readline: error on falsy values for callback

It was intended, according to in-test comments and common behaviour,
that callbacks be either `undefined` or a function, but falsy values
were being accepted as meaning "no callback".

PR-URL: https://github.com/nodejs/node/pull/28109
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/test/parallel/test-readline-interface.js b/test/parallel/test-readline-interface.js
index 2dff11f2a2..93c4b12511 100644
--- a/test/parallel/test-readline-interface.js
+++ b/test/parallel/test-readline-interface.js
@@ -366,6 +366,26 @@ function isWarned(emitter) {
       type: TypeError,
       code: 'ERR_INVALID_OPT_VALUE'
     });
+
+    common.expectsError(function() {
+      readline.createInterface({
+        input: fi,
+        completer: ''
+      });
+    }, {
+      type: TypeError,
+      code: 'ERR_INVALID_OPT_VALUE'
+    });
+
+    common.expectsError(function() {
+      readline.createInterface({
+        input: fi,
+        completer: false
+      });
+    }, {
+      type: TypeError,
+      code: 'ERR_INVALID_OPT_VALUE'
+    });
   }
 
   // Constructor throws if historySize is not a positive number