Fix: allow unexpected fields in responses

littlepay/api/__init__.py

@@ -1,4 +1,5 @@
 from dataclasses import dataclass
+from inspect import signature
 from typing import Generator, Protocol, TypeVar
 
 from authlib.integrations.requests_client import OAuth2Session
@@ -8,13 +9,45 @@
 TResponse = TypeVar("TResponse")
 
 
+def from_kwargs(cls, **kwargs):
+    """
+    Helper function meant to be used as a @classmethod
+    for instantiating a dataclass and allowing unexpected fields
+
+    See https://stackoverflow.com/a/55101438
+    """
+    # fetch the constructor's signature
+    class_fields = {field for field in signature(cls).parameters}
+
+    # split the kwargs into native ones and new ones
+    native_args, new_args = {}, {}
+    for name, val in kwargs.items():
+        if name in class_fields:
+            native_args[name] = val
+        else:
+            new_args[name] = val
+
+    # use the native ones to create the class ...
+    instance = cls(**native_args)
+
+    # ... and add the new ones by hand
+    for new_name, new_val in new_args.items():
+        setattr(instance, new_name, new_val)
+
+    return instance
+
+
 @dataclass
 class ListResponse:
     """An API response with list and total_count attributes."""
 
     list: list
     total_count: int
 
+    @classmethod
+    def from_kwargs(cls, **kwargs):
+        return from_kwargs(cls, **kwargs)
+
 
 class ClientProtocol(Protocol):
     """Protocol describing key functionality for an API connection."""

littlepay/api/client.py

@@ -127,7 +127,8 @@ def _delete(self, endpoint: str) -> bool:
     def _get(self, endpoint: str, response_cls: TResponse, **kwargs) -> TResponse:
         response = self.oauth.get(endpoint, headers=self.headers, params=kwargs)
         response.raise_for_status()
-        return response_cls(**response.json())
+
+        return response_cls.from_kwargs(**response.json())
 
     def _get_list(self, endpoint: str, **kwargs) -> Generator[dict, None, None]:
         params = dict(page=1, per_page=100)

littlepay/api/funding_sources.py

@@ -4,6 +4,8 @@
 
 from littlepay.api import ClientProtocol
 
+from . import from_kwargs
+
 
 @dataclass
 class FundingSourceResponse:
@@ -25,6 +27,10 @@ class FundingSourceResponse:
     token_key_id: Optional[str] = None
     icc_hash: Optional[str] = None
 
+    @classmethod
+    def from_kwargs(cls, **kwargs):
+        return from_kwargs(cls, **kwargs)
+
 
 @dataclass
 class FundingSourceDateFields:
@@ -65,6 +71,10 @@ class FundingSourceGroupResponse(FundingSourceDateFields):
     group_id: str
     label: str
 
+    @classmethod
+    def from_kwargs(cls, **kwargs):
+        return from_kwargs(cls, **kwargs)
+
 
 class FundingSourcesMixin(ClientProtocol):
     """Mixin implements APIs for funding sources."""

littlepay/api/groups.py

@@ -2,7 +2,7 @@
 from datetime import datetime, timezone
 from typing import Generator
 
-from littlepay.api import ClientProtocol
+from littlepay.api import ClientProtocol, from_kwargs
 from littlepay.api.funding_sources import FundingSourceDateFields, FundingSourcesMixin
 
 
@@ -24,11 +24,19 @@ def csv_header() -> str:
         instance = GroupResponse("", "", "")
         return ",".join(vars(instance).keys())
 
+    @classmethod
+    def from_kwargs(cls, **kwargs):
+        return from_kwargs(cls, **kwargs)
+
 
 @dataclass(kw_only=True)
 class GroupFundingSourceResponse(FundingSourceDateFields):
     id: str
 
+    @classmethod
+    def from_kwargs(cls, **kwargs):
+        return from_kwargs(cls, **kwargs)
+
 
 class GroupsMixin(ClientProtocol):
     """Mixin implements APIs for concession groups."""

littlepay/api/products.py

@@ -1,7 +1,7 @@
 from dataclasses import dataclass
 from typing import Generator
 
-from littlepay.api import ClientProtocol
+from littlepay.api import ClientProtocol, from_kwargs
 from littlepay.api.groups import GroupsMixin
 
 
@@ -26,6 +26,10 @@ def csv_header() -> str:
         instance = ProductResponse("", "", "", "", "", "")
         return ",".join(vars(instance).keys())
 
+    @classmethod
+    def from_kwargs(cls, **kwargs):
+        return from_kwargs(cls, **kwargs)
+
 
 class ProductsMixin(GroupsMixin, ClientProtocol):
     """Mixin implements APIs for products."""

tests/api/test_client.py

@@ -8,7 +8,7 @@
 import pytest
 from requests import HTTPError
 
-from littlepay.api import ListResponse
+from littlepay.api import ListResponse, from_kwargs
 from littlepay.api.client import _client_from_active_config, _fix_bearer_token_header, _json_post_credentials, Client
 from littlepay.config import Config
 
@@ -48,12 +48,21 @@ class SampleResponse:
     two: str
     three: int
 
+    @classmethod
+    def from_kwargs(cls, **kwargs):
+        return from_kwargs(cls, **kwargs)
+
 
 @pytest.fixture
 def SampleResponse_json():
     return {"one": "single", "two": "double", "three": 3}
 
 
+@pytest.fixture
+def SampleResponse_json_with_unexpected_field():
+    return {"one": "single", "two": "double", "three": 3, "four": "4"}
+
+
 @pytest.fixture
 def default_list_params():
     return dict(page=1, per_page=100)
@@ -232,6 +241,26 @@ def test_Client_get_params(mocker, make_client: ClientFunc, url, SampleResponse_
     assert result.three == 3
 
 
+def test_Client_get_response_has_unexpected_fields(
+    mocker, make_client: ClientFunc, url, SampleResponse_json_with_unexpected_field
+):
+    client = make_client()
+    mock_response = mocker.Mock(
+        raise_for_status=mocker.Mock(return_value=False),
+        json=mocker.Mock(return_value=SampleResponse_json_with_unexpected_field),
+    )
+    req_spy = mocker.patch.object(client.oauth, "get", return_value=mock_response)
+
+    result = client._get(url, SampleResponse)
+
+    req_spy.assert_called_once_with(url, headers=client.headers, params={})
+    assert isinstance(result, SampleResponse)
+    assert result.one == "single"
+    assert result.two == "double"
+    assert result.three == 3
+    assert result.four == "4"
+
+
 def test_Client_get_error_status(mocker, make_client: ClientFunc, url):
     client = make_client()
     mock_response = mocker.Mock(raise_for_status=mocker.Mock(side_effect=HTTPError))
@@ -243,6 +272,13 @@ def test_Client_get_error_status(mocker, make_client: ClientFunc, url):
     req_spy.assert_called_once_with(url, headers=client.headers, params={})
 
 
+def test_ListResponse_unexpected_fields():
+    response_json = {"list": [1, 2, 3], "total_count": 3, "unexpected_field": "test value"}
+
+    # this test will fail if any error occurs from instantiating the class
+    ListResponse.from_kwargs(**response_json)
+
+
 def test_Client_get_list(mocker, make_client: ClientFunc, url, default_list_params, ListResponse_sample):
     client = make_client()
     req_spy = mocker.patch.object(client, "_get", return_value=ListResponse_sample)

tests/api/test_funding_sources.py

@@ -59,6 +59,25 @@ def mock_ClientProtocol_get_list_FundingSourceGroup(mocker, ListResponse_Funding
     )
 
 
+def test_FundingSourceResponse_unexpected_fields():
+    response_json = {
+        "id": "0",
+        "card_first_digits": "0000",
+        "card_last_digits": "0000",
+        "card_expiry_month": "11",
+        "card_expiry_year": "24",
+        "card_scheme": "Visa",
+        "form_factor": "unknown",
+        "participant_id": "cst",
+        "is_fpan": True,
+        "related_funding_sources": [],
+        "unexpected_field": "test value",
+    }
+
+    # this test will fail if any error occurs from instantiating the class
+    FundingSourceResponse.from_kwargs(**response_json)
+
+
 def test_FundingSourceDateFields(expected_expiry_str, expected_expiry):
     fields = FundingSourceDateFields(
         created_date=expected_expiry_str, updated_date=expected_expiry_str, expiry_date=expected_expiry_str
@@ -69,6 +88,13 @@ def test_FundingSourceDateFields(expected_expiry_str, expected_expiry):
     assert fields.expiry_date == expected_expiry
 
 
+def test_FundingSourceGroupResponse_unexpected_fields():
+    response_json = {"id": "id", "group_id": "group_id", "label": "label", "unexpected_field": "test value"}
+
+    # this test will fail if any error occurs from instantiating the class
+    FundingSourceGroupResponse.from_kwargs(**response_json)
+
+
 def test_FundingSourceGroupResponse_no_dates():
     response = FundingSourceGroupResponse(id="id", group_id="group_id", label="label")
 

tests/api/test_groups.py

@@ -69,6 +69,13 @@ def mock_ClientProtocol_put_update_concession_group_funding_source(mocker):
     return mocker.patch("littlepay.api.ClientProtocol._put", side_effect=lambda *args, **kwargs: response)
 
 
+def test_GroupResponse_unexpected_fields():
+    response_json = {"id": "id", "label": "label", "participant_id": "participant", "unexpected_field": "test value"}
+
+    # this test will fail if any error occurs from instantiating the class
+    GroupResponse.from_kwargs(**response_json)
+
+
 def test_GroupResponse_csv():
     group = GroupResponse("id", "label", "participant")
     assert group.csv() == "id,label,participant"
@@ -81,6 +88,13 @@ def test_GroupResponse_csv_header():
     assert GroupResponse.csv_header() == "id,label,participant_id"
 
 
+def test_GroupFundingSourceResponse_unexpected_fields():
+    response_json = {"id": "id", "unexpected_field": "test value"}
+
+    # this test will fail if any error occurs from instantiating the class
+    GroupFundingSourceResponse.from_kwargs(**response_json)
+
+
 def test_GroupFundingSourceResponse_no_dates():
     response = GroupFundingSourceResponse(id="id")
 

tests/api/test_products.py

@@ -45,6 +45,21 @@ def mock_ClientProtocol_post(mocker):
     return mocker.patch("littlepay.api.ClientProtocol._post", side_effect=lambda *args, **kwargs: response)
 
 
+def test_ProductResponse_unexpected_fields():
+    response_json = {
+        "id": "id",
+        "code": "code",
+        "status": "status",
+        "type": "type",
+        "description": "description",
+        "participant_id": "participant",
+        "unexpected_field": "test value",
+    }
+
+    # this test will fail if any error occurs from instantiating the class
+    ProductResponse.from_kwargs(**response_json)
+
+
 def test_ProductResponse_csv():
     product = ProductResponse("id", "code", "status", "type", "description", "participant")
     assert product.csv() == "id,code,status,type,description,participant"