Simple marshmallow enum field with support for apispec

fields.py

# Loosely based on https://github.com/h/marshmallow_enum

from marshmallow.fields import Field


class EnumField(Field):
    default_error_messages = {
        'invalid': 'Invalid enum value {input}',
    }

    def __init__(self, enum_type, *args, **kwargs):
        self.enum = enum_type

        super(EnumField, self).__init__(*args, **kwargs)

        # Detect type of enum and make it available to apispec
        values = [e.value for e in self.enum if e.value is not None]
        if all(isinstance(v, int) for v in values):
            self.metadata['type'] = 'integer'
        elif all(isinstance(v, (float, int)) for v in values):
            self.metadata['type'] = 'number'
        elif all(isinstance(v, bool) for v in values):
            self.metadata['type'] = 'boolean'
        elif all(isinstance(v, str) for v in values):
            self.metadata['type'] = 'string'

        # Ensure all enum values are made available to apispec
        self.metadata['enum'] = sorted([e.value for e in self.enum])

    def _serialize(self, value, attr, obj):
        if value is None:
            return None
        return value.value

    def _deserialize(self, value, attr, data, **kwargs):
        if value is None:
            return None
        try:
            return self.enum(value)
        except ValueError:
            self.fail('invalid', input=value, value=value)

    def fail(self, key, **kwargs):
        kwargs['values'] = ', '.join([str(mem.value) for mem in self.enum])
        super(EnumField, self).fail(key, **kwargs)