From 0a210f36033e69c16dae8757c7e949f27860b4eb Mon Sep 17 00:00:00 2001
From: Manuel Spigolon <manuel.spigolon@nearform.com>
Date: Sat, 24 Sep 2022 09:33:11 +0200
Subject: [PATCH] fix: default option accepts undefined as value

---
 lib/internal/util/parse_args/parse_args.js |  4 ++--
 test/parallel/test-parse-args.mjs          | 13 +++++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/lib/internal/util/parse_args/parse_args.js b/lib/internal/util/parse_args/parse_args.js
index db7dca4cdaf09a..0c0ed4b347fd5a 100644
--- a/lib/internal/util/parse_args/parse_args.js
+++ b/lib/internal/util/parse_args/parse_args.js
@@ -331,8 +331,8 @@ const parseArgs = (config = kEmptyObject) => {
         validateBoolean(multipleOption, `options.${longOption}.multiple`);
       }
 
-      if (ObjectHasOwn(optionConfig, 'default')) {
-        const defaultValue = objectGetOwn(optionConfig, 'default');
+      const defaultValue = objectGetOwn(optionConfig, 'default');
+      if (defaultValue !== undefined) {
         if (optionType === 'string' && !multipleOption) {
           validateString(defaultValue, `options.${longOption}.default`);
         } else if (optionType === 'string' && multipleOption) {
diff --git a/test/parallel/test-parse-args.mjs b/test/parallel/test-parse-args.mjs
index be9ef8b039f61d..ae39869cd36101 100644
--- a/test/parallel/test-parse-args.mjs
+++ b/test/parallel/test-parse-args.mjs
@@ -833,6 +833,19 @@ test('default must be a boolean when option type is boolean', () => {
   );
 });
 
+test('default must accept undefined value', () => {
+  const args = [];
+  const options = { alpha: { type: 'boolean', default: undefined } };
+  const result = parseArgs({ args, options });
+  const expected = {
+    values: {
+      __proto__: null,
+    },
+    positionals: []
+  };
+  assert.deepStrictEqual(result, expected);
+});
+
 test('default must be a boolean array when option type is boolean and multiple', () => {
   const args = [];
   const options = { alpha: { type: 'boolean', multiple: true, default: 'not an array' } };