QmlDesigner: Prevent prototype chains cycles

A cycle would lead to an endless loop. So we throw an exception for
synchronization. Maybe we can add later more information to user so
he can easily resolve the error.

Task-number: QDS-4457
Change-Id: I83092ccdff030a610942c155571a0bfa899e808c
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/plugins/qmldesigner/designercore/projectstorage/projectstorage.h

@@ -555,7 +555,7 @@ private:
             return Sqlite::CallbackControl::Continue;
         };
 
-        updatePrototypeToNullStatement.readCallback(callback, &prototypeId);
+        updatePrototypeIdToNullStatement.readCallback(callback, &prototypeId);
     }
 
     void deleteType(TypeId typeId,
@@ -640,6 +640,7 @@ private:
             }
 
             updateTypePrototypeStatement.write(&prototype.typeId, &prototypeId, &prototypeNameId);
+            checkForPrototypeChainCycle(prototype.typeId);
         }
     }
 
@@ -1093,6 +1094,18 @@ private:
         synchronizeEnumerationDeclarations(typeId, type.enumerationDeclarations);
     }
 
+    void checkForPrototypeChainCycle(TypeId typeId)
+    {
+        auto callback = [=](long long currentTypeId) {
+            if (typeId == TypeId{currentTypeId})
+                throw PrototypeChainCycle{};
+
+            return Sqlite::CallbackControl::Continue;
+        };
+
+        selectTypeIdsForPrototypeChainIdStatement.readCallback(callback, &typeId);
+    }
+
     void syncPrototypes(Storage::Type &type)
     {
         if (Utils::visit([](auto &&typeName) -> bool { return typeName.name.isEmpty(); },
@@ -1106,6 +1119,7 @@ private:
                 throw TypeNameDoesNotExists{};
 
             updatePrototypeStatement.write(&type.typeId, &prototypeId, &prototypeTypeNameId);
+            checkForPrototypeChainCycle(type.typeId);
         }
     }
 
@@ -1517,11 +1531,8 @@ public:
     Initializer initializer;
     ReadWriteStatement<1> upsertTypeStatement{
         "INSERT INTO types(importId, name,  accessSemantics, sourceId) VALUES(?1, ?2, "
-        "?3, nullif(?4, -1)) ON "
-        "CONFLICT DO UPDATE SET prototypeId=excluded.prototypeId, "
-        "accessSemantics=excluded.accessSemantics, sourceId=excluded.sourceId WHERE "
-        "prototypeId iS NOT excluded.prototypeId OR accessSemantics IS NOT "
-        "excluded.accessSemantics OR "
+        "?3, nullif(?4, -1)) ON CONFLICT DO UPDATE SET  accessSemantics=excluded.accessSemantics, "
+        "sourceId=excluded.sourceId WHERE accessSemantics IS NOT excluded.accessSemantics OR "
         "sourceId IS NOT excluded.sourceId RETURNING typeId",
         database};
     WriteStatement updatePrototypeStatement{
@@ -1819,13 +1830,21 @@ public:
     ReadStatement<1> selectPropertyDeclarationIdStatement{
         "SELECT propertyDeclarationId FROM propertyDeclarations WHERE propertyDeclarationId=?",
         database};
-    ReadWriteStatement<3> updatePrototypeToNullStatement{
+    ReadWriteStatement<3> updatePrototypeIdToNullStatement{
         "UPDATE types SET prototypeId=NULL WHERE prototypeId=?1 RETURNING "
         "typeId, prototypeNameId, sourceId",
         database};
     ReadStatement<1> selectTypeIdStatement{"SELECT typeId FROM types WHERE typeId=?", database};
     WriteStatement updateTypePrototypeStatement{
         "UPDATE types SET prototypeId=?2, prototypeNameId=?3 WHERE typeId=?1", database};
+    mutable ReadStatement<1> selectTypeIdsForPrototypeChainIdStatement{
+        "WITH RECURSIVE "
+        "  prototypes(typeId) AS ("
+        "       SELECT prototypeId FROM types WHERE typeId=? "
+        "    UNION ALL "
+        "      SELECT prototypeId FROM types JOIN prototypes USING(typeId)) "
+        "SELECT typeId FROM prototypes",
+        database};
 };
 
 } // namespace QmlDesigner

src/plugins/qmldesigner/designercore/projectstorage/projectstorageexceptions.h

@@ -89,4 +89,10 @@ public:
     const char *what() const noexcept override { return "The property name does not exist!"; }
 };
 
+class PrototypeChainCycle : std::exception
+{
+public:
+    const char *what() const noexcept override { return "There is a prototype chain cycle!"; }
+};
+
 } // namespace QmlDesigner

tests/unit/unittest/projectstorage-test.cpp

@@ -912,8 +912,15 @@ TEST_F(ProjectStorageSlowTest, SynchronizeTypesAddsNewTypesThrowsWithWrongExport
 TEST_F(ProjectStorageSlowTest, SynchronizeTypesAddsNewTypesWithMissingImportAndExportedPrototypeName)
 {
     Storage::Types types{createTypes()};
+    types.push_back(Storage::Type{importId3,
+                                  "QObject2",
+                                  Storage::NativeType{},
+                                  TypeAccessSemantics::Reference,
+                                  sourceId4,
+                                  importIds,
+                                  {Storage::ExportedType{"Object2"}, Storage::ExportedType{"Obj2"}}});
     storage.synchronizeDocuments({Storage::Document{sourceId1, {importId1}}});
-    types[1].prototype = Storage::ExportedType{"Object"};
+    types[1].prototype = Storage::ExportedType{"Object2"};
 
     ASSERT_THROW(storage.synchronizeTypes(types, {sourceId1, sourceId2}),
                  QmlDesigner::TypeNameDoesNotExists);
@@ -3070,4 +3077,40 @@ TEST_F(ProjectStorageSlowTest, ChangePrototypeTypeNameThrowsForWrongNativeProtot
                  QmlDesigner::TypeNameDoesNotExists);
 }
 
+TEST_F(ProjectStorageSlowTest, ThrowForPrototypeChainCycles)
+{
+    Storage::Types types{createTypes()};
+    types[1].prototype = Storage::ExportedType{"Object2"};
+    types.push_back(Storage::Type{importId3,
+                                  "QObject2",
+                                  Storage::ExportedType{"Item"},
+                                  TypeAccessSemantics::Reference,
+                                  sourceId3,
+                                  importIds,
+                                  {Storage::ExportedType{"Object2"}, Storage::ExportedType{"Obj2"}}});
+
+    ASSERT_THROW(storage.synchronizeTypes(types, {sourceId1, sourceId2, sourceId3}),
+                 QmlDesigner::PrototypeChainCycle);
+}
+
+TEST_F(ProjectStorageSlowTest, ThrowForTypeIdAndPrototypeIdAreTheSame)
+{
+    Storage::Types types{createTypes()};
+    types[1].prototype = Storage::ExportedType{"Object"};
+
+    ASSERT_THROW(storage.synchronizeTypes(types, {sourceId1, sourceId2}),
+                 QmlDesigner::PrototypeChainCycle);
+}
+
+TEST_F(ProjectStorageSlowTest, ThrowForTypeIdAndPrototypeIdAreTheSameForRelinking)
+{
+    Storage::Types types{createTypes()};
+    types[0].propertyDeclarations[0].typeName = Storage::ExportedType{"Object"};
+    types[0].prototype = Storage::ExportedType{"Object"};
+    storage.synchronizeTypes(types, {sourceId1, sourceId2});
+    types[1].prototype = Storage::ExportedType{"Item"};
+    types[1].typeName = "QObject2";
+
+    ASSERT_THROW(storage.synchronizeTypes({types[1]}, {sourceId2}), QmlDesigner::PrototypeChainCycle);
+}
 } // namespace