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>

4 files changed, 25 insertions, 3 deletions

diff --git a/src/corelib/io/qdir.cpp b/src/corelib/io/qdir.cpp
index 85ea2cb139..39422c3401 100644
--- a/src/corelib/io/qdir.cpp
+++ b/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;
diff --git a/src/corelib/tools/qregularexpression.cpp b/src/corelib/tools/qregularexpression.cpp
index 1bd06a73cd..6f0e572f41 100644
--- a/src/corelib/tools/qregularexpression.cpp
+++ b/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
@@ -1995,6 +2000,17 @@ QString QRegularExpression::wildcardToRegularExpression(const QString &pattern)
 }
 
 /*!
+    \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
 
     Constructs a valid, empty QRegularExpressionMatch object. The regular
diff --git a/src/corelib/tools/qregularexpression.h b/src/corelib/tools/qregularexpression.h
index 388aa7a8ca..f9e7029550 100644
--- a/src/corelib/tools/qregularexpression.h
+++ b/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); }
diff --git a/src/corelib/tools/qstringlist.cpp b/src/corelib/tools/qstringlist.cpp
index e9b7397a74..712ba74716 100644
--- a/src/corelib/tools/qstringlist.cpp
+++ b/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) {