fix(event_handler): prioritize static over dynamic route to prevent order of route registration mismatch (aws-powertools#2458)

Co-authored-by: heitorlessa <[email protected]>

Author: 2 people

aws_lambda_powertools/event_handler/api_gateway.py

@@ -483,7 +483,8 @@ def __init__(
             with api gateways with multiple custom mappings.
         """
         self._proxy_type = proxy_type
-        self._routes: List[Route] = []
+        self._dynamic_routes: List[Route] = []
+        self._static_routes: List[Route] = []
         self._route_keys: List[str] = []
         self._exception_handlers: Dict[Type, Callable] = {}
         self._cors = cors
@@ -515,7 +516,17 @@ def register_resolver(func: Callable):
                 cors_enabled = cors
 
             for item in methods:
-                self._routes.append(Route(item, self._compile_regex(rule), func, cors_enabled, compress, cache_control))
+                _route = Route(item, self._compile_regex(rule), func, cors_enabled, compress, cache_control)
+
+                # The more specific route wins.
+                # We store dynamic (/studies/{studyid}) and static routes (/studies/fetch) separately.
+                # Then attempt a match for static routes before dynamic routes.
+                # This ensures that the most specific route is prioritized and processed first (studies/fetch).
+                if _route.rule.groups > 0:
+                    self._dynamic_routes.append(_route)
+                else:
+                    self._static_routes.append(_route)
+
                 route_key = item + rule
                 if route_key in self._route_keys:
                     warnings.warn(
@@ -624,7 +635,7 @@ def _resolve(self) -> ResponseBuilder:
         """Resolves the response or return the not found response"""
         method = self.current_event.http_method.upper()
         path = self._remove_prefix(self.current_event.path)
-        for route in self._routes:
+        for route in self._static_routes + self._dynamic_routes:
             if method != route.method:
                 continue
             match_results: Optional[Match] = route.rule.match(path)

tests/functional/event_handler/test_api_gateway.py

@@ -298,7 +298,7 @@ def handler(event, context):
         return app.resolve(event, context)
 
     # Also check the route configurations
-    routes = app._routes
+    routes = app._static_routes
     assert len(routes) == 5
     for route in routes:
         if route.func == get_func:
@@ -1205,7 +1205,7 @@ def patch_func():
     app.include_router(router)
 
     # Also check check the route configurations
-    routes = app._routes
+    routes = app._static_routes
     assert len(routes) == 5
     for route in routes:
         if route.func == get_func:
@@ -1647,3 +1647,26 @@ def get_message():
     assert response["multiValueHeaders"]["Content-Type"] == [content_types.APPLICATION_JSON]
     response_body = json.loads(response["body"])
     assert response_body["message"] == "success"
+
+
+def test_route_match_prioritize_full_match():
+    # GIVEN a Http API V1, with a function registered with two routes
+    app = APIGatewayRestResolver()
+    router = Router()
+
+    @router.get("/my/{path}")
+    def dynamic_handler() -> Response:
+        return Response(200, content_types.APPLICATION_JSON, json.dumps({"hello": "dynamic"}))
+
+    @router.get("/my/path")
+    def static_handler() -> Response:
+        return Response(200, content_types.APPLICATION_JSON, json.dumps({"hello": "static"}))
+
+    app.include_router(router)
+
+    # WHEN calling the event handler with /foo/dynamic
+    response = app(LOAD_GW_EVENT, {})
+
+    # THEN the static_handler should have been called, because it fully matches the path directly
+    response_body = json.loads(response["body"])
+    assert response_body["hello"] == "static"