union passthrough: add accept_ints_as_floats

Author: Tinche

src/cattrs/strategies/_unions.py

@@ -139,7 +139,9 @@ def structure_tagged_union(
     converter.register_structure_hook(union, structure_tagged_union)
 
 
-def configure_union_passthrough(union: Any, converter: BaseConverter) -> None:
+def configure_union_passthrough(
+    union: Any, converter: BaseConverter, accept_ints_as_floats: bool = True
+) -> None:
     """
     Configure the converter to support validating and passing through unions of the
     provided types and their subsets.
@@ -205,6 +207,16 @@ def make_structure_native_union(exact_type: Any) -> Callable:
             and not is_literal(a)
         }
 
+        # By default, when floats are part of the union, accept ints too.
+        if (
+            accept_ints_as_floats
+            and int in args
+            and float in args
+            and float in non_literal_classes
+            and int not in non_literal_classes
+        ):
+            non_literal_classes.add(int)
+
         if spillover:
             spillover_type = (
                 Union[tuple(spillover)] if len(spillover) > 1 else next(iter(spillover))

tests/strategies/test_native_unions.py …sts/strategies/test_union_passthrough.pytests/strategies/test_native_unions.py renamed to tests/strategies/test_union_passthrough.py tests/strategies/test_native_unions.py renamed to tests/strategies/test_union_passthrough.py

@@ -9,7 +9,7 @@
 import pytest
 from attrs import define
 
-from cattrs import BaseConverter
+from cattrs import BaseConverter, ClassValidationError, Converter
 from cattrs.strategies import configure_union_passthrough
 
 
@@ -109,3 +109,35 @@ class B:
 
     with pytest.raises(TypeError):
         converter.structure((), union)
+
+
+def test_int_is_float(converter: BaseConverter) -> None:
+    """By default, ints can also be accepted when floats are.
+
+    When the strategy gets initialized with both ints and floats,
+    unions that only contain floats also accept ints by default.
+    """
+
+    configure_union_passthrough(Union[int, float, str, None], converter)
+
+    assert converter.structure(1, Union[float, str, None]) == 1
+    assert isinstance(converter.structure(1, Union[float, str, None]), int)
+
+
+def test_int_is_not_float(converter: BaseConverter) -> None:
+    """Ints can be configured to be separate."""
+
+    @define
+    class A:
+        a: int
+
+    configure_union_passthrough(
+        Union[int, float], converter, accept_ints_as_floats=False
+    )
+
+    with pytest.raises(
+        ClassValidationError
+        if isinstance(converter, Converter) and converter.detailed_validation
+        else TypeError
+    ):
+        converter.structure(1, Union[float, A])