plugin

11 files changed, 178 insertions, 61 deletions

diff --git a/src/mailman/rest/docs/membership.rst b/src/mailman/rest/docs/membership.rst
index b0b5e1254..6e24d14f9 100644
--- a/src/mailman/rest/docs/membership.rst
+++ b/src/mailman/rest/docs/membership.rst
@@ -642,7 +642,6 @@ won't have to approve her subscription request.
     ...           'display_name': 'Elly Person',
     ...           'pre_verified': True,
     ...           'pre_confirmed': True,
-    ...           'pre_approved': True,
     ...           })
     content-length: 0
     content-type: application/json; charset=UTF-8
@@ -699,7 +698,6 @@ list with her preferred address.
     ...     'subscriber': user_id,
     ...     'pre_verified': True,
     ...     'pre_confirmed': True,
-    ...     'pre_approved': True,
     ...     })
     content-length: 0
     content-type: application/json; charset=UTF-8
diff --git a/src/mailman/rest/docs/sub-moderation.rst b/src/mailman/rest/docs/sub-moderation.rst
index 92c0c8849..8bf95fcd2 100644
--- a/src/mailman/rest/docs/sub-moderation.rst
+++ b/src/mailman/rest/docs/sub-moderation.rst
@@ -13,8 +13,8 @@ A mailing list starts with no pending subscription or unsubscription requests.
 
     >>> ant = create_list('ant@example.com')
     >>> ant.admin_immed_notify = False
-    >>> from mailman.interfaces.mailinglist import SubscriptionPolicy
-    >>> ant.subscription_policy = SubscriptionPolicy.moderate
+    >>> from mailman.workflows.subscription import ModerationSubscriptionPolicy
+    >>> ant.subscription_policy = ModerationSubscriptionPolicy
     >>> transaction.commit()
     >>> dump_json('http://localhost:9001/3.0/lists/ant.example.com/requests')
     http_etag: "..."
@@ -31,7 +31,6 @@ is returned to track her subscription request.
     ...           'subscriber': 'anne@example.com',
     ...           'display_name': 'Anne Person',
     ...           'pre_verified': True,
-    ...           'pre_confirmed': True,
     ...           })
     http_etag: ...
     token: 0000000000000000000000000000000000000001
@@ -48,7 +47,7 @@ The subscription request can be viewed in the REST API.
         list_id: ant.example.com
         token: 0000000000000000000000000000000000000001
         token_owner: moderator
-        type: subscription
+        type: sub-policy-moderate
         when: 2005-08-01T07:49:23
     http_etag: "..."
     start: 0
@@ -69,7 +68,7 @@ You can view an individual membership change request by providing the token
     list_id: ant.example.com
     token: 0000000000000000000000000000000000000001
     token_owner: moderator
-    type: subscription
+    type: sub-policy-moderate
     when: 2005-08-01T07:49:23
 
 
diff --git a/src/mailman/rest/listconf.py b/src/mailman/rest/listconf.py
index b62d34529..70f04999c 100644
--- a/src/mailman/rest/listconf.py
+++ b/src/mailman/rest/listconf.py
@@ -24,14 +24,17 @@ from mailman.interfaces.archiver import ArchivePolicy
 from mailman.interfaces.autorespond import ResponseAction
 from mailman.interfaces.digests import DigestFrequency
 from mailman.interfaces.mailinglist import (
-    DMARCMitigateAction, IAcceptableAliasSet, IMailingList, ReplyToMunging,
-    SubscriptionPolicy)
+    DMARCMitigateAction, IAcceptableAliasSet, IMailingList, ReplyToMunging)
 from mailman.interfaces.template import ITemplateManager
+from mailman.interfaces.workflows import ISubscriptionWorkflow
 from mailman.rest.helpers import (
     GetterSetter, bad_request, etag, no_content, not_found, okay)
 from mailman.rest.validator import (
     PatchValidator, ReadOnlyPATCHRequestError, UnknownPATCHRequestError,
-    Validator, enum_validator, list_of_strings_validator)
+    Validator, enum_validator, list_of_strings_validator, policy_validator)
+from mailman.workflows.subscription import (
+    ConfirmModerationSubscriptionPolicy, ConfirmSubscriptionPolicy,
+    ModerationSubscriptionPolicy, OpenSubscriptionPolicy)
 from public import public
 from zope.component import getUtility
 
@@ -86,6 +89,20 @@ class URIAttributeMapper(GetterSetter):
         getUtility(ITemplateManager).set(template_name, obj.list_id, value)
 
 
+class SubscriptionPolicyMapper(GetterSetter):
+
+    def get(self, obj, attribute):
+        assert IMailingList.providedBy(obj), obj
+        old_sub_map = {
+            OpenSubscriptionPolicy: 'open',
+            ConfirmSubscriptionPolicy: 'confirm',
+            ModerationSubscriptionPolicy: 'moderate',
+            ConfirmModerationSubscriptionPolicy: 'confirm_then_moderate'
+            }
+        cls = getattr(obj, attribute)
+        return old_sub_map.get(cls, cls.name)
+
+
 # Additional validators for converting from web request strings to internal
 # data types.  See below for details.
 
@@ -179,7 +196,8 @@ ATTRIBUTES = dict(
     request_address=GetterSetter(None),
     send_welcome_message=GetterSetter(as_boolean),
     subject_prefix=GetterSetter(str),
-    subscription_policy=GetterSetter(enum_validator(SubscriptionPolicy)),
+    subscription_policy=SubscriptionPolicyMapper(
+            policy_validator(ISubscriptionWorkflow)),
     volume=GetterSetter(None),
     )
 
diff --git a/src/mailman/rest/members.py b/src/mailman/rest/members.py
index 3ff712259..2d5b95115 100644
--- a/src/mailman/rest/members.py
+++ b/src/mailman/rest/members.py
@@ -17,7 +17,6 @@
 
 """REST for members."""
 
-from lazr.config import as_boolean
 from mailman.app.membership import add_member, delete_member
 from mailman.interfaces.action import Action
 from mailman.interfaces.address import IAddress
@@ -198,22 +197,43 @@ class AllMembers(_MemberBase):
 
     def on_post(self, request, response):
         """Create a new member."""
-        try:
-            validator = Validator(
-                list_id=str,
-                subscriber=subscriber_validator(self.api),
-                display_name=str,
-                delivery_mode=enum_validator(DeliveryMode),
-                role=enum_validator(MemberRole),
-                pre_verified=as_boolean,
-                pre_confirmed=as_boolean,
-                pre_approved=as_boolean,
-                _optional=('delivery_mode', 'display_name', 'role',
-                           'pre_verified', 'pre_confirmed', 'pre_approved'))
-            arguments = validator(request)
-        except ValueError as error:
-            bad_request(response, str(error))
+        # Validate the params manually as the subscription_policy workflow
+        # attributes are dynamic, so parse all known and optional attirbutes
+        # and leave the rest to policy_kwargs.
+        required_arguments = ['list_id', 'subscriber']
+        known_arguments = dict(list_id=str,
+                               subscriber=subscriber_validator(self.api),
+                               display_name=str,
+                               delivery_mode=enum_validator(DeliveryMode),
+                               role=enum_validator(MemberRole))
+
+        arguments = {}
+        policy_kwargs = {}
+
+        wrong = []
+        for key, value in request.params.items():
+            try:
+                if key in known_arguments:
+                    converter = known_arguments[key]
+                    arguments[key] = converter(value)
+                else:
+                    policy_kwargs[key] = value
+            except ValueError:
+                wrong.append(key)
+
+        if len(wrong) > 0:
+            params = ', '.join(wrong)
+            bad_request(response,
+                        'Cannot convert parameters: {}'.format(params))
             return
+
+        missing = [key for key in required_arguments if key not in arguments]
+        if len(missing) > 0:
+            bad_request(response, 'Missing parameters: {}'.format(missing))
+            return
+        # XXX policy_kwargs are string, while subscription workflows expects
+        # whatever.
+
         # Dig the mailing list out of the arguments.
         list_id = arguments.pop('list_id')
         mlist = getUtility(IListManager).get_by_list_id(list_id)
@@ -247,20 +267,13 @@ class AllMembers(_MemberBase):
         # nonmembers go through the legacy API for now.
         role = arguments.pop('role', MemberRole.member)
         if role is MemberRole.member:
-            # Get the pre_ flags for the subscription workflow.
-            pre_verified = arguments.pop('pre_verified', False)
-            pre_confirmed = arguments.pop('pre_confirmed', False)
-            pre_approved = arguments.pop('pre_approved', False)
             # Now we can run the registration process until either the
             # subscriber is subscribed, or the workflow is paused for
             # verification, confirmation, or approval.
             registrar = ISubscriptionManager(mlist)
             try:
                 token, token_owner, member = registrar.register(
-                    subscriber,
-                    pre_verified=pre_verified,
-                    pre_confirmed=pre_confirmed,
-                    pre_approved=pre_approved)
+                    subscriber, **policy_kwargs)
             except AlreadySubscribedError:
                 conflict(response, b'Member already subscribed')
                 return
diff --git a/src/mailman/rest/sub_moderation.py b/src/mailman/rest/sub_moderation.py
index 47745b729..ad1c5751b 100644
--- a/src/mailman/rest/sub_moderation.py
+++ b/src/mailman/rest/sub_moderation.py
@@ -16,13 +16,16 @@
 # GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
 
 """REST API for held subscription requests."""
+from itertools import chain
 
 from mailman.app.moderator import send_rejection
+from mailman.config import config
 from mailman.core.i18n import _
 from mailman.interfaces.action import Action
 from mailman.interfaces.member import AlreadySubscribedError
 from mailman.interfaces.pending import IPendings
 from mailman.interfaces.subscriptions import ISubscriptionManager
+from mailman.interfaces.workflows import ISubscriptionWorkflow
 from mailman.rest.helpers import (
     CollectionMixin, bad_request, child, conflict, etag, no_content,
     not_found, okay)
@@ -122,8 +125,15 @@ class SubscriptionRequests(_ModerationBase, CollectionMixin):
         self._mlist = mlist
 
     def _get_collection(self, request):
-        pendings = getUtility(IPendings).find(
-            mlist=self._mlist, pend_type='subscription')
+        sub_workflows = [workflow_class
+                         for workflow_class in config.workflows.values()
+                         if ISubscriptionWorkflow.implementedBy(workflow_class)
+                         ]
+        generators = [getUtility(IPendings).find(mlist=self._mlist,
+                                                 pend_type=sub_workflow.name)
+                      for
+                      sub_workflow in sub_workflows]
+        pendings = chain.from_iterable(generators)
         return [token for token, pendable in pendings]
 
     def on_get(self, request, response):
diff --git a/src/mailman/rest/tests/test_listconf.py b/src/mailman/rest/tests/test_listconf.py
index 782effd29..bb88feb61 100644
--- a/src/mailman/rest/tests/test_listconf.py
+++ b/src/mailman/rest/tests/test_listconf.py
@@ -22,11 +22,11 @@ import unittest
 from mailman.app.lifecycle import create_list
 from mailman.database.transaction import transaction
 from mailman.interfaces.digests import DigestFrequency
-from mailman.interfaces.mailinglist import (
-    IAcceptableAliasSet, SubscriptionPolicy)
+from mailman.interfaces.mailinglist import IAcceptableAliasSet
 from mailman.interfaces.template import ITemplateManager
 from mailman.testing.helpers import call_api
 from mailman.testing.layers import RESTLayer
+from mailman.workflows.subscription import ConfirmModerationSubscriptionPolicy
 from urllib.error import HTTPError
 from zope.component import getUtility
 
@@ -197,7 +197,7 @@ class TestConfiguration(unittest.TestCase):
         self.assertEqual(response.status_code, 204)
         # And now we verify that it has the requested setting.
         self.assertEqual(self._mlist.subscription_policy,
-                         SubscriptionPolicy.confirm_then_moderate)
+                         ConfirmModerationSubscriptionPolicy)
 
     def test_patch_attribute_double(self):
         with self.assertRaises(HTTPError) as cm:
diff --git a/src/mailman/rest/tests/test_membership.py b/src/mailman/rest/tests/test_membership.py
index e5a2ce283..bb0134ac5 100644
--- a/src/mailman/rest/tests/test_membership.py
+++ b/src/mailman/rest/tests/test_membership.py
@@ -23,7 +23,6 @@ from mailman.app.lifecycle import create_list
 from mailman.config import config
 from mailman.database.transaction import transaction
 from mailman.interfaces.bans import IBanManager
-from mailman.interfaces.mailinglist import SubscriptionPolicy
 from mailman.interfaces.member import DeliveryMode, MemberRole
 from mailman.interfaces.subscriptions import ISubscriptionManager, TokenOwner
 from mailman.interfaces.usermanager import IUserManager
@@ -33,6 +32,8 @@ from mailman.testing.helpers import (
     set_preferred, subscribe, wait_for_webservice)
 from mailman.testing.layers import ConfigLayer, RESTLayer
 from mailman.utilities.datetime import now
+from mailman.workflows.subscription import (
+    ConfirmModerationSubscriptionPolicy, ModerationSubscriptionPolicy)
 from urllib.error import HTTPError
 from zope.component import getUtility
 
@@ -93,7 +94,6 @@ class TestMembership(unittest.TestCase):
                 'subscriber': 'anne@example.com',
                 'pre_verified': True,
                 'pre_confirmed': True,
-                'pre_approved': True,
                 })
         self.assertEqual(cm.exception.code, 409)
         self.assertEqual(cm.exception.reason, 'Member already subscribed')
@@ -108,7 +108,6 @@ class TestMembership(unittest.TestCase):
                 'subscriber': 'anne@example.com',
                 'pre_verified': False,
                 'pre_confirmed': False,
-                'pre_approved': False,
                 })
         self.assertEqual(cm.exception.code, 409)
         self.assertEqual(cm.exception.reason, 'Member already subscribed')
@@ -123,7 +122,6 @@ class TestMembership(unittest.TestCase):
                 'subscriber': '00000000000000000000000000000001',
                 'pre_verified': True,
                 'pre_confirmed': True,
-                'pre_approved': True,
                 })
         self.assertEqual(cm.exception.code, 400)
         self.assertEqual(cm.exception.reason, 'User has no preferred address')
@@ -135,7 +133,6 @@ class TestMembership(unittest.TestCase):
                 'subscriber': '00000000000000000000000000000801',
                 'pre_verified': True,
                 'pre_confirmed': True,
-                'pre_approved': True,
                 })
         self.assertEqual(cm.exception.code, 400)
         self.assertEqual(cm.exception.reason, 'No such user')
@@ -153,7 +150,6 @@ class TestMembership(unittest.TestCase):
                 'subscriber': 'ANNE@example.com',
                 'pre_verified': True,
                 'pre_confirmed': True,
-                'pre_approved': True,
                 })
         self.assertEqual(cm.exception.code, 409)
         self.assertEqual(cm.exception.reason, 'Member already subscribed')
@@ -171,7 +167,6 @@ class TestMembership(unittest.TestCase):
                 'subscriber': 'anne@example.com',
                 'pre_verified': True,
                 'pre_confirmed': True,
-                'pre_approved': True,
                 })
         self.assertEqual(cm.exception.code, 409)
         self.assertEqual(cm.exception.reason, 'Member already subscribed')
@@ -195,7 +190,6 @@ class TestMembership(unittest.TestCase):
             'display_name': 'Hugh Person',
             'pre_verified': True,
             'pre_confirmed': True,
-            'pre_approved': True,
             })
         self.assertEqual(json, None)
         self.assertEqual(response.status_code, 201)
@@ -231,10 +225,10 @@ class TestMembership(unittest.TestCase):
         # to subscribe again.
         registrar = ISubscriptionManager(self._mlist)
         with transaction():
-            self._mlist.subscription_policy = SubscriptionPolicy.moderate
+            self._mlist.subscription_policy = ModerationSubscriptionPolicy
             anne = self._usermanager.create_address('anne@example.com')
             token, token_owner, member = registrar.register(
-                anne, pre_verified=True, pre_confirmed=True)
+                anne, pre_verified=True)
             self.assertEqual(token_owner, TokenOwner.moderator)
             self.assertIsNone(member)
         with self.assertRaises(HTTPError) as cm:
@@ -242,7 +236,6 @@ class TestMembership(unittest.TestCase):
                 'list_id': 'test.example.com',
                 'subscriber': 'anne@example.com',
                 'pre_verified': True,
-                'pre_confirmed': True,
                 })
         self.assertEqual(cm.exception.code, 409)
         self.assertEqual(cm.exception.reason,
@@ -255,7 +248,7 @@ class TestMembership(unittest.TestCase):
         registrar = ISubscriptionManager(self._mlist)
         with transaction():
             self._mlist.subscription_policy = (
-                SubscriptionPolicy.confirm_then_moderate)
+                ConfirmModerationSubscriptionPolicy)
             anne = self._usermanager.create_address('anne@example.com')
             token, token_owner, member = registrar.register(
                 anne, pre_verified=True)
@@ -645,7 +638,6 @@ class TestAPI31Members(unittest.TestCase):
                 'subscriber': '00000000000000000000000000000001',
                 'pre_verified': True,
                 'pre_confirmed': True,
-                'pre_approved': True,
                 })
         self.assertEqual(response.status_code, 201)
         self.assertEqual(
@@ -681,7 +673,6 @@ class TestAPI31Members(unittest.TestCase):
                 'subscriber': '1',
                 'pre_verified': True,
                 'pre_confirmed': True,
-                'pre_approved': True,
                 })
         # This is a bad request because the `subscriber` value isn't something
         # that's known to the system, in API 3.1.  It's not technically a 404
diff --git a/src/mailman/rest/tests/test_moderation.py b/src/mailman/rest/tests/test_moderation.py
index 0a9bb2608..5b55eb575 100644
--- a/src/mailman/rest/tests/test_moderation.py
+++ b/src/mailman/rest/tests/test_moderation.py
@@ -24,7 +24,6 @@ from mailman.app.lifecycle import create_list
 from mailman.app.moderator import hold_message
 from mailman.database.transaction import transaction
 from mailman.interfaces.bans import IBanManager
-from mailman.interfaces.mailinglist import SubscriptionPolicy
 from mailman.interfaces.requests import IListRequests, RequestType
 from mailman.interfaces.subscriptions import ISubscriptionManager
 from mailman.interfaces.usermanager import IUserManager
@@ -32,6 +31,7 @@ from mailman.testing.helpers import (
     call_api, get_queue_messages, set_preferred,
     specialized_message_from_string as mfs)
 from mailman.testing.layers import RESTLayer
+from mailman.workflows.subscription import ModerationSubscriptionPolicy
 from pkg_resources import resource_filename
 from urllib.error import HTTPError
 from zope.component import getUtility
@@ -296,10 +296,9 @@ class TestSubscriptionModeration(unittest.TestCase):
         # Anne tries to subscribe to a list that only requests moderator
         # approval.
         with transaction():
-            self._mlist.subscription_policy = SubscriptionPolicy.moderate
+            self._mlist.subscription_policy = ModerationSubscriptionPolicy
             token, token_owner, member = self._registrar.register(
-                self._anne,
-                pre_verified=True, pre_confirmed=True)
+                self._anne, pre_verified=True)
         # There's now one request in the queue, and it's waiting on moderator
         # approval.
         json, response = call_api(
diff --git a/src/mailman/rest/tests/test_users.py b/src/mailman/rest/tests/test_users.py
index 97f4b76d2..4c97e5c1d 100644
--- a/src/mailman/rest/tests/test_users.py
+++ b/src/mailman/rest/tests/test_users.py
@@ -437,7 +437,7 @@ class TestLP1074374(unittest.TestCase):
             list_id='test.example.com',
             subscriber='anne@example.com',
             role='member',
-            pre_verified=True, pre_confirmed=True, pre_approved=True))
+            pre_verified=True, pre_confirmed=True))
         # This is not the Anne you're looking for.  (IOW, the new Anne is a
         # different user).
         json, response = call_api(
diff --git a/src/mailman/rest/tests/test_validator.py b/src/mailman/rest/tests/test_validator.py
index 0d197032e..95855d170 100644
--- a/src/mailman/rest/tests/test_validator.py
+++ b/src/mailman/rest/tests/test_validator.py
@@ -22,9 +22,14 @@ import unittest
 from mailman.core.api import API30, API31
 from mailman.interfaces.action import Action
 from mailman.interfaces.usermanager import IUserManager
+from mailman.interfaces.workflows import (ISubscriptionWorkflow,
+                                          IUnsubscriptionWorkflow)
 from mailman.rest.validator import (
-    enum_validator, list_of_strings_validator, subscriber_validator)
+    enum_validator, list_of_strings_validator, policy_validator,
+    subscriber_validator)
 from mailman.testing.layers import RESTLayer
+from mailman.workflows.subscription import ConfirmSubscriptionPolicy
+from mailman.workflows.unsubscription import ConfirmUnsubscriptionPolicy
 from zope.component import getUtility
 
 
@@ -91,3 +96,40 @@ class TestValidators(unittest.TestCase):
 
     def test_enum_validator_blank(self):
         self.assertEqual(enum_validator(Action, allow_blank=True)(''), None)
+
+    def test_policy_validator_wrong_policy_class(self):
+        self.assertRaises(ValueError, policy_validator, None)
+
+    def test_policy_validator_sub_name(self):
+        self.assertEqual(policy_validator(ISubscriptionWorkflow)(
+                ConfirmSubscriptionPolicy.name), ConfirmSubscriptionPolicy)
+
+    def test_policy_validator_sub_class(self):
+        self.assertEqual(policy_validator(ISubscriptionWorkflow)(
+                ConfirmSubscriptionPolicy), ConfirmSubscriptionPolicy)
+
+    def test_policy_validator_sub_backward_compat(self):
+        self.assertEqual(policy_validator(ISubscriptionWorkflow)('confirm'),
+                         ConfirmSubscriptionPolicy)
+
+    def test_policy_validator_sub_wrong_policy(self):
+        validator = policy_validator(ISubscriptionWorkflow)
+        with self.assertRaises(ValueError):
+            validator('not a subscription policy')
+
+    def test_policy_validator_unsub_name(self):
+        self.assertEqual(policy_validator(IUnsubscriptionWorkflow)(
+                ConfirmUnsubscriptionPolicy.name), ConfirmUnsubscriptionPolicy)
+
+    def test_policy_validator_unsub_class(self):
+        self.assertEqual(policy_validator(IUnsubscriptionWorkflow)(
+                ConfirmUnsubscriptionPolicy), ConfirmUnsubscriptionPolicy)
+
+    def test_policy_validator_unsub_backward_compat(self):
+        self.assertEqual(policy_validator(IUnsubscriptionWorkflow)('confirm'),
+                         ConfirmUnsubscriptionPolicy)
+
+    def test_policy_validator_unsub_wrong_policy(self):
+        validator = policy_validator(IUnsubscriptionWorkflow)
+        with self.assertRaises(ValueError):
+            validator('not an unsubscription policy')
diff --git a/src/mailman/rest/validator.py b/src/mailman/rest/validator.py
index b325fdc84..d5f684df9 100644
--- a/src/mailman/rest/validator.py
+++ b/src/mailman/rest/validator.py
@@ -16,15 +16,35 @@
 # GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
 
 """REST web form validation."""
-
+from mailman.config import config
 from mailman.interfaces.address import IEmailValidator
 from mailman.interfaces.errors import MailmanError
 from mailman.interfaces.languages import ILanguageManager
+from mailman.interfaces.workflows import (ISubscriptionWorkflow,
+                                          IUnsubscriptionWorkflow)
+from mailman.workflows.subscription import (
+    ConfirmModerationSubscriptionPolicy, ConfirmSubscriptionPolicy,
+    ModerationSubscriptionPolicy, OpenSubscriptionPolicy)
+from mailman.workflows.unsubscription import (
+    ConfirmModerationUnsubscriptionPolicy, ConfirmUnsubscriptionPolicy,
+    ModerationUnsubscriptionPolicy, OpenUnsubscriptionPolicy)
 from public import public
 from zope.component import getUtility
 
 
 COMMASPACE = ', '
+OLD_SUB_MAP = {
+    'open': OpenSubscriptionPolicy,
+    'confirm': ConfirmSubscriptionPolicy,
+    'moderate': ModerationSubscriptionPolicy,
+    'confirm_then_moderate': ConfirmModerationSubscriptionPolicy
+    }
+OLD_UNSUB_MAP = {
+    'open': OpenUnsubscriptionPolicy,
+    'confirm': ConfirmUnsubscriptionPolicy,
+    'moderate': ModerationUnsubscriptionPolicy,
+    'confirm_then_moderate': ConfirmModerationUnsubscriptionPolicy
+    }
 
 
 @public
@@ -100,6 +120,33 @@ def list_of_strings_validator(values):
 
 
 @public
+class policy_validator:
+    """"""
+
+    def __init__(self, policy_interface):
+        self._policy_interface = policy_interface
+        if policy_interface is ISubscriptionWorkflow:
+            self._old_map = OLD_SUB_MAP
+        elif policy_interface is IUnsubscriptionWorkflow:
+            self._old_map = OLD_UNSUB_MAP
+        else:
+            raise ValueError('Expected a workflow interface.')
+
+    def __call__(self, policy):
+        if self._policy_interface.implementedBy(policy):
+            return policy
+        if (policy in config.workflows and
+                self._policy_interface.implementedBy(
+                        config.workflows[policy])):
+            return config.workflows[policy]
+        # For backwards compatibility.
+        policy = self._old_map.get(policy, None)
+        if policy is not None:
+            return policy
+        raise ValueError('Unknown policy: {}'.format(policy))
+
+
+@public
 class Validator:
     """A validator of parameter input."""