[App] PoC: Add support for Request (#16047)

.gitignore

@@ -110,8 +110,8 @@ celerybeat-schedule
 
 # dotenv
 .env
-.env_staging
-.env_local
+.env.staging
+.env.local
 
 # virtualenv
 .venv

src/lightning_app/CHANGELOG.md

@@ -13,6 +13,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Added a progres bar while connecting to an app through the CLI ([#16035](https://github.com/Lightning-AI/lightning/pull/16035))
 
 
+- Added partial support for fastapi `Request` annotation in `configure_api` handlers ([#16047](https://github.com/Lightning-AI/lightning/pull/16047))
+
+
 ### Changed
 
 -

src/lightning_app/api/http_methods.py

@@ -2,12 +2,14 @@ import asyncio
 import inspect
 import time
 from copy import deepcopy
+from dataclasses import dataclass
 from functools import wraps
 from multiprocessing import Queue
 from typing import Any, Callable, Dict, List, Optional
 from uuid import uuid4
 
-from fastapi import FastAPI, HTTPException
+from fastapi import FastAPI, HTTPException, Request
+from lightning_utilities.core.apply_func import apply_to_collection
 
 from lightning_app.api.request_types import _APIRequest, _CommandRequest, _RequestResponse
 from lightning_app.utilities.app_helpers import Logger
@@ -19,6 +21,77 @@ def _signature_proxy_function():
     pass
 
 
+@dataclass
+class _FastApiMockRequest:
+    """This class is meant to mock FastAPI Request class that isn't pickle-able.
+
+    If a user relies on FastAPI Request annotation, the Lightning framework
+    patches the annotation before pickling and replace them right after.
+
+    Finally, the FastAPI request is converted back to the _FastApiMockRequest
+    before being delivered to the users.
+
+    Example:
+
+        import lightning as L
+        from fastapi import Request
+        from lightning.app.api import Post
+
+        class Flow(L.LightningFlow):
+
+            def request(self, request: Request) -> OutputRequestModel:
+                ...
+
+            def configure_api(self):
+                return [Post("/api/v1/request", self.request)]
+    """
+
+    _body: Optional[str] = None
+    _json: Optional[str] = None
+    _method: Optional[str] = None
+    _headers: Optional[Dict] = None
+
+    @property
+    def receive(self):
+        raise NotImplementedError
+
+    @property
+    def method(self):
+        raise self._method
+
+    @property
+    def headers(self):
+        return self._headers
+
+    def body(self):
+        return self._body
+
+    def json(self):
+        return self._json
+
+    def stream(self):
+        raise NotImplementedError
+
+    def form(self):
+        raise NotImplementedError
+
+    def close(self):
+        raise NotImplementedError
+
+    def is_disconnected(self):
+        raise NotImplementedError
+
+
+async def _mock_fastapi_request(request: Request):
+    # TODO: Add more requests parameters.
+    return _FastApiMockRequest(
+        _body=await request.body(),
+        _json=await request.json(),
+        _headers=request.headers,
+        _method=request.method,
+    )
+
+
 class _HttpMethod:
     def __init__(self, route: str, method: Callable, method_name: Optional[str] = None, timeout: int = 30, **kwargs):
         """This class is used to inject user defined methods within the App Rest API.
@@ -34,6 +107,7 @@ class _HttpMethod:
         self.method_annotations = method.__annotations__
         # TODO: Validate the signature contains only pydantic models.
         self.method_signature = inspect.signature(method)
+
         if not self.attached_to_flow:
             self.component_name = method.__name__
             self.method = method
@@ -43,10 +117,16 @@ class _HttpMethod:
         self.timeout = timeout
         self.kwargs = kwargs
 
+        # Enable the users to rely on FastAPI annotation typing with Request.
+        # Note: Only a part of the Request functionatilities are supported.
+        self._patch_fast_api_request()
+
     def add_route(self, app: FastAPI, request_queue: Queue, responses_store: Dict[str, Any]) -> None:
         # 1: Get the route associated with the http method.
         route = getattr(app, self.__class__.__name__.lower())
 
+        self._unpatch_fast_api_request()
+
         # 2: Create a proxy function with the signature of the wrapped method.
         fn = deepcopy(_signature_proxy_function)
         fn.__annotations__ = self.method_annotations
@@ -69,6 +149,11 @@ class _HttpMethod:
             @wraps(_signature_proxy_function)
             async def _handle_request(*args, **kwargs):
                 async def fn(*args, **kwargs):
+                    args, kwargs = apply_to_collection((args, kwargs), Request, _mock_fastapi_request)
+                    for k, v in kwargs.items():
+                        if hasattr(v, "__await__"):
+                            kwargs[k] = await v
+
                     request_id = str(uuid4()).split("-")[0]
                     logger.debug(f"Processing request {request_id} for route: {self.route}")
                     request_queue.put(
@@ -101,6 +186,26 @@ class _HttpMethod:
         # 4: Register the user provided route to the Rest API.
         route(self.route, **self.kwargs)(_handle_request)
 
+    def _patch_fast_api_request(self):
+        """This function replaces signature annotation for Request with its mock."""
+        for k, v in self.method_annotations.items():
+            if v == Request:
+                self.method_annotations[k] = _FastApiMockRequest
+
+        for v in self.method_signature.parameters.values():
+            if v._annotation == Request:
+                v._annotation = _FastApiMockRequest
+
+    def _unpatch_fast_api_request(self):
+        """This function replaces back signature annotation to fastapi Request."""
+        for k, v in self.method_annotations.items():
+            if v == _FastApiMockRequest:
+                self.method_annotations[k] = Request
+
+        for v in self.method_signature.parameters.values():
+            if v._annotation == _FastApiMockRequest:
+                v._annotation = Request
+
 
 class Post(_HttpMethod):
     pass

tests/tests_app/core/test_lightning_api.py

@@ -12,7 +12,7 @@ import aiohttp
 import pytest
 import requests
 from deepdiff import DeepDiff, Delta
-from fastapi import HTTPException
+from fastapi import HTTPException, Request
 from httpx import AsyncClient
 from pydantic import BaseModel
 
@@ -479,10 +479,13 @@ class FlowAPI(LightningFlow):
         if self.counter == 501:
             self._exit()
 
-    def request(self, config: InputRequestModel) -> OutputRequestModel:
+    def request(self, config: InputRequestModel, request: Request) -> OutputRequestModel:
         self.counter += 1
         if config.index % 5 == 0:
             raise HTTPException(status_code=400, detail="HERE")
+        assert request.body()
+        assert request.json()
+        assert request.headers
         return OutputRequestModel(name=config.name, counter=self.counter)
 
     def configure_api(self):