Utils: Add FilePath.hasFileAccess()

FilePath::hasFileAccess allows a user to test if a specific device
can access files. This is faster than calling "exists()" as it does
not have to actually check anything on the device.

Task-number: QTCREATORBUG-28531
Change-Id: I94b5b9e0ae020b81f126c61fd06bb25f3d4a88cb
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/libs/utils/filepath.cpp

@@ -932,9 +932,9 @@ void FilePath::setFromString(const QStringView fileNameView)
     setParts({}, {}, fileNameView);
 }
 
-DeviceFileAccess *FilePath::fileAccess() const
+expected_str<DeviceFileAccess *> getFileAccess(const FilePath &filePath)
 {
-    if (!needsDevice())
+    if (!filePath.needsDevice())
         return DesktopDeviceFileAccess::instance();
 
     if (!s_deviceHooks.fileAccess) {
@@ -943,12 +943,23 @@ DeviceFileAccess *FilePath::fileAccess() const
         return DesktopDeviceFileAccess::instance();
     }
 
+    return s_deviceHooks.fileAccess(filePath);
+}
+
+DeviceFileAccess *FilePath::fileAccess() const
+{
     static DeviceFileAccess dummy;
-    const expected_str<DeviceFileAccess *> access = s_deviceHooks.fileAccess(*this);
+    const expected_str<DeviceFileAccess *> access = getFileAccess(*this);
     QTC_ASSERT_EXPECTED(access, return &dummy);
     return *access ? *access : &dummy;
 }
 
+bool FilePath::hasFileAccess() const
+{
+    const expected_str<DeviceFileAccess *> access = getFileAccess(*this);
+    return access && access.value();
+}
+
 /*!
     Constructs a FilePath from \a filePath. The \a defaultExtension is appended
     to \a filePath if that does not have an extension already.

src/libs/utils/filepath.h

@@ -212,6 +212,7 @@ public:
     // There are usually other means available. E.g. distinguishing based
     // on FilePath::osType().
     bool needsDevice() const;
+    bool hasFileAccess() const;
 
     bool isSameDevice(const FilePath &other) const;
     bool isSameFile(const FilePath &other) const;

src/libs/utils/fsengine/fsengine.cpp

@@ -36,7 +36,7 @@ FilePaths FSEngine::registeredDeviceRoots()
 
 void FSEngine::addDevice(const FilePath &deviceRoot)
 {
-    if (deviceRoot.exists())
+    if (deviceRoot.hasFileAccess())
         deviceRoots().append(deviceRoot);
 }
 
@@ -53,7 +53,7 @@ FilePaths &FSEngine::deviceRoots()
 
 QStringList &FSEngine::deviceSchemes()
 {
-    static QStringList g_deviceSchemes {"device"};
+    static QStringList g_deviceSchemes{"device"};
     return g_deviceSchemes;
 }