Move ellipsis typing workaround to lsst.utils.

doc/changes/DM-36108.misc.md

@@ -0,0 +1 @@
+Moved the typing workaround for the built-in `Ellipsis` (`...`) singleton to `utils`.

python/lsst/daf/butler/core/utils.py

@@ -34,7 +34,7 @@
 from lsst.utils.iteration import ensure_iterable
 
 if TYPE_CHECKING:
-    from ..registry.wildcards import Ellipsis, EllipsisType
+    from lsst.utils.ellipsis import Ellipsis, EllipsisType
 
 
 _LOG = logging.getLogger(__name__)

python/lsst/daf/butler/registry/dimensions/table.py

@@ -29,6 +29,7 @@
 from typing import AbstractSet, Any, Dict, Iterable, Iterator, List, Mapping, Optional, Sequence, Set, Union
 
 import sqlalchemy
+from lsst.utils.ellipsis import Ellipsis, EllipsisType
 
 from ...core import (
     DatabaseDimensionElement,
@@ -56,7 +57,6 @@
     StaticTablesContext,
 )
 from ..queries import QueryBuilder
-from ..wildcards import Ellipsis, EllipsisType
 
 _LOG = logging.getLogger(__name__)
 

python/lsst/daf/butler/registry/wildcards.py

@@ -43,6 +43,7 @@
 )
 
 import sqlalchemy
+from lsst.utils.ellipsis import Ellipsis, EllipsisType
 from lsst.utils.iteration import ensure_iterable
 from pydantic import BaseModel
 
@@ -51,29 +52,8 @@
 from ._collectionType import CollectionType
 
 if TYPE_CHECKING:
-    # Workaround for `...` not having an exposed type in Python, borrowed from
-    # https://github.com/python/typing/issues/684#issuecomment-548203158
-    # Along with that, we need to either use `Ellipsis` instead of `...` for
-    # the actual sentinal value internally, and tell MyPy to ignore conversions
-    # from `...` to `Ellipsis` at the public-interface boundary.
-    #
-    # `Ellipsis` and `EllipsisType` should be directly imported from this
-    # module by related code that needs them; hopefully that will stay confined
-    # to `lsst.daf.butler.registry`.  Putting these in __all__ is bad for
-    # Sphinx, and probably more confusing than helpful overall.
-    from enum import Enum
-
     from .interfaces import CollectionManager, CollectionRecord
 
-    class EllipsisType(Enum):
-        Ellipsis = "..."
-
-    Ellipsis = EllipsisType.Ellipsis
-
-else:
-    EllipsisType = type(Ellipsis)
-    Ellipsis = Ellipsis
-
 
 @dataclass
 class CategorizedWildcard: