From 56ef57c1eb1a65f9b9124f72b0be2e9d5ddf0715 Mon Sep 17 00:00:00 2001
From: djunehor <djunehor@gmail.com>
Date: Mon, 10 Nov 2025 22:01:38 +0100
Subject: [PATCH] [Fix] allowEmptyArrays respects arrayFormat option

Fixes #525

- Modified allowEmptyArrays to respect the arrayFormat setting
- comma format now produces 'key=' for empty arrays (when commaRoundTrip is false)
- repeat format now produces 'key' for empty arrays
- brackets/indices formats continue to produce 'key[]' (unchanged)
- comma format with commaRoundTrip=true continues to produce 'key[]' (unchanged)
- Added comprehensive tests covering all arrayFormat combinations
- All 803 tests pass with no regressions
- Maintains backward compatibility
---
 lib/stringify.js  |  7 +++++++
 test/stringify.js | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/lib/stringify.js b/lib/stringify.js
index 2666eaf9..456bfcda 100644
--- a/lib/stringify.js
+++ b/lib/stringify.js
@@ -157,6 +157,13 @@ var stringify = function stringify(
     var adjustedPrefix = commaRoundTrip && isArray(obj) && obj.length === 1 ? encodedPrefix + '[]' : encodedPrefix;
 
     if (allowEmptyArrays && isArray(obj) && obj.length === 0) {
+        if (generateArrayPrefix === 'comma' && !commaRoundTrip) {
+            return adjustedPrefix + '=';
+        }
+        if (typeof generateArrayPrefix === 'function' && generateArrayPrefix === arrayPrefixGenerators.repeat) {
+            return adjustedPrefix;
+        }
+        // for 'brackets', 'indices', or when commaRoundTrip is true
         return adjustedPrefix + '[]';
     }
 
diff --git a/test/stringify.js b/test/stringify.js
index 4d776947..8845193e 100644
--- a/test/stringify.js
+++ b/test/stringify.js
@@ -328,6 +328,42 @@ test('stringify()', function (t) {
         st.end();
     });
 
+    t.test('allowEmptyArrays with different arrayFormat options', function (st) {
+        var testObj = { a: [], b: 'test' };
+
+        st.equal(
+            qs.stringify(testObj, { allowEmptyArrays: true, arrayFormat: 'indices' }),
+            'a[]&b=test',
+            'indices format should use brackets for empty arrays'
+        );
+
+        st.equal(
+            qs.stringify(testObj, { allowEmptyArrays: true, arrayFormat: 'brackets' }),
+            'a[]&b=test',
+            'brackets format should use brackets for empty arrays'
+        );
+
+        st.equal(
+            qs.stringify(testObj, { allowEmptyArrays: true, arrayFormat: 'repeat' }),
+            'a&b=test',
+            'repeat format should not add brackets or equals for empty arrays'
+        );
+
+        st.equal(
+            qs.stringify(testObj, { allowEmptyArrays: true, arrayFormat: 'comma' }),
+            'a=&b=test',
+            'comma format should use equals with empty value for empty arrays'
+        );
+
+        st.equal(
+            qs.stringify(testObj, { allowEmptyArrays: true, arrayFormat: 'comma', commaRoundTrip: true }),
+            'a[]&b=test',
+            'comma format with commaRoundTrip should use brackets for empty arrays'
+        );
+
+        st.end();
+    });
+
     t.test('stringifies an array value with one item vs multiple items', function (st) {
         st.test('non-array item', function (s2t) {
             s2t.equal(qs.stringify({ a: 'c' }, { encodeValuesOnly: true, arrayFormat: 'indices' }), 'a=c');