Move instrument requirement into OpaClient init

Author: tpoliaw

src/blueapi/service/authorization.py

@@ -43,9 +43,11 @@ async def _call_opa(self, endpoint, data: Mapping[str, Any]) -> bool:
 
     @classmethod
     def for_config(
-        cls, instrument: str, config: OpaConfig | None
+        cls, instrument: str | None, config: OpaConfig | None
     ) -> AbstractAsyncContextManager[Self | None]:
         if config:
+            if not instrument:
+                raise ValueError("Instrument name is required for OPA client")
             return aclosing(cls(instrument, config))
         LOGGER.info("No OPA config provided - not creating OpaClient")
         return nullcontext()

src/blueapi/service/main.py

@@ -94,11 +94,9 @@ def teardown_runner():
 def lifespan(config: ApplicationConfig):
     @asynccontextmanager
     async def inner(app: FastAPI):
-        if not (meta := config.env.metadata):
-            raise ValueError("Instrument name is required in metadata")
-
+        meta = config.env.metadata
         setup_runner(config)
-        async with OpaClient.for_config(meta.instrument, config.opa) as opa:
+        async with OpaClient.for_config(meta and meta.instrument, config.opa) as opa:
             app.state.authz = opa
             yield
         teardown_runner()