TaskTree: Add runBlocking() helpers

To be used in non-main threads and in autotests.

Change-Id: If37be854f65c9cfe94eb781a28dc8db4365809e1
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/libs/solutions/tasking/tasktree.cpp

@@ -3,7 +3,10 @@
 
 #include "tasktree.h"
 
+#include <QEventLoop>
+#include <QFutureWatcher>
 #include <QSet>
+#include <QTimer>
 
 namespace Tasking {
 
@@ -1444,6 +1447,54 @@ bool TaskTree::isRunning() const
     return d->m_root && d->m_root->isRunning();
 }
 
+bool TaskTree::runBlocking(const QFuture<void> &future, int timeoutMs)
+{
+    if (isRunning() || future.isCanceled())
+        return false;
+
+    bool ok = false;
+    QEventLoop loop;
+
+    const auto finalize = [&loop, &ok](bool success) {
+        ok = success;
+        // Otherwise, the tasks from inside the running tree that were deleteLater()
+        // will be leaked. Refer to the QObject::deleteLater() docs.
+        QMetaObject::invokeMethod(&loop, [&loop] { loop.quit(); }, Qt::QueuedConnection);
+    };
+
+    QFutureWatcher<void> watcher;
+    connect(&watcher, &QFutureWatcherBase::canceled, this, &TaskTree::stop);
+    watcher.setFuture(future);
+
+    connect(this, &TaskTree::done, &loop, [finalize] { finalize(true); });
+    connect(this, &TaskTree::errorOccurred, &loop, [finalize] { finalize(false); });
+    start();
+    if (!isRunning())
+        return ok;
+
+    QTimer timer;
+    if (timeoutMs) {
+        timer.setSingleShot(true);
+        timer.setInterval(timeoutMs);
+        connect(&timer, &QTimer::timeout, this, &TaskTree::stop);
+        timer.start();
+    }
+
+    loop.exec(QEventLoop::ExcludeUserInputEvents);
+    if (!ok) {
+        auto nonConstFuture = future;
+        nonConstFuture.cancel();
+    }
+    return ok;
+}
+
+bool TaskTree::runBlocking(int timeoutMs)
+{
+    QPromise<void> dummy;
+    dummy.start();
+    return runBlocking(dummy.future(), timeoutMs);
+}
+
 int TaskTree::taskCount() const
 {
     return d->m_root ? d->m_root->taskCount() : 0;

src/libs/solutions/tasking/tasktree.h

@@ -9,6 +9,11 @@
 #include <QObject>
 #include <QSharedPointer>
 
+QT_BEGIN_NAMESPACE
+template <class T>
+class QFuture;
+QT_END_NAMESPACE
+
 namespace Tasking {
 
 class ExecutionContextActivator;
@@ -369,6 +374,12 @@ public:
     void stop();
     bool isRunning() const;
 
+    // Helper methods. They execute a local event loop with ExcludeUserInputEvents.
+    // The passed future is used for listening to the cancel event.
+    // Don't use it in main thread. To be used in non-main threads or in auto tests.
+    bool runBlocking(const QFuture<void> &future, int timeoutMs = 0);
+    bool runBlocking(int timeoutMs = 0);
+
     int taskCount() const;
     int progressMaximum() const { return taskCount(); }
     int progressValue() const; // all finished / skipped / stopped tasks, groups itself excluded