qt: Remove left-over partial files more persistently

* lang/qt/src/Makefile.am: Add new files.
* lang/qt/src/cleaner.cpp, lang/qt/src/cleaner.h: New.
* lang/qt/src/util.cpp (PartialFileGuard::~PartialFileGuard): Call
Cleaner::removeFile instead of removeFile.
* lang/qt/src/util.cpp, lang/qt/src/util.h (removeFile): Remove.
--

If the initial attempt to remove the file fails then a Cleaner is
created that tries to remove the file at regular intervals (10 s)
and on destruction (which happens on application shutdown).

GnuPG-bug-id: 6584

lang/qt/src/Makefile.am

@@ -32,6 +32,7 @@ EXTRA_DIST = QGpgmeConfig.cmake.in.in QGpgmeConfigVersion.cmake.in \
              QGpgmeQt6Config-w32.cmake.in.in QGpgmeQt6ConfigVersion.cmake.in
 
 qgpgme_sources = \
+    cleaner.cpp \
     dataprovider.cpp \
     debug.cpp \
     decryptverifyarchivejob.cpp \
@@ -176,6 +177,7 @@ camelcase_headers= \
 
 private_qgpgme_headers = \
     changeexpiryjob_p.h \
+    cleaner.h \
     decryptverifyarchivejob_p.h \
     encryptarchivejob_p.h \
     encryptjob_p.h \
@@ -235,6 +237,7 @@ qgpgme_moc_sources = \
     changeexpiryjob.moc \
     changeownertrustjob.moc \
     changepasswdjob.moc \
+    cleaner.moc \
     decryptjob.moc \
     decryptverifyarchivejob.moc \
     decryptverifyjob.moc \

lang/qt/src/cleaner.cpp

@@ -0,0 +1,99 @@
+/*
+    cleaner.cpp
+
+    This file is part of qgpgme, the Qt API binding for gpgme
+    Copyright (c) 2023 g10 Code GmbH
+    Software engineering by Ingo Klöcker <dev@ingo-kloecker.de>
+
+    QGpgME is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License as
+    published by the Free Software Foundation; either version 2 of the
+    License, or (at your option) any later version.
+
+    QGpgME is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+
+    In addition, as a special exception, the copyright holders give
+    permission to link the code of this program with any edition of
+    the Qt library by Trolltech AS, Norway (or with modified versions
+    of Qt that use the same license as Qt), and distribute linked
+    combinations including the two.  You must obey the GNU General
+    Public License in all respects for all of the code used other than
+    Qt.  If you modify this file, you may extend this exception to
+    your version of the file, but you are not obligated to do so.  If
+    you do not wish to do so, delete this exception statement from
+    your version.
+*/
+
+#include "cleaner.h"
+
+#include <qgpgme_debug.h>
+
+#include <QCoreApplication>
+#include <QFile>
+
+#include <chrono>
+
+static const auto timeout = std::chrono::seconds{10};
+
+static bool remove_file(const QString &filePath)
+{
+    if (filePath.isEmpty()) {
+        qCWarning(QGPGME_LOG) << __func__ << "- called with empty file path";
+        return true;
+    }
+    if (QFile::exists(filePath)) {
+        qCDebug(QGPGME_LOG) << __func__ << "- Removing file" << filePath;
+        if (!QFile::remove(filePath)) {
+            qCDebug(QGPGME_LOG) << __func__ << "- Removing file" << filePath << "failed";
+            return false;
+        }
+    } else {
+        qCDebug(QGPGME_LOG) << __func__ << "- File" << filePath << "doesn't exist";
+    }
+    return true;
+}
+
+void Cleaner::removeFile(const QString &filePath)
+{
+    if (!remove_file(filePath)) {
+        // use invokeMethod because we might not be called from the GUI thread
+        // but we want to delegate the Cleaner's clean-up to the application instance
+        QMetaObject::invokeMethod(qApp, [filePath]() {
+            new Cleaner{filePath, qApp};
+        }, Qt::QueuedConnection);
+    }
+}
+
+Cleaner::Cleaner(const QString &filePath, QObject *parent)
+    : QObject{parent}
+    , mFilePath{filePath}
+{
+    qCDebug(QGPGME_LOG) << this << __func__ << filePath;
+    mTimer.setSingleShot(true);
+    mTimer.callOnTimeout([this]() {
+        if (remove_file(mFilePath)) {
+            mFilePath.clear();
+            deleteLater();
+        } else {
+            mTimer.start(timeout);
+        }
+    });
+    mTimer.start(timeout);
+}
+
+Cleaner::~Cleaner()
+{
+    qCDebug(QGPGME_LOG) << this << __func__;
+    if (!mFilePath.isEmpty()) {
+        remove_file(mFilePath);
+    }
+}
+
+#include "cleaner.moc"

lang/qt/src/cleaner.h

@@ -0,0 +1,60 @@
+/*
+    cleaner.h
+
+    This file is part of qgpgme, the Qt API binding for gpgme
+    Copyright (c) 2023 g10 Code GmbH
+    Software engineering by Ingo Klöcker <dev@ingo-kloecker.de>
+
+    QGpgME is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License as
+    published by the Free Software Foundation; either version 2 of the
+    License, or (at your option) any later version.
+
+    QGpgME is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+
+    In addition, as a special exception, the copyright holders give
+    permission to link the code of this program with any edition of
+    the Qt library by Trolltech AS, Norway (or with modified versions
+    of Qt that use the same license as Qt), and distribute linked
+    combinations including the two.  You must obey the GNU General
+    Public License in all respects for all of the code used other than
+    Qt.  If you modify this file, you may extend this exception to
+    your version of the file, but you are not obligated to do so.  If
+    you do not wish to do so, delete this exception statement from
+    your version.
+*/
+
+#ifndef __QGPGME_CLEANER_H__
+#define __QGPGME_CLEANER_H__
+
+#include <QObject>
+#include <QString>
+#include <QTimer>
+
+/** Helper class that tries to remove files at regular intervals and on destruction. */
+class Cleaner : public QObject
+{
+    Q_OBJECT
+public:
+    /** Tries to remove the file. If this fails it creates a Cleaner for the file. */
+    static void removeFile(const QString &filePath);
+
+private:
+    explicit Cleaner(const QString &filePath, QObject *parent=nullptr);
+    ~Cleaner() override;
+
+    Q_DISABLE_COPY_MOVE(Cleaner)
+
+private:
+    QString mFilePath;
+    QTimer mTimer;
+};
+
+#endif // __QGPGME_CLEANER_H__

lang/qt/src/util.cpp

@@ -37,6 +37,7 @@
 
 #include "util.h"
 
+#include "cleaner.h"
 #include "qgpgme_debug.h"
 
 #include <QFile>
@@ -68,17 +69,6 @@ QStringList toFingerprints(const std::vector<GpgME::Key> &keys)
     return fprs;
 }
 
-void removeFile(const QString &fileName)
-{
-    if (QFile::exists(fileName)) {
-        if (QFile::remove(fileName)) {
-            qCDebug(QGPGME_LOG) << __func__ << "- Removed file" << fileName;
-        } else {
-            qCDebug(QGPGME_LOG) << __func__ << "- Removing file" << fileName << "failed";
-        }
-    }
-}
-
 /**
  * Generates a string of random characters for the file names of temporary files.
  * Never use this for generating passwords or similar use cases requiring highly
@@ -157,7 +147,7 @@ PartialFileGuard::PartialFileGuard(const QString &fileName)
 PartialFileGuard::~PartialFileGuard()
 {
     if (!mTempFileName.isEmpty()) {
-        removeFile(mTempFileName);
+        Cleaner::removeFile(mTempFileName);
     }
 }
 

lang/qt/src/util.h

@@ -55,8 +55,6 @@ std::vector<std::string> toStrings(const QStringList &l);
 
 QStringList toFingerprints(const std::vector<GpgME::Key> &keys);
 
-void removeFile(const QString &fileName);
-
 /**
  * Helper for using a temporary "part" file for writing a result to, similar
  * to what browsers do when downloading files.