From 1f72edcda9f0173203344be53219b5ab2fefd116 Mon Sep 17 00:00:00 2001
From: Christian Kandeler <christian.kandeler@qt.io>
Date: Wed, 5 Aug 2020 16:33:12 +0200
Subject: [PATCH] Wizards: Fix crash

... if the project has no classes.
Apparently, one must not call QFutureInterface::reportsResults() with an
empty list, so prevent that.
Also, for simplicity, make sure we have only one possible point of
deletion for the watcher.

Change-Id: I68c3813459533ced86610e88bea81b6a9d170ca5
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
---
 src/plugins/projectexplorer/jsonwizard/jsonfieldpage.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/plugins/projectexplorer/jsonwizard/jsonfieldpage.cpp b/src/plugins/projectexplorer/jsonwizard/jsonfieldpage.cpp
index 5c11d434006..9cfb13feac7 100644
--- a/src/plugins/projectexplorer/jsonwizard/jsonfieldpage.cpp
+++ b/src/plugins/projectexplorer/jsonwizard/jsonfieldpage.cpp
@@ -632,7 +632,7 @@ void LineEditField::setupCompletion(FancyLineEdit *lineEdit)
     if (!classesFilter)
         return;
     classesFilter->prepareSearch({});
-    const auto watcher = new QFutureWatcher<LocatorFilterEntry>(lineEdit);
+    const auto watcher = new QFutureWatcher<LocatorFilterEntry>;
     const auto handleResults = [this, lineEdit, watcher](int firstIndex, int endIndex) {
         QSet<QString> namespaces;
         QStringList classes;
@@ -681,13 +681,15 @@ void LineEditField::setupCompletion(FancyLineEdit *lineEdit)
         }
         completionList.sort();
         lineEdit->setSpecialCompleter(new QCompleter(completionList, lineEdit));
-        watcher->deleteLater();
     };
     QObject::connect(watcher, &QFutureWatcher<LocatorFilterEntry>::resultsReadyAt, lineEdit,
                      handleResults);
+    QObject::connect(watcher, &QFutureWatcher<LocatorFilterEntry>::finished,
+                     watcher, &QFutureWatcher<LocatorFilterEntry>::deleteLater);
     watcher->setFuture(runAsync([classesFilter](QFutureInterface<LocatorFilterEntry> &f) {
         const QList<LocatorFilterEntry> matches = classesFilter->matchesFor(f, {});
-        f.reportResults(QVector<LocatorFilterEntry>(matches.cbegin(), matches.cend()));
+        if (!matches.isEmpty())
+            f.reportResults(QVector<LocatorFilterEntry>(matches.cbegin(), matches.cend()));
         f.reportFinished();
     }));
 }