Fix: Make grain optional (default None) in GroupByParam (#104)

* Make grain optional in GroupByParam

* Update contextmanager return types from Iterator to Generator for basedpyright compatibility

* Use existing customer__customer_type categorical dimension for test

Author: jairus-m

.changes/unreleased/Fixes-20260521-210810.yaml

@@ -0,0 +1,3 @@
+kind: Fixes
+body: Make grain optional (default None) in GroupByParam so categorical group_by dimensions do not require a grain field
+time: 2026-05-21T21:08:10.518263-07:00

dbtsl/api/adbc/client/asyncio.py

@@ -1,6 +1,6 @@
 import asyncio
 from contextlib import asynccontextmanager
-from typing import AsyncIterator, Optional
+from typing import AsyncGenerator, Optional
 
 import pyarrow as pa
 from typing_extensions import Self, Unpack
@@ -34,7 +34,7 @@ def __init__(
         self._loop = asyncio.get_running_loop()
 
     @asynccontextmanager
-    async def session(self) -> AsyncIterator[Self]:
+    async def session(self) -> AsyncGenerator[Self, None]:
         """Open a connection in the underlying ADBC driver.
 
         All requests made during the same session will reuse the same connection.

dbtsl/api/adbc/client/sync.py

@@ -1,5 +1,5 @@
 from contextlib import contextmanager
-from typing import Iterator, Optional
+from typing import Generator, Optional
 
 import pyarrow as pa
 from typing_extensions import Self, Unpack
@@ -32,7 +32,7 @@ def __init__(
         super().__init__(server_host, environment_id, auth_token, url_format)
 
     @contextmanager
-    def session(self) -> Iterator[Self]:
+    def session(self) -> Generator[Self, None, None]:
         """Open a connection in the underlying ADBC driver.
 
         All requests made during the same session will reuse the same connection.

dbtsl/api/graphql/client/asyncio.py

@@ -2,7 +2,7 @@
 import time
 from builtins import TimeoutError as BuiltinTimeoutError
 from contextlib import asynccontextmanager
-from typing import AsyncIterator, Dict, Optional, Union
+from typing import AsyncGenerator, Dict, Optional, Union
 
 import pyarrow as pa
 from gql import gql
@@ -83,7 +83,7 @@ def _create_transport(self, url: str, headers: Dict[str, str]) -> AIOHTTPTranspo
         )
 
     @asynccontextmanager
-    async def session(self) -> AsyncIterator[Self]:
+    async def session(self) -> AsyncGenerator[Self, None]:
         """Open a session in the underlying aiohttp transport.
 
         A "session" is a TCP connection with the server. All operations

dbtsl/api/graphql/client/sync.py

@@ -1,6 +1,6 @@
 import time
 from contextlib import contextmanager
-from typing import Dict, Iterator, Optional, Union
+from typing import Dict, Generator, Optional, Union
 
 import pyarrow as pa
 from gql import gql
@@ -71,7 +71,7 @@ def _create_transport(self, url: str, headers: Dict[str, str]) -> RequestsHTTPTr
         )
 
     @contextmanager
-    def session(self) -> Iterator[Self]:
+    def session(self) -> Generator[Self, None, None]:
         """Open a session in the underlying requests transport.
 
         A "session" is a TCP connection with the server. All operations

dbtsl/api/shared/query_params.py

@@ -17,7 +17,7 @@ class GroupByParam:
 
     name: str
     type: GroupByType
-    grain: Optional[str]
+    grain: Optional[str] = None
 
 
 @dataclass(frozen=True)

dbtsl/client/asyncio.py

@@ -1,5 +1,5 @@
 from contextlib import asynccontextmanager
-from typing import AsyncIterator, Optional, Union
+from typing import AsyncGenerator, Optional, Union
 
 from typing_extensions import Self
 
@@ -49,7 +49,7 @@ def __init__(
         )
 
     @asynccontextmanager
-    async def session(self) -> AsyncIterator[Self]:
+    async def session(self) -> AsyncGenerator[Self, None]:
         """Establish a connection with the dbt Semantic Layer's servers."""
         if self._has_session:
             raise ValueError("Cannot open session within session.")

dbtsl/client/sync.py

@@ -1,5 +1,5 @@
 from contextlib import contextmanager
-from typing import Iterator, Optional, Union
+from typing import Generator, Optional, Union
 
 from typing_extensions import Self
 
@@ -49,7 +49,7 @@ def __init__(
         )
 
     @contextmanager
-    def session(self) -> Iterator[Self]:
+    def session(self) -> Generator[Self, None, None]:
         """Establish a connection with the dbt Semantic Layer's servers."""
         if self._has_session:
             raise ValueError("Cannot open session within session.")

tests/query_test_cases.py

@@ -51,4 +51,9 @@
             GroupByParam(name="metric_time", grain="week", type=GroupByType.DIMENSION),
         ],
     },
+    # group by param object without grain (categorical dimension)
+    {
+        "metrics": ["order_total"],
+        "group_by": [GroupByParam(name="customer__customer_type", type=GroupByType.DIMENSION)],
+    },
 ]