Refactor HomeserverConfig so it can be typechecked (#6137)

33 files changed, 385 insertions, 79 deletions

diff --git a/synapse/config/_base.py b/synapse/config/_base.py
index 31f6530978..08619404bb 100644
--- a/synapse/config/_base.py
+++ b/synapse/config/_base.py
@@ -18,7 +18,9 @@
 import argparse
 import errno
 import os
+from collections import OrderedDict
 from textwrap import dedent
+from typing import Any, MutableMapping, Optional
 
 from six import integer_types
 
@@ -51,7 +53,56 @@ Missing mandatory `server_name` config option.
 """
 
 
+def path_exists(file_path):
+    """Check if a file exists
+
+    Unlike os.path.exists, this throws an exception if there is an error
+    checking if the file exists (for example, if there is a perms error on
+    the parent dir).
+
+    Returns:
+        bool: True if the file exists; False if not.
+    """
+    try:
+        os.stat(file_path)
+        return True
+    except OSError as e:
+        if e.errno != errno.ENOENT:
+            raise e
+        return False
+
+
 class Config(object):
+    """
+    A configuration section, containing configuration keys and values.
+
+    Attributes:
+        section (str): The section title of this config object, such as
+            "tls" or "logger". This is used to refer to it on the root
+            logger (for example, `config.tls.some_option`). Must be
+            defined in subclasses.
+    """
+
+    section = None
+
+    def __init__(self, root_config=None):
+        self.root = root_config
+
+    def __getattr__(self, item: str) -> Any:
+        """
+        Try and fetch a configuration option that does not exist on this class.
+
+        This is so that existing configs that rely on `self.value`, where value
+        is actually from a different config section, continue to work.
+        """
+        if item in ["generate_config_section", "read_config"]:
+            raise AttributeError(item)
+
+        if self.root is None:
+            raise AttributeError(item)
+        else:
+            return self.root._get_unclassed_config(self.section, item)
+
     @staticmethod
     def parse_size(value):
         if isinstance(value, integer_types):
@@ -88,22 +139,7 @@ class Config(object):
 
     @classmethod
     def path_exists(cls, file_path):
-        """Check if a file exists
-
-        Unlike os.path.exists, this throws an exception if there is an error
-        checking if the file exists (for example, if there is a perms error on
-        the parent dir).
-
-        Returns:
-            bool: True if the file exists; False if not.
-        """
-        try:
-            os.stat(file_path)
-            return True
-        except OSError as e:
-            if e.errno != errno.ENOENT:
-                raise e
-            return False
+        return path_exists(file_path)
 
     @classmethod
     def check_file(cls, file_path, config_name):
@@ -136,42 +172,106 @@ class Config(object):
         with open(file_path) as file_stream:
             return file_stream.read()
 
-    def invoke_all(self, name, *args, **kargs):
-        """Invoke all instance methods with the given name and arguments in the
-        class's MRO.
+
+class RootConfig(object):
+    """
+    Holder of an application's configuration.
+
+    What configuration this object holds is defined by `config_classes`, a list
+    of Config classes that will be instantiated and given the contents of a
+    configuration file to read. They can then be accessed on this class by their
+    section name, defined in the Config or dynamically set to be the name of the
+    class, lower-cased and with "Config" removed.
+    """
+
+    config_classes = []
+
+    def __init__(self):
+        self._configs = OrderedDict()
+
+        for config_class in self.config_classes:
+            if config_class.section is None:
+                raise ValueError("%r requires a section name" % (config_class,))
+
+            try:
+                conf = config_class(self)
+            except Exception as e:
+                raise Exception("Failed making %s: %r" % (config_class.section, e))
+            self._configs[config_class.section] = conf
+
+    def __getattr__(self, item: str) -> Any:
+        """
+        Redirect lookups on this object either to config objects, or values on
+        config objects, so that `config.tls.blah` works, as well as legacy uses
+        of things like `config.server_name`. It will first look up the config
+        section name, and then values on those config classes.
+        """
+        if item in self._configs.keys():
+            return self._configs[item]
+
+        return self._get_unclassed_config(None, item)
+
+    def _get_unclassed_config(self, asking_section: Optional[str], item: str):
+        """
+        Fetch a config value from one of the instantiated config classes that
+        has not been fetched directly.
+
+        Args:
+            asking_section: If this check is coming from a Config child, which
+                one? This section will not be asked if it has the value.
+            item: The configuration value key.
+
+        Raises:
+            AttributeError if no config classes have the config key. The body
+                will contain what sections were checked.
+        """
+        for key, val in self._configs.items():
+            if key == asking_section:
+                continue
+
+            if item in dir(val):
+                return getattr(val, item)
+
+        raise AttributeError(item, "not found in %s" % (list(self._configs.keys()),))
+
+    def invoke_all(self, func_name: str, *args, **kwargs) -> MutableMapping[str, Any]:
+        """
+        Invoke a function on all instantiated config objects this RootConfig is
+        configured to use.
 
         Args:
-            name (str): Name of function to invoke
+            func_name: Name of function to invoke
             *args
             **kwargs
-
         Returns:
-            list: The list of the return values from each method called
+            ordered dictionary of config section name and the result of the
+            function from it.
         """
-        results = []
-        for cls in type(self).mro():
-            if name in cls.__dict__:
-                results.append(getattr(cls, name)(self, *args, **kargs))
-        return results
+        res = OrderedDict()
+
+        for name, config in self._configs.items():
+            if hasattr(config, func_name):
+                res[name] = getattr(config, func_name)(*args, **kwargs)
+
+        return res
 
     @classmethod
-    def invoke_all_static(cls, name, *args, **kargs):
-        """Invoke all static methods with the given name and arguments in the
-        class's MRO.
+    def invoke_all_static(cls, func_name: str, *args, **kwargs):
+        """
+        Invoke a static function on config objects this RootConfig is
+        configured to use.
 
         Args:
-            name (str): Name of function to invoke
+            func_name: Name of function to invoke
             *args
             **kwargs
-
         Returns:
-            list: The list of the return values from each method called
+            ordered dictionary of config section name and the result of the
+            function from it.
         """
-        results = []
-        for c in cls.mro():
-            if name in c.__dict__:
-                results.append(getattr(c, name)(*args, **kargs))
-        return results
+        for config in cls.config_classes:
+            if hasattr(config, func_name):
+                getattr(config, func_name)(*args, **kwargs)
 
     def generate_config(
         self,
@@ -187,7 +287,8 @@ class Config(object):
         tls_private_key_path=None,
         acme_domain=None,
     ):
-        """Build a default configuration file
+        """
+        Build a default configuration file
 
         This is used when the user explicitly asks us to generate a config file
         (eg with --generate_config).
@@ -242,6 +343,7 @@ class Config(object):
         Returns:
             str: the yaml config file
         """
+
         return "\n\n".join(
             dedent(conf)
             for conf in self.invoke_all(
@@ -257,7 +359,7 @@ class Config(object):
                 tls_certificate_path=tls_certificate_path,
                 tls_private_key_path=tls_private_key_path,
                 acme_domain=acme_domain,
-            )
+            ).values()
         )
 
     @classmethod
@@ -444,7 +546,7 @@ class Config(object):
                 )
 
             (config_path,) = config_files
-            if not cls.path_exists(config_path):
+            if not path_exists(config_path):
                 print("Generating config file %s" % (config_path,))
 
                 if config_args.data_directory:
@@ -469,7 +571,7 @@ class Config(object):
                     open_private_ports=config_args.open_private_ports,
                 )
 
-                if not cls.path_exists(config_dir_path):
+                if not path_exists(config_dir_path):
                     os.makedirs(config_dir_path)
                 with open(config_path, "w") as config_file:
                     config_file.write("# vim:ft=yaml\n\n")
@@ -518,7 +620,7 @@ class Config(object):
 
         return obj
 
-    def parse_config_dict(self, config_dict, config_dir_path, data_dir_path):
+    def parse_config_dict(self, config_dict, config_dir_path=None, data_dir_path=None):
         """Read the information from the config dict into this Config object.
 
         Args:
@@ -607,3 +709,6 @@ def find_config_files(search_paths):
             else:
                 config_files.append(config_path)
     return config_files
+
+
+__all__ = ["Config", "RootConfig"]
diff --git a/synapse/config/_base.pyi b/synapse/config/_base.pyi
new file mode 100644
index 0000000000..86bc965ee4
--- /dev/null
+++ b/synapse/config/_base.pyi
@@ -0,0 +1,135 @@
+from typing import Any, List, Optional
+
+from synapse.config import (
+    api,
+    appservice,
+    captcha,
+    cas,
+    consent_config,
+    database,
+    emailconfig,
+    groups,
+    jwt_config,
+    key,
+    logger,
+    metrics,
+    password,
+    password_auth_providers,
+    push,
+    ratelimiting,
+    registration,
+    repository,
+    room_directory,
+    saml2_config,
+    server,
+    server_notices_config,
+    spam_checker,
+    stats,
+    third_party_event_rules,
+    tls,
+    tracer,
+    user_directory,
+    voip,
+    workers,
+)
+
+class ConfigError(Exception): ...
+
+MISSING_REPORT_STATS_CONFIG_INSTRUCTIONS: str
+MISSING_REPORT_STATS_SPIEL: str
+MISSING_SERVER_NAME: str
+
+def path_exists(file_path: str): ...
+
+class RootConfig:
+    server: server.ServerConfig
+    tls: tls.TlsConfig
+    database: database.DatabaseConfig
+    logging: logger.LoggingConfig
+    ratelimit: ratelimiting.RatelimitConfig
+    media: repository.ContentRepositoryConfig
+    captcha: captcha.CaptchaConfig
+    voip: voip.VoipConfig
+    registration: registration.RegistrationConfig
+    metrics: metrics.MetricsConfig
+    api: api.ApiConfig
+    appservice: appservice.AppServiceConfig
+    key: key.KeyConfig
+    saml2: saml2_config.SAML2Config
+    cas: cas.CasConfig
+    jwt: jwt_config.JWTConfig
+    password: password.PasswordConfig
+    email: emailconfig.EmailConfig
+    worker: workers.WorkerConfig
+    authproviders: password_auth_providers.PasswordAuthProviderConfig
+    push: push.PushConfig
+    spamchecker: spam_checker.SpamCheckerConfig
+    groups: groups.GroupsConfig
+    userdirectory: user_directory.UserDirectoryConfig
+    consent: consent_config.ConsentConfig
+    stats: stats.StatsConfig
+    servernotices: server_notices_config.ServerNoticesConfig
+    roomdirectory: room_directory.RoomDirectoryConfig
+    thirdpartyrules: third_party_event_rules.ThirdPartyRulesConfig
+    tracer: tracer.TracerConfig
+
+    config_classes: List = ...
+    def __init__(self) -> None: ...
+    def invoke_all(self, func_name: str, *args: Any, **kwargs: Any): ...
+    @classmethod
+    def invoke_all_static(cls, func_name: str, *args: Any, **kwargs: Any) -> None: ...
+    def __getattr__(self, item: str): ...
+    def parse_config_dict(
+        self,
+        config_dict: Any,
+        config_dir_path: Optional[Any] = ...,
+        data_dir_path: Optional[Any] = ...,
+    ) -> None: ...
+    read_config: Any = ...
+    def generate_config(
+        self,
+        config_dir_path: str,
+        data_dir_path: str,
+        server_name: str,
+        generate_secrets: bool = ...,
+        report_stats: Optional[str] = ...,
+        open_private_ports: bool = ...,
+        listeners: Optional[Any] = ...,
+        database_conf: Optional[Any] = ...,
+        tls_certificate_path: Optional[str] = ...,
+        tls_private_key_path: Optional[str] = ...,
+        acme_domain: Optional[str] = ...,
+    ): ...
+    @classmethod
+    def load_or_generate_config(cls, description: Any, argv: Any): ...
+    @classmethod
+    def load_config(cls, description: Any, argv: Any): ...
+    @classmethod
+    def add_arguments_to_parser(cls, config_parser: Any) -> None: ...
+    @classmethod
+    def load_config_with_parser(cls, parser: Any, argv: Any): ...
+    def generate_missing_files(
+        self, config_dict: dict, config_dir_path: str
+    ) -> None: ...
+
+class Config:
+    root: RootConfig
+    def __init__(self, root_config: Optional[RootConfig] = ...) -> None: ...
+    def __getattr__(self, item: str, from_root: bool = ...): ...
+    @staticmethod
+    def parse_size(value: Any): ...
+    @staticmethod
+    def parse_duration(value: Any): ...
+    @staticmethod
+    def abspath(file_path: Optional[str]): ...
+    @classmethod
+    def path_exists(cls, file_path: str): ...
+    @classmethod
+    def check_file(cls, file_path: str, config_name: str): ...
+    @classmethod
+    def ensure_directory(cls, dir_path: str): ...
+    @classmethod
+    def read_file(cls, file_path: str, config_name: str): ...
+
+def read_config_files(config_files: List[str]): ...
+def find_config_files(search_paths: List[str]): ...
diff --git a/synapse/config/api.py b/synapse/config/api.py
index dddea79a8a..74cd53a8ed 100644
--- a/synapse/config/api.py
+++ b/synapse/config/api.py
@@ -18,6 +18,8 @@ from ._base import Config
 
 
 class ApiConfig(Config):
+    section = "api"
+
     def read_config(self, config, **kwargs):
         self.room_invite_state_types = config.get(
             "room_invite_state_types",
diff --git a/synapse/config/appservice.py b/synapse/config/appservice.py
index 28d36b1bc3..9b4682222d 100644
--- a/synapse/config/appservice.py
+++ b/synapse/config/appservice.py
@@ -30,6 +30,8 @@ logger = logging.getLogger(__name__)
 
 
 class AppServiceConfig(Config):
+    section = "appservice"
+
     def read_config(self, config, **kwargs):
         self.app_service_config_files = config.get("app_service_config_files", [])
         self.notify_appservices = config.get("notify_appservices", True)
diff --git a/synapse/config/captcha.py b/synapse/config/captcha.py
index 8dac8152cf..44bd5c6799 100644
--- a/synapse/config/captcha.py
+++ b/synapse/config/captcha.py
@@ -16,6 +16,8 @@ from ._base import Config
 
 
 class CaptchaConfig(Config):
+    section = "captcha"
+
     def read_config(self, config, **kwargs):
         self.recaptcha_private_key = config.get("recaptcha_private_key")
         self.recaptcha_public_key = config.get("recaptcha_public_key")
diff --git a/synapse/config/cas.py b/synapse/config/cas.py
index ebe34d933b..b916c3aa66 100644
--- a/synapse/config/cas.py
+++ b/synapse/config/cas.py
@@ -22,6 +22,8 @@ class CasConfig(Config):
     cas_server_url: URL of CAS server
     """
 
+    section = "cas"
+
     def read_config(self, config, **kwargs):
         cas_config = config.get("cas_config", None)
         if cas_config:
diff --git a/synapse/config/consent_config.py b/synapse/config/consent_config.py
index 48976e17b1..62c4c44d60 100644
--- a/synapse/config/consent_config.py
+++ b/synapse/config/consent_config.py
@@ -73,6 +73,9 @@ DEFAULT_CONFIG = """\
 
 
 class ConsentConfig(Config):
+
+    section = "consent"
+
     def __init__(self, *args):
         super(ConsentConfig, self).__init__(*args)
 
diff --git a/synapse/config/database.py b/synapse/config/database.py
index 118aafbd4a..0e2509f0b1 100644
--- a/synapse/config/database.py
+++ b/synapse/config/database.py
@@ -21,6 +21,8 @@ from ._base import Config
 
 
 class DatabaseConfig(Config):
+    section = "database"
+
     def read_config(self, config, **kwargs):
         self.event_cache_size = self.parse_size(config.get("event_cache_size", "10K"))
 
diff --git a/synapse/config/emailconfig.py b/synapse/config/emailconfig.py
index d9b43de660..658897a77e 100644
--- a/synapse/config/emailconfig.py
+++ b/synapse/config/emailconfig.py
@@ -28,6 +28,8 @@ from ._base import Config, ConfigError
 
 
 class EmailConfig(Config):
+    section = "email"
+
     def read_config(self, config, **kwargs):
         # TODO: We should separate better the email configuration from the notification
         # and account validity config.
diff --git a/synapse/config/groups.py b/synapse/config/groups.py
index 2a522b5f44..d6862d9a64 100644
--- a/synapse/config/groups.py
+++ b/synapse/config/groups.py
@@ -17,6 +17,8 @@ from ._base import Config
 
 
 class GroupsConfig(Config):
+    section = "groups"
+
     def read_config(self, config, **kwargs):
         self.enable_group_creation = config.get("enable_group_creation", False)
         self.group_creation_prefix = config.get("group_creation_prefix", "")
diff --git a/synapse/config/homeserver.py b/synapse/config/homeserver.py
index 72acad4f18..6e348671c7 100644
--- a/synapse/config/homeserver.py
+++ b/synapse/config/homeserver.py
@@ -14,6 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from ._base import RootConfig
 from .api import ApiConfig
 from .appservice import AppServiceConfig
 from .captcha import CaptchaConfig
@@ -46,36 +47,37 @@ from .voip import VoipConfig
 from .workers import WorkerConfig
 
 
-class HomeServerConfig(
-    ServerConfig,
-    TlsConfig,
-    DatabaseConfig,
-    LoggingConfig,
-    RatelimitConfig,
-    ContentRepositoryConfig,
-    CaptchaConfig,
-    VoipConfig,
-    RegistrationConfig,
-    MetricsConfig,
-    ApiConfig,
-    AppServiceConfig,
-    KeyConfig,
-    SAML2Config,
-    CasConfig,
-    JWTConfig,
-    PasswordConfig,
-    EmailConfig,
-    WorkerConfig,
-    PasswordAuthProviderConfig,
-    PushConfig,
-    SpamCheckerConfig,
-    GroupsConfig,
-    UserDirectoryConfig,
-    ConsentConfig,
-    StatsConfig,
-    ServerNoticesConfig,
-    RoomDirectoryConfig,
-    ThirdPartyRulesConfig,
-    TracerConfig,
-):
-    pass
+class HomeServerConfig(RootConfig):
+
+    config_classes = [
+        ServerConfig,
+        TlsConfig,
+        DatabaseConfig,
+        LoggingConfig,
+        RatelimitConfig,
+        ContentRepositoryConfig,
+        CaptchaConfig,
+        VoipConfig,
+        RegistrationConfig,
+        MetricsConfig,
+        ApiConfig,
+        AppServiceConfig,
+        KeyConfig,
+        SAML2Config,
+        CasConfig,
+        JWTConfig,
+        PasswordConfig,
+        EmailConfig,
+        WorkerConfig,
+        PasswordAuthProviderConfig,
+        PushConfig,
+        SpamCheckerConfig,
+        GroupsConfig,
+        UserDirectoryConfig,
+        ConsentConfig,
+        StatsConfig,
+        ServerNoticesConfig,
+        RoomDirectoryConfig,
+        ThirdPartyRulesConfig,
+        TracerConfig,
+    ]
diff --git a/synapse/config/jwt_config.py b/synapse/config/jwt_config.py
index 36d87cef03..a568726985 100644
--- a/synapse/config/jwt_config.py
+++ b/synapse/config/jwt_config.py
@@ -23,6 +23,8 @@ MISSING_JWT = """Missing jwt library. This is required for jwt login.
 
 
 class JWTConfig(Config):
+    section = "jwt"
+
     def read_config(self, config, **kwargs):
         jwt_config = config.get("jwt_config", None)
         if jwt_config:
diff --git a/synapse/config/key.py b/synapse/config/key.py
index f039f96e9c..ec5d430afb 100644
--- a/synapse/config/key.py
+++ b/synapse/config/key.py
@@ -92,6 +92,8 @@ class TrustedKeyServer(object):
 
 
 class KeyConfig(Config):
+    section = "key"
+
     def read_config(self, config, config_dir_path, **kwargs):
         # the signing key can be specified inline or in a separate file
         if "signing_key" in config:
diff --git a/synapse/config/logger.py b/synapse/config/logger.py
index 767ecfdf09..d609ec111b 100644
--- a/synapse/config/logger.py
+++ b/synapse/config/logger.py
@@ -84,6 +84,8 @@ root:
 
 
 class LoggingConfig(Config):
+    section = "logging"
+
     def read_config(self, config, **kwargs):
         self.log_config = self.abspath(config.get("log_config"))
         self.no_redirect_stdio = config.get("no_redirect_stdio", False)
diff --git a/synapse/config/metrics.py b/synapse/config/metrics.py
index ec35a6b868..282a43bddb 100644
--- a/synapse/config/metrics.py
+++ b/synapse/config/metrics.py
@@ -34,6 +34,8 @@ class MetricsFlags(object):
 
 
 class MetricsConfig(Config):
+    section = "metrics"
+
     def read_config(self, config, **kwargs):
         self.enable_metrics = config.get("enable_metrics", False)
         self.report_stats = config.get("report_stats", None)
diff --git a/synapse/config/password.py b/synapse/config/password.py
index d5b5953f2f..2a634ac751 100644
--- a/synapse/config/password.py
+++ b/synapse/config/password.py
@@ -20,6 +20,8 @@ class PasswordConfig(Config):
     """Password login configuration
     """
 
+    section = "password"
+
     def read_config(self, config, **kwargs):
         password_config = config.get("password_config", {})
         if password_config is None:
diff --git a/synapse/config/password_auth_providers.py b/synapse/config/password_auth_providers.py
index c50e244394..9746bbc681 100644
--- a/synapse/config/password_auth_providers.py
+++ b/synapse/config/password_auth_providers.py
@@ -23,6 +23,8 @@ LDAP_PROVIDER = "ldap_auth_provider.LdapAuthProvider"
 
 
 class PasswordAuthProviderConfig(Config):
+    section = "authproviders"
+
     def read_config(self, config, **kwargs):
         self.password_providers = []  # type: List[Any]
         providers = []
diff --git a/synapse/config/push.py b/synapse/config/push.py
index 1b932722a5..0910958649 100644
--- a/synapse/config/push.py
+++ b/synapse/config/push.py
@@ -18,6 +18,8 @@ from ._base import Config
 
 
 class PushConfig(Config):
+    section = "push"
+
     def read_config(self, config, **kwargs):
         push_config = config.get("push", {})
         self.push_include_content = push_config.get("include_content", True)
diff --git a/synapse/config/ratelimiting.py b/synapse/config/ratelimiting.py
index 587e2862b7..947f653e03 100644
--- a/synapse/config/ratelimiting.py
+++ b/synapse/config/ratelimiting.py
@@ -36,6 +36,8 @@ class FederationRateLimitConfig(object):
 
 
 class RatelimitConfig(Config):
+    section = "ratelimiting"
+
     def read_config(self, config, **kwargs):
 
         # Load the new-style messages config if it exists. Otherwise fall back
diff --git a/synapse/config/registration.py b/synapse/config/registration.py
index bef89e2bf4..b3e3e6dda2 100644
--- a/synapse/config/registration.py
+++ b/synapse/config/registration.py
@@ -24,6 +24,8 @@ from synapse.util.stringutils import random_string_with_symbols
 
 
 class AccountValidityConfig(Config):
+    section = "accountvalidity"
+
     def __init__(self, config, synapse_config):
         self.enabled = config.get("enabled", False)
         self.renew_by_email_enabled = "renew_at" in config
@@ -77,6 +79,8 @@ class AccountValidityConfig(Config):
 
 
 class RegistrationConfig(Config):
+    section = "registration"
+
     def read_config(self, config, **kwargs):
         self.enable_registration = bool(
             strtobool(str(config.get("enable_registration", False)))
diff --git a/synapse/config/repository.py b/synapse/config/repository.py
index 14740891f3..d0205e14b9 100644
--- a/synapse/config/repository.py
+++ b/synapse/config/repository.py
@@ -78,6 +78,8 @@ def parse_thumbnail_requirements(thumbnail_sizes):
 
 
 class ContentRepositoryConfig(Config):
+    section = "media"
+
     def read_config(self, config, **kwargs):
 
         # Only enable the media repo if either the media repo is enabled or the
diff --git a/synapse/config/room_directory.py b/synapse/config/room_directory.py
index a92693017b..7c9f05bde4 100644
--- a/synapse/config/room_directory.py
+++ b/synapse/config/room_directory.py
@@ -19,6 +19,8 @@ from ._base import Config, ConfigError
 
 
 class RoomDirectoryConfig(Config):
+    section = "roomdirectory"
+
     def read_config(self, config, **kwargs):
         self.enable_room_list_search = config.get("enable_room_list_search", True)
 
diff --git a/synapse/config/saml2_config.py b/synapse/config/saml2_config.py
index ab34b41ca8..c407e13680 100644
--- a/synapse/config/saml2_config.py
+++ b/synapse/config/saml2_config.py
@@ -55,6 +55,8 @@ def _dict_merge(merge_dict, into_dict):
 
 
 class SAML2Config(Config):
+    section = "saml2"
+
     def read_config(self, config, **kwargs):
         self.saml2_enabled = False
 
diff --git a/synapse/config/server.py b/synapse/config/server.py
index 709bd387e5..afc4d6a4ab 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -58,6 +58,8 @@ on how to configure the new listener.
 
 
 class ServerConfig(Config):
+    section = "server"
+
     def read_config(self, config, **kwargs):
         self.server_name = config["server_name"]
         self.server_context = config.get("server_context", None)
diff --git a/synapse/config/server_notices_config.py b/synapse/config/server_notices_config.py
index 6d4285ef93..6ea2ea8869 100644
--- a/synapse/config/server_notices_config.py
+++ b/synapse/config/server_notices_config.py
@@ -59,6 +59,8 @@ class ServerNoticesConfig(Config):
             None if server notices are not enabled.
     """
 
+    section = "servernotices"
+
     def __init__(self, *args):
         super(ServerNoticesConfig, self).__init__(*args)
         self.server_notices_mxid = None
diff --git a/synapse/config/spam_checker.py b/synapse/config/spam_checker.py
index e40797ab50..36e0ddab5c 100644
--- a/synapse/config/spam_checker.py
+++ b/synapse/config/spam_checker.py
@@ -19,6 +19,8 @@ from ._base import Config
 
 
 class SpamCheckerConfig(Config):
+    section = "spamchecker"
+
     def read_config(self, config, **kwargs):
         self.spam_checker = None
 
diff --git a/synapse/config/stats.py b/synapse/config/stats.py
index b18ddbd1fa..62485189ea 100644
--- a/synapse/config/stats.py
+++ b/synapse/config/stats.py
@@ -25,6 +25,8 @@ class StatsConfig(Config):
     Configuration for the behaviour of synapse's stats engine
     """
 
+    section = "stats"
+
     def read_config(self, config, **kwargs):
         self.stats_enabled = True
         self.stats_bucket_size = 86400 * 1000
diff --git a/synapse/config/third_party_event_rules.py b/synapse/config/third_party_event_rules.py
index b3431441b9..10a99c792e 100644
--- a/synapse/config/third_party_event_rules.py
+++ b/synapse/config/third_party_event_rules.py
@@ -19,6 +19,8 @@ from ._base import Config
 
 
 class ThirdPartyRulesConfig(Config):
+    section = "thirdpartyrules"
+
     def read_config(self, config, **kwargs):
         self.third_party_event_rules = None
 
diff --git a/synapse/config/tls.py b/synapse/config/tls.py
index fc47ba3e9a..f06341eb67 100644
--- a/synapse/config/tls.py
+++ b/synapse/config/tls.py
@@ -18,6 +18,7 @@ import os
 import warnings
 from datetime import datetime
 from hashlib import sha256
+from typing import List
 
 import six
 
@@ -33,7 +34,9 @@ logger = logging.getLogger(__name__)
 
 
 class TlsConfig(Config):
-    def read_config(self, config, config_dir_path, **kwargs):
+    section = "tls"
+
+    def read_config(self, config: dict, config_dir_path: str, **kwargs):
 
         acme_config = config.get("acme", None)
         if acme_config is None:
@@ -57,7 +60,7 @@ class TlsConfig(Config):
         self.tls_certificate_file = self.abspath(config.get("tls_certificate_path"))
         self.tls_private_key_file = self.abspath(config.get("tls_private_key_path"))
 
-        if self.has_tls_listener():
+        if self.root.server.has_tls_listener():
             if not self.tls_certificate_file:
                 raise ConfigError(
                     "tls_certificate_path must be specified if TLS-enabled listeners are "
@@ -108,7 +111,7 @@ class TlsConfig(Config):
         )
 
         # Support globs (*) in whitelist values
-        self.federation_certificate_verification_whitelist = []
+        self.federation_certificate_verification_whitelist = []  # type: List[str]
         for entry in fed_whitelist_entries:
             try:
                 entry_regex = glob_to_regex(entry.encode("ascii").decode("ascii"))
diff --git a/synapse/config/tracer.py b/synapse/config/tracer.py
index 85d99a3166..8be1346113 100644
--- a/synapse/config/tracer.py
+++ b/synapse/config/tracer.py
@@ -19,6 +19,8 @@ from ._base import Config, ConfigError
 
 
 class TracerConfig(Config):
+    section = "tracing"
+
     def read_config(self, config, **kwargs):
         opentracing_config = config.get("opentracing")
         if opentracing_config is None:
diff --git a/synapse/config/user_directory.py b/synapse/config/user_directory.py
index f6313e17d4..c8d19c5d6b 100644
--- a/synapse/config/user_directory.py
+++ b/synapse/config/user_directory.py
@@ -21,6 +21,8 @@ class UserDirectoryConfig(Config):
     Configuration for the behaviour of the /user_directory API
     """
 
+    section = "userdirectory"
+
     def read_config(self, config, **kwargs):
         self.user_directory_search_enabled = True
         self.user_directory_search_all_users = False
diff --git a/synapse/config/voip.py b/synapse/config/voip.py
index 2ca0e1cf70..a68a3068aa 100644
--- a/synapse/config/voip.py
+++ b/synapse/config/voip.py
@@ -16,6 +16,8 @@ from ._base import Config
 
 
 class VoipConfig(Config):
+    section = "voip"
+
     def read_config(self, config, **kwargs):
         self.turn_uris = config.get("turn_uris", [])
         self.turn_shared_secret = config.get("turn_shared_secret")
diff --git a/synapse/config/workers.py b/synapse/config/workers.py
index 1ec4998625..fef72ed974 100644
--- a/synapse/config/workers.py
+++ b/synapse/config/workers.py
@@ -21,6 +21,8 @@ class WorkerConfig(Config):
     They have their own pid_file and listener configuration. They use the
     replication_url to talk to the main synapse process."""
 
+    section = "worker"
+
     def read_config(self, config, **kwargs):
         self.worker_app = config.get("worker_app")