Implement exact match expression builder for QRegularExpression

QRegularExpression doesn't offer a direct equivalent of QRegExp's exact
match.

There are several places in the Qt sources that use this feature. This
patch implements a small helper function that builds the expression as
recommended in the documentation and updates the related code.

[ChangeLog][Core][Tools] QRegularExpression now provides
anchoredPattern() which is a helper function to build regular
expressions used for exact matching.

Change-Id: Idbbf142c4c5cb9b62abf8229f4ce85fd4409e5d0
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qdir.cpp

@@ -2129,7 +2129,7 @@ bool QDir::match(const QStringList &filters, const QString &fileName)
         QString wildcard = QRegularExpression::wildcardToRegularExpression(*sit);
         // Insensitive exact match
         // (see Notes for QRegExp Users in QRegularExpression's documentation)
-        QRegularExpression rx(QLatin1String("\\A(?:") + wildcard + QLatin1String(")\\z"),
+        QRegularExpression rx(QRegularExpression::anchoredPattern(wildcard),
                               QRegularExpression::CaseInsensitiveOption);
         if (rx.match(fileName).hasMatch())
             return true;

src/corelib/tools/qregularexpression.cpp

@@ -483,6 +483,11 @@ QT_BEGIN_NAMESPACE
     Note the usage of the non-capturing group in order to preserve the meaning
     of the branch operator inside the pattern.
 
+    The QRegularExpression::anchoredPattern() helper method does exactly that for
+    you.
+
+    \sa anchoredPattern
+
     \section3 Porting from QRegExp's Partial Matching
 
     When using QRegExp::exactMatch(), if an exact match was not found, one
@@ -1994,6 +1999,17 @@ QString QRegularExpression::wildcardToRegularExpression(const QString &pattern)
     return rx;
 }
 
+/*!
+    \fn QRegularExpression::anchoredPattern(const QString &expression)
+
+    \since 5.12
+
+    Returns the expression wrapped between the \c{\A} and \c{\z} anchors to be
+    used for exact matching.
+
+    \sa {Porting from QRegExp's Exact Matching}
+*/
+
 /*!
     \since 5.1
 

src/corelib/tools/qregularexpression.h

@@ -142,6 +142,12 @@ public:
 
     static QString escape(const QString &str);
     static QString wildcardToRegularExpression(const QString &str);
+    static inline QString anchoredPattern(const QString &expression)
+    {
+        return QLatin1String("\\A(?:")
+               + expression
+               + QLatin1String(")\\z");
+    }
 
     bool operator==(const QRegularExpression &re) const;
     inline bool operator!=(const QRegularExpression &re) const { return !operator==(re); }

src/corelib/tools/qstringlist.cpp

@@ -692,7 +692,7 @@ int QtPrivate::QStringList_indexOf(const QStringList *that, const QRegularExpres
     if (from < 0)
         from = qMax(from + that->size(), 0);
 
-    QString exactPattern = QLatin1String("\\A(?:") + re.pattern() + QLatin1String(")\\z");
+    QString exactPattern = QRegularExpression::anchoredPattern(re.pattern());
     QRegularExpression exactRe(exactPattern, re.patternOptions());
 
     for (int i = from; i < that->size(); ++i) {
@@ -722,7 +722,7 @@ int QtPrivate::QStringList_lastIndexOf(const QStringList *that, const QRegularEx
     else if (from >= that->size())
         from = that->size() - 1;
 
-    QString exactPattern = QLatin1String("\\A(?:") + re.pattern() + QLatin1String(")\\z");
+    QString exactPattern = QRegularExpression::anchoredPattern(re.pattern());
     QRegularExpression exactRe(exactPattern, re.patternOptions());
 
     for (int i = from; i >= 0; --i) {

src/gui/util/qvalidator.cpp

@@ -1079,7 +1079,7 @@ void QRegularExpressionValidatorPrivate::setRegularExpression(const QRegularExpr
 
     if (origRe != re) {
         usedRe = origRe = re; // copies also the pattern options
-        usedRe.setPattern(QLatin1String("\\A(?:") + re.pattern() + QLatin1String(")\\z"));
+        usedRe.setPattern(QRegularExpression::anchoredPattern(re.pattern()));
         emit q->regularExpressionChanged(re);
         emit q->changed();
     }

src/widgets/dialogs/qfilesystemmodel.cpp

@@ -2032,10 +2032,8 @@ bool QFileSystemModelPrivate::passNameFilters(const QFileSystemNode *node) const
                                             : QRegularExpression::CaseInsensitiveOption;
 
         for (const auto &nameFilter : nameFilters) {
-            const QString wildcard = QLatin1String("\\A(?:")
-                                     + QRegularExpression::wildcardToRegularExpression(nameFilter)
-                                     + QLatin1String(")\\z");
-            QRegularExpression rx(wildcard, options);
+            const QString wildcard = QRegularExpression::wildcardToRegularExpression(nameFilter);
+            QRegularExpression rx(QRegularExpression::anchoredPattern(wildcard), options);
             QRegularExpressionMatch match = rx.match(node->fileName);
             if (match.hasMatch())
                 return true;