qmllint: Break inheritance cycles

Previously we would run into infinite loops on those. Mind that qmllint
will reject a file called Window.qml that imports QtQuick.Window and
then instantiates a Window {}. Such a thing is bad style.

Task-number: QTBUG-82817
Change-Id: I6db82ca1794c3020dcb7d7e837fe44f72bca5029
Reviewed-by: Maximilian Goldstein <max.goldstein@qt.io>
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

5 files changed, 27 insertions, 0 deletions

diff --git a/tests/auto/qml/qmllint/data/Cycle1.qml b/tests/auto/qml/qmllint/data/Cycle1.qml
new file mode 100644
index 0000000000..8095e9f732
--- /dev/null
+++ b/tests/auto/qml/qmllint/data/Cycle1.qml
@@ -0,0 +1,2 @@
+import QtQml 2.0
+Cycle2 {}
diff --git a/tests/auto/qml/qmllint/data/Cycle2.qml b/tests/auto/qml/qmllint/data/Cycle2.qml
new file mode 100644
index 0000000000..90c376fcda
--- /dev/null
+++ b/tests/auto/qml/qmllint/data/Cycle2.qml
@@ -0,0 +1,2 @@
+import QtQml 2.0
+Cycle3 {}
diff --git a/tests/auto/qml/qmllint/data/Cycle3.qml b/tests/auto/qml/qmllint/data/Cycle3.qml
new file mode 100644
index 0000000000..f4cba68653
--- /dev/null
+++ b/tests/auto/qml/qmllint/data/Cycle3.qml
@@ -0,0 +1,2 @@
+import QtQml 2.0
+Cycle1 {}
diff --git a/tests/auto/qml/qmllint/tst_qmllint.cpp b/tests/auto/qml/qmllint/tst_qmllint.cpp
index ed968d6623..8697495a6f 100644
--- a/tests/auto/qml/qmllint/tst_qmllint.cpp
+++ b/tests/auto/qml/qmllint/tst_qmllint.cpp
@@ -164,6 +164,10 @@ void TestQmllint::dirtyQmlCode_data()
             << QStringLiteral("incompleteQmltypes.qml")
             << QString("Warning: Type \"QPalette\" of member \"palette\" not found at 5:26")
             << QString();
+    QTest::newRow("inheritanceCylce")
+            << QStringLiteral("Cycle1.qml")
+            << QString("Warning: Cycle2 is part of an inheritance cycle: Cycle2 -> Cycle3 -> Cycle1 -> Cycle2")
+            << QString();
 }
 
 void TestQmllint::dirtyQmlCode()
diff --git a/tools/qmllint/findunqualified.cpp b/tools/qmllint/findunqualified.cpp
index 5bb9b62529..9bb9395015 100644
--- a/tools/qmllint/findunqualified.cpp
+++ b/tools/qmllint/findunqualified.cpp
@@ -367,11 +367,28 @@ void FindUnqualifiedIDVisitor::importFileOrDirectory(const QString &fileOrDirect
 
 void FindUnqualifiedIDVisitor::importExportedNames(const QStringRef &prefix, QString name)
 {
+    QList<ScopeTree::ConstPtr> scopes;
     for (;;) {
         ScopeTree::ConstPtr scope = m_exportedName2Scope.value(m_exportedName2Scope.contains(name)
                                                                ? name
                                                                : prefix + QLatin1Char('.') + name);
         if (scope) {
+            if (scopes.contains(scope)) {
+                QString inheritenceCycle = name;
+                for (const auto seen: qAsConst(scopes)) {
+                    inheritenceCycle.append(QLatin1String(" -> "));
+                    inheritenceCycle.append(seen->superclassName());
+                }
+
+                m_colorOut.write(QLatin1String("Warning: "), Warning);
+                m_colorOut.write(QString::fromLatin1("%1 is part of an inheritance cycle: %2\n")
+                                 .arg(name)
+                                 .arg(inheritenceCycle));
+                m_unknownImports.insert(name);
+                m_visitFailed = true;
+                break;
+            }
+            scopes.append(scope);
             const auto properties = scope->properties();
             for (auto property : properties) {
                 property.setType(m_exportedName2Scope.value(property.typeName()).get());