diff --git a/src/libs/utils/asynctask.h b/src/libs/utils/asynctask.h
index bb537cef168..e035977401b 100644
--- a/src/libs/utils/asynctask.h
+++ b/src/libs/utils/asynctask.h
@@ -66,8 +66,9 @@ public:
     bool isCanceled() const { return m_watcher.isCanceled(); }
 
     QFuture<ResultType> future() const { return m_watcher.future(); }
-    ResultType result() const { return m_watcher.result(); } // TODO: warn when isRunning?
-    QList<ResultType> results() const { return m_watcher.future().results(); }
+    ResultType result() const { return m_watcher.result(); }
+    QList<ResultType> results() const { return future().results(); }
+    bool isResultAvailable() const { return future().resultCount(); }
 
 private:
     StartHandler m_startHandler;
diff --git a/src/plugins/cppeditor/cppprojectupdater.cpp b/src/plugins/cppeditor/cppprojectupdater.cpp
index 91bcd943b12..a784d3bb794 100644
--- a/src/plugins/cppeditor/cppprojectupdater.cpp
+++ b/src/plugins/cppeditor/cppprojectupdater.cpp
@@ -67,7 +67,8 @@ void CppProjectUpdater::update(const ProjectUpdateInfo &projectUpdateInfo,
         async.setFutureSynchronizer(&m_futureSynchronizer);
     };
     const auto onInfoGeneratorDone = [=](const AsyncTask<ProjectInfo::ConstPtr> &async) {
-        storage->projectInfo = async.result();
+        if (async.isResultAvailable())
+            storage->projectInfo = async.result();
     };
     QList<TaskItem> tasks{parallel};
     tasks.append(Async<ProjectInfo::ConstPtr>(setupInfoGenerator, onInfoGeneratorDone));
diff --git a/src/plugins/diffeditor/diffeditorplugin.cpp b/src/plugins/diffeditor/diffeditorplugin.cpp
index e18a0e27972..2a813206657 100644
--- a/src/plugins/diffeditor/diffeditorplugin.cpp
+++ b/src/plugins/diffeditor/diffeditorplugin.cpp
@@ -109,24 +109,25 @@ DiffFilesController::DiffFilesController(IDocument *document)
     setDisplayName(Tr::tr("Diff"));
     using namespace Tasking;
 
-    const TreeStorage<QList<FileData>> storage;
+    const TreeStorage<QList<std::optional<FileData>>> storage;
 
     const auto setupTree = [this, storage](TaskTree &taskTree) {
-        QList<FileData> *outputList = storage.activeStorage();
+        QList<std::optional<FileData>> *outputList = storage.activeStorage();
 
         const auto setupDiff = [this](AsyncTask<FileData> &async, const ReloadInput &reloadInput) {
             async.setAsyncCallData(DiffFile(ignoreWhitespace(), contextLineCount()), reloadInput);
             async.setFutureSynchronizer(Internal::DiffEditorPlugin::futureSynchronizer());
         };
         const auto onDiffDone = [outputList](const AsyncTask<FileData> &async, int i) {
-            (*outputList)[i] = async.result();
+            if (async.isResultAvailable())
+                (*outputList)[i] = async.result();
         };
 
         const QList<ReloadInput> inputList = reloadInputList();
         outputList->resize(inputList.size());
 
         using namespace std::placeholders;
-        QList<TaskItem> tasks {parallel, continueOnDone};
+        QList<TaskItem> tasks {parallel, optional};
         for (int i = 0; i < inputList.size(); ++i) {
             tasks.append(Async<FileData>(std::bind(setupDiff, _1, inputList.at(i)),
                                          std::bind(onDiffDone, _1, i)));
@@ -134,7 +135,13 @@ DiffFilesController::DiffFilesController(IDocument *document)
         taskTree.setupRoot(tasks);
     };
     const auto onTreeDone = [this, storage] {
-        setDiffFiles(*storage.activeStorage());
+        const QList<std::optional<FileData>> &results = *storage.activeStorage();
+        QList<FileData> finalList;
+        for (const std::optional<FileData> &result : results) {
+            if (result.has_value())
+                finalList.append(*result);
+        }
+        setDiffFiles(finalList);
     };
     const auto onTreeError = [this, storage] {
         setDiffFiles({});
diff --git a/src/plugins/diffeditor/sidebysidediffeditorwidget.cpp b/src/plugins/diffeditor/sidebysidediffeditorwidget.cpp
index 5bc887b90aa..da69e607840 100644
--- a/src/plugins/diffeditor/sidebysidediffeditorwidget.cpp
+++ b/src/plugins/diffeditor/sidebysidediffeditorwidget.cpp
@@ -874,7 +874,7 @@ void SideBySideDiffEditorWidget::showDiff()
     m_controller.setBusyShowing(true);
 
     connect(m_asyncTask.get(), &AsyncTaskBase::done, this, [this] {
-        if (m_asyncTask->isCanceled()) {
+        if (m_asyncTask->isCanceled() || !m_asyncTask->isResultAvailable()) {
             for (SideDiffEditorWidget *editor : m_editor)
                 editor->clearAll(Tr::tr("Retrieving data failed."));
         } else {
diff --git a/src/plugins/diffeditor/unifieddiffeditorwidget.cpp b/src/plugins/diffeditor/unifieddiffeditorwidget.cpp
index 8c8bee05c27..b937b919f7c 100644
--- a/src/plugins/diffeditor/unifieddiffeditorwidget.cpp
+++ b/src/plugins/diffeditor/unifieddiffeditorwidget.cpp
@@ -458,7 +458,7 @@ void UnifiedDiffEditorWidget::showDiff()
     m_asyncTask->setFutureSynchronizer(DiffEditorPlugin::futureSynchronizer());
     m_controller.setBusyShowing(true);
     connect(m_asyncTask.get(), &AsyncTaskBase::done, this, [this] {
-        if (m_asyncTask->isCanceled()) {
+        if (m_asyncTask->isCanceled() || !m_asyncTask->isResultAvailable()) {
             setPlainText(Tr::tr("Retrieving data failed."));
         } else {
             const ShowResult result = m_asyncTask->result();
diff --git a/src/plugins/projectexplorer/extracompiler.cpp b/src/plugins/projectexplorer/extracompiler.cpp
index ff7c061790e..ab72d3608ff 100644
--- a/src/plugins/projectexplorer/extracompiler.cpp
+++ b/src/plugins/projectexplorer/extracompiler.cpp
@@ -340,7 +340,7 @@ Tasking::TaskItem ProcessExtraCompiler::taskItemImpl(const ContentProvider &prov
         async.setFutureSynchronizer(futureSynchronizer());
     };
     const auto taskDone = [=](const AsyncTask<FileNameToContentsHash> &async) {
-        if (async.results().size() == 0)
+        if (!async.isResultAvailable())
             return;
         const FileNameToContentsHash data = async.result();
         if (data.isEmpty())