Add a convenience function QTemporaryDir::filePath()

It allows to write more readable code:
    QString filePath = tmpDir.filePath(fileName);
instead of
    QString filePath = tmpDir.path() + QLatin1Char('/') + fileName;

Change-Id: I85aa54fd365e3bdd3ca41018ead7ed8741352b16
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: David Faure <david.faure@kdab.com>

src/corelib/io/qtemporarydir.cpp

@@ -304,6 +304,33 @@ QString QTemporaryDir::path() const
     return d_ptr->success ? d_ptr->pathOrError : QString();
 }
 
+/*!
+    \since 5.8
+
+    Returns the path name of a file in the temporary directory.
+    Does \e not check if the file actually exists in the directory.
+    Redundant multiple separators or "." and ".." directories in
+    \a fileName are not removed (see QDir::cleanPath()). Absolute
+    paths are not allowed.
+*/
+QString QTemporaryDir::filePath(const QString &fileName) const
+{
+    if (QDir::isAbsolutePath(fileName)) {
+        qWarning("QTemporaryDir::filePath: Absolute paths are not allowed: %s", qUtf8Printable(fileName));
+        return QString();
+    }
+
+    if (!d_ptr->success)
+        return QString();
+
+    QString ret = d_ptr->pathOrError;
+    if (!fileName.isEmpty()) {
+        ret += QLatin1Char('/');
+        ret += fileName;
+    }
+    return ret;
+}
+
 /*!
    Returns \c true if the QTemporaryDir is in auto remove
    mode. Auto-remove mode will automatically delete the directory from

src/corelib/io/qtemporarydir.h

@@ -65,6 +65,7 @@ public:
     bool remove();
 
     QString path() const;
+    QString filePath(const QString &fileName) const;
 
 private:
     QScopedPointer<QTemporaryDirPrivate> d_ptr;

tests/auto/corelib/io/qtemporarydir/tst_qtemporarydir.cpp

@@ -57,6 +57,8 @@ private slots:
     void fileTemplate_data();
     void getSetCheck();
     void fileName();
+    void filePath_data();
+    void filePath();
     void autoRemove();
     void nonWritableCurrentDir();
     void openOnRootDrives();
@@ -204,6 +206,29 @@ void tst_QTemporaryDir::fileName()
     QCOMPARE(absoluteFilePath, absoluteTempPath);
 }
 
+void tst_QTemporaryDir::filePath_data()
+{
+    QTest::addColumn<QString>("templatePath");
+    QTest::addColumn<QString>("fileName");
+
+    QTest::newRow("0") << QString() << "/tmpfile";
+    QTest::newRow("1") << QString() << "tmpfile";
+    QTest::newRow("2") << "XXXXX" << "tmpfile";
+    QTest::newRow("3") << "YYYYY" << "subdir/file";
+}
+
+void tst_QTemporaryDir::filePath()
+{
+    QFETCH(QString, templatePath);
+    QFETCH(QString, fileName);
+
+    QTemporaryDir dir(templatePath);
+    const QString filePath = dir.filePath(fileName);
+    const QString expectedFilePath = QDir::isAbsolutePath(fileName) ?
+                                     QString() : dir.path() + QLatin1Char('/') + fileName;
+    QCOMPARE(filePath, expectedFilePath);
+}
+
 void tst_QTemporaryDir::autoRemove()
 {
     // Test auto remove