Prevent interpreter crashes when displaying uninitialized Janus objects

Python/src/pyJanus.cpp

@@ -51,19 +51,19 @@ void init_Janus(py::module_ &m)
       .def_property_readonly("xml_filename", &Janus::getXmlFileName)
 
       .def("__repr__",
-           [](Janus &self)
+           [](const Janus &self)
            {
              std::ostringstream out;
-             out << "Janus(xml_filename='" << self.getXmlFileName() << ")"
+             out << "Janus(xml_filename='" << self.getXmlFileName() << "')"
                  << " at JanusInstance<"
-                 << self.getVariableDef().front().getJanusInstance() << ">";
+                 << &self << ">";
              return out.str();
            })
       .def("__str__",
            [](const Janus &self)
            {
              std::ostringstream out;
-             out << "Janus(xml_filename='" << self.getXmlFileName() << ")";
+             out << "Janus(xml_filename='" << self.getXmlFileName() << "')";
              return out.str();
            });
 }

Python/tests/test_janus_representation.py

@@ -0,0 +1,39 @@
+import os
+import re
+import subprocess
+import sys
+
+import pyJanus
+
+
+def test_empty_janus_repr():
+    # Isolate the call so a native crash is reported as a test failure instead
+    # of terminating the entire test suite.
+    result = subprocess.run(
+        [sys.executable, "-c", "import pyJanus; print(repr(pyJanus.Janus()))"],
+        capture_output=True,
+        text=True,
+        timeout=30,
+    )
+
+    assert result.returncode == 0, result.stderr
+    assert re.fullmatch(
+        r"Janus\(xml_filename=''\) at JanusInstance<[^<>\s]+>\n",
+        result.stdout,
+    )
+
+
+def test_empty_janus_str():
+    text = str(pyJanus.Janus())
+    assert text == "Janus(xml_filename='')"
+
+
+def test_loaded_janus_representation():
+    xml_path = f"{os.path.dirname(__file__)}/../../Examples/CombinedExample.xml"
+    janus = pyJanus.Janus(xml_path)
+    expected = f"Janus(xml_filename='{janus.xml_filename}')"
+    variable = janus.get_variabledef("angleOfAttack")
+    instance = repr(variable).split(" from ", 1)[1]
+
+    assert str(janus) == expected
+    assert repr(janus) == f"{expected} at {instance}"