Fix code is None in CodeExercise with ExerciseRegistry (PR #57)

When the code is None in the CodeExercise and a ExerciseRegistry is given, then an error is raised when the save cue box is created, because the cue_widget is None.

src/scwidgets/exercise/_widget_code_exercise.py

@@ -327,21 +327,28 @@ def __init__(
             self._load_button = None
             self._save_cue_box = None
         else:
-            save_widgets_to_observe = [self._code]
-            save_traits_to_observe = ["function_body"]
+            save_widgets_to_observe = []
+            save_traits_to_observe = []
+
+            if self._cue_code is not None:
+                save_widgets_to_observe.append(self._code)
+                save_traits_to_observe.append("function_body")
+
             if self._parameter_panel is not None:
                 save_widgets_to_observe.extend(self._parameter_panel.parameters_widget)
                 save_traits_to_observe.extend(self._parameter_panel.parameters_trait)
-            self._cue_code = SaveCueBox(
-                save_widgets_to_observe,
-                save_traits_to_observe,
-                self._cue_code,
-                cued=True,
-            )
+
+            if self._cue_code is not None:
+                self._cue_code = SaveCueBox(
+                    save_widgets_to_observe,
+                    save_traits_to_observe,
+                    self._cue_code,
+                    cued=True,
+                )
 
             self._save_cue_box = self._cue_code
             self._save_button = SaveResetCueButton(
-                self._cue_code,
+                SaveCueBox(Box()),  # dummy cue box, because we set cues later on
                 self._on_click_save_action,
                 cued=True,
                 disable_on_successful_action=kwargs.pop(
@@ -354,7 +361,7 @@ def __init__(
                 button_tooltip="Loads your code and parameters from the loaded file",
             )
             self._load_button = SaveResetCueButton(
-                self._cue_code,
+                SaveCueBox(Box()),  # dummy cue box, because we set cues later on
                 self._on_click_load_action,
                 cued=True,
                 disable_on_successful_action=kwargs.pop(

tests/test_code.py

@@ -1,4 +1,5 @@
-from typing import Callable, List
+import os
+from typing import Callable, List, Optional
 
 import numpy as np
 import pytest
@@ -8,7 +9,7 @@
 from scwidgets.check import Check, CheckRegistry, ChecksResult
 from scwidgets.code import CodeInput
 from scwidgets.cue import CueObject
-from scwidgets.exercise import CodeExercise
+from scwidgets.exercise import CodeExercise, ExerciseRegistry
 
 from .test_check import multi_param_check, single_param_check
 
@@ -76,7 +77,7 @@ def test_invalid_code_theme_raises_error(self):
 
 def get_code_exercise(
     checks: List[Check],
-    code: Callable = None,
+    code: Optional[Callable] = None,
     include_checks=True,
     include_params=True,
     tunable_params=False,
@@ -221,3 +222,35 @@ def test_erroneous_run_code(self, code_ex):
             match="NameError in code input: name 'bug' is not defined.*",
         ):
             code_ex.run_code(**code_ex.parameters)
+
+    @pytest.mark.parametrize(
+        "function",
+        [
+            None,
+            TestCodeInput.mock_function_1,
+        ],
+    )
+    def test_save_registry(self, function):
+        """
+        Verifies that the CodeExercise works with an answer_registry.
+        """
+
+        def print_success(code_ex: CodeExercise | None):
+            code_ex.cue_outputs[0].display_object = "Success"
+
+        cue_output = CueObject("Not initialized")
+        exercise_registry = ExerciseRegistry()
+
+        code_ex = CodeExercise(
+            code=function,
+            parameters={"parameter": fixed(5)},
+            exercise_registry=exercise_registry,
+            exercise_key="test_save_registry_ex",
+            cue_outputs=[cue_output],
+            update_func=print_success,
+        )
+
+        exercise_registry._student_name_text.value = "test_save_registry-student_name"
+        exercise_registry.create_new_file()
+        code_ex._save_button.click()
+        os.remove("test_save_registry-student_name.json")

tox.ini

@@ -42,7 +42,7 @@ deps =
 commands =
     # converts the python files to ipython notebooks
     jupytext tests/notebooks/*.py --to ipynb
-    pytest {posargs:-v --reruns 2} --driver Firefox
+    pytest {posargs:-v --reruns 4} --driver Firefox
 
 [testenv:tests-lab-4]
 description =
@@ -75,7 +75,7 @@ deps =
 commands =
     # converts the python files to ipython notebooks
     jupytext tests/notebooks/*.py --to ipynb
-    pytest {posargs:-v --reruns 2} -m "not matplotlib" --driver Firefox
+    pytest {posargs:-v --reruns 4} -m "not matplotlib" --driver Firefox
 
 [testenv:coverage]
 # We do coverage in a separate environment that skips the selenium tests but