  I've determined that reason is that the
password prompt string passed to comint-output-filter begins with a
carriage return character (^M), and when the rest of the prompt string
begins with "Password" (which it can on this system),
comint-password-prompt-regexp does not match it and thus
comint-watch-for-password-prompt returns nil instead of calling
comint-send-invisible.

So far I haven't found out where the carriage return is coming from,
maybe it's openssh (on the system where the carriage return occurs in
the prompt string I have openssh-8.2p1, on the system where the carriage
return does not occur openssh-7.9p1; if anyone knows the answer, or has
a suggestion how to find out, I'd appreciate hearing it).  Of course, I
can just customize comint-password-prompt-regexp to match the prompt
with the carriage return.  But I'm asking here because, if this should
be a more general issue, maybe the default value of
comint-password-prompt-regexp should be changed.  In bug#31075 Noam
Postavsky pondered whether eshell-password-prompt-regexp should replace
comint-password-prompt-regexp, noting that "the eshell regexp looks much
simpler".  And indeed, on the system where the carriage return occurs in
the prompt string, using ssh in the Emacs shell (M-x eshell) does use
the minibuffer for password input and it is hidden; and if I set
comint-password-prompt-regexp to eshell-password-prompt-regexp, then I
also get minibuffer hidden input in shell-mode.

So should comint-password-prompt-regexp be replaced by
eshell-password-prompt-regexp?

Steve Berman