Use generic msgspec structs to fix variance issues

mtg_ssm/scryfall/fetcher.py

@@ -2,7 +2,7 @@
 
 import gzip
 import os
-from typing import List, cast
+from typing import List
 
 import appdirs
 import msgspec
@@ -54,24 +54,27 @@ def _fetch_endpoint(endpoint: str) -> bytes:
 def scryfetch() -> ScryfallDataSet:  # pylint: disable=too-many-locals
     """Retrieve and deserialize Scryfall object data."""
     print("Reading data from scryfall")
-    scrylist_decoder = msgspec.json.Decoder(ScryList)
+    bulk_data = msgspec.json.decode(
+        _fetch_endpoint(BULK_DATA_ENDPOINT), type=ScryList[ScryBulkData]
+    ).data
 
-    bulk_data_list = scrylist_decoder.decode(_fetch_endpoint(BULK_DATA_ENDPOINT))
-    bulk_data = cast(List[ScryBulkData], bulk_data_list.data)
-
-    sets_list = scrylist_decoder.decode(_fetch_endpoint(SETS_ENDPOINT))
-    sets_data = cast(List[ScrySet], sets_list.data)
+    scrylistset_decoder = msgspec.json.Decoder(ScryList[ScrySet])
+    sets_list = scrylistset_decoder.decode(_fetch_endpoint(SETS_ENDPOINT))
+    sets_data = sets_list.data
     while sets_list.has_more and sets_list.next_page is not None:
-        sets_list = scrylist_decoder.decode(_fetch_endpoint(sets_list.next_page))
-        sets_data += cast(List[ScrySet], sets_list.data)
+        sets_list = scrylistset_decoder.decode(_fetch_endpoint(sets_list.next_page))
+        sets_data += sets_list.data
 
-    migrations_list = scrylist_decoder.decode(_fetch_endpoint(MIGRATIONS_ENDPOINT))
-    migrations_data = cast(List[ScryMigration], migrations_list.data)
+    scrylistmigration_decoder = msgspec.json.Decoder(ScryList[ScryMigration])
+    migrations_list = scrylistmigration_decoder.decode(
+        _fetch_endpoint(MIGRATIONS_ENDPOINT)
+    )
+    migrations_data = migrations_list.data
     while migrations_list.has_more and migrations_list.next_page is not None:
-        migrations_list = scrylist_decoder.decode(
+        migrations_list = scrylistmigration_decoder.decode(
             _fetch_endpoint(migrations_list.next_page)
         )
-        migrations_data += cast(List[ScryMigration], migrations_list.data)
+        migrations_data += migrations_list.data
 
     [cards_endpoint] = [bd.download_uri for bd in bulk_data if bd.type == BULK_TYPE]
     cards_data = msgspec.json.decode(

mtg_ssm/scryfall/models.py

@@ -3,10 +3,11 @@
 import datetime as dt
 from decimal import Decimal
 from enum import Enum
-from typing import Dict, List, Literal, Optional, Union
+from typing import Dict, Generic, List, Literal, Optional, TypeVar, Union
 from uuid import UUID
 
 from msgspec import Struct
+from typing_extensions import TypeAlias
 
 
 class ScryColor(str, Enum):
@@ -451,16 +452,27 @@ class ScryMigration(
     note: Optional[str] = None
 
 
+ScryListable: TypeAlias = Union[
+    ScryBulkData,
+    ScryCard,
+    ScryMigration,
+    ScrySet,
+]
+
+_ScryListableT = TypeVar("_ScryListableT", bound=ScryListable)
+
+
 class ScryList(
     Struct,
+    Generic[_ScryListableT],
     tag_field="object",
     tag="list",
     kw_only=True,
     omit_defaults=True,
 ):
     """Model for https://scryfall.com/docs/api/lists"""
 
-    data: List[Union[ScrySet, ScryCard, ScryBulkData, ScryMigration]]
+    data: List[_ScryListableT]
     has_more: bool
     next_page: Optional[str] = None
     total_cards: Optional[int] = None

pyproject.toml

@@ -40,7 +40,7 @@ classifiers = [
 
 dependencies = [
     "appdirs~=1.4",
-    "msgspec~=0.13",
+    "msgspec~=0.15",
     "openpyxl~=3.0",
     "requests~=2.27",
     'requests-cache~=0.9.8',

tests/conftest.py

@@ -2,7 +2,7 @@
 # pylint: disable=redefined-outer-name
 
 from pathlib import Path
-from typing import Dict, Generator, List, cast
+from typing import Dict, Generator, List
 from uuid import UUID
 
 import msgspec
@@ -44,18 +44,18 @@ def cards_data() -> List[ScryCard]:
 def sets_data() -> List[ScrySet]:
     """Fixture containing all test set data."""
     with SETS_DATA_FILE.open("rb") as sets_data_file:
-        sets_list = msgspec.json.decode(sets_data_file.read(), type=ScryList)
-    return cast(List[ScrySet], sets_list.data)
+        sets_list = msgspec.json.decode(sets_data_file.read(), type=ScryList[ScrySet])
+    return sets_list.data
 
 
 @pytest.fixture(scope="session")
 def migrations_data() -> List[ScryMigration]:
     """Fixture containing all test migrations data."""
     with MIGRATIONS_DATA_FILE.open("rb") as migrations_data_file:
         migrations_list = msgspec.json.decode(
-            migrations_data_file.read(), type=ScryList
+            migrations_data_file.read(), type=ScryList[ScryMigration]
         )
-    return cast(List[ScryMigration], migrations_list.data)
+    return migrations_list.data
 
 
 @pytest.fixture(scope="session")

tests/gen_testdata.py

@@ -4,7 +4,6 @@
 
 import copy
 from pathlib import Path
-from typing import List, cast
 
 import msgspec
 
@@ -85,9 +84,10 @@ def main() -> None:  # pylint: disable=too-many-locals,too-many-statements
     print("Fetching scryfall data")
     scrydata = fetcher.scryfetch()
     bulk_data_list = msgspec.json.decode(
-        fetcher._fetch_endpoint(fetcher.BULK_DATA_ENDPOINT), type=models.ScryList
+        fetcher._fetch_endpoint(fetcher.BULK_DATA_ENDPOINT),
+        type=models.ScryList[models.ScryBulkData],
     )
-    bulk_data = cast(List[models.ScryBulkData], bulk_data_list.data)
+    bulk_data = bulk_data_list.data
 
     print("Selecting sets")
     accepted_sets = sorted(