fix: typeerror

Author: msto

fgpyo/util/metric.py

@@ -391,10 +391,17 @@ def asdict(metric: Metric) -> Dict[str, Any]:
 
     Returns:
         A dictionary representation of the given metric.
+
+    Raises:
+        TypeError: If the given metric is not an instance of a `dataclass` or `attr.s`-decorated
+        Metric.
     """
     if _is_dataclass_instance(metric):
         return dataclasses.asdict(metric)
     elif _is_attrs_instance(metric):
         return attr.asdict(metric)
     else:
-        assert False, "Unreachable"
+        raise TypeError(
+            "The provided metric is not an instance of a `dataclass` or `attr.s`-decorated Metric "
+            f"class: {metric.__class__}"
+        )

fgpyo/util/tests/test_metric.py

@@ -553,3 +553,18 @@ def test_asdict(data_and_classes: DataBuilder) -> None:
     """Test that asdict works as expected on both dataclass and attr.s decoreated metrics."""
 
     assert asdict(data_and_classes.Person(name="name", age=42)) == {"name": "name", "age": 42}
+
+
+def test_asdict_raises() -> None:
+    """Test that we raise a TypeError when asdict is called on a non-metric class."""
+
+    class UndecoratedMetric(Metric["UndecoratedMetric"]):
+        foo: int
+        bar: str
+
+        def __init__(self, foo: int, bar: str):
+            self.foo = foo
+            self.bar = bar
+
+    with pytest.raises(TypeError, match="The provided metric is not an instance"):
+        asdict(UndecoratedMetric(foo=1, bar="a"))