From c5b5bee6f2a779c4156b30d3465a0b6ef42ed0f5 Mon Sep 17 00:00:00 2001
From: simonkundrik <117163790+simonkundrik@users.noreply.github.com>
Date: Fri, 10 Jul 2026 18:03:41 +0300
Subject: [PATCH] fix: array sub-type option respects its value, not just its
 presence

An array option configured with a falsy sub-type such as
`{ key: 'foo', number: false }` still enabled that coercion, because the
sub-type (`boolean`/`string`/`number`) was chosen by key existence
rather than by value. As a result `{ number: false }` (and
`{ number: undefined }`) coerced array values to numbers, turning
non-numeric values into NaN.

Only enable the sub-type coercion when its value is truthy.

Fixes #415
---
 lib/yargs-parser.ts   | 6 +++++-
 test/yargs-parser.mjs | 7 +++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/lib/yargs-parser.ts b/lib/yargs-parser.ts
index 48a2d0f2..105510ac 100644
--- a/lib/yargs-parser.ts
+++ b/lib/yargs-parser.ts
@@ -121,7 +121,11 @@ export class YargsParser {
           string: 'strings',
           number: 'numbers'
         }
-        return arrayFlagKeys[key]
+        // Only enable the sub-type coercion when its value is truthy, so an
+        // explicit falsy value such as `{ number: false }` is ignored (#415).
+        return typeof opt === 'object' && (opt as Record<string, unknown>)[key]
+          ? arrayFlagKeys[key]
+          : undefined
       }).filter(Boolean).pop()
 
       // assign key to be coerced
diff --git a/test/yargs-parser.mjs b/test/yargs-parser.mjs
index 4c692375..fc420ba0 100644
--- a/test/yargs-parser.mjs
+++ b/test/yargs-parser.mjs
@@ -1867,6 +1867,13 @@ describe('yargs-parser', function () {
       result.should.have.property('x').that.is.an('array').and.to.deep.equal([5, 2])
     })
 
+    it('should not coerce array values as numbers when `number` is false (#415)', function () {
+      const result = parser(['--foo', 'dog', 'cat'], {
+        array: [{ key: 'foo', number: false }]
+      })
+      result.should.have.property('foo').that.deep.equals(['dog', 'cat'])
+    })
+
     it('should respect the type `string` option for arrays', function () {
       const result = parser(['-x=5', '2'], {
         configuration: {