Merge pull request #69 from OpenNTI/enum_choice

Add StrEnumChoice, a Choice that builds its vocabulary from a StrEnum

Author: jamadden

CHANGES.rst

@@ -2,17 +2,19 @@
  Changes
 =========
 
-1.20.2 (unreleased)
+1.21.0 (unreleased)
 ===================
 
-- Nothing changed yet.
+- Add ``field.StrEnumChoice``, a schema field that uses a ``StrEnum``
+  as its vocabulary and returns enum members (e.g., ``Color.RED``)
+  in ``fromUnicode``.
 
 
 1.20.1 (2026-06-25)
 ===================
 
 - Add some minimal typing information. In particular this makes
-  subclasses of ``SchemaConfigured`` for type-friendly.
+  subclasses of ``SchemaConfigured`` more type-friendly.
 
 
 1.20.0 (2026-06-01)

src/nti/schema/field.py

@@ -14,6 +14,7 @@
 # stdlib imports
 import numbers
 import re
+from enum import StrEnum
 from typing import Any
 
 import zope.interface.common.idatetime
@@ -50,18 +51,19 @@
 from zope.schema.interfaces import IFromUnicode
 from zope.schema.interfaces import InvalidValue
 
-from nti.schema import MessageFactory as _
-from nti.schema.interfaces import BeforeDictAssignedEvent
-from nti.schema.interfaces import BeforeObjectAssignedEvent
-from nti.schema.interfaces import BeforeSchemaFieldAssignedEvent
-from nti.schema.interfaces import BeforeSequenceAssignedEvent
-from nti.schema.interfaces import BeforeSetAssignedEvent
-from nti.schema.interfaces import BeforeTextAssignedEvent
-from nti.schema.interfaces import BeforeTextLineAssignedEvent
-from nti.schema.interfaces import IFromObject
-from nti.schema.interfaces import IListOrTuple
-from nti.schema.interfaces import IVariant
-from nti.schema.interfaces import VariantValidationError
+from . import MessageFactory as _
+from .interfaces import BeforeDictAssignedEvent
+from .interfaces import BeforeObjectAssignedEvent
+from .interfaces import BeforeSchemaFieldAssignedEvent
+from .interfaces import BeforeSequenceAssignedEvent
+from .interfaces import BeforeSetAssignedEvent
+from .interfaces import BeforeTextAssignedEvent
+from .interfaces import BeforeTextLineAssignedEvent
+from .interfaces import IFromObject
+from .interfaces import IListOrTuple
+from .interfaces import IVariant
+from .interfaces import IStrEnumChoice
+from .interfaces import VariantValidationError
 
 __docformat__ = "restructuredtext en"
 
@@ -154,10 +156,10 @@ def set(self, context, value): # pylint:disable=redefined-builtin
     cls.set = set
 
 def __with_set(eventfactory=BeforeSchemaFieldAssignedEvent):
-    def X(cls):
+    def attach_set(cls):
         __make_set(cls, eventfactory)
         return cls
-    return X
+    return attach_set
 
 def _fixup_Object_field(field, early_error=False):
     # TODO: Refactor and simplify.
@@ -585,9 +587,9 @@ def __init__(self, sch, min_length=0, max_length=None, **kwargs):
         # But to work with the superclass, we have to pass it as a keyword arg.
         # it's weird.
         super().__init__(schema=sch,
-                                        min_length=min_length,
-                                        max_length=max_length,
-                                        **kwargs)
+                         min_length=min_length,
+                         max_length=max_length,
+                         **kwargs)
 
 class Int(FieldValidationMixin, schema.Int):
 
@@ -617,6 +619,38 @@ class Number(FieldValidationMixin, schema.Float):
 class ValidChoice(FieldValidationMixin, schema.Choice):
     pass
 
+@interface.implementer(IStrEnumChoice)
+class StrEnumChoice(ValidChoice):
+    """
+    A Choice field that takes its values from
+    a :class:`~StrEnum`.
+
+    .. versionadded:: NEXT
+    """
+
+    def __init__(self, enum: type[StrEnum], **kwargs) -> None:
+        if 'values' in kwargs or 'source' in kwargs or 'vocabulary' in kwargs:
+            raise TypeError('Illegal keyword; values come from the enum')
+        super().__init__(
+            values=list(e.value for e in enum),
+            **kwargs
+        )
+        self.__enum = enum
+
+    @property
+    def enum(self):
+        return self.__enum
+
+    def fromUnicode(self, value):
+        # First validate the value is a member of the values
+        # list we provided (the enum members), raising
+        # the correct error if not.
+        value = super().fromUnicode(value)
+        # Then, return the actual enum member.
+        # Subscripting the class expects the
+        # attribute name; calling it expects the value.
+        return self.__enum(value)
+
 @__with_set()
 class ValidBytesLine(FieldValidationMixin, schema.BytesLine):
     pass

src/nti/schema/interfaces.py

@@ -185,6 +185,17 @@ def fromObject(obj):
         possible.
         """
 
+class IStrEnumChoice(sch_interfaces.IChoice):
+    """
+    A choice that gets its values and validates them
+    against a :class:`~StrEnum`.
+
+    .. versionadded:: NEXT
+    """
+
+    enum = Attribute("The StrEnum subclass given to the constructor.")
+
+
 class IVariant(sch_interfaces.IField, IFromObject):
     """
     Similar to :class:`zope.schema.interfaces.IObject`, but