readline: fix behaviour of Interface plugged to a non-terminal output

Fixes: https://github.com/nodejs/node/issues/36773

PR-URL: https://github.com/nodejs/node/pull/36774
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/readline.js

@@ -282,9 +282,6 @@ function Interface(input, output, completer, terminal) {
     input.on('keypress', onkeypress);
     input.on('end', ontermend);
 
-    // Current line
-    this.line = '';
-
     this._setRawMode(true);
     this.terminal = true;
 
@@ -300,6 +297,9 @@ function Interface(input, output, completer, terminal) {
     self.once('close', onSelfCloseWithTerminal);
   }
 
+  // Current line
+  this.line = '';
+
   input.resume();
 }
 

test/parallel/test-repl-no-terminal.js

@@ -0,0 +1,7 @@
+'use strict';
+const common = require('../common');
+
+const repl = require('repl');
+const r = repl.start({ terminal: false });
+r.setupHistory('/nonexistent/file', common.mustSucceed());
+process.stdin.unref?.();