Q{File,FileInfo,Dir}: add std::filesystem::path overloads

Add some overloads where (I thought) it makes sense for QDir and QFile
to accept std::filesystem::path objects. Currently my thinking is to
not add overloads for static functions where std::filesystem can already
do the same job, e.g. create directory or file.

Template and enable_if is needed due to both QString and
std::filesystem::path being able to be constructed from string literals.

The common shared code is currently in QFile because QDir had an
implicit include of QFile, made explicit in this patch, and QFileInfo
has an include to QFile as well.

The QT_HAS_STD_FILESYSTEM macro is visible in user-code which I
currently take advantage of in the tests, and users could too.

Change-Id: I8d05d3c34c6c17e20972a6a2053862b8891d6c3c
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

3 files changed, 54 insertions, 0 deletions

diff --git a/tests/auto/corelib/io/qfile/stdinprocess/stdinprocess.pro b/tests/auto/corelib/io/qfile/stdinprocess/stdinprocess.pro
index 512da8939b..bc48a9fb39 100644
--- a/tests/auto/corelib/io/qfile/stdinprocess/stdinprocess.pro
+++ b/tests/auto/corelib/io/qfile/stdinprocess/stdinprocess.pro
@@ -2,3 +2,4 @@ SOURCES += main.cpp
 QT = core
 
 load(qt_test_helper)
+CONFIG += c++17
diff --git a/tests/auto/corelib/io/qfile/test.pro b/tests/auto/corelib/io/qfile/test.pro
index 7a2767bf3c..47b778bc33 100644
--- a/tests/auto/corelib/io/qfile/test.pro
+++ b/tests/auto/corelib/io/qfile/test.pro
@@ -24,3 +24,5 @@ TESTDATA += \
     resources/file1.ext1
 
 win32:!winrt: QMAKE_USE += ole32 uuid
+
+CONFIG += c++17
diff --git a/tests/auto/corelib/io/qfile/tst_qfile.cpp b/tests/auto/corelib/io/qfile/tst_qfile.cpp
index 350bff0652..b8f0d29078 100644
--- a/tests/auto/corelib/io/qfile/tst_qfile.cpp
+++ b/tests/auto/corelib/io/qfile/tst_qfile.cpp
@@ -282,6 +282,8 @@ private slots:
     void moveToTrash_data();
     void moveToTrash();
 
+    void stdfilesystem();
+
 private:
 #ifdef BUILTIN_TESTDATA
     QSharedPointer<QTemporaryDir> m_dataDir;
@@ -3812,5 +3814,54 @@ void tst_QFile::moveToTrash()
     }
 }
 
+void tst_QFile::stdfilesystem()
+{
+#if QT_CONFIG(cxx17_filesystem)
+    namespace fs = std::filesystem;
+    auto toFSPath = [](const QFile &file) { return fs::path(file.fileName().toStdU16String()); };
+    fs::path path { "./path" };
+    QFile file(path);
+    QCOMPARE(toFSPath(file), path);
+
+    QCOMPARE(path, file.filesystemFileName());
+
+    {
+        QFile parentedFile(path, this);
+        QCOMPARE(file.fileName(), parentedFile.fileName());
+        QCOMPARE(parentedFile.parent(), this);
+    }
+
+    path = path / "filename";
+    file.setFileName(path);
+    QCOMPARE(toFSPath(file), path);
+
+    path = "test-file";
+    file.setFileName(path);
+    QVERIFY(file.open(QIODevice::WriteOnly));
+    file.close();
+
+    path = "tile-fest";
+    QVERIFY(file.rename(path));
+    QVERIFY(fs::exists(path));
+    fs::path linkfile { "test-link" };
+    QVERIFY(file.link(linkfile));
+    QVERIFY(fs::exists(linkfile));
+
+    fs::path copyfile { "copy-file" };
+    QVERIFY(file.copy(copyfile));
+    QVERIFY(fs::exists(copyfile));
+
+    QFileDevice::Permissions p = QFile::permissions(path);
+    QVERIFY(p.testFlag(QFile::WriteUser) || p.testFlag(QFile::WriteOwner)); // some we know for sure
+    if (p.testFlag(QFile::ReadUser))
+        p.setFlag(QFile::ReadUser, false);
+    else if (p.testFlag(QFile::ReadOwner))
+        p.setFlag(QFile::ReadOwner, false);
+    QVERIFY(QFile::setPermissions(path, p));
+#else
+    QSKIP("Not supported");
+#endif
+}
+
 QTEST_MAIN(tst_QFile)
 #include "tst_qfile.moc"