Add Pydantic v1 version of ColumnSpec.

It should be safe to revert this commit once we require Pydantic v2.

python/lsst/daf/butler/column_spec.py

@@ -50,10 +50,11 @@
 from lsst.sphgeom import Region
 
 from . import arrow_utils, ddl
+from ._compat import _BaseModelCompat
 from ._timespan import Timespan
 
 
-class ColumnSpec(pydantic.BaseModel, ABC):
+class ColumnSpec(_BaseModelCompat, ABC):
     """Base class for descriptions of table columns."""
 
     name: str = pydantic.Field(description="""Name of the column.""")
@@ -183,6 +184,7 @@ class IntColumnSpec(ColumnSpec):
 
     def to_arrow(self) -> arrow_utils.ToArrow:
         # Docstring inherited.
+        assert self.nullable is not None, "nullable=None should be resolved by validators"
         return arrow_utils.ToArrow.for_primitive(self.name, pa.uint64(), nullable=self.nullable)
 
 
@@ -203,6 +205,7 @@ def to_sql_spec(self, **kwargs: Any) -> ddl.FieldSpec:
 
     def to_arrow(self) -> arrow_utils.ToArrow:
         # Docstring inherited.
+        assert self.nullable is not None, "nullable=None should be resolved by validators"
         return arrow_utils.ToArrow.for_primitive(self.name, pa.string(), nullable=self.nullable)
 
 
@@ -223,6 +226,7 @@ def to_sql_spec(self, **kwargs: Any) -> ddl.FieldSpec:
 
     def to_arrow(self) -> arrow_utils.ToArrow:
         # Docstring inherited.
+        assert self.nullable is not None, "nullable=None should be resolved by validators"
         return arrow_utils.ToArrow.for_primitive(
             self.name,
             # The size for Arrow binary columns is a fixed size, not a maximum
@@ -242,6 +246,7 @@ class FloatColumnSpec(ColumnSpec):
 
     def to_arrow(self) -> arrow_utils.ToArrow:
         # Docstring inherited.
+        assert self.nullable is not None, "nullable=None should be resolved by validators"
         return arrow_utils.ToArrow.for_primitive(self.name, pa.float64(), nullable=self.nullable)
 
 
@@ -255,6 +260,7 @@ class BoolColumnSpec(ColumnSpec):
 
     def to_arrow(self) -> arrow_utils.ToArrow:
         # Docstring inherited.
+        assert self.nullable is not None, "nullable=None should be resolved by validators"
         return arrow_utils.ToArrow.for_primitive(self.name, pa.bool_(), nullable=self.nullable)
 
 
@@ -273,6 +279,7 @@ class RegionColumnSpec(ColumnSpec):
 
     def to_arrow(self) -> arrow_utils.ToArrow:
         # Docstring inherited.
+        assert self.nullable is not None, "nullable=None should be resolved by validators"
         return arrow_utils.ToArrow.for_region(self.name, nullable=self.nullable)
 
 
@@ -288,6 +295,7 @@ class TimespanColumnSpec(ColumnSpec):
 
     def to_arrow(self) -> arrow_utils.ToArrow:
         # Docstring inherited.
+        assert self.nullable is not None, "nullable=None should be resolved by validators"
         return arrow_utils.ToArrow.for_timespan(self.name, nullable=self.nullable)
 
 

python/lsst/daf/butler/dimensions/_config.py

@@ -36,6 +36,7 @@
 import pydantic
 from lsst.resources import ResourcePath, ResourcePathExpression
 
+from .._compat import PYDANTIC_V2
 from .._config import Config, ConfigSubset
 from .._topology import TopologicalSpace
 from ..column_spec import default_nullable, not_nullable
@@ -53,13 +54,20 @@
 # have a version.
 _DEFAULT_NAMESPACE = "daf_butler"
 
+if PYDANTIC_V2:
+    AnnotatedKeyColumnSpec: TypeAlias = Annotated[
+        KeyColumnSpec, pydantic.Field(discriminator="type"), pydantic.AfterValidator(not_nullable)
+    ]
+    AnnotatedMetadataColumnSpec: TypeAlias = Annotated[
+        MetadataColumnSpec, pydantic.Field(discriminator="type"), pydantic.AfterValidator(default_nullable)
+    ]
+else:
 
-AnnotatedKeyColumnSpec: TypeAlias = Annotated[
-    KeyColumnSpec, pydantic.Field(discriminator="type"), pydantic.AfterValidator(not_nullable)
-]
-AnnotatedMetadataColumnSpec: TypeAlias = Annotated[
-    MetadataColumnSpec, pydantic.Field(discriminator="type"), pydantic.AfterValidator(default_nullable)
-]
+    class _KeyColumnModel(pydantic.BaseModel):
+        spec: KeyColumnSpec = pydantic.Field(discriminator="type")
+
+    class _MetadataColumnModel(pydantic.BaseModel):
+        spec: MetadataColumnSpec = pydantic.Field(discriminator="type")
 
 
 class DimensionConfig(ConfigSubset):
@@ -202,17 +210,28 @@ def _extractElementVisitors(self) -> Iterator[DimensionConstructionVisitor]:
             `StandardDimensionCombination` to an under-construction
             `DimensionUniverse`.
         """
-        # MyPy is confused by the typing.Annotated usage and/or how Pydantic
-        # annotated TypeAdapter.
-        key_adapter: pydantic.TypeAdapter[KeyColumnSpec] = pydantic.TypeAdapter(
-            AnnotatedKeyColumnSpec  # type: ignore
-        )
-        metadata_adapter: pydantic.TypeAdapter[MetadataColumnSpec] = pydantic.TypeAdapter(
-            AnnotatedMetadataColumnSpec  # type: ignore
-        )
+        if PYDANTIC_V2:
+            # MyPy is confused by the typing.Annotated usage and/or how
+            # Pydantic annotated TypeAdapter.
+            key_adapter: pydantic.TypeAdapter[KeyColumnSpec] = pydantic.TypeAdapter(  # type: ignore
+                AnnotatedKeyColumnSpec  # type: ignore
+            )
+            validate_key = key_adapter.validate_python
+            metadata_adapter: pydantic.TypeAdapter[MetadataColumnSpec] = pydantic.TypeAdapter(  # type: ignore
+                AnnotatedMetadataColumnSpec  # type: ignore
+            )
+            validate_metadata = metadata_adapter.validate_python
+        else:
+
+            def validate_key(value: Any) -> KeyColumnSpec:  # type: ignore[misc]
+                return not_nullable(_KeyColumnModel(spec=value).spec)  # type: ignore[return-value]
+
+            def validate_metadata(value: Any) -> MetadataColumnSpec:  # type: ignore[misc]
+                return default_nullable(_MetadataColumnModel(spec=value).spec)  # type: ignore[return-value]
+
         for name, subconfig in self["elements"].items():
-            metadata_columns = [metadata_adapter.validate_python(c) for c in subconfig.get("metadata", ())]
-            unique_keys = [key_adapter.validate_python(c) for c in subconfig.get("keys", ())]
+            metadata_columns = [validate_metadata(c) for c in subconfig.get("metadata", ())]
+            unique_keys = [validate_key(c) for c in subconfig.get("keys", ())]
             if subconfig.get("governor", False):
                 unsupported = {"required", "implied", "viewOf", "alwaysJoin"}
                 if not unsupported.isdisjoint(subconfig.keys()):