port fix from cog (#15)

src/py/empyc/empyc/dataclasses/BUILD

@@ -1 +1,5 @@
 python_sources()
+
+python_tests(
+    name="tests",
+)

src/py/empyc/empyc/dataclasses/__init__.py

@@ -4,6 +4,7 @@
 
 """
 
+import copy
 import dataclasses
 import enum
 import json
@@ -111,9 +112,9 @@ def recursive_from_dict(
     :param data: the mapping to use as constructor arguments
     :skip_unknown: if ``True``, will prune invalid keys
     :returns: an instantiated dataclass object
-    :raises TypeError: If the instantiation was unsuccesful
+    :raises TypeError: If the instantiation was unsuccessful
     """
-    return _recursive_instantiate(cls, data, skip_unknown)
+    return _recursive_instantiate(cls, copy.deepcopy(data), skip_unknown)
 
 
 def _handle_tuple(field, obj, key, value):

src/py/empyc/empyc/dataclasses/tests.py

@@ -0,0 +1,76 @@
+import copy
+import json
+import string
+from dataclasses import dataclass
+from typing import Dict, List
+
+import pytest
+
+import empyc.dataclasses
+
+
+def compare_no_ws(a, b):
+    remove = {ord(c): None for c in string.punctuation + string.whitespace}
+
+    assert a.translate(remove) == b.translate(remove)
+
+
+@dataclass
+class Inner:
+    list_data: List[int]
+
+
+@dataclass
+class Outer:
+    inner_data: Inner
+    something_else: Dict[str, str]
+
+
+@pytest.fixture
+def outer() -> Outer:
+    return Outer(inner_data=Inner(list_data=[1, 2, 3]), something_else={"hello": "world"})
+
+
+@pytest.fixture
+def outer_dict() -> Outer:
+    return {
+        "inner_data": {"list_data": [1, 2, 3]},
+        "something_else": {"hello": "world"},
+    }
+
+
+@pytest.fixture
+def outer_json() -> Outer:
+    return """{
+    "inner_data": {"list_data": [1,2,3]},
+    "something_else": {"hello": "world"}
+}"""
+
+
+def test_outer_to_json(outer, outer_json):
+    compare_no_ws(empyc.dataclasses.to_json(outer), outer_json)
+
+
+def test_from_dict_no_modify(outer_dict):
+    indata = copy.deepcopy(outer_dict)
+    _ = empyc.dataclasses.recursive_from_dict(Outer, indata)
+
+    assert indata == outer_dict
+
+
+def test_outer_from_dict(outer, outer_dict):
+    other = empyc.dataclasses.recursive_from_dict(Outer, outer_dict)
+    assert other == outer
+
+
+def test_outer_from_json(outer, outer_json):
+    other = empyc.dataclasses.recursive_from_dict(Outer, json.loads(outer_json))
+    assert other == outer
+
+
+def test_outer_roundtrip(outer):
+    other = empyc.dataclasses.recursive_from_dict(
+        Outer, json.loads(empyc.dataclasses.to_json(outer))
+    )
+
+    assert other == outer