Catch Exceptions in smart_deepcopy (#4187)

* Catch Exceptions in smart_deepcopy

* address feedback

changes/4184-coneybeare.md

@@ -0,0 +1 @@
+Catch certain raised errors in `smart_deepcopy` and revert to `deepcopy` if so.

pydantic/utils.py

@@ -684,9 +684,14 @@ def smart_deepcopy(obj: Obj) -> Obj:
     obj_type = obj.__class__
     if obj_type in IMMUTABLE_NON_COLLECTIONS_TYPES:
         return obj  # fastest case: obj is immutable and not collection therefore will not be copied anyway
-    elif not obj and obj_type in BUILTIN_COLLECTIONS:
-        # faster way for empty collections, no need to copy its members
-        return obj if obj_type is tuple else obj.copy()  # type: ignore  # tuple doesn't have copy method
+    try:
+        if not obj and obj_type in BUILTIN_COLLECTIONS:
+            # faster way for empty collections, no need to copy its members
+            return obj if obj_type is tuple else obj.copy()  # type: ignore  # tuple doesn't have copy method
+    except (TypeError, ValueError, RuntimeError):
+        # do we really dare to catch ALL errors? Seems a bit risky
+        pass
+
     return deepcopy(obj)  # slowest way when we actually might need a deepcopy
 
 

tests/test_utils.py

@@ -461,6 +461,17 @@ def test_smart_deepcopy_collection(collection, mocker):
     assert smart_deepcopy(collection) is expected_value
 
 
+@pytest.mark.parametrize('error', [TypeError, ValueError, RuntimeError])
+def test_smart_deepcopy_error(error, mocker):
+    class RaiseOnBooleanOperation(str):
+        def __bool__(self):
+            raise error('raised error')
+
+    obj = RaiseOnBooleanOperation()
+    expected_value = deepcopy(obj)
+    assert smart_deepcopy(obj) == expected_value
+
+
 T = TypeVar('T')