QByteArray: make replace() consistent with QString's

Assuming QString has seen a lot more effort put into this, simply copy
the preamble of QString::replace(ptr, n, ptr, n, cs) over to the
corresponding QByteArray::replace(view, view) function, so they behave
the same.

On reviewer request, change d.size == 0 to isEmpty(), in both functions'
preambles.

[ChangeLog][QtCore][Important Behavior Changes][QByteArray] replace()
is now consistent with QString::replace() in its treatment of empty
haystacks and needles.

Fixes: QTBUG-134079
Change-Id: I2366febee7de4646d6b33c39d2338760b58f2ec4
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>

Author: marcmutz

src/corelib/text/qbytearray.cpp

@@ -2532,12 +2532,19 @@ QByteArray &QByteArray::replace(QByteArrayView before, QByteArrayView after)
     const char *a = after.data();
     qsizetype asize = after.size();
 
+    if (isEmpty()) {
+        if (bsize)
+            return *this;
+    } else {
+        if (b == a && bsize == asize)
+            return *this;
+    }
+    if (asize == 0 && bsize == 0)
+        return *this;
+
     if (bsize == 1 && asize == 1)
         return replace(*b, *a); // use the fast char-char algorithm
 
-    if (isNull() || (b == a && bsize == asize))
-        return *this;
-
     // protect against before or after being part of this
     std::string pinnedNeedle, pinnedReplacement;
     if (QtPrivate::q_points_into_range(a, d)) {

src/corelib/text/qstring.cpp

@@ -3864,7 +3864,7 @@ QString &QString::replace(const QChar *before, qsizetype blen,
                           const QChar *after, qsizetype alen,
                           Qt::CaseSensitivity cs)
 {
-    if (d.size == 0) {
+    if (isEmpty()) {
         if (blen)
             return *this;
     } else {

tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp

@@ -1590,15 +1590,7 @@ void tst_QByteArray::replaceWithEmptyNeedleInsertsBeforeEachChar()
             // shared
             auto copy = haystack;
             copy.replace(needle, replacement);
-            if (isByteArray) {
-                QEXPECT_FAIL("/<null>/<null>/a/", "QTBUG-134079", Continue);
-                QEXPECT_FAIL("/<null>//a/",       "QTBUG-134079", Continue);
-            }
             QCOMPARE(copy.isNull(), result.isNull());
-            if (isByteArray) {
-                QEXPECT_FAIL("/<null>/<null>/a/", "QTBUG-134079", Continue);
-                QEXPECT_FAIL("/<null>//a/",       "QTBUG-134079", Continue);
-            }
             QCOMPARE(copy, result);
         }
         {

tests/auto/corelib/text/qstringapisymmetry/tst_qstringapisymmetry.cpp

@@ -2543,19 +2543,11 @@ void tst_QStringApiSymmetry::replace_split_impl() const
     {
         auto copy = haystack;
         copy.replace(needle, replacement);
-        if constexpr (std::is_same_v<Haystack, QByteArray>) {
-            QEXPECT_FAIL("null ~= null$",  "QTBUG-134079", Continue);
-            QEXPECT_FAIL("null ~= empty$", "QTBUG-134079", Continue);
-        }
         QCOMPARE(copy, result);
     }
     {
         auto copy = detached(haystack);
         copy.replace(needle, replacement);
-        if constexpr (std::is_same_v<Haystack, QByteArray>) {
-            QEXPECT_FAIL("null ~= null$",  "QTBUG-134079", Continue);
-            QEXPECT_FAIL("null ~= empty$", "QTBUG-134079", Continue);
-        }
         QCOMPARE(copy, result);
     }
 }