Index: kdevplatform/shell/openprojectdialog.h
===================================================================
--- kdevplatform/shell/openprojectdialog.h
+++ kdevplatform/shell/openprojectdialog.h
@@ -67,6 +67,7 @@
 private:
     bool execNativeDialog();
     void validateProjectInfo();
+    QUrl m_projectDirUrl;
     QUrl m_url;
     QUrl m_selected;
     QString m_projectName;
Index: kdevplatform/shell/openprojectdialog.cpp
===================================================================
--- kdevplatform/shell/openprojectdialog.cpp
+++ kdevplatform/shell/openprojectdialog.cpp
@@ -15,6 +15,7 @@
 #include <QPushButton>
 #include <QFileInfo>
 #include <QFileDialog>
+#include <QRegularExpression>
 
 #include <KColorScheme>
 #include <KIO/StatJob>
@@ -73,6 +74,7 @@
                                      const QUrl& repoUrl, IPlugin* vcsOrProviderPlugin,
                                      QWidget* parent)
     : KAssistantDialog( parent )
+    , m_projectDirUrl(QUrl())
     , m_urlIsDirectory(false)
     , sourcePage(nullptr)
     , openPage(nullptr)
@@ -272,7 +274,9 @@
             }
             page->populateProjectFileCombo(choices);
         }
-        m_url.setPath( m_url.path() + QLatin1Char('/') + m_url.fileName() + QLatin1Char('.') + ShellExtension::getInstance()->projectFileExtension() );
+        if (!m_url.toLocalFile().endsWith(QLatin1Char('.') + ShellExtension::getInstance()->projectFileExtension())) {
+          m_url.setPath( m_url.path() + QLatin1Char('/') + m_url.fileName() + QLatin1Char('.') + ShellExtension::getInstance()->projectFileExtension() );
+        }
     } else {
         setAppropriate( projectInfoPage, false );
         m_url = url;
@@ -310,7 +314,35 @@
 
 void OpenProjectDialog::validateProjectName( const QString& name )
 {
-    m_projectName = name;
+    if (name != m_projectName) {
+        bool settingName = currentPage() == projectInfoPage;
+        m_projectName = name;
+        if (m_projectDirUrl.isEmpty() && settingName) {
+            // cache the selected project directory
+            const auto urlInfo = ::urlInfo(m_url);
+            if (urlInfo.isValid && urlInfo.isDir) {
+                m_projectDirUrl = m_url.adjusted(QUrl::StripTrailingSlash);
+            } else {
+                // if !urlInfo.isValid the url almost certainly refers to a file that doesn't exist (yet)
+                // With the Generic Makefile proj.manager it can be the project file url, for instance.
+                m_projectDirUrl = m_url.adjusted(QUrl::RemoveFilename | QUrl::StripTrailingSlash);
+            }
+        }
+        const QUrl url(m_projectDirUrl);
+        // construct a version of the project name that's safe for use as a filename:
+        // TODO: do an additional replace of QDir::separator() with "@"?
+        QString safeName = m_projectName;
+        safeName.replace(QRegularExpression(QStringLiteral("[\\\\/]")), QStringLiteral("@"));
+        safeName = safeName.replace(QLatin1Char(':'), QLatin1Char('='));
+        safeName = safeName.replace(QRegExp(QStringLiteral("\\s")), QStringLiteral("_"));
+        safeName += QLatin1Char('.') + ShellExtension::getInstance()->projectFileExtension();
+        // don't interfere with m_url when validateOpenUrl() is also likely to change it
+        if (settingName) {
+            m_url.setPath(url.path() + QLatin1Char('/') + safeName);
+            m_urlIsDirectory = false;
+            qCDebug(SHELL) << "project name:" << m_projectName << "file name:" << safeName << "in" << url.path();
+        }
+    }
     validateProjectInfo();
 }
 
Index: kdevplatform/shell/projectcontroller.cpp
===================================================================
--- kdevplatform/shell/projectcontroller.cpp
+++ kdevplatform/shell/projectcontroller.cpp
@@ -423,6 +423,9 @@
     KSharedConfigPtr cfg = KSharedConfig::openConfig( configPath, KConfig::SimpleConfig );
     KConfigGroup grp = cfg->group( "Project" );
     QString defaultName = dlg->projectFileUrl().adjusted(QUrl::RemoveFilename | QUrl::StripTrailingSlash).fileName();
+    qCDebug(SHELL) << "configPath=" << configPath << "defaultName=" << defaultName
+        << "projName=" << dlg->projectName() << "projectMan=" << dlg->projectManager()
+        << "grp.Name=" << grp.readEntry( "Name", QString() ) << "grp.Manager=" << grp.readEntry( "Manager", QString() );
     return (grp.readEntry( "Name", QString() ) == dlg->projectName() || dlg->projectName() == defaultName) &&
            grp.readEntry( "Manager", QString() ) == dlg->projectManager();
 }
@@ -438,19 +441,27 @@
     }
 
     QUrl projectFileUrl = dlg->projectFileUrl();
-    qCDebug(SHELL) << "selected project:" << projectFileUrl << dlg->projectName() << dlg->projectManager();
+    qCDebug(SHELL) << "selected project:" << projectFileUrl << "selectedUrl=" << dlg->selectedUrl()
+        << "projectName=" << dlg->projectName() << "projectManager=" << dlg->projectManager();
     if ( dlg->projectManager() == QLatin1String("<built-in>") ) {
         return projectFileUrl;
     }
 
     // controls if existing project file should be saved
     bool writeProjectConfigToFile = true;
     if( projectFileExists( projectFileUrl ) )
     {
-        // check whether config is equal
-        bool shouldAsk = true;
-        if( projectFileUrl == dlg->selectedUrl() )
+        // check whether we should question the user about overriding an existing project file or not.
+        // We don't need to do that when the file we're importing (dlg->selectedUrl) is already an
+        // existing .kdev4 project file (we just verified that it exists):
+        bool isKDevProject = QFileInfo(dlg->selectedUrl().url()).suffix() == QStringLiteral("kdev4");
+        bool shouldAsk = !isKDevProject;
+        if( !isKDevProject && projectFileUrl == dlg->selectedUrl() )
         {
+            // We're importing a project from another type of project file, post the
+            // override dialog if there's a discrepancy between the project file URL
+            // and the information stored in the dialog and the project settings.
+            qCWarning(SHELL) << "Importing a foreign project type:" << projectFileUrl.url();
             if( projectFileUrl.isLocalFile() )
             {
                 shouldAsk = !equalProjectFile( projectFileUrl.toLocalFile(), dlg );
@@ -490,18 +501,24 @@
             } else if ( ret == KMessageBox::Cancel )
             {
                 return QUrl();
-            } // else fall through and write new file
+            } else {
+               // confusion can arise when an existing project is overridden and the old settings
+               // file remains (http://phabricator.kde.org/T6262). The .kdev4 directory can
+               // contain settings files for other projects which shouldn't be deleted, so
+               // we delete just the settings file for this project.
+               Path settingsFile(projectFileUrl);
+               settingsFile.setLastPathSegment(QStringLiteral(".kdev4"));
+               settingsFile.addPath(projectFileUrl.fileName());
+               qCDebug(SHELL) << "Deleting old settings file before overriding it:" << settingsFile;
+               auto delJob = KIO::del(settingsFile.toUrl());
+               delJob->exec();
+            }
         } else {
             writeProjectConfigToFile = false;
         }
     }
 
     if (writeProjectConfigToFile) {
-        Path projectConfigDir(projectFileUrl);
-        projectConfigDir.setLastPathSegment(QStringLiteral(".kdev4"));
-        auto delJob = KIO::del(projectConfigDir.toUrl());
-        delJob->exec();
-
         if (!writeProjectSettingsToConfigFile(projectFileUrl, dlg)) {
             KMessageBox::error(d->m_core->uiControllerInternal()->defaultMainWindow(),
                 i18n("Unable to create configuration file %1", projectFileUrl.url()));