Prevent subclasses of bytes being converted to bytes (#3707)

* adding a test

* fix and add change description

changes/3706-samuelcolvin.md

@@ -0,0 +1 @@
+Prevent subclasses of bytes being converted to bytes

pydantic/validators.py

@@ -76,7 +76,7 @@ def strict_str_validator(v: Any) -> Union[str]:
     raise errors.StrError()
 
 
-def bytes_validator(v: Any) -> bytes:
+def bytes_validator(v: Any) -> Union[bytes]:
     if isinstance(v, bytes):
         return v
     elif isinstance(v, bytearray):

tests/test_edge_cases.py

@@ -1906,3 +1906,29 @@ def test_arbitrary_types_allowed_custom_eq():
             arbitrary_types_allowed = True
 
     assert Model().x == Foo()
+
+
+def test_bytes_subclass():
+    class MyModel(BaseModel):
+        my_bytes: bytes
+
+    class BytesSubclass(bytes):
+        def __new__(cls, data: bytes):
+            self = bytes.__new__(cls, data)
+            return self
+
+    m = MyModel(my_bytes=BytesSubclass(b'foobar'))
+    assert m.my_bytes.__class__ == BytesSubclass
+
+
+def test_int_subclass():
+    class MyModel(BaseModel):
+        my_int: int
+
+    class IntSubclass(int):
+        def __new__(cls, data: int):
+            self = int.__new__(cls, data)
+            return self
+
+    m = MyModel(my_int=IntSubclass(123))
+    assert m.my_int.__class__ == IntSubclass