patx/micropie
Add middleware ability to mount subapps via `_subapp`
Commit 57973dc · patx · 2025-07-19T14:05:28-04:00
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diff --git a/docs/release_notes.md b/docs/release_notes.md
index a43eeb7..fa9c5d4 100644
--- a/docs/release_notes.md
+++ b/docs/release_notes.md
@@ -1,6 +1,7 @@
[](https://patx.github.io/micropie)
## Releases Notes
+- **[0.19](https://github.com/patx/micropie/releases/tag/v0.19)** - Easier debugging with `traceback`. Add `_sub_app` attribute to allow middleware to mount other ASGI applications
- **[0.18](https://github.com/patx/micropie/releases/tag/v0.18)** - Ensure handlers that return async generators are killed upon client disconnect to prevent memory leaks
- **[0.17](https://github.com/patx/micropie/releases/tag/v0.17)** - Change API of lifespan events to match API of middlewaress, eg. `app.startup_handlers.append(handler)`
- **[0.16](https://github.com/patx/micropie/releases/tag/v0.16)** - Add support for lifespan events using `on_startup` and `on_shutdown`
diff --git a/examples/middleware/subapp.py b/examples/middleware/subapp.py
new file mode 100644
index 0000000..84af163
--- /dev/null
+++ b/examples/middleware/subapp.py
@@ -0,0 +1,44 @@
+from micropie import App, HttpMiddleware, Request
+
+# Define the Sub-App
+class ApiApp(App):
+ async def index(self):
+ return {"message": "Welcome to the API!"}
+
+ async def users(self, user_id: str):
+ return {"user_id": user_id, "message": f"User {user_id} from API"}
+
+# Define a Middleware to Mount the Sub-App
+class SubAppMiddleware(HttpMiddleware):
+ def __init__(self, mount_path: str, subapp: App):
+ self.mount_path = mount_path.lstrip("/")
+ self.subapp = subapp
+
+ async def before_request(self, request):
+ path = request.scope["path"].lstrip("/")
+ if path.startswith(self.mount_path):
+ # Set the subapp and the remaining path
+ request._subapp = self.subapp
+ request._subapp_path = path[len(self.mount_path):].lstrip("/") or "/"
+ return None # Continue processing
+ return None # Not a subapp path, continue with main app
+
+ async def after_request(
+ self, request, status_code, response_body, extra_headers):
+ return None # No changes to response
+
+# Define the Main App
+class MainApp(App):
+ async def index(self):
+ return {"message": "Welcome to the Main App!"}
+
+ async def hello(self, name: str):
+ return {"message": f"Hello, {name} from Main App!"}
+
+# Create and Configure the Apps
+app = MainApp()
+api_app = ApiApp()
+
+# Mount the sub-app at /api
+subapp_middleware = SubAppMiddleware(mount_path="/api", subapp=api_app)
+app.middlewares.append(subapp_middleware)
diff --git a/micropie.py b/micropie.py
index 4024822..0f8ffc2 100644
--- a/micropie.py
+++ b/micropie.py
@@ -481,7 +481,12 @@ class App:
)
await self._send_response(send, status_code, response_body, extra_headers)
return
-
+ if hasattr(request, "_subapp"):
+ new_scope = dict(scope)
+ new_scope["path"] = request._subapp_path
+ new_scope["root_path"] = scope.get("root_path", "") + "/" + self.middlewares[0].mount_path
+ await request._subapp(new_scope, receive, send)
+ return
# Parse path and find handler
path: str = scope["path"].lstrip("/")
parts: List[str] = path.split("/") if path else []