Validate the type of dynamic values

CHANGELOG.md

@@ -13,6 +13,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Python version `3.12` tested during CI
 - Python version `3.12` added to package classifiers
 
+### Fixed
+
+- Raise `ValueError` when dynamic value returns the wrong type.
+
 ### Removed
 
 - Support for Python version `3.7`.

columbo/_interaction.py

@@ -636,7 +636,10 @@ def to_value(
     if isinstance(value, value_type):
         return value
     if callable(value):
-        return value(answers)
+        result = value(answers)
+        if isinstance(result, value_type):
+            return result
+        raise ValueError(f"Invalid dynamic value: {result}")
     raise ValueError(f"Invalid value: {value}")
 
 

tests/interaction_test.py

@@ -494,6 +494,11 @@ def test_to_value__invalid_type__exception():
         to_value(object(), SOME_ANSWERS, str)  # type: ignore[arg-type]
 
 
+def test_to_value__invalid_dynamic_type__exception():
+    with pytest.raises(ValueError):
+        to_value(lambda _: object(), SOME_ANSWERS, str)  # type: ignore[arg-type,return-value]
+
+
 def test_to_labeled_options__invalid_type__exception():
     with pytest.raises(ValueError):
         to_labeled_options(object(), SOME_ANSWERS)  # type: ignore[arg-type]