Set the state of QTemporaryFileEngine properly prior to reopening

QTemporaryFileEngine does not store the pattern, so it needs to get it
again from QTemporaryFilePrivate prior to reopening the file. It's
possible to lose the pattern when remove() is called on the object.

Task-number: QTBUG-46156
Change-Id: I66a35ce5f88941f29aa6ffff13dfc7f83d4fa3a2
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
Reviewed-by: David Faure <david.faure@kdab.com>

src/corelib/io/qsavefile.cpp

@@ -215,7 +215,8 @@ bool QSaveFile::open(OpenMode mode)
             d->finalFileName = existingFile.filePath();
     }
 
-    d->fileEngine = new QTemporaryFileEngine(d->finalFileName, 0666);
+    d->fileEngine = new QTemporaryFileEngine;
+    static_cast<QTemporaryFileEngine *>(d->fileEngine)->initialize(d->finalFileName, 0666);
     // Same as in QFile: QIODevice provides the buffering, so there's no need to request it from the file engine.
     if (!d->fileEngine->open(mode | QIODevice::Unbuffered)) {
         QFileDevice::FileError err = d->fileEngine->error();

src/corelib/io/qtemporaryfile.cpp

@@ -409,14 +409,24 @@ QTemporaryFilePrivate::~QTemporaryFilePrivate()
 QAbstractFileEngine *QTemporaryFilePrivate::engine() const
 {
     if (!fileEngine) {
-        if (fileName.isEmpty())
-            fileEngine = new QTemporaryFileEngine(templateName, 0600);
-        else
-            fileEngine = new QTemporaryFileEngine(fileName, 0600, false);
+        fileEngine = new QTemporaryFileEngine;
+        resetFileEngine();
     }
     return fileEngine;
 }
 
+void QTemporaryFilePrivate::resetFileEngine() const
+{
+    if (!fileEngine)
+        return;
+
+    QTemporaryFileEngine *tef = static_cast<QTemporaryFileEngine *>(fileEngine);
+    if (fileName.isEmpty())
+        tef->initialize(templateName, 0600);
+    else
+        tef->initialize(fileName, 0600, false);
+}
+
 QString QTemporaryFilePrivate::defaultTemplateName()
 {
     QString baseName;
@@ -769,6 +779,13 @@ bool QTemporaryFile::open(OpenMode flags)
         }
     }
 
+    // reset the engine state so it creates a new, unique file name from the template;
+    // equivalent to:
+    //    delete d->fileEngine;
+    //    d->fileEngine = 0;
+    //    d->engine();
+    d->resetFileEngine();
+
     if (QFile::open(flags)) {
         d->fileName = d->fileEngine->fileName(QAbstractFileEngine::DefaultName);
         return true;

src/corelib/io/qtemporaryfile_p.h

@@ -64,6 +64,7 @@ protected:
     ~QTemporaryFilePrivate();
 
     QAbstractFileEngine *engine() const;
+    void resetFileEngine() const;
 
     bool autoRemove;
     QString templateName;
@@ -77,22 +78,17 @@ class QTemporaryFileEngine : public QFSFileEngine
 {
     Q_DECLARE_PRIVATE(QFSFileEngine)
 public:
-
-    QTemporaryFileEngine(const QString &file,
-                         quint32 fileMode,
-                         bool fileIsTemplate = true) :
-        QFSFileEngine(),
-        fileMode(fileMode),
-        filePathIsTemplate(fileIsTemplate),
-        filePathWasTemplate(fileIsTemplate)
+    void initialize(const QString &file, quint32 mode, bool nameIsTemplate = true)
     {
         Q_D(QFSFileEngine);
+        Q_ASSERT(!isReallyOpen());
+        fileMode = mode;
+        filePathIsTemplate = filePathWasTemplate = nameIsTemplate;
         d->fileEntry = QFileSystemEntry(file);
 
         if (!filePathIsTemplate)
             QFSFileEngine::setFileName(file);
     }
-
     ~QTemporaryFileEngine();
 
     bool isReallyOpen();

tests/auto/corelib/io/qtemporaryfile/tst_qtemporaryfile.cpp

@@ -353,6 +353,7 @@ void tst_QTemporaryFile::removeAndReOpen()
         QVERIFY(!QFile::exists(fileName));
 
         QVERIFY(file.open());
+        QCOMPARE(QFileInfo(file.fileName()).path(), QFileInfo(fileName).path());
         fileName = file.fileName();
         QVERIFY(QFile::exists(fileName));
     }