lsp: Delay server ready until after features are initialized

Related to the previous commit, the server was declaring itself ready
before all the `initialized` handlers of the features were processed.

This commit therefore attempts to be more correct by delaying the
resolution of the `ready` future until after the execution of these
handlers. However, the previous commit also demonstrates how this
already insufficient to ensure correct behaviour as other
requests/notifications are free to be serviced concurrently with
`initialized`.

The "obvious" fix for this would be to move all setup code into the
`initialize` handler, but there is at least one situation where this
cannot be done and that is the configuration system. Initializing the
configuration system involves making `workspace/configuration` requests
to the client - which are forbidden until after the `initialize` result
has been sent!

As I write this, perhaps the other "obvious" solution is to have all of
the message handlers in `esbonio/server/setup.py` consult the state of
the `ready` future before proceeding... but for some reason (I can't quite
articulate why) that doesn't feel like an ideal solution...

Author: alcarney

lib/esbonio/esbonio/server/server.py

@@ -152,7 +152,6 @@ async def initialized(self, params: types.InitializedParams):
             self._register_did_change_configuration_handler(),
             self._register_did_change_watched_files_handler(),
         )
-        self._ready.set_result(True)
 
     def lsp_shutdown(self, params: None):
         """Called when the server is instructed to ``shutdown`` by the client."""

lib/esbonio/esbonio/server/setup.py

@@ -70,6 +70,7 @@ async def on_initialized(
     ):
         await ls.initialized(params)
         await call_features(ls, "initialized", params)
+        ls.ready.set_result(True)
 
     @server.feature(types.SHUTDOWN)
     async def on_shutdown(ls: EsbonioLanguageServer, params: None):