feat: validate default values

copier/user_data.py

@@ -227,7 +227,6 @@ def _check_type(cls, v, values):
 
     def get_default(self) -> Any:
         """Get the default value for this question, casted to its expected type."""
-        cast_fn = self.get_cast_fn()
         try:
             result = self.answers.init[self.var_name]
         except KeyError:
@@ -240,7 +239,7 @@ def get_default(self) -> Any:
                     if self.default is MISSING:
                         return MISSING
                     result = self.render_value(self.default)
-        result = cast_answer_type(result, cast_fn)
+        result = cast_answer_type(result, self.get_type_name())
         return result
 
     def get_default_rendered(self) -> Union[bool, str, Choice, None, MissingType]:
@@ -300,7 +299,7 @@ def _formatted_choices(self) -> Sequence[Choice]:
 
     def filter_answer(self, answer) -> Any:
         """Cast the answer to the desired type."""
-        return cast_answer_type(answer, self.get_cast_fn())
+        return cast_answer_type(answer, self.get_type_name())
 
     def get_message(self) -> str:
         """Get the message that will be printed to the user."""
@@ -360,16 +359,12 @@ def get_questionary_structure(self) -> AnyByStrDict:
         result.update({"type": questionary_type})
         return result
 
-    def get_cast_fn(self) -> Callable:
-        """Obtain function to cast user answer to desired type."""
-        type_name = self.get_type_name()
-        if type_name not in CAST_STR_TO_NATIVE:
-            raise InvalidTypeError("Invalid question type")
-        return CAST_STR_TO_NATIVE.get(type_name, parse_yaml_string)
-
     def get_type_name(self) -> str:
         """Render the type name and return it."""
-        return self.render_value(self.type)
+        type_name = self.render_value(self.type)
+        if type_name not in CAST_STR_TO_NATIVE:
+            raise InvalidTypeError("Invalid question type")
+        return type_name
 
     def get_multiline(self) -> bool:
         """Get the value for multiline."""
@@ -415,10 +410,10 @@ def render_value(
 
     def parse_answer(self, answer: Any) -> Any:
         """Parse the answer according to the question's type."""
-        cast_fn = self.get_cast_fn()
-        ans = cast_answer_type(answer, cast_fn)
+        type_name = self.get_type_name()
+        ans = cast_answer_type(answer, type_name)
         choice_values = {
-            cast_answer_type(choice.value, cast_fn)
+            cast_answer_type(choice.value, type_name)
             for choice in self._formatted_choices
         }
         if choice_values and ans not in choice_values:
@@ -450,13 +445,25 @@ def load_answersfile_data(
         return {}
 
 
-def cast_answer_type(answer: Any, type_fn: Callable) -> Any:
+def cast_answer_type(answer: Any, type_name: str) -> Any:
     """Cast answer to expected type."""
+    try:
+        type_fn = CAST_STR_TO_NATIVE[type_name]
+    except KeyError:
+        raise InvalidTypeError("Invalid answer type")
+    # Only JSON or YAML questions support `None` as an answer
+    if answer is None and type_name not in {"json", "yaml"}:
+        raise TypeError(
+            f'Invalid answer of type "{type(answer)}" to question of type '
+            f'"{type_name}"'
+        )
     try:
         return type_fn(answer)
     except (TypeError, AttributeError):
         # JSON or YAML failed because it wasn't a string; no need to convert
-        return answer
+        if type_name in {"json", "yaml"}:
+            return answer
+        raise
 
 
 CAST_STR_TO_NATIVE: Mapping[str, Callable] = {

tests/test_complex_questions.py

@@ -84,7 +84,7 @@ def template_path(tmp_path_factory: pytest.TempPathFactory) -> str:
                         three: third
                 choose_number:
                     help: This must be a number
-                    default: null
+                    default: -1.1
                     type: float
                     choices:
                         - -1.1
@@ -159,7 +159,7 @@ def test_api(template_path: str, tmp_path: Path) -> None:
             choose_list: "first"
             choose_tuple: "second"
             choose_dict: "third"
-            choose_number: null
+            choose_number: -1.1
             minutes_under_water: 10
             optional_value: null
         """

tests/test_copy.py

@@ -540,3 +540,82 @@ def test_required_choice_question_without_data(
     )
     with pytest.raises(ValueError, match='Question "question" is required'):
         copier.copy(str(src), dst, defaults=True)
+
+
+@pytest.mark.parametrize(
+    "type_name, default, expected",
+    [
+        ("str", "string", does_not_raise()),
+        ("str", "1.0", does_not_raise()),
+        ("str", 1.0, does_not_raise()),
+        ("str", None, pytest.raises(TypeError)),
+        ("int", 1, does_not_raise()),
+        ("int", 1.0, does_not_raise()),
+        ("int", "1", does_not_raise()),
+        ("int", "1.0", pytest.raises(ValueError)),
+        ("int", "no-int", pytest.raises(ValueError)),
+        ("int", None, pytest.raises(TypeError)),
+        ("float", 1.1, does_not_raise()),
+        ("float", 1, does_not_raise()),
+        ("float", "1.1", does_not_raise()),
+        ("float", "no-float", pytest.raises(ValueError)),
+        ("float", None, pytest.raises(TypeError)),
+        ("bool", True, does_not_raise()),
+        ("bool", False, does_not_raise()),
+        ("bool", "y", does_not_raise()),
+        ("bool", "n", does_not_raise()),
+        ("bool", None, pytest.raises(TypeError)),
+        ("json", '"string"', does_not_raise()),
+        ("json", "1", does_not_raise()),
+        ("json", 1, does_not_raise()),
+        ("json", "1.1", does_not_raise()),
+        ("json", 1.1, does_not_raise()),
+        ("json", "true", does_not_raise()),
+        ("json", True, does_not_raise()),
+        ("json", "false", does_not_raise()),
+        ("json", False, does_not_raise()),
+        ("json", "{}", does_not_raise()),
+        ("json", {}, does_not_raise()),
+        ("json", "[]", does_not_raise()),
+        ("json", [], does_not_raise()),
+        ("json", "null", does_not_raise()),
+        ("json", None, does_not_raise()),
+        ("yaml", '"string"', does_not_raise()),
+        ("yaml", "string", does_not_raise()),
+        ("yaml", "1", does_not_raise()),
+        ("yaml", 1, does_not_raise()),
+        ("yaml", "1.1", does_not_raise()),
+        ("yaml", 1.1, does_not_raise()),
+        ("yaml", "true", does_not_raise()),
+        ("yaml", True, does_not_raise()),
+        ("yaml", "false", does_not_raise()),
+        ("yaml", False, does_not_raise()),
+        ("yaml", "{}", does_not_raise()),
+        ("yaml", {}, does_not_raise()),
+        ("yaml", "[]", does_not_raise()),
+        ("yaml", [], does_not_raise()),
+        ("yaml", "null", does_not_raise()),
+        ("yaml", None, does_not_raise()),
+    ],
+)
+def test_validate_default_value(
+    tmp_path_factory: pytest.TempPathFactory,
+    type_name: str,
+    default: Any,
+    expected: ContextManager[None],
+) -> None:
+    src, dst = map(tmp_path_factory.mktemp, ("src", "dst"))
+    build_file_tree(
+        {
+            (src / "copier.yml"): yaml.dump(
+                {
+                    "q": {
+                        "type": type_name,
+                        "default": default,
+                    }
+                }
+            )
+        }
+    )
+    with expected:
+        copier.copy(str(src), dst, defaults=True)