Locator: Do not block main event loop

There are multiple locator filters (SpotlightLocatorFilter,
JavaScriptFilter, HelpIndexFilter, the LanguageClient filters) that
depend on the main event loop, and might lock up if that does not run
anymore.

So we cannot use waitForFinished. Cancel a running locator search, and
tell the plugin manager that we need to wait for asynchronous events to
finish before shutting down.

Amends cb5977fbad

Change-Id: Id0b3dc75bc22f21b34be39c3bdbec915b60bdee6
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/plugins/coreplugin/coreplugin.cpp

@@ -443,7 +443,8 @@ QString CorePlugin::msgCrashpadInformation()
 ExtensionSystem::IPlugin::ShutdownFlag CorePlugin::aboutToShutdown()
 {
     Find::aboutToShutdown();
-    m_locator->aboutToShutdown();
+    ExtensionSystem::IPlugin::ShutdownFlag shutdownFlag = m_locator->aboutToShutdown(
+        [this] { emit asynchronousShutdownFinished(); });
     m_mainWindow->aboutToShutdown();
-    return SynchronousShutdown;
+    return shutdownFlag;
 }

src/plugins/coreplugin/locator/locator.cpp

@@ -169,7 +169,8 @@ bool Locator::delayedInitialize()
     return true;
 }
 
-void Locator::aboutToShutdown()
+ExtensionSystem::IPlugin::ShutdownFlag Locator::aboutToShutdown(
+    const std::function<void()> &emitAsynchronousShutdownFinished)
 {
     m_shuttingDown = true;
     m_refreshTimer.stop();
@@ -177,7 +178,7 @@ void Locator::aboutToShutdown()
         m_refreshTask.cancel();
         m_refreshTask.waitForFinished();
     }
-    emit aboutToShutdownOccurred();
+    return LocatorWidget::aboutToShutdown(emitAsynchronousShutdownFinished);
 }
 
 void Locator::loadSettings()

src/plugins/coreplugin/locator/locator.h

@@ -29,11 +29,14 @@
 #include "locatorconstants.h"
 
 #include <coreplugin/actionmanager/command.h>
+#include <extensionsystem/iplugin.h>
 
 #include <QFuture>
 #include <QObject>
 #include <QTimer>
 
+#include <functional>
+
 namespace Core {
 namespace Internal {
 
@@ -48,7 +51,8 @@ public:
     ~Locator() override;
 
     static Locator *instance();
-    void aboutToShutdown();
+    ExtensionSystem::IPlugin::ShutdownFlag aboutToShutdown(
+        const std::function<void()> &emitAsynchronousShutdownFinished);
 
     void initialize();
     void extensionsInitialized();
@@ -63,7 +67,6 @@ public:
 
 signals:
     void filtersChanged();
-    void aboutToShutdownOccurred();
 
 public slots:
     void refresh(QList<ILocatorFilter *> filters);

src/plugins/coreplugin/locator/locatorwidget.cpp

@@ -72,6 +72,7 @@ const int LocatorEntryRole = int(HighlightingItemRole::User);
 namespace Core {
 namespace Internal {
 
+bool LocatorWidget::m_shuttingDown = false;
 QFuture<void> LocatorWidget::m_sharedFuture;
 LocatorWidget *LocatorWidget::m_sharedFutureOrigin = nullptr;
 
@@ -619,13 +620,6 @@ LocatorWidget::LocatorWidget(Locator *locator) :
     connect(qApp, &QApplication::focusChanged, this, &LocatorWidget::updatePreviousFocusWidget);
 
     connect(locator, &Locator::filtersChanged, this, &LocatorWidget::updateFilterList);
-    connect(locator, &Locator::aboutToShutdownOccurred, this, [this]() {
-        m_shuttingDown = true;
-        if (m_entriesWatcher->isRunning()) {
-            m_entriesWatcher->cancel();
-            m_entriesWatcher->waitForFinished();
-        }
-    });
     updateFilterList();
 }
 
@@ -912,6 +906,22 @@ void LocatorWidget::scheduleAcceptEntry(const QModelIndex &index)
     }
 }
 
+ExtensionSystem::IPlugin::ShutdownFlag LocatorWidget::aboutToShutdown(
+    const std::function<void()> &emitAsynchronousShutdownFinished)
+{
+    m_shuttingDown = true;
+    if (m_sharedFuture.isRunning()) {
+        Utils::onFinished(m_sharedFuture,
+                          Locator::instance(),
+                          [emitAsynchronousShutdownFinished](const QFuture<void> &) {
+                              emitAsynchronousShutdownFinished();
+                          });
+        m_sharedFuture.cancel();
+        return ExtensionSystem::IPlugin::AsynchronousShutdown;
+    }
+    return ExtensionSystem::IPlugin::SynchronousShutdown;
+}
+
 void LocatorWidget::acceptEntry(int row)
 {
     if (row < 0 || row >= m_locatorModel->rowCount())

src/plugins/coreplugin/locator/locatorwidget.h

@@ -27,12 +27,15 @@
 
 #include "locator.h"
 
+#include <extensionsystem/iplugin.h>
 #include <utils/optional.h>
 
 #include <QFutureWatcher>
 #include <QPointer>
 #include <QWidget>
 
+#include <functional>
+
 QT_BEGIN_NAMESPACE
 class QAbstractItemModel;
 class QAction;
@@ -63,6 +66,9 @@ public:
 
     void scheduleAcceptEntry(const QModelIndex &index);
 
+    static ExtensionSystem::IPlugin::ShutdownFlag aboutToShutdown(
+        const std::function<void()> &emitAsynchronousShutdownFinished);
+
 signals:
     void showCurrentItemToolTip();
     void lostFocus();
@@ -91,16 +97,17 @@ private:
 
     LocatorModel *m_locatorModel = nullptr;
 
+    static bool m_shuttingDown;
+    static QFuture<void> m_sharedFuture;
+    static LocatorWidget *m_sharedFutureOrigin;
+
     QMenu *m_filterMenu = nullptr;
     QAction *m_refreshAction = nullptr;
     QAction *m_configureAction = nullptr;
     Utils::FancyLineEdit *m_fileLineEdit = nullptr;
     QTimer m_showPopupTimer;
     QFutureWatcher<LocatorFilterEntry> *m_entriesWatcher = nullptr;
-    static QFuture<void> m_sharedFuture;
-    static LocatorWidget *m_sharedFutureOrigin;
     QString m_requestedCompletionText;
-    bool m_shuttingDown = false;
     bool m_needsClearResult = true;
     bool m_updateRequested = false;
     bool m_rerunAfterFinished = false;