From deada9450273f397a011f402b91a3a4216a62f0b Mon Sep 17 00:00:00 2001
From: Yipeng Zhao <daggerjames.zhao@gmail.com>
Date: Sun, 9 Jun 2019 22:52:01 +0800
Subject: [PATCH] [Fix] `stringify`: fix arrayFormat comma with empty
 array/objects

---
 lib/stringify.js  |  9 ++++++---
 test/stringify.js | 21 +++++++++++++++++++++
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/lib/stringify.js b/lib/stringify.js
index 5d22260c..da5380a8 100644
--- a/lib/stringify.js
+++ b/lib/stringify.js
@@ -80,7 +80,7 @@ var stringify = function stringify(
                 return serializeDate(value);
             }
             return value;
-        }).join(',');
+        });
     }
 
     if (obj === null) {
@@ -106,7 +106,10 @@ var stringify = function stringify(
     }
 
     var objKeys;
-    if (isArray(filter)) {
+    if (generateArrayPrefix === 'comma' && isArray(obj)) {
+        // we need to join elements in
+        objKeys = [{ value: obj.length > 0 ? obj.join(',') || null : undefined }];
+    } else if (isArray(filter)) {
         objKeys = filter;
     } else {
         var keys = Object.keys(obj);
@@ -115,7 +118,7 @@ var stringify = function stringify(
 
     for (var i = 0; i < objKeys.length; ++i) {
         var key = objKeys[i];
-        var value = obj[key];
+        var value = typeof key === 'object' && key.value !== undefined ? key.value : obj[key];
 
         if (skipNulls && value === null) {
             continue;
diff --git a/test/stringify.js b/test/stringify.js
index 49692184..cbd90b2c 100644
--- a/test/stringify.js
+++ b/test/stringify.js
@@ -336,6 +336,27 @@ test('stringify()', function (t) {
         st.end();
     });
 
+    t.test('stringifies an empty array in different arrayFormat', function (st) {
+        st.equal(qs.stringify({ a: [], b: [null], c: 'c' }, { encode: false }), 'b[0]=&c=c');
+        // arrayFormat default
+        st.equal(qs.stringify({ a: [], b: [null], c: 'c' }, { encode: false, arrayFormat: 'indices' }), 'b[0]=&c=c');
+        st.equal(qs.stringify({ a: [], b: [null], c: 'c' }, { encode: false, arrayFormat: 'brackets' }), 'b[]=&c=c');
+        st.equal(qs.stringify({ a: [], b: [null], c: 'c' }, { encode: false, arrayFormat: 'repeat' }), 'b=&c=c');
+        st.equal(qs.stringify({ a: [], b: [null], c: 'c' }, { encode: false, arrayFormat: 'comma' }), 'b=&c=c');
+        // with strictNullHandling
+        st.equal(qs.stringify({ a: [], b: [null], c: 'c' }, { encode: false, arrayFormat: 'indices', strictNullHandling: true }), 'b[0]&c=c');
+        st.equal(qs.stringify({ a: [], b: [null], c: 'c' }, { encode: false, arrayFormat: 'brackets', strictNullHandling: true }), 'b[]&c=c');
+        st.equal(qs.stringify({ a: [], b: [null], c: 'c' }, { encode: false, arrayFormat: 'repeat', strictNullHandling: true }), 'b&c=c');
+        st.equal(qs.stringify({ a: [], b: [null], c: 'c' }, { encode: false, arrayFormat: 'comma', strictNullHandling: true }), 'b&c=c');
+        // with skipNulls
+        st.equal(qs.stringify({ a: [], b: [null], c: 'c' }, { encode: false, arrayFormat: 'indices', skipNulls: true }), 'c=c');
+        st.equal(qs.stringify({ a: [], b: [null], c: 'c' }, { encode: false, arrayFormat: 'brackets', skipNulls: true }), 'c=c');
+        st.equal(qs.stringify({ a: [], b: [null], c: 'c' }, { encode: false, arrayFormat: 'repeat', skipNulls: true }), 'c=c');
+        st.equal(qs.stringify({ a: [], b: [null], c: 'c' }, { encode: false, arrayFormat: 'comma', skipNulls: true }), 'c=c');
+
+        st.end();
+    });
+
     t.test('stringifies a null object', { skip: !Object.create }, function (st) {
         var obj = Object.create(null);
         obj.a = 'b';