Manually generate the default config yaml, remove most of the commandline arguments for synapse anticipating that people will use the yaml instead. Simpify implementing config options by not requiring the classes to hit the super class

synapse/config/database.py

@@ -14,28 +14,21 @@
 # limitations under the License.
 
 from ._base import Config
-import os
-import yaml
 
 
 class DatabaseConfig(Config):
-    def __init__(self, args):
-        super(DatabaseConfig, self).__init__(args)
-        if args.database_path == ":memory:":
-            self.database_path = ":memory:"
-        else:
-            self.database_path = self.abspath(args.database_path)
-        self.event_cache_size = self.parse_size(args.event_cache_size)
 
-        if args.database_config:
-            with open(args.database_config) as f:
-                self.database_config = yaml.safe_load(f)
-        else:
+    def read_config(self, config):
+        self.event_cache_size = self.parse_size(
+            config.get("event_cache_size", "10K")
+        )
+
+        self.database_config = config.get("database")
+
+        if self.database_config is None:
             self.database_config = {
                 "name": "sqlite3",
-                "args": {
-                    "database": self.database_path,
-                },
+                "args": {},
             }
 
         name = self.database_config.get("name", None)
@@ -50,24 +43,36 @@ class DatabaseConfig(Config):
         else:
             raise RuntimeError("Unsupported database type '%s'" % (name,))
 
-    @classmethod
-    def add_arguments(cls, parser):
-        super(DatabaseConfig, cls).add_arguments(parser)
+        self.set_databasepath(config.get("database_path"))
+
+    def default_config(self, config, config_dir_path):
+        database_path = self.abspath("homeserver.db")
+        return """\
+        # Database configuration
+        database:
+          # The database engine name
+          name: "sqlite3"
+          # Arguments to pass to the engine
+          args:
+            # Path to the database
+            database: "%(database_path)s"
+        # Number of events to cache in memory.
+        event_cache_size: "10K"
+        """ % locals()
+
+    def read_arguments(self, args):
+        self.set_databasepath(args.database_path)
+
+    def set_databasepath(self, database_path):
+        if database_path != ":memory:":
+            database_path = self.abspath(database_path)
+        if self.database_config.get("name", None) == "sqlite3":
+            if database_path is not None:
+                self.database_config["database"] = database_path
+
+    def add_arguments(self, parser):
         db_group = parser.add_argument_group("database")
         db_group.add_argument(
-            "-d", "--database-path", default="homeserver.db",
-            metavar="SQLITE_DATABASE_PATH", help="The database name."
+            "-d", "--database-path", metavar="SQLITE_DATABASE_PATH",
+            help="The path to a sqlite database to use."
         )
-        db_group.add_argument(
-            "--event-cache-size", default="100K",
-            help="Number of events to cache in memory."
-        )
-        db_group.add_argument(
-            "--database-config", default=None,
-            help="Location of the database configuration file."
-        )
-
-    @classmethod
-    def generate_config(cls, args, config_dir_path):
-        super(DatabaseConfig, cls).generate_config(args, config_dir_path)
-        args.database_path = os.path.abspath(args.database_path)