Convert strings in synapse.api.constants to enums or Final

This change makes mypy type the constants as `Literal`s instead of
`str`s, allowing code of the following form to pass mypy:
```py
def do_something(
    membership: Literal[Membership.JOIN, Membership.LEAVE], ...
):
    ...

do_something(Membership.JOIN, ...)
```

Author: Sean Quah

changelog.d/11356.misc

@@ -1 +1 @@
-Add `Final` annotation to string constants in `synapse.api.constants` so that they get typed as `Literal`s.
+Convert most string constants in `synapse.api.constants` into enums, so that they are usable as `Literal`s, and make the rest `Final`.

synapse/api/auth.py

@@ -34,7 +34,7 @@
 from synapse.http.site import SynapseRequest
 from synapse.logging import opentracing as opentracing
 from synapse.storage.databases.main.registration import TokenLookupResult
-from synapse.types import Requester, StateMap, UserID, create_requester
+from synapse.types import MutableStateMap, Requester, StateMap, UserID, create_requester
 from synapse.util.caches.lrucache import LruCache
 from synapse.util.macaroons import get_value_from_macaroon, satisfy_expiry
 
@@ -511,7 +511,7 @@ async def check_can_change_room_list(self, room_id: str, user: UserID) -> bool:
             room_id, EventTypes.PowerLevels, ""
         )
 
-        auth_events = {}
+        auth_events: MutableStateMap[EventBase] = {}
         if power_level_event:
             auth_events[(EventTypes.PowerLevels, "")] = power_level_event
 

synapse/api/constants.py

@@ -19,6 +19,8 @@
 
 from typing_extensions import Final
 
+from synapse.util.enum import StrEnum
+
 # the max size of a (canonical-json-encoded) event
 MAX_PDU_SIZE = 65536
 
@@ -37,221 +39,218 @@
 MAX_GROUP_ROLEID_LENGTH = 255
 
 
-class Membership:
-
+class Membership(StrEnum):
     """Represents the membership states of a user in a room."""
 
-    INVITE: Final = "invite"
-    JOIN: Final = "join"
-    KNOCK: Final = "knock"
-    LEAVE: Final = "leave"
-    BAN: Final = "ban"
-    LIST: Final = (INVITE, JOIN, KNOCK, LEAVE, BAN)
+    INVITE = "invite"
+    JOIN = "join"
+    KNOCK = "knock"
+    LEAVE = "leave"
+    BAN = "ban"
 
 
-class PresenceState:
+class PresenceState(StrEnum):
     """Represents the presence state of a user."""
 
-    OFFLINE: Final = "offline"
-    UNAVAILABLE: Final = "unavailable"
-    ONLINE: Final = "online"
-    BUSY: Final = "org.matrix.msc3026.busy"
+    OFFLINE = "offline"
+    UNAVAILABLE = "unavailable"
+    ONLINE = "online"
+    BUSY = "org.matrix.msc3026.busy"
 
 
-class JoinRules:
-    PUBLIC: Final = "public"
-    KNOCK: Final = "knock"
-    INVITE: Final = "invite"
-    PRIVATE: Final = "private"
+class JoinRules(StrEnum):
+    PUBLIC = "public"
+    KNOCK = "knock"
+    INVITE = "invite"
+    PRIVATE = "private"
     # As defined for MSC3083.
-    RESTRICTED: Final = "restricted"
+    RESTRICTED = "restricted"
 
 
-class RestrictedJoinRuleTypes:
+class RestrictedJoinRuleTypes(StrEnum):
     """Understood types for the allow rules in restricted join rules."""
 
-    ROOM_MEMBERSHIP: Final = "m.room_membership"
+    ROOM_MEMBERSHIP = "m.room_membership"
 
 
-class LoginType:
-    PASSWORD: Final = "m.login.password"
-    EMAIL_IDENTITY: Final = "m.login.email.identity"
-    MSISDN: Final = "m.login.msisdn"
-    RECAPTCHA: Final = "m.login.recaptcha"
-    TERMS: Final = "m.login.terms"
-    SSO: Final = "m.login.sso"
-    DUMMY: Final = "m.login.dummy"
-    REGISTRATION_TOKEN: Final = "org.matrix.msc3231.login.registration_token"
+class LoginType(StrEnum):
+    PASSWORD = "m.login.password"
+    EMAIL_IDENTITY = "m.login.email.identity"
+    MSISDN = "m.login.msisdn"
+    RECAPTCHA = "m.login.recaptcha"
+    TERMS = "m.login.terms"
+    SSO = "m.login.sso"
+    DUMMY = "m.login.dummy"
+    REGISTRATION_TOKEN = "org.matrix.msc3231.login.registration_token"
 
 
 # This is used in the `type` parameter for /register when called by
 # an appservice to register a new user.
 APP_SERVICE_REGISTRATION_TYPE: Final = "m.login.application_service"
 
 
-class EventTypes:
-    Member: Final = "m.room.member"
-    Create: Final = "m.room.create"
-    Tombstone: Final = "m.room.tombstone"
-    JoinRules: Final = "m.room.join_rules"
-    PowerLevels: Final = "m.room.power_levels"
-    Aliases: Final = "m.room.aliases"
-    Redaction: Final = "m.room.redaction"
-    ThirdPartyInvite: Final = "m.room.third_party_invite"
-    RelatedGroups: Final = "m.room.related_groups"
-
-    RoomHistoryVisibility: Final = "m.room.history_visibility"
-    CanonicalAlias: Final = "m.room.canonical_alias"
-    Encrypted: Final = "m.room.encrypted"
-    RoomAvatar: Final = "m.room.avatar"
-    RoomEncryption: Final = "m.room.encryption"
-    GuestAccess: Final = "m.room.guest_access"
+class EventTypes(StrEnum):
+    Member = "m.room.member"
+    Create = "m.room.create"
+    Tombstone = "m.room.tombstone"
+    JoinRules = "m.room.join_rules"
+    PowerLevels = "m.room.power_levels"
+    Aliases = "m.room.aliases"
+    Redaction = "m.room.redaction"
+    ThirdPartyInvite = "m.room.third_party_invite"
+    RelatedGroups = "m.room.related_groups"
+
+    RoomHistoryVisibility = "m.room.history_visibility"
+    CanonicalAlias = "m.room.canonical_alias"
+    Encrypted = "m.room.encrypted"
+    RoomAvatar = "m.room.avatar"
+    RoomEncryption = "m.room.encryption"
+    GuestAccess = "m.room.guest_access"
 
     # These are used for validation
-    Message: Final = "m.room.message"
-    Topic: Final = "m.room.topic"
-    Name: Final = "m.room.name"
+    Message = "m.room.message"
+    Topic = "m.room.topic"
+    Name = "m.room.name"
 
-    ServerACL: Final = "m.room.server_acl"
-    Pinned: Final = "m.room.pinned_events"
+    ServerACL = "m.room.server_acl"
+    Pinned = "m.room.pinned_events"
 
-    Retention: Final = "m.room.retention"
+    Retention = "m.room.retention"
 
-    Dummy: Final = "org.matrix.dummy_event"
+    Dummy = "org.matrix.dummy_event"
 
-    SpaceChild: Final = "m.space.child"
-    SpaceParent: Final = "m.space.parent"
+    SpaceChild = "m.space.child"
+    SpaceParent = "m.space.parent"
 
-    MSC2716_INSERTION: Final = "org.matrix.msc2716.insertion"
-    MSC2716_BATCH: Final = "org.matrix.msc2716.batch"
-    MSC2716_MARKER: Final = "org.matrix.msc2716.marker"
+    MSC2716_INSERTION = "org.matrix.msc2716.insertion"
+    MSC2716_BATCH = "org.matrix.msc2716.batch"
+    MSC2716_MARKER = "org.matrix.msc2716.marker"
 
 
-class ToDeviceEventTypes:
-    RoomKeyRequest: Final = "m.room_key_request"
+class ToDeviceEventTypes(StrEnum):
+    RoomKeyRequest = "m.room_key_request"
 
 
-class DeviceKeyAlgorithms:
+class DeviceKeyAlgorithms(StrEnum):
     """Spec'd algorithms for the generation of per-device keys"""
 
-    ED25519: Final = "ed25519"
-    CURVE25519: Final = "curve25519"
-    SIGNED_CURVE25519: Final = "signed_curve25519"
+    ED25519 = "ed25519"
+    CURVE25519 = "curve25519"
+    SIGNED_CURVE25519 = "signed_curve25519"
 
 
-class EduTypes:
-    Presence: Final = "m.presence"
+class EduTypes(StrEnum):
+    Presence = "m.presence"
 
 
-class RejectedReason:
-    AUTH_ERROR: Final = "auth_error"
+class RejectedReason(StrEnum):
+    AUTH_ERROR = "auth_error"
 
 
-class RoomCreationPreset:
-    PRIVATE_CHAT: Final = "private_chat"
-    PUBLIC_CHAT: Final = "public_chat"
-    TRUSTED_PRIVATE_CHAT: Final = "trusted_private_chat"
+class RoomCreationPreset(StrEnum):
+    PRIVATE_CHAT = "private_chat"
+    PUBLIC_CHAT = "public_chat"
+    TRUSTED_PRIVATE_CHAT = "trusted_private_chat"
 
 
-class ThirdPartyEntityKind:
-    USER: Final = "user"
-    LOCATION: Final = "location"
+class ThirdPartyEntityKind(StrEnum):
+    USER = "user"
+    LOCATION = "location"
 
 
 ServerNoticeMsgType: Final = "m.server_notice"
 ServerNoticeLimitReached: Final = "m.server_notice.usage_limit_reached"
 
 
-class UserTypes:
+class UserTypes(StrEnum):
     """Allows for user type specific behaviour. With the benefit of hindsight
     'admin' and 'guest' users should also be UserTypes. Normal users are type None
     """
 
-    SUPPORT: Final = "support"
-    BOT: Final = "bot"
-    ALL_USER_TYPES: Final = (SUPPORT, BOT)
+    SUPPORT = "support"
+    BOT = "bot"
 
 
-class RelationTypes:
+class RelationTypes(StrEnum):
     """The types of relations known to this server."""
 
-    ANNOTATION: Final = "m.annotation"
-    REPLACE: Final = "m.replace"
-    REFERENCE: Final = "m.reference"
-    THREAD: Final = "io.element.thread"
+    ANNOTATION = "m.annotation"
+    REPLACE = "m.replace"
+    REFERENCE = "m.reference"
+    THREAD = "io.element.thread"
 
 
-class LimitBlockingTypes:
+class LimitBlockingTypes(StrEnum):
     """Reasons that a server may be blocked"""
 
-    MONTHLY_ACTIVE_USER: Final = "monthly_active_user"
-    HS_DISABLED: Final = "hs_disabled"
+    MONTHLY_ACTIVE_USER = "monthly_active_user"
+    HS_DISABLED = "hs_disabled"
 
 
-class EventContentFields:
+class EventContentFields(StrEnum):
     """Fields found in events' content, regardless of type."""
 
     # Labels for the event, cf https://github.com/matrix-org/matrix-doc/pull/2326
-    LABELS: Final = "org.matrix.labels"
+    LABELS = "org.matrix.labels"
 
     # Timestamp to delete the event after
     # cf https://github.com/matrix-org/matrix-doc/pull/2228
-    SELF_DESTRUCT_AFTER: Final = "org.matrix.self_destruct_after"
+    SELF_DESTRUCT_AFTER = "org.matrix.self_destruct_after"
 
     # cf https://github.com/matrix-org/matrix-doc/pull/1772
-    ROOM_TYPE: Final = "type"
+    ROOM_TYPE = "type"
 
     # Whether a room can federate.
-    FEDERATE: Final = "m.federate"
+    FEDERATE = "m.federate"
 
     # The creator of the room, as used in `m.room.create` events.
-    ROOM_CREATOR: Final = "creator"
+    ROOM_CREATOR = "creator"
 
     # Used in m.room.guest_access events.
-    GUEST_ACCESS: Final = "guest_access"
+    GUEST_ACCESS = "guest_access"
 
     # Used on normal messages to indicate they were historically imported after the fact
-    MSC2716_HISTORICAL: Final = "org.matrix.msc2716.historical"
+    MSC2716_HISTORICAL = "org.matrix.msc2716.historical"
     # For "insertion" events to indicate what the next batch ID should be in
     # order to connect to it
-    MSC2716_NEXT_BATCH_ID: Final = "org.matrix.msc2716.next_batch_id"
+    MSC2716_NEXT_BATCH_ID = "org.matrix.msc2716.next_batch_id"
     # Used on "batch" events to indicate which insertion event it connects to
-    MSC2716_BATCH_ID: Final = "org.matrix.msc2716.batch_id"
+    MSC2716_BATCH_ID = "org.matrix.msc2716.batch_id"
     # For "marker" events
-    MSC2716_MARKER_INSERTION: Final = "org.matrix.msc2716.marker.insertion"
+    MSC2716_MARKER_INSERTION = "org.matrix.msc2716.marker.insertion"
 
     # The authorising user for joining a restricted room.
-    AUTHORISING_USER: Final = "join_authorised_via_users_server"
+    AUTHORISING_USER = "join_authorised_via_users_server"
 
 
-class RoomTypes:
+class RoomTypes(StrEnum):
     """Understood values of the room_type field of m.room.create events."""
 
-    SPACE: Final = "m.space"
+    SPACE = "m.space"
 
 
-class RoomEncryptionAlgorithms:
-    MEGOLM_V1_AES_SHA2: Final = "m.megolm.v1.aes-sha2"
-    DEFAULT: Final = MEGOLM_V1_AES_SHA2
+class RoomEncryptionAlgorithms(StrEnum):
+    MEGOLM_V1_AES_SHA2 = "m.megolm.v1.aes-sha2"
+    DEFAULT = MEGOLM_V1_AES_SHA2
 
 
-class AccountDataTypes:
-    DIRECT: Final = "m.direct"
-    IGNORED_USER_LIST: Final = "m.ignored_user_list"
+class AccountDataTypes(StrEnum):
+    DIRECT = "m.direct"
+    IGNORED_USER_LIST = "m.ignored_user_list"
 
 
-class HistoryVisibility:
-    INVITED: Final = "invited"
-    JOINED: Final = "joined"
-    SHARED: Final = "shared"
-    WORLD_READABLE: Final = "world_readable"
+class HistoryVisibility(StrEnum):
+    INVITED = "invited"
+    JOINED = "joined"
+    SHARED = "shared"
+    WORLD_READABLE = "world_readable"
 
 
-class GuestAccess:
-    CAN_JOIN: Final = "can_join"
+class GuestAccess(StrEnum):
+    CAN_JOIN = "can_join"
     # anything that is not "can_join" is considered "forbidden", but for completeness:
-    FORBIDDEN: Final = "forbidden"
+    FORBIDDEN = "forbidden"
 
 
-class ReadReceiptEventFields:
-    MSC2285_HIDDEN: Final = "org.matrix.msc2285.hidden"
+class ReadReceiptEventFields(StrEnum):
+    MSC2285_HIDDEN = "org.matrix.msc2285.hidden"

synapse/event_auth.py

@@ -840,7 +840,7 @@ def get_public_keys(invite_event: EventBase) -> List[Dict[str, Any]]:
 
 def auth_types_for_event(
     room_version: RoomVersion, event: Union[EventBase, EventBuilder]
-) -> Set[Tuple[str, str]]:
+) -> Set[Tuple[EventTypes, str]]:
     """Given an event, return a list of (EventType, StateKey) that may be
     needed to auth the event. The returned list may be a superset of what
     would actually be required depending on the full state of the room.

synapse/events/validator.py

@@ -189,7 +189,9 @@ def validate_builder(self, event: Union[EventBase, EventBuilder]) -> None:
             if "membership" not in event.content:
                 raise SynapseError(400, "Content has not membership key")
 
-            if event.content["membership"] not in Membership.LIST:
+            try:
+                Membership(event.content["membership"])
+            except ValueError:
                 raise SynapseError(400, "Invalid membership key")
 
             self._ensure_state_event(event)