Discover moderated content models dynamically

Replace the hand-maintained moderated-model lists (the per-type branches in
moderation_state_column_visible and the moderationobjecttype2model dict) with a
registry built from __moderation_object_type__ declared on each model, and
factor the duplicated mutual-block clause into a shared helper.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: aapeliv

app/backend/src/couchers/models/conversations.py

@@ -10,6 +10,7 @@
 from couchers.constants import DATETIME_INFINITY, DATETIME_MINUS_INFINITY
 from couchers.models.base import Base
 from couchers.models.host_requests import HostRequestStatus
+from couchers.models.moderation import ModerationObjectType
 from couchers.utils import now
 
 if TYPE_CHECKING:
@@ -38,6 +39,7 @@ class GroupChat(Base, kw_only=True):
 
     __tablename__ = "group_chats"
     __moderation_author_column__ = "creator_id"
+    __moderation_object_type__ = ModerationObjectType.group_chat
 
     conversation_id: Mapped[int] = mapped_column("id", ForeignKey("conversations.id"), primary_key=True)
 

app/backend/src/couchers/models/discussions.py

@@ -5,6 +5,7 @@
 from sqlalchemy.orm import Mapped, column_property, mapped_column, relationship
 
 from couchers.models.base import Base, communities_seq
+from couchers.models.moderation import ModerationObjectType
 
 if TYPE_CHECKING:
     from couchers.models import Cluster, User
@@ -17,6 +18,7 @@ class Discussion(Base, kw_only=True):
 
     __tablename__ = "discussions"
     __moderation_author_column__ = "creator_user_id"
+    __moderation_object_type__ = ModerationObjectType.discussion
 
     id: Mapped[int] = mapped_column(
         BigInteger, communities_seq, primary_key=True, server_default=communities_seq.next_value(), init=False
@@ -84,6 +86,7 @@ class Comment(Base, kw_only=True):
 
     __tablename__ = "comments"
     __moderation_author_column__ = "author_user_id"
+    __moderation_object_type__ = ModerationObjectType.comment
 
     id: Mapped[int] = mapped_column(BigInteger, primary_key=True, init=False)
 
@@ -104,6 +107,7 @@ class Reply(Base, kw_only=True):
 
     __tablename__ = "replies"
     __moderation_author_column__ = "author_user_id"
+    __moderation_object_type__ = ModerationObjectType.reply
 
     id: Mapped[int] = mapped_column(BigInteger, primary_key=True, init=False)
 

app/backend/src/couchers/models/events.py

@@ -24,6 +24,7 @@
 from sqlalchemy.sql.elements import ColumnElement
 
 from couchers.models.base import Base, Geom, communities_seq
+from couchers.models.moderation import ModerationObjectType
 from couchers.utils import get_coordinates
 
 if TYPE_CHECKING:
@@ -112,6 +113,7 @@ class Event(Base, kw_only=True):
 class EventOccurrence(Base, kw_only=True):
     __tablename__ = "event_occurrences"
     __moderation_author_column__ = "creator_user_id"
+    __moderation_object_type__ = ModerationObjectType.event_occurrence
 
     id: Mapped[int] = mapped_column(
         BigInteger, communities_seq, primary_key=True, server_default=communities_seq.next_value(), init=False

app/backend/src/couchers/models/host_requests.py

@@ -9,6 +9,7 @@
 from sqlalchemy.sql import expression
 
 from couchers.models.base import Base, Geom
+from couchers.models.moderation import ModerationObjectType
 from couchers.utils import date_in_timezone, now
 
 if TYPE_CHECKING:
@@ -41,6 +42,7 @@ class HostRequest(Base, kw_only=True):
 
     __tablename__ = "host_requests"
     __moderation_author_column__ = "initiator_user_id"
+    __moderation_object_type__ = ModerationObjectType.host_request
 
     conversation_id: Mapped[int] = mapped_column("id", ForeignKey("conversations.id"), primary_key=True)
     initiator_user_id: Mapped[int] = mapped_column(ForeignKey("users.id"), index=True)

app/backend/src/couchers/models/moderation.py

@@ -7,16 +7,26 @@
 
 import enum
 from datetime import datetime
-from typing import TYPE_CHECKING
+from functools import cache
+from typing import TYPE_CHECKING, Any, NamedTuple
 
 from sqlalchemy import BigInteger, DateTime, Enum, ForeignKey, Index, String, func
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from couchers.models.base import Base, moderation_seq
 
 if TYPE_CHECKING:
+    from couchers.models.conversations import GroupChat
+    from couchers.models.discussions import Comment, Discussion, Reply
+    from couchers.models.events import EventOccurrence
+    from couchers.models.host_requests import HostRequest
+    from couchers.models.rest import FriendRelationship
     from couchers.models.users import User
 
+    type ModeratedContentModel = type[
+        HostRequest | GroupChat | FriendRelationship | EventOccurrence | Comment | Reply | Discussion
+    ]
+
 
 class ModerationVisibility(enum.Enum):
     # Only visible to moderators
@@ -186,3 +196,33 @@ class ModerationLog(Base, kw_only=True):
 
     def __repr__(self) -> str:
         return f"ModerationLog(id={self.id}, state_id={self.moderation_state_id}, action={self.action}, moderator={self.moderator_user_id}, time={self.time})"
+
+
+class ModeratedModel(NamedTuple):
+    """A model governed by the UMS, with its moderation metadata resolved."""
+
+    object_type: ModerationObjectType
+    model: ModeratedContentModel
+    # the InstrumentedAttribute of the model's author column; Any avoids descriptor-unwrapping on access
+    author_column: Any
+
+
+@cache
+def get_moderated_models() -> dict[ModerationObjectType, ModeratedModel]:
+    """
+    Maps each ModerationObjectType to its model and resolved moderation metadata.
+
+    Discovered from every mapped model that declares __moderation_object_type__, so the moderation
+    metadata stays on the models themselves rather than in a separate hand-maintained list.
+    """
+    models: dict[ModerationObjectType, ModeratedModel] = {}
+    for mapper in Base.registry.mappers:
+        cls = mapper.class_
+        if not hasattr(cls, "__moderation_object_type__"):
+            continue
+        models[cls.__moderation_object_type__] = ModeratedModel(
+            object_type=cls.__moderation_object_type__,
+            model=cls,
+            author_column=getattr(cls, cls.__moderation_author_column__),
+        )
+    return models

app/backend/src/couchers/models/rest.py

@@ -29,6 +29,7 @@
 
 from couchers.constants import GUIDELINES_VERSION
 from couchers.models.base import Base, Geom
+from couchers.models.moderation import ModerationObjectType
 from couchers.models.users import HostingStatus
 from couchers.utils import now
 
@@ -73,6 +74,7 @@ class FriendRelationship(Base, kw_only=True):
 
     __tablename__ = "friend_relationships"
     __moderation_author_column__ = "from_user_id"
+    __moderation_object_type__ = ModerationObjectType.friend_request
 
     id: Mapped[int] = mapped_column(BigInteger, primary_key=True, init=False)
 

app/backend/src/couchers/servicers/moderation.py

@@ -1,5 +1,4 @@
 import logging
-from typing import TYPE_CHECKING
 
 import grpc
 from sqlalchemy import and_, exists, not_, or_, select
@@ -36,14 +35,12 @@
     NotificationDelivery,
     Reply,
     User,
+    get_moderated_models,
 )
 from couchers.proto import moderation_pb2, moderation_pb2_grpc
 from couchers.proto.internal import jobs_pb2
 from couchers.utils import Timestamp_from_datetime, now
 
-if TYPE_CHECKING:
-    from couchers.sql import _ModeratedContent
-
 logger = logging.getLogger(__name__)
 
 MAX_PAGINATION_LENGTH = 1_000
@@ -123,17 +120,6 @@
     moderation_pb2.MODERATION_OBJECT_TYPE_DISCUSSION: ModerationObjectType.discussion,
 }
 
-# Mapping from ModerationObjectType to the SQLAlchemy model class
-moderationobjecttype2model: dict[ModerationObjectType, _ModeratedContent] = {
-    ModerationObjectType.host_request: HostRequest,
-    ModerationObjectType.group_chat: GroupChat,
-    ModerationObjectType.friend_request: FriendRelationship,
-    ModerationObjectType.event_occurrence: EventOccurrence,
-    ModerationObjectType.comment: Comment,
-    ModerationObjectType.reply: Reply,
-    ModerationObjectType.discussion: Discussion,
-}
-
 
 def bulk_set_user_content_visibility(
     session: Session,
@@ -147,10 +133,9 @@ def bulk_set_user_content_visibility(
     final_reason = reason or f"Bulk visibility update for user {user.id} to {new_visibility.name}"
 
     author_exists_clauses = []
-    for model in moderationobjecttype2model.values():
-        author_col = getattr(model, model.__moderation_author_column__)
+    for entry in get_moderated_models().values():
         author_exists_clauses.append(
-            exists().where(and_(model.moderation_state_id == ModerationState.id, author_col == user.id))
+            exists().where(and_(entry.model.moderation_state_id == ModerationState.id, entry.author_column == user.id))
         )
 
     states = session.execute(select(ModerationState).where(or_(*author_exists_clauses))).scalars().all()
@@ -346,13 +331,12 @@ def GetModerationQueue(
 
             # Use EXISTS for efficient author filtering
             author_exists_clauses = []
-            for model in moderationobjecttype2model.values():
-                author_col = getattr(model, model.__moderation_author_column__)
+            for entry in get_moderated_models().values():
                 author_exists_clauses.append(
                     exists().where(
                         and_(
-                            model.moderation_state_id == ModerationQueueItem.moderation_state_id,
-                            author_col == author_user_id,
+                            entry.model.moderation_state_id == ModerationQueueItem.moderation_state_id,
+                            entry.author_column == author_user_id,
                         )
                     )
                 )
@@ -687,13 +671,12 @@ def ListModerationStates(
 
         if request.author_user_id:
             author_exists_clauses = []
-            for model in moderationobjecttype2model.values():
-                author_col = getattr(model, model.__moderation_author_column__)
+            for entry in get_moderated_models().values():
                 author_exists_clauses.append(
                     exists().where(
                         and_(
-                            model.moderation_state_id == ModerationState.id,
-                            author_col == request.author_user_id,
+                            entry.model.moderation_state_id == ModerationState.id,
+                            entry.author_column == request.author_user_id,
                         )
                     )
                 )