Use a hack-default of "" instead of None to make typing easier

Signed-off-by: Michał Górny <mgorny@quansight.com>

Author: mgorny

variantlib/api.py

@@ -337,7 +337,6 @@ def get_variant_environment_dict(
 ) -> dict[str, set[str] | str]:
     """Get the dict for packaging Marker.evaluate()"""
 
-    assert variant_desc.label is not None
     ret: dict[str, set[str] | str] = {
         "variant_namespaces": {vprop.namespace for vprop in variant_desc.properties},
         "variant_features": {
@@ -371,7 +370,6 @@ def get_variant_label(
     """
 
     if custom_label is None:
-        assert variant_desc.label is not None
         return variant_desc.label
 
     warnings.warn(

variantlib/models/variant.py

@@ -162,7 +162,7 @@ class VariantDescription(BaseModel):
         default_factory=list,
     )
 
-    label: str | None = field(
+    label: str = field(
         metadata={
             "validator": lambda val: validate_and(
                 [
@@ -172,7 +172,7 @@ class VariantDescription(BaseModel):
                 value=val,
             ),
         },
-        default=None,
+        default="",
     )
 
     def __post_init__(self) -> None:
@@ -185,7 +185,7 @@ def __post_init__(self) -> None:
             object.__setattr__(self, "properties", sorted(self.properties))
 
         # default the label to "null" or hexdigest
-        if self.label is None:
+        if not self.label:
             with contextlib.suppress(AttributeError):
                 object.__setattr__(
                     self,

variantlib/variant_dist_info.py

@@ -56,5 +56,4 @@ def variant_desc(self) -> VariantDescription:
 
     @variant_desc.setter
     def variant_desc(self, new_desc: VariantDescription) -> None:
-        assert new_desc.label is not None
         self.variants = {new_desc.label: new_desc}