Mark Module API error imports as re-exported and mark Synapse as containing type annotations

MANIFEST.in

@@ -8,6 +8,7 @@ include demo/demo.tls.dh
 include demo/*.py
 include demo/*.sh
 
+include synapse/py.typed
 recursive-include synapse/storage *.sql
 recursive-include synapse/storage *.sql.postgres
 recursive-include synapse/storage *.sql.sqlite

changelog.d/11054.misc

@@ -0,0 +1 @@
+Mark the Synapse package as containing type annotations and fix export declarations so that Synapse pluggable modules may be type checked against Synapse.

synapse/module_api/errors.py

@@ -14,9 +14,16 @@
 
 """Exception types which are exposed as part of the stable module API"""
 
-from synapse.api.errors import (  # noqa: F401
+from synapse.api.errors import (
     InvalidClientCredentialsError,
     RedirectException,
     SynapseError,
 )
-from synapse.config._base import ConfigError  # noqa: F401
+from synapse.config._base import ConfigError
+
+__all__ = [
+    "InvalidClientCredentialsError",
+    "RedirectException",
+    "SynapseError",
+    "ConfigError",
+]