Fix errors when running updates in a directory requiring elevation

isWritable() is not a reliable way to check for permissions on Windows.
Instead, just try to create a file.

The alternative would be to set the magic qt_ntfs_permission_lookup
variable to 1. Anyhow, this might slow down things and cause other
regressions ...

Task-number: QTIFW-746
Change-Id: I1b5637670bfcfe29966f0545ce2c6b1f663a9738
Reviewed-by: Iikka Eklund <iikka.eklund@theqtcompany.com>
Reviewed-by: Karsten Heimrich <karsten.heimrich@theqtcompany.com>

2 files changed, 2 insertions, 2 deletions

diff --git a/Changelog b/Changelog
index 4eef4bccd..a7a823618 100644
--- a/Changelog
+++ b/Changelog
@@ -4,6 +4,7 @@
 - Fix handling of system proxy with credentials. (QTBUG-46547)
 - Unify selection of language for translations. (QTIFW-390)
 - Fix return value of component.installAction() when updating. (QTIFW-727)
+- Fix errors when updating an installation requiring elevation on Windows. (QTIFW-746)
 - Documentation updates.
 
 2.0.1
diff --git a/src/libs/installer/packagemanagercore_p.cpp b/src/libs/installer/packagemanagercore_p.cpp
index 7d2864cfb..542d51603 100644
--- a/src/libs/installer/packagemanagercore_p.cpp
+++ b/src/libs/installer/packagemanagercore_p.cpp
@@ -1604,9 +1604,8 @@ bool PackageManagerCorePrivate::runPackageUpdater()
         //to have some progress for the cleanup/write component.xml step
         ProgressCoordinator::instance()->addReservePercentagePoints(1);
 
-        const QString packagesXml = componentsXmlPath();
         // check if we need admin rights and ask before the action happens
-        if (!QFileInfo(installerBinaryPath()).isWritable() || !QFileInfo(packagesXml).isWritable())
+        if (!QTemporaryFile(targetDir() + QStringLiteral("/XXXXXX")).open())
             adminRightsGained = m_core->gainAdminRights();
 
         const QList<Component *> componentsToInstall = m_core->orderedComponentsToInstall();