Standardise the module interface (#10062)

This PR adds a common configuration section for all modules (see docs). These modules are then loaded at startup by the homeserver. Modules register their hooks and web resources using the new `register_[...]_callbacks` and `register_web_resource` methods of the module API.

synapse/config/_base.pyi

@@ -16,6 +16,7 @@ from synapse.config import (
     key,
     logger,
     metrics,
+    modules,
     oidc,
     password_auth_providers,
     push,
@@ -85,6 +86,7 @@ class RootConfig:
     thirdpartyrules: third_party_event_rules.ThirdPartyRulesConfig
     tracer: tracer.TracerConfig
     redis: redis.RedisConfig
+    modules: modules.ModulesConfig
 
     config_classes: List = ...
     def __init__(self) -> None: ...

synapse/config/homeserver.py

@@ -1,5 +1,4 @@
-# Copyright 2014-2016 OpenMarket Ltd
-# Copyright 2018 New Vector Ltd
+# Copyright 2021 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -30,6 +29,7 @@ from .jwt import JWTConfig
 from .key import KeyConfig
 from .logger import LoggingConfig
 from .metrics import MetricsConfig
+from .modules import ModulesConfig
 from .oidc import OIDCConfig
 from .password_auth_providers import PasswordAuthProviderConfig
 from .push import PushConfig
@@ -56,6 +56,7 @@ from .workers import WorkerConfig
 class HomeServerConfig(RootConfig):
 
     config_classes = [
+        ModulesConfig,
         ServerConfig,
         TlsConfig,
         FederationConfig,

synapse/config/modules.py

@@ -0,0 +1,49 @@
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# 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 Any, Dict, List, Tuple
+
+from synapse.config._base import Config, ConfigError
+from synapse.util.module_loader import load_module
+
+
+class ModulesConfig(Config):
+    section = "modules"
+
+    def read_config(self, config: dict, **kwargs):
+        self.loaded_modules: List[Tuple[Any, Dict]] = []
+
+        configured_modules = config.get("modules") or []
+        for i, module in enumerate(configured_modules):
+            config_path = ("modules", "<item %i>" % i)
+            if not isinstance(module, dict):
+                raise ConfigError("expected a mapping", config_path)
+
+            self.loaded_modules.append(load_module(module, config_path))
+
+    def generate_config_section(self, **kwargs):
+        return """
+            ## Modules ##
+
+            # Server admins can expand Synapse's functionality with external modules.
+            #
+            # See https://matrix-org.github.io/synapse/develop/modules.html for more
+            # documentation on how to configure or create custom modules for Synapse.
+            #
+            modules:
+                # - module: my_super_module.MySuperClass
+                #   config:
+                #       do_thing: true
+                # - module: my_other_super_module.SomeClass
+                #   config: {}
+            """

synapse/config/spam_checker.py

@@ -42,18 +42,3 @@ class SpamCheckerConfig(Config):
                 self.spam_checkers.append(load_module(spam_checker, config_path))
         else:
             raise ConfigError("spam_checker syntax is incorrect")
-
-    def generate_config_section(self, **kwargs):
-        return """\
-        # Spam checkers are third-party modules that can block specific actions
-        # of local users, such as creating rooms and registering undesirable
-        # usernames, as well as remote users by redacting incoming events.
-        #
-        spam_checker:
-           #- module: "my_custom_project.SuperSpamChecker"
-           #  config:
-           #    example_option: 'things'
-           #- module: "some_other_project.BadEventStopper"
-           #  config:
-           #    example_stop_events_from: ['@bad:example.com']
-        """