Core: Fix VarSet add property dialog Esc segfault (#17215)

* Core: Fix VarSet add property dialog Esc segfault

* Core: Improve the way disconnect is handled

* Core: Add a check for a non-existing property

src/Gui/DlgAddPropertyVarSet.cpp

@@ -37,7 +37,6 @@
 #include "DlgAddPropertyVarSet.h"
 #include "ui_DlgAddPropertyVarSet.h"
 #include "MainWindow.h"
-#include "ViewProviderDocumentObject.h"
 #include "ViewProviderVarSet.h"
 
 FC_LOG_LEVEL_INIT("DlgAddPropertyVarSet", true, true)
@@ -99,8 +98,8 @@ void DlgAddPropertyVarSet::initializeGroup()
     }
 
     comboBoxGroup.setEditText(QString::fromStdString(groupNamesSorted[0]));
-    connect(&comboBoxGroup, &EditFinishedComboBox::editFinished,
-            this, &DlgAddPropertyVarSet::onEditFinished);
+    connComboBoxGroup = connect(&comboBoxGroup, &EditFinishedComboBox::editFinished,
+                                this, &DlgAddPropertyVarSet::onEditFinished);
 }
 
 void DlgAddPropertyVarSet::getSupportedTypes(std::vector<Base::Type>& types)
@@ -140,8 +139,8 @@ void DlgAddPropertyVarSet::initializeTypes()
     ui->comboBoxType->setCompleter(&completerType);
     ui->comboBoxType->setInsertPolicy(QComboBox::NoInsert);
 
-    connect(ui->comboBoxType, &QComboBox::currentTextChanged,
-            this, &DlgAddPropertyVarSet::onEditFinished);
+    connComboBoxType = connect(ui->comboBoxType, &QComboBox::currentTextChanged,
+                               this, &DlgAddPropertyVarSet::onEditFinished);
 }
 
 /*
@@ -167,9 +166,9 @@ void DlgAddPropertyVarSet::initializeWidgets(ViewProviderVarSet* viewProvider)
 
     connect(this, &QDialog::finished,
             this, [viewProvider](int result) { viewProvider->onFinished(result); });
-    connect(ui->lineEditName, &QLineEdit::editingFinished,
-            this, &DlgAddPropertyVarSet::onEditFinished);
-    connect(ui->lineEditName, &QLineEdit::textChanged,
+    connLineEditNameEditFinished = connect(ui->lineEditName, &QLineEdit::editingFinished,
+                                           this, &DlgAddPropertyVarSet::onEditFinished);
+    connLineEditNameTextChanged = connect(ui->lineEditName, &QLineEdit::textChanged,
             this, &DlgAddPropertyVarSet::onNamePropertyChanged);
 
     std::string title = "Add a property to " + varSet->getFullName();
@@ -300,6 +299,10 @@ void DlgAddPropertyVarSet::changePropertyToAdd() {
     assert(name == namePropertyToAdd);
 
     App::Property* prop = varSet->getPropertyByName(namePropertyToAdd.c_str());
+    if (prop == nullptr) {
+        // this should not happen because this method assumes the property exists
+        FC_THROWM(Base::RuntimeError, "A property with name '" << name << "' does not exist.");
+    }
 
     std::string group = comboBoxGroup.currentText().toStdString();
     if (prop->getGroup() != group) {
@@ -473,6 +476,16 @@ void DlgAddPropertyVarSet::accept()
 void DlgAddPropertyVarSet::reject()
 {
     App::Document* doc = varSet->getDocument();
+    // On reject we can disconnect the signal handlers because nothing useful
+    // is to be done.  Otherwise, signals may activate the handlers that assume
+    // that a new property has been created, an assumption that will be
+    // violated by aborting the transaction because it will remove the newly
+    // created property.
+    disconnect(connComboBoxGroup);
+    disconnect(connComboBoxType);
+    disconnect(connLineEditNameEditFinished);
+    disconnect(connLineEditNameTextChanged);
+
     // a transaction is not pending if a name has not been determined.
     if (doc->hasPendingTransaction()) {
         doc->abortTransaction();

src/Gui/DlgAddPropertyVarSet.h

@@ -125,6 +125,12 @@ private:
     std::string namePropertyToAdd;
     std::unique_ptr<PropertyEditor::PropertyItem> propertyItem;
     std::unique_ptr<App::ObjectIdentifier> objectIdentifier;
+
+    // connections
+    QMetaObject::Connection connComboBoxGroup;
+    QMetaObject::Connection connComboBoxType;
+    QMetaObject::Connection connLineEditNameEditFinished;
+    QMetaObject::Connection connLineEditNameTextChanged;
 };
 
 } // namespace Dialog