QStringMatcher: add a method that returns a string view of the pattern

The existing pattern() method always returns a QString, which means that
if the matcher was constructed using a QStringView, pattern() would
uncoditionally convert it to a QString.

This is useful to check if a match is exact:
auto pattern = matcher.patternView();
if (pattern.size() == needle.size() && matcher.indexIn(needle) == 0)
    ....

This may be needed for a later change in QStringList::contains();
regardless of that, this change makes sense on its own.

Change-Id: I49018551dd22a8f88cf6b9f878a5166902a26f58
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/text/qstringmatcher.cpp

@@ -242,6 +242,15 @@ QString QStringMatcher::pattern() const
     return q_sv.toString();
 }
 
+/*!
+    \fn QStringView QStringMatcher::patternView() const noexcept
+    \since 6.7
+
+    Returns a string view of the pattern that this string matcher will search for.
+
+    \sa setPattern()
+*/
+
 /*!
     Sets the case sensitivity setting of this string matcher to \a
     cs.

src/corelib/text/qstringmatcher.h

@@ -40,6 +40,9 @@ public:
     { return indexIn(QStringView(str, length), from); }
     qsizetype indexIn(QStringView str, qsizetype from = 0) const;
     QString pattern() const;
+    QStringView patternView() const noexcept
+    { return q_sv; }
+
     inline Qt::CaseSensitivity caseSensitivity() const { return q_cs; }
 
 private:

tests/auto/corelib/text/qstringmatcher/tst_qstringmatcher.cpp

@@ -24,6 +24,7 @@ void tst_QStringMatcher::qstringmatcher()
     QCOMPARE(matcher.caseSensitivity(), Qt::CaseSensitive);
     QCOMPARE(matcher.indexIn("foo", 1), 1);
     QCOMPARE(matcher.pattern(), QString());
+    QCOMPARE(matcher.patternView(), QStringView());
 }
 
 // public Qt::CaseSensitivity caseSensitivity() const
@@ -143,6 +144,7 @@ void tst_QStringMatcher::assignOperator()
 
     QStringMatcher m2 = m1;
     QCOMPARE(m2.pattern(), needle);
+    QCOMPARE(m2.patternView(), needle);
     QCOMPARE(m2.indexIn(hayStack), 3);
 }