From 8ed2bc919432aaa2f7304b1a6207c056365cc22c Mon Sep 17 00:00:00 2001
From: Ahmad Samir <a.samirh78@gmail.com>
Date: Thu, 15 Jun 2023 02:39:19 +0300
Subject: [PATCH] QByteArray: change append(QByteArray) to match QStringBuilder
 behavior

I.e. concatenating a null byte array and an empty-but-not-null byte
array should result in an empty-but-not-null byte array.

This matches the behavior of QString::append(QString) too.

Fixes: QTBUG-114238
Pick-to: 6.6
Change-Id: Id36d10ee09c08041b7dabda102df48ca6d413d8b
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 src/corelib/text/qbytearray.cpp                | 11 ++++++++---
 .../corelib/text/qbytearray/tst_qbytearray.cpp | 18 ++++++++++++++++++
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/corelib/text/qbytearray.cpp b/src/corelib/text/qbytearray.cpp
index 7f8349131d..42921e99d7 100644
--- a/src/corelib/text/qbytearray.cpp
+++ b/src/corelib/text/qbytearray.cpp
@@ -2044,9 +2044,14 @@ QByteArray &QByteArray::prepend(const QByteArray &ba)
 
 QByteArray &QByteArray::append(const QByteArray &ba)
 {
-    if (size() == 0 && ba.size() > d->freeSpaceAtEnd() && ba.d.isMutable())
-        return (*this = ba);
-    return append(QByteArrayView(ba));
+    if (!ba.isNull()) {
+        if (isNull()) {
+            operator=(ba);
+        } else if (ba.size()) {
+            append(QByteArrayView(ba));
+        }
+    }
+    return *this;
 }
 
 /*!
diff --git a/tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp b/tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp
index bc84e25651..f5e149836a 100644
--- a/tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp
+++ b/tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp
@@ -53,6 +53,7 @@ private slots:
     void append();
     void appendExtended_data();
     void appendExtended();
+    void appendEmptyNull();
     void assign();
     void assignShared();
     void assignUsesPrependBuffer();
@@ -937,6 +938,23 @@ void tst_QByteArray::appendExtended()
     QCOMPARE(array.size(), 11);
 }
 
+void tst_QByteArray::appendEmptyNull()
+{
+    QByteArray a;
+    QVERIFY(a.isEmpty());
+    QVERIFY(a.isNull());
+
+    QByteArray b("");
+    QVERIFY(b.isEmpty());
+    QVERIFY(!b.isNull());
+
+    // Concatenating a null and an empty-but-not-null byte arrays results in
+    // an empty but not null byte array
+    QByteArray r = a + b;
+    QVERIFY(r.isEmpty());
+    QVERIFY(!r.isNull());
+}
+
 void tst_QByteArray::assign()
 {
     // QByteArray &assign(QByteArrayView)