fix liniting issues and add type annotations

nominatim/server/sanic/server.py

@@ -7,6 +7,7 @@
 """
 Server implementation using the sanic webserver framework.
 """
+from typing import Any, Optional
 from pathlib import Path
 
 import sanic
@@ -22,18 +23,30 @@ CONTENT_TYPE = {
   'xml': 'text/xml; charset=utf-8'
 }
 
-def usage_error(msg):
+def usage_error(msg: str) -> sanic.HTTPResponse:
+    """ Format the response for an error with the query parameters.
+    """
     return sanic.response.text(msg, status=400)
 
 
-def api_response(request, result):
+def api_response(request: sanic.Request, result: Any) -> sanic.HTTPResponse:
+    """ Render a response from the query results using the configured
+        formatter.
+    """
     body = request.ctx.formatter.format(result, request.ctx.format)
     return sanic.response.text(body,
-                               content_type=CONTENT_TYPE.get(request.ctx.format, 'application/json'))
+                               content_type=CONTENT_TYPE.get(request.ctx.format,
+                                                             'application/json'))
 
 
-@api.on_request
-async def extract_format(request):
+@api.on_request # type: ignore[misc]
+async def extract_format(request: sanic.Request) -> Optional[sanic.HTTPResponse]:
+    """ Get and check the 'format' parameter and prepare the formatter.
+        `ctx.result_type` describes the expected return type and
+        `ctx.default_format` the format value to assume when no parameter
+        is present.
+    """
+    assert request.route is not None
     request.ctx.formatter = request.app.ctx.formatters[request.route.ctx.result_type]
 
     request.ctx.format = request.args.get('format', request.route.ctx.default_format)
@@ -41,13 +54,19 @@ async def extract_format(request):
         return usage_error("Parameter 'format' must be one of: " +
                            ', '.join(request.ctx.formatter.list_formats()))
 
+    return None
+
 
 @api.get('/status', ctx_result_type=StatusResult, ctx_default_format='text')
-async def status(request):
+async def status(request: sanic.Request) -> sanic.HTTPResponse:
+    """ Implementation of status endpoint.
+    """
     return api_response(request,await request.app.ctx.api.status())
 
 
 def get_application(project_dir: Path) -> sanic.Sanic:
+    """ Create a Nominatim sanic ASGI application.
+    """
     app = sanic.Sanic("NominatimInstance")
 
     app.ctx.api = NominatimAPIAsync(project_dir)
@@ -58,5 +77,3 @@ def get_application(project_dir: Path) -> sanic.Sanic:
     app.blueprint(api)
 
     return app
-
-