Allow `process-contact' not to block

* doc/lispref/processes.texi (Process Information): Document it.

* lisp/simple.el (list-processes--refresh): Don't wait for contact
information for non-setup processes.

* src/process.c (Fprocess_contact): Take an optional parameter to
avoid blocking (bug#37408).

1 files changed, 4 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 567f3cbb403..e8d3dffd3bd 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -2131,6 +2131,10 @@ valid event type.
 * Lisp Changes in Emacs 27.1
 
 +++
+** 'process-contact' now takes an optional NO-BLOCK parameter to allow
+not waiting for a process to be set up.
+
++++
 ** The new 'quit-window-hook' is now run first when executing the
 'quit-window' command.