finetune scd2 typing

dlt/common/schema/typing.py

@@ -231,8 +231,11 @@ class TWriteDispositionDict(TypedDict):
     disposition: TWriteDisposition
 
 
-class TMergeDispositionDict(TWriteDispositionDict, total=False):
+class TMergeDispositionDict(TWriteDispositionDict):
     strategy: Optional[TLoaderMergeStrategy]
+
+
+class TScd2StrategyDict(TMergeDispositionDict, total=False):
     validity_column_names: Optional[List[str]]
     active_record_timestamp: Optional[TAnyDateTime]
     boundary_timestamp: Optional[TAnyDateTime]
@@ -241,7 +244,9 @@ class TMergeDispositionDict(TWriteDispositionDict, total=False):
     natural_key: Optional[str]
 
 
-TWriteDispositionConfig = Union[TWriteDisposition, TWriteDispositionDict, TMergeDispositionDict]
+TWriteDispositionConfig = Union[
+    TWriteDisposition, TWriteDispositionDict, TMergeDispositionDict, TScd2StrategyDict
+]
 
 
 class _TTableSchemaBase(TTableProcessingHints, total=False):

dlt/extract/hints.py

@@ -12,6 +12,7 @@
     TTableSchemaColumns,
     TWriteDispositionConfig,
     TMergeDispositionDict,
+    TScd2StrategyDict,
     TAnySchemaColumns,
     TTableFormat,
     TSchemaContract,
@@ -454,6 +455,7 @@ def _merge_merge_disposition_dict(dict_: Dict[str, Any]) -> None:
             dict_["x-merge-strategy"] = merge_strategy
 
         if merge_strategy == "scd2":
+            md_dict = cast(TScd2StrategyDict, md_dict)
             if "boundary_timestamp" in md_dict:
                 dict_["x-boundary-timestamp"] = md_dict["boundary_timestamp"]
             if "retire_if_absent" in md_dict:
@@ -532,6 +534,7 @@ def validate_write_disposition_hint(wd: TTableHintTemplate[TWriteDispositionConf
                 )
 
             if wd.get("strategy") == "scd2":
+                wd = cast(TScd2StrategyDict, wd)
                 for ts in ("active_record_timestamp", "boundary_timestamp"):
                     if (
                         ts == "active_record_timestamp"