"""Simple Base for ASGI Apps."""
from __future__ import annotations
from functools import partial
from inspect import isclass
from typing import TYPE_CHECKING, Callable, Dict, List, Optional, Set, Type, Union # py38
from http_router import PrefixedRoute
from asgi_tools.router import Router
from .errors import ASGIConnectionClosedError, ASGIInvalidMethodError, ASGINotFoundError
from .logs import logger
from .middleware import LifespanMiddleware, StaticFilesMiddleware, parse_response
from .request import Request
from .response import Response, ResponseError
from .utils import iscoroutinefunction, to_awaitable
if TYPE_CHECKING:
import logging
from pathlib import Path
from http_router.types import TMethods, TPath
from .types import (
TASGIReceive,
TASGIScope,
TASGISend,
TExceptionHandler,
TVCallable,
TVExceptionHandler,
)
[docs]class App:
"""A helper to build ASGI Applications.
Features:
* Routing
* ASGI-Tools :class:`Request`, :class:`Response`
* Exception management
* Static files
* Lifespan events
* Simplest middlewares
:param debug: Enable debug mode (more logging, raise unhandled exceptions)
:type debug: bool, False
:param logger: Custom logger for the application
:type logger: logging.Logger
:param static_url_prefix: A prefix for static files
:type static_url_prefix: str, "/static"
:param static_folders: A list of folders to look static files
:type static_folders: list[str]
:param trim_last_slash: Consider "/path" and "/path/" as the same
:type trim_last_slash: bool, False
"""
exception_handlers: Dict[Type[BaseException], TExceptionHandler]
def __init__(
self,
*,
debug: bool = False,
logger: logging.Logger = logger,
static_url_prefix: str = "/static",
static_folders: Optional[List[Union[str, Path]]] = None,
trim_last_slash: bool = False,
):
"""Initialize router and lifespan middleware."""
# Register base exception handlers
self.exception_handlers = {
ASGIConnectionClosedError: to_awaitable(lambda _, __: None),
}
# Setup routing
self.router = Router(
trim_last_slash=trim_last_slash, validator=callable, converter=to_awaitable
)
# Setup logging
self.logger = logger
# Setup app
self.__app__ = self.__match__
# Setup lifespan
self.lifespan = LifespanMiddleware(
self.__process__, ignore_errors=not debug, logger=self.logger
)
# Enable middleware for static files
if static_folders and static_url_prefix:
md = StaticFilesMiddleware.setup(folders=static_folders, url_prefix=static_url_prefix)
self.middleware(md)
# Debug mode
self.debug = debug
# Handle unknown exceptions
if not debug:
async def handle_unknown_exception(_: Request, exc: BaseException) -> Response:
self.logger.exception(exc)
return ResponseError.INTERNAL_SERVER_ERROR()
self.exception_handlers[Exception] = handle_unknown_exception
self.internal_middlewares: List = []
async def __call__(self, scope: TASGIScope, receive: TASGIReceive, send: TASGISend) -> None:
"""Convert the given scope into a request and process."""
await self.lifespan(scope, receive, send)
async def __process__(self, scope: TASGIScope, receive: TASGIReceive, send: TASGISend):
"""Send ASGI messages."""
scope["app"] = self
request = Request(scope, receive, send)
try:
response: Optional[Response] = await self.__app__(request, receive, send)
if response is not None:
await response(scope, receive, send)
# Handle exceptions
except BaseException as exc: # noqa: BLE001
for etype in type(exc).mro():
if etype in self.exception_handlers:
await parse_response(
await self.exception_handlers[etype](request, exc),
)(scope, receive, send)
break
else:
if isinstance(exc, Response):
await exc(scope, receive, send)
else:
raise
async def __match__(
self, request: Request, _: TASGIReceive, send: TASGISend
) -> Optional[Response]:
"""Find and call a callback, parse a response, handle exceptions."""
scope = request.scope
path = f"{ scope.get('root_path', '') }{ scope['path'] }"
try:
match = self.router(path, scope.get("method", "GET"))
except ASGINotFoundError as exc:
raise ResponseError.NOT_FOUND() from exc
except ASGIInvalidMethodError as exc:
raise ResponseError.METHOD_NOT_ALLOWED() from exc
scope["endpoint"] = match.target
scope["path_params"] = {} if match.params is None else match.params
response = await match.target(request) # type: ignore[]
if scope["type"] == "http":
return parse_response(response)
# TODO: Do we need to close websockets automatically?
# if scope_type == "websocket" send websocket.close
return None
def __route__(self, router: Router, *prefixes: str, **_) -> "App":
"""Mount self as a nested application."""
for prefix in prefixes:
route = RouteApp(prefix, set(), target=self)
router.dynamic.insert(0, route)
return self
[docs] def middleware(self, md: TVCallable, *, insert_first: bool = False) -> TVCallable:
"""Register a middleware."""
# Register as a simple middleware
if iscoroutinefunction(md):
if md not in self.internal_middlewares:
if insert_first:
self.internal_middlewares.insert(0, md)
else:
self.internal_middlewares.append(md)
app = self.__match__
for md in reversed(self.internal_middlewares):
app = partial(md, app)
self.__app__ = app
else:
self.lifespan.bind(md(self.lifespan.app))
return md
[docs] def route(self, *paths: TPath, methods: Optional[TMethods] = None, **opts):
"""Register a route."""
return self.router.route(*paths, methods=methods, **opts)
[docs] def on_startup(self, fn: Callable) -> None:
"""Register a startup handler."""
return self.lifespan.on_startup(fn)
[docs] def on_shutdown(self, fn: Callable) -> None:
"""Register a shutdown handler."""
return self.lifespan.on_shutdown(fn)
[docs] def on_error(self, etype: Type[BaseException]):
"""Register an exception handler.
.. code-block::
@app.on_error(TimeoutError)
async def timeout(request, error):
return 'Something bad happens'
@app.on_error(ResponseError)
async def process_http_errors(request, response_error):
if response_error.status_code == 404:
return render_template('page_not_found.html'), 404
return response_error
"""
assert isclass(etype), f"Invalid exception type: {etype}"
assert issubclass(etype, BaseException), f"Invalid exception type: {etype}"
def recorder(handler: TVExceptionHandler) -> TVExceptionHandler:
self.exception_handlers[etype] = to_awaitable(handler)
return handler
return recorder
class RouteApp(PrefixedRoute):
"""Custom route to submount an application."""
def __init__(self, path: str, methods: Set, target: App):
"""Create app callable."""
path = path.rstrip("/")
def app(request: Request):
subrequest = request.__copy__(path=request.path[len(path) :])
return target.__app__(subrequest, request.receive, request.send)
super().__init__(path, methods, app)