Port the PresenceRouter module interface to the new generic interface (#10524)

Port the PresenceRouter module interface to the new generic interface introduced in v1.37.0

9 files changed, 326 insertions, 69 deletions

diff --git a/changelog.d/10524.feature b/changelog.d/10524.feature
new file mode 100644
index 0000000000..288c9bd74e
--- /dev/null
+++ b/changelog.d/10524.feature
@@ -0,0 +1 @@
+Port the PresenceRouter module interface to the new generic interface.
\ No newline at end of file
diff --git a/docs/modules.md b/docs/modules.md
index 9a430390a4..ae8d6f5b73 100644
--- a/docs/modules.md
+++ b/docs/modules.md
@@ -282,6 +282,52 @@ the request is a server admin.
 Modules can modify the `request_content` (by e.g. adding events to its `initial_state`),
 or deny the room's creation by raising a `module_api.errors.SynapseError`.
 
+#### Presence router callbacks
+
+Presence router callbacks allow module developers to specify additional users (local or remote)
+to receive certain presence updates from local users. Presence router callbacks can be 
+registered using the module API's `register_presence_router_callbacks` method.
+
+The available presence router callbacks are:
+
+```python 
+async def get_users_for_states(
+    self,
+    state_updates: Iterable["synapse.api.UserPresenceState"],
+) -> Dict[str, Set["synapse.api.UserPresenceState"]]:
+```
+**Requires** `get_interested_users` to also be registered
+
+Called when processing updates to the presence state of one or more users. This callback can
+be used to instruct the server to forward that presence state to specific users. The module
+must return a dictionary that maps from Matrix user IDs (which can be local or remote) to the
+`UserPresenceState` changes that they should be forwarded.
+
+Synapse will then attempt to send the specified presence updates to each user when possible.
+
+```python
+async def get_interested_users(
+        self, 
+        user_id: str
+) -> Union[Set[str], "synapse.module_api.PRESENCE_ALL_USERS"]
+```
+**Requires** `get_users_for_states` to also be registered
+
+Called when determining which users someone should be able to see the presence state of. This
+callback should return complementary results to `get_users_for_state` or the presence information 
+may not be properly forwarded.
+
+The callback is given the Matrix user ID for a local user that is requesting presence data and
+should return the Matrix user IDs of the users whose presence state they are allowed to
+query. The returned users can be local or remote. 
+
+Alternatively the callback can return `synapse.module_api.PRESENCE_ALL_USERS`
+to indicate that the user should receive updates from all known users.
+
+For example, if the user `@alice:example.org` is passed to this method, and the Set 
+`{"@bob:example.com", "@charlie:somewhere.org"}` is returned, this signifies that Alice 
+should receive presence updates sent by Bob and Charlie, regardless of whether these users 
+share a room.
 
 ### Porting an existing module that uses the old interface
 
diff --git a/docs/presence_router_module.md b/docs/presence_router_module.md
index 4a3e720240..face54fe2b 100644
--- a/docs/presence_router_module.md
+++ b/docs/presence_router_module.md
@@ -1,3 +1,9 @@
+<h2 style="color:red">
+This page of the Synapse documentation is now deprecated. For up to date
+documentation on setting up or writing a presence router module, please see
+<a href="modules.md">this page</a>.
+</h2>
+
 # Presence Router Module
 
 Synapse supports configuring a module that can specify additional users
diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml
index aeebcaf45f..6030e85a08 100644
--- a/docs/sample_config.yaml
+++ b/docs/sample_config.yaml
@@ -108,20 +108,6 @@ presence:
   #
   #enabled: false
 
-  # Presence routers are third-party modules that can specify additional logic
-  # to where presence updates from users are routed.
-  #
-  presence_router:
-    # The custom module's class. Uncomment to use a custom presence router module.
-    #
-    #module: "my_custom_router.PresenceRouter"
-
-    # Configuration options of the custom module. Refer to your module's
-    # documentation for available options.
-    #
-    #config:
-    #  example_option: 'something'
-
 # Whether to require authentication to retrieve profile data (avatars,
 # display names) of other users through the client API. Defaults to
 # 'false'. Note that profile data is also available via the federation
diff --git a/synapse/app/_base.py b/synapse/app/_base.py
index 50a02f51f5..39e28aff9f 100644
--- a/synapse/app/_base.py
+++ b/synapse/app/_base.py
@@ -37,6 +37,7 @@ from synapse.app import check_bind_error
 from synapse.app.phone_stats_home import start_phone_stats_home
 from synapse.config.homeserver import HomeServerConfig
 from synapse.crypto import context_factory
+from synapse.events.presence_router import load_legacy_presence_router
 from synapse.events.spamcheck import load_legacy_spam_checkers
 from synapse.events.third_party_rules import load_legacy_third_party_event_rules
 from synapse.logging.context import PreserveLoggingContext
@@ -370,6 +371,7 @@ async def start(hs: "HomeServer"):
 
     load_legacy_spam_checkers(hs)
     load_legacy_third_party_event_rules(hs)
+    load_legacy_presence_router(hs)
 
     # If we've configured an expiry time for caches, start the background job now.
     setup_expire_lru_cache_entries(hs)
diff --git a/synapse/config/server.py b/synapse/config/server.py
index 187b4301a0..871422ea28 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -248,6 +248,7 @@ class ServerConfig(Config):
             self.use_presence = config.get("use_presence", True)
 
         # Custom presence router module
+        # This is the legacy way of configuring it (the config should now be put in the modules section)
         self.presence_router_module_class = None
         self.presence_router_config = None
         presence_router_config = presence_config.get("presence_router")
@@ -858,20 +859,6 @@ class ServerConfig(Config):
           #
           #enabled: false
 
-          # Presence routers are third-party modules that can specify additional logic
-          # to where presence updates from users are routed.
-          #
-          presence_router:
-            # The custom module's class. Uncomment to use a custom presence router module.
-            #
-            #module: "my_custom_router.PresenceRouter"
-
-            # Configuration options of the custom module. Refer to your module's
-            # documentation for available options.
-            #
-            #config:
-            #  example_option: 'something'
-
         # Whether to require authentication to retrieve profile data (avatars,
         # display names) of other users through the client API. Defaults to
         # 'false'. Note that profile data is also available via the federation
diff --git a/synapse/events/presence_router.py b/synapse/events/presence_router.py
index 6c37c8a7a4..eb4556cdc1 100644
--- a/synapse/events/presence_router.py
+++ b/synapse/events/presence_router.py
@@ -11,45 +11,115 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
-from typing import TYPE_CHECKING, Dict, Iterable, Set, Union
+import logging
+from typing import (
+    TYPE_CHECKING,
+    Awaitable,
+    Callable,
+    Dict,
+    Iterable,
+    List,
+    Optional,
+    Set,
+    Union,
+)
 
 from synapse.api.presence import UserPresenceState
+from synapse.util.async_helpers import maybe_awaitable
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
+GET_USERS_FOR_STATES_CALLBACK = Callable[
+    [Iterable[UserPresenceState]], Awaitable[Dict[str, Set[UserPresenceState]]]
+]
+GET_INTERESTED_USERS_CALLBACK = Callable[
+    [str], Awaitable[Union[Set[str], "PresenceRouter.ALL_USERS"]]
+]
+
+logger = logging.getLogger(__name__)
+
+
+def load_legacy_presence_router(hs: "HomeServer"):
+    """Wrapper that loads a presence router module configured using the old
+    configuration, and registers the hooks they implement.
+    """
+
+    if hs.config.presence_router_module_class is None:
+        return
+
+    module = hs.config.presence_router_module_class
+    config = hs.config.presence_router_config
+    api = hs.get_module_api()
+
+    presence_router = module(config=config, module_api=api)
+
+    # The known hooks. If a module implements a method which name appears in this set,
+    # we'll want to register it.
+    presence_router_methods = {
+        "get_users_for_states",
+        "get_interested_users",
+    }
+
+    # All methods that the module provides should be async, but this wasn't enforced
+    # in the old module system, so we wrap them if needed
+    def async_wrapper(f: Optional[Callable]) -> Optional[Callable[..., Awaitable]]:
+        # f might be None if the callback isn't implemented by the module. In this
+        # case we don't want to register a callback at all so we return None.
+        if f is None:
+            return None
+
+        def run(*args, **kwargs):
+            # mypy doesn't do well across function boundaries so we need to tell it
+            # f is definitely not None.
+            assert f is not None
+
+            return maybe_awaitable(f(*args, **kwargs))
+
+        return run
+
+    # Register the hooks through the module API.
+    hooks = {
+        hook: async_wrapper(getattr(presence_router, hook, None))
+        for hook in presence_router_methods
+    }
+
+    api.register_presence_router_callbacks(**hooks)
+
 
 class PresenceRouter:
     """
     A module that the homeserver will call upon to help route user presence updates to
-    additional destinations. If a custom presence router is configured, calls will be
-    passed to that instead.
+    additional destinations.
     """
 
     ALL_USERS = "ALL"
 
     def __init__(self, hs: "HomeServer"):
-        self.custom_presence_router = None
+        # Initially there are no callbacks
+        self._get_users_for_states_callbacks: List[GET_USERS_FOR_STATES_CALLBACK] = []
+        self._get_interested_users_callbacks: List[GET_INTERESTED_USERS_CALLBACK] = []
 
-        # Check whether a custom presence router module has been configured
-        if hs.config.presence_router_module_class:
-            # Initialise the module
-            self.custom_presence_router = hs.config.presence_router_module_class(
-                config=hs.config.presence_router_config, module_api=hs.get_module_api()
+    def register_presence_router_callbacks(
+        self,
+        get_users_for_states: Optional[GET_USERS_FOR_STATES_CALLBACK] = None,
+        get_interested_users: Optional[GET_INTERESTED_USERS_CALLBACK] = None,
+    ):
+        # PresenceRouter modules are required to implement both of these methods
+        # or neither of them as they are assumed to act in a complementary manner
+        paired_methods = [get_users_for_states, get_interested_users]
+        if paired_methods.count(None) == 1:
+            raise RuntimeError(
+                "PresenceRouter modules must register neither or both of the paired callbacks: "
+                "[get_users_for_states, get_interested_users]"
             )
 
-            # Ensure the module has implemented the required methods
-            required_methods = ["get_users_for_states", "get_interested_users"]
-            for method_name in required_methods:
-                if not hasattr(self.custom_presence_router, method_name):
-                    raise Exception(
-                        "PresenceRouter module '%s' must implement all required methods: %s"
-                        % (
-                            hs.config.presence_router_module_class.__name__,
-                            ", ".join(required_methods),
-                        )
-                    )
+        # Append the methods provided to the lists of callbacks
+        if get_users_for_states is not None:
+            self._get_users_for_states_callbacks.append(get_users_for_states)
+
+        if get_interested_users is not None:
+            self._get_interested_users_callbacks.append(get_interested_users)
 
     async def get_users_for_states(
         self,
@@ -66,14 +136,40 @@ class PresenceRouter:
           A dictionary of user_id -> set of UserPresenceState, indicating which
           presence updates each user should receive.
         """
-        if self.custom_presence_router is not None:
-            # Ask the custom module
-            return await self.custom_presence_router.get_users_for_states(
-                state_updates=state_updates
-            )
 
-        # Don't include any extra destinations for presence updates
-        return {}
+        # Bail out early if we don't have any callbacks to run.
+        if len(self._get_users_for_states_callbacks) == 0:
+            # Don't include any extra destinations for presence updates
+            return {}
+
+        users_for_states = {}
+        # run all the callbacks for get_users_for_states and combine the results
+        for callback in self._get_users_for_states_callbacks:
+            try:
+                result = await callback(state_updates)
+            except Exception as e:
+                logger.warning("Failed to run module API callback %s: %s", callback, e)
+                continue
+
+            if not isinstance(result, Dict):
+                logger.warning(
+                    "Wrong type returned by module API callback %s: %s, expected Dict",
+                    callback,
+                    result,
+                )
+                continue
+
+            for key, new_entries in result.items():
+                if not isinstance(new_entries, Set):
+                    logger.warning(
+                        "Wrong type returned by module API callback %s: %s, expected Set",
+                        callback,
+                        new_entries,
+                    )
+                    break
+                users_for_states.setdefault(key, set()).update(new_entries)
+
+        return users_for_states
 
     async def get_interested_users(self, user_id: str) -> Union[Set[str], ALL_USERS]:
         """
@@ -92,12 +188,36 @@ class PresenceRouter:
             A set of user IDs to return presence updates for, or ALL_USERS to return all
             known updates.
         """
-        if self.custom_presence_router is not None:
-            # Ask the custom module for interested users
-            return await self.custom_presence_router.get_interested_users(
-                user_id=user_id
-            )
 
-        # A custom presence router is not defined.
-        # Don't report any additional interested users
-        return set()
+        # Bail out early if we don't have any callbacks to run.
+        if len(self._get_interested_users_callbacks) == 0:
+            # Don't report any additional interested users
+            return set()
+
+        interested_users = set()
+        # run all the callbacks for get_interested_users and combine the results
+        for callback in self._get_interested_users_callbacks:
+            try:
+                result = await callback(user_id)
+            except Exception as e:
+                logger.warning("Failed to run module API callback %s: %s", callback, e)
+                continue
+
+            # If one of the callbacks returns ALL_USERS then we can stop calling all
+            # of the other callbacks, since the set of interested_users is already as
+            # large as it can possibly be
+            if result == PresenceRouter.ALL_USERS:
+                return PresenceRouter.ALL_USERS
+
+            if not isinstance(result, Set):
+                logger.warning(
+                    "Wrong type returned by module API callback %s: %s, expected set",
+                    callback,
+                    result,
+                )
+                continue
+
+            # Add the new interested users to the set
+            interested_users.update(result)
+
+        return interested_users
diff --git a/synapse/module_api/__init__.py b/synapse/module_api/__init__.py
index 82725853bc..84bb7264a4 100644
--- a/synapse/module_api/__init__.py
+++ b/synapse/module_api/__init__.py
@@ -32,6 +32,7 @@ from twisted.internet import defer
 from twisted.web.resource import IResource
 
 from synapse.events import EventBase
+from synapse.events.presence_router import PresenceRouter
 from synapse.http.client import SimpleHttpClient
 from synapse.http.server import (
     DirectServeHtmlResource,
@@ -57,6 +58,8 @@ This package defines the 'stable' API which can be used by extension modules whi
 are loaded into Synapse.
 """
 
+PRESENCE_ALL_USERS = PresenceRouter.ALL_USERS
+
 __all__ = [
     "errors",
     "make_deferred_yieldable",
@@ -70,6 +73,7 @@ __all__ = [
     "DirectServeHtmlResource",
     "DirectServeJsonResource",
     "ModuleApi",
+    "PRESENCE_ALL_USERS",
 ]
 
 logger = logging.getLogger(__name__)
@@ -111,6 +115,7 @@ class ModuleApi:
         self._spam_checker = hs.get_spam_checker()
         self._account_validity_handler = hs.get_account_validity_handler()
         self._third_party_event_rules = hs.get_third_party_event_rules()
+        self._presence_router = hs.get_presence_router()
 
     #################################################################################
     # The following methods should only be called during the module's initialisation.
@@ -130,6 +135,11 @@ class ModuleApi:
         """Registers callbacks for third party event rules capabilities."""
         return self._third_party_event_rules.register_third_party_rules_callbacks
 
+    @property
+    def register_presence_router_callbacks(self):
+        """Registers callbacks for presence router capabilities."""
+        return self._presence_router.register_presence_router_callbacks
+
     def register_web_resource(self, path: str, resource: IResource):
         """Registers a web resource to be served at the given path.
 
diff --git a/tests/events/test_presence_router.py b/tests/events/test_presence_router.py
index 6b87f571b8..3b3866bff8 100644
--- a/tests/events/test_presence_router.py
+++ b/tests/events/test_presence_router.py
@@ -17,7 +17,7 @@ from unittest.mock import Mock
 import attr
 
 from synapse.api.constants import EduTypes
-from synapse.events.presence_router import PresenceRouter
+from synapse.events.presence_router import PresenceRouter, load_legacy_presence_router
 from synapse.federation.units import Transaction
 from synapse.handlers.presence import UserPresenceState
 from synapse.module_api import ModuleApi
@@ -34,7 +34,7 @@ class PresenceRouterTestConfig:
     users_who_should_receive_all_presence = attr.ib(type=List[str], default=[])
 
 
-class PresenceRouterTestModule:
+class LegacyPresenceRouterTestModule:
     def __init__(self, config: PresenceRouterTestConfig, module_api: ModuleApi):
         self._config = config
         self._module_api = module_api
@@ -77,6 +77,53 @@ class PresenceRouterTestModule:
         return config
 
 
+class PresenceRouterTestModule:
+    def __init__(self, config: PresenceRouterTestConfig, api: ModuleApi):
+        self._config = config
+        self._module_api = api
+        api.register_presence_router_callbacks(
+            get_users_for_states=self.get_users_for_states,
+            get_interested_users=self.get_interested_users,
+        )
+
+    async def get_users_for_states(
+        self, state_updates: Iterable[UserPresenceState]
+    ) -> Dict[str, Set[UserPresenceState]]:
+        users_to_state = {
+            user_id: set(state_updates)
+            for user_id in self._config.users_who_should_receive_all_presence
+        }
+        return users_to_state
+
+    async def get_interested_users(
+        self, user_id: str
+    ) -> Union[Set[str], PresenceRouter.ALL_USERS]:
+        if user_id in self._config.users_who_should_receive_all_presence:
+            return PresenceRouter.ALL_USERS
+
+        return set()
+
+    @staticmethod
+    def parse_config(config_dict: dict) -> PresenceRouterTestConfig:
+        """Parse a configuration dictionary from the homeserver config, do
+        some validation and return a typed PresenceRouterConfig.
+
+        Args:
+            config_dict: The configuration dictionary.
+
+        Returns:
+            A validated config object.
+        """
+        # Initialise a typed config object
+        config = PresenceRouterTestConfig()
+
+        config.users_who_should_receive_all_presence = config_dict.get(
+            "users_who_should_receive_all_presence"
+        )
+
+        return config
+
+
 class PresenceRouterTestCase(FederatingHomeserverTestCase):
     servlets = [
         admin.register_servlets,
@@ -86,9 +133,17 @@ class PresenceRouterTestCase(FederatingHomeserverTestCase):
     ]
 
     def make_homeserver(self, reactor, clock):
-        return self.setup_test_homeserver(
+        hs = self.setup_test_homeserver(
             federation_transport_client=Mock(spec=["send_transaction"]),
         )
+        # Load the modules into the homeserver
+        module_api = hs.get_module_api()
+        for module, config in hs.config.modules.loaded_modules:
+            module(config=config, api=module_api)
+
+        load_legacy_presence_router(hs)
+
+        return hs
 
     def prepare(self, reactor, clock, homeserver):
         self.sync_handler = self.hs.get_sync_handler()
@@ -98,7 +153,7 @@ class PresenceRouterTestCase(FederatingHomeserverTestCase):
         {
             "presence": {
                 "presence_router": {
-                    "module": __name__ + ".PresenceRouterTestModule",
+                    "module": __name__ + ".LegacyPresenceRouterTestModule",
                     "config": {
                         "users_who_should_receive_all_presence": [
                             "@presence_gobbler:test",
@@ -109,7 +164,28 @@ class PresenceRouterTestCase(FederatingHomeserverTestCase):
             "send_federation": True,
         }
     )
+    def test_receiving_all_presence_legacy(self):
+        self.receiving_all_presence_test_body()
+
+    @override_config(
+        {
+            "modules": [
+                {
+                    "module": __name__ + ".PresenceRouterTestModule",
+                    "config": {
+                        "users_who_should_receive_all_presence": [
+                            "@presence_gobbler:test",
+                        ]
+                    },
+                },
+            ],
+            "send_federation": True,
+        }
+    )
     def test_receiving_all_presence(self):
+        self.receiving_all_presence_test_body()
+
+    def receiving_all_presence_test_body(self):
         """Test that a user that does not share a room with another other can receive
         presence for them, due to presence routing.
         """
@@ -203,7 +279,7 @@ class PresenceRouterTestCase(FederatingHomeserverTestCase):
         {
             "presence": {
                 "presence_router": {
-                    "module": __name__ + ".PresenceRouterTestModule",
+                    "module": __name__ + ".LegacyPresenceRouterTestModule",
                     "config": {
                         "users_who_should_receive_all_presence": [
                             "@presence_gobbler1:test",
@@ -216,7 +292,30 @@ class PresenceRouterTestCase(FederatingHomeserverTestCase):
             "send_federation": True,
         }
     )
+    def test_send_local_online_presence_to_with_module_legacy(self):
+        self.send_local_online_presence_to_with_module_test_body()
+
+    @override_config(
+        {
+            "modules": [
+                {
+                    "module": __name__ + ".PresenceRouterTestModule",
+                    "config": {
+                        "users_who_should_receive_all_presence": [
+                            "@presence_gobbler1:test",
+                            "@presence_gobbler2:test",
+                            "@far_away_person:island",
+                        ]
+                    },
+                },
+            ],
+            "send_federation": True,
+        }
+    )
     def test_send_local_online_presence_to_with_module(self):
+        self.send_local_online_presence_to_with_module_test_body()
+
+    def send_local_online_presence_to_with_module_test_body(self):
         """Tests that send_local_presence_to_users sends local online presence to a set
         of specified local and remote users, with a custom PresenceRouter module enabled.
         """