Fix and test correct setting of unit parents

autotests/integrationtests/iresourcerepository_integration/test_iresourcerepository.cpp

@@ -26,6 +26,8 @@
 #include "core/resourcerepository.h"
 #include "core/contributorrepository.h"
 #include "core/language.h"
+#include "core/icourse.h"
+#include "core/unit.h"
 #include "../src/settings.h"
 
 void TestIResourceRepository::init()
@@ -84,6 +86,7 @@ void TestIResourceRepository::performInterfaceTests(IResourceRepository *interfa
     QVERIFY(german != nullptr); // ensure that German language was found
     QCOMPARE(interface->courses(german->id()).count(), 1); // there is exactly one German course
     QCOMPARE(interface->courses(nullptr).count(), 2); // all courses in total are 2
+    QVERIFY(interface->courses().first()->units().size() > 0);
 }
 
 QTEST_GUILESS_MAIN(TestIResourceRepository)

autotests/unittests/courseresource/test_courseresource.cpp

@@ -72,6 +72,7 @@ void TestCourseResource::loadCourseResource()
     QVERIFY(course.language() != nullptr);
     QCOMPARE(course.language()->id(), "de");
     QCOMPARE(course.units().count(), 1);
+    QCOMPARE(course.units().first()->course(), &course);
 
     const auto unit = course.units().first();
     QVERIFY(unit != nullptr);
@@ -114,10 +115,11 @@ void TestCourseResource::unitAddAndRemoveHandling()
     QSignalSpy spyAdded(&course, SIGNAL(unitAdded()));
     QCOMPARE(spyAboutToBeAdded.count(), 0);
     QCOMPARE(spyAdded.count(), 0);
-    course.addUnit(std::move(unit));
+    auto sharedUnit = course.addUnit(std::move(unit));
     QCOMPARE(course.units().count(), initialUnitNumber + 1);
     QCOMPARE(spyAboutToBeAdded.count(), 1);
     QCOMPARE(spyAdded.count(), 1);
+    QCOMPARE(sharedUnit->course(), &course);
 }
 
 void TestCourseResource::coursePropertyChanges()

autotests/unittests/editablecourseresource/test_editablecourseresource.cpp

@@ -81,6 +81,7 @@ void TestEditableCourseResource::loadCourseResource()
     QVERIFY(course.language() != nullptr);
     QCOMPARE(course.language()->id(), "de");
     QCOMPARE(course.units().count(), 1);
+    QCOMPARE(course.units().first()->course(), &course);
 
     const auto unit = course.units().first();
     QVERIFY(unit != nullptr);
@@ -120,10 +121,11 @@ void TestEditableCourseResource::unitAddAndRemoveHandling()
     QSignalSpy spyAdded(&course, SIGNAL(unitAdded()));
     QCOMPARE(spyAboutToBeAdded.count(), 0);
     QCOMPARE(spyAdded.count(), 0);
-    course.addUnit(std::move(unit));
+    auto sharedUnit = course.addUnit(std::move(unit));
     QCOMPARE(course.units().count(), initialUnitNumber + 1);
     QCOMPARE(spyAboutToBeAdded.count(), 1);
     QCOMPARE(spyAdded.count(), 1);
+    QCOMPARE(sharedUnit->course(), &course);
 }
 
 void TestEditableCourseResource::coursePropertyChanges()

src/core/resources/courseresource.cpp

@@ -247,6 +247,7 @@ void CourseResource::setLanguage(std::shared_ptr<Language> language)
 std::shared_ptr<Unit> CourseResource::addUnit(std::unique_ptr<Unit> unit)
 {
     std::shared_ptr<Unit> storedUnit(std::move(unit));
+    storedUnit->setCourse(this);
     emit unitAboutToBeAdded(storedUnit, d->m_units.count() - 1);
     d->m_units.append(storedUnit);
     emit unitAdded();

src/core/resources/editablecourseresource.cpp

@@ -40,6 +40,11 @@ EditableCourseResource::EditableCourseResource(const QUrl &path, IResourceReposi
     , m_course(new CourseResource(path, repository))
 {
     QQmlEngine::setObjectOwnership(this, QQmlEngine::CppOwnership);
+
+    for (auto unit : m_course->units()) {
+        unit->setCourse(this);
+    }
+
     connect(m_course.get(), &ICourse::unitAboutToBeAdded, this, &ICourse::unitAboutToBeAdded);
     connect(m_course.get(), &ICourse::unitAdded, this, &ICourse::unitAdded);
     connect(m_course.get(), &CourseResource::idChanged, this, &EditableCourseResource::idChanged);
@@ -153,7 +158,9 @@ bool EditableCourseResource::exportCourse(const QUrl &filePath)
 std::shared_ptr<Unit> EditableCourseResource::addUnit(std::unique_ptr<Unit> unit)
 {
     setModified(true);
-    return m_course->addUnit(std::move(unit));
+    auto sharedUnit = m_course->addUnit(std::move(unit));
+    sharedUnit->setCourse(this);
+    return sharedUnit;
 }
 
 QVector<std::shared_ptr<Unit>> EditableCourseResource::units()