tty: remove NODE_TTY_UNSAFE_ASYNC

Nothing but trouble can ever come from it.

PR-URL: #12057
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

doc/api/cli.md

@@ -393,16 +393,6 @@ Path to the file used to store the persistent REPL history. The default path is
 to an empty string (`""` or `" "`) disables persistent REPL history.
 
 
-### `NODE_TTY_UNSAFE_ASYNC=1`
-<!-- YAML
-added: v6.4.0
--->
-
-When set to `1`, writes to `stdout` and `stderr` will be non-blocking and
-asynchronous when outputting to a TTY on platforms which support async stdio.
-Setting this will void any guarantee that stdio will not be interleaved or
-dropped at program exit. **Use of this mode is not recommended.**
-
 ### `NODE_EXTRA_CA_CERTS=file`
 <!-- YAML
 added: v7.3.0

doc/node.1

@@ -260,13 +260,6 @@ Path to the file used to store the persistent REPL history. The default path
 is \fB~/.node_repl_history\fR, which is overridden by this variable. Setting the
 value to an empty string ("" or " ") disables persistent REPL history.
 
-.TP
-.BR NODE_TTY_UNSAFE_ASYNC =\fI1\fR
-When set to \fI1\fR, writes to stdout and stderr will be non-blocking and
-asynchronous when outputting to a TTY on platforms which support async stdio.
-Setting this will void any guarantee that stdio will not be interleaved or
-dropped at program exit. \fBAvoid use.\fR
-
 .TP
 .BR OPENSSL_CONF = \fIfile\fR
 Load an OpenSSL configuration file on startup. Among other uses, this can be

lib/tty.js

@@ -74,7 +74,7 @@ function WriteStream(fd) {
   // this behaviour has become expected due historical functionality on OS X,
   // even though it was originally intended to change in v1.0.2 (Libuv 1.2.1).
   // Ref: https://github.com/nodejs/node/pull/1771#issuecomment-119351671
-  this._handle.setBlocking(process.env.NODE_TTY_UNSAFE_ASYNC !== '1');
+  this._handle.setBlocking(true);
 
   var winSize = new Array(2);
   var err = this._handle.getWindowSize(winSize);