JezK
Edit File: ctx.py
import contextvars import sys import typing as t from functools import update_wrapper from types import TracebackType from werkzeug.exceptions import HTTPException from . import typing as ft from .globals import _cv_app from .globals import _cv_request from .signals import appcontext_popped from .signals import appcontext_pushed if t.TYPE_CHECKING: # pragma: no cover from .app import Flask from .sessions import SessionMixin from .wrappers import Request # a singleton sentinel value for parameter defaults _sentinel = object() class _AppCtxGlobals: """A plain object. Used as a namespace for storing data during an application context. Creating an app context automatically creates this object, which is made available as the :data:`g` proxy. .. describe:: 'key' in g Check whether an attribute is present. .. versionadded:: 0.10 .. describe:: iter(g) Return an iterator over the attribute names. .. versionadded:: 0.10 """ # Define attr methods to let mypy know this is a namespace object # that has arbitrary attributes. def __getattr__(self, name: str) -> t.Any: try: return self.__dict__[name] except KeyError: raise AttributeError(name) from None def __setattr__(self, name: str, value: t.Any) -> None: self.__dict__[name] = value def __delattr__(self, name: str) -> None: try: del self.__dict__[name] except KeyError: raise AttributeError(name) from None def get(self, name: str, default: t.Optional[t.Any] = None) -> t.Any: """Get an attribute by name, or a default value. Like :meth:`dict.get`. :param name: Name of attribute to get. :param default: Value to return if the attribute is not present. .. versionadded:: 0.10 """ return self.__dict__.get(name, default) def pop(self, name: str, default: t.Any = _sentinel) -> t.Any: """Get and remove an attribute by name. Like :meth:`dict.pop`. :param name: Name of attribute to pop. :param default: Value to return if the attribute is not present, instead of raising a ``KeyError``. .. versionadded:: 0.11 """ if default is _sentinel: return self.__dict__.pop(name) else: return self.__dict__.pop(name, default) def setdefault(self, name: str, default: t.Any = None) -> t.Any: """Get the value of an attribute if it is present, otherwise set and return a default value. Like :meth:`dict.setdefault`. :param name: Name of attribute to get. :param default: Value to set and return if the attribute is not present. .. versionadded:: 0.11 """ return self.__dict__.setdefault(name, default) def __contains__(self, item: str) -> bool: return item in self.__dict__ def __iter__(self) -> t.Iterator[str]: return iter(self.__dict__) def __repr__(self) -> str: ctx = _cv_app.get(None) if ctx is not None: return f"<flask.g of '{ctx.app.name}'>" return object.__repr__(self) def after_this_request(f: ft.AfterRequestCallable) -> ft.AfterRequestCallable: """Executes a function after this request. This is useful to modify response objects. The function is passed the response object and has to return the same or a new one. Example:: @app.route('/') def index(): @after_this_request def add_header(response): response.headers['X-Foo'] = 'Parachute' return response return 'Hello World!' This is more useful if a function other than the view function wants to modify a response. For instance think of a decorator that wants to add some headers without converting the return value into a response object. .. versionadded:: 0.9 """ ctx = _cv_request.get(None) if ctx is None: raise RuntimeError( "'after_this_request' can only be used when a request" " context is active, such as in a view function." ) ctx._after_request_functions.append(f) return f def copy_current_request_context(f: t.Callable) -> t.Callable: """A helper function that decorates a function to retain the current request context. This is useful when working with greenlets. The moment the function is decorated a copy of the request context is created and then pushed when the function is called. The current session is also included in the copied request context. Example:: import gevent from flask import copy_current_request_context @app.route('/') def index(): @copy_current_request_context def do_some_work(): # do some work here, it can access flask.request or # flask.session like you would otherwise in the view function. ... gevent.spawn(do_some_work) return 'Regular response' .. versionadded:: 0.10 """ ctx = _cv_request.get(None) if ctx is None: raise RuntimeError( "'copy_current_request_context' can only be used when a" " request context is active, such as in a view function." ) ctx = ctx.copy() def wrapper(*args, **kwargs): with ctx: return ctx.app.ensure_sync(f)(*args, **kwargs) return update_wrapper(wrapper, f) def has_request_context() -> bool: """If you have code that wants to test if a request context is there or not this function can be used. For instance, you may want to take advantage of request information if the request object is available, but fail silently if it is unavailable. :: class User(db.Model): def __init__(self, username, remote_addr=None): self.username = username if remote_addr is None and has_request_context(): remote_addr = request.remote_addr self.remote_addr = remote_addr Alternatively you can also just test any of the context bound objects (such as :class:`request` or :class:`g`) for truthness:: class User(db.Model): def __init__(self, username, remote_addr=None): self.username = username if remote_addr is None and request: remote_addr = request.remote_addr self.remote_addr = remote_addr .. versionadded:: 0.7 """ return _cv_request.get(None) is not None def has_app_context() -> bool: """Works like :func:`has_request_context` but for the application context. You can also just do a boolean check on the :data:`current_app` object instead. .. versionadded:: 0.9 """ return _cv_app.get(None) is not None class AppContext: """The app context contains application-specific information. An app context is created and pushed at the beginning of each request if one is not already active. An app context is also pushed when running CLI commands. """ def __init__(self, app: "Flask") -> None: self.app = app self.url_adapter = app.create_url_adapter(None) self.g: _AppCtxGlobals = app.app_ctx_globals_class() self._cv_tokens: t.List[contextvars.Token] = [] def push(self) -> None: """Binds the app context to the current context.""" self._cv_tokens.append(_cv_app.set(self)) appcontext_pushed.send(self.app) def pop(self, exc: t.Optional[BaseException] = _sentinel) -> None: # type: ignore """Pops the app context.""" try: if len(self._cv_tokens) == 1: if exc is _sentinel: exc = sys.exc_info()[1] self.app.do_teardown_appcontext(exc) finally: ctx = _cv_app.get() _cv_app.reset(self._cv_tokens.pop()) if ctx is not self: raise AssertionError( f"Popped wrong app context. ({ctx!r} instead of {self!r})" ) appcontext_popped.send(self.app) def __enter__(self) -> "AppContext": self.push() return self def __exit__( self, exc_type: t.Optional[type], exc_value: t.Optional[BaseException], tb: t.Optional[TracebackType], ) -> None: self.pop(exc_value) class RequestContext: """The request context contains per-request information. The Flask app creates and pushes it at the beginning of the request, then pops it at the end of the request. It will create the URL adapter and request object for the WSGI environment provided. Do not attempt to use this class directly, instead use :meth:`~flask.Flask.test_request_context` and :meth:`~flask.Flask.request_context` to create this object. When the request context is popped, it will evaluate all the functions registered on the application for teardown execution (:meth:`~flask.Flask.teardown_request`). The request context is automatically popped at the end of the request. When using the interactive debugger, the context will be restored so ``request`` is still accessible. Similarly, the test client can preserve the context after the request ends. However, teardown functions may already have closed some resources such as database connections. """ def __init__( self, app: "Flask", environ: dict, request: t.Optional["Request"] = None, session: t.Optional["SessionMixin"] = None, ) -> None: self.app = app if request is None: request = app.request_class(environ) request.json_module = app.json # type: ignore[misc] self.request: Request = request self.url_adapter = None try: self.url_adapter = app.create_url_adapter(self.request) except HTTPException as e: self.request.routing_exception = e self.flashes: t.Optional[t.List[t.Tuple[str, str]]] = None self.session: t.Optional["SessionMixin"] = session # Functions that should be executed after the request on the response # object. These will be called before the regular "after_request" # functions. self._after_request_functions: t.List[ft.AfterRequestCallable] = [] self._cv_tokens: t.List[t.Tuple[contextvars.Token, t.Optional[AppContext]]] = [] def copy(self) -> "RequestContext": """Creates a copy of this request context with the same request object. This can be used to move a request context to a different greenlet. Because the actual request object is the same this cannot be used to move a request context to a different thread unless access to the request object is locked. .. versionadded:: 0.10 .. versionchanged:: 1.1 The current session object is used instead of reloading the original data. This prevents `flask.session` pointing to an out-of-date object. """ return self.__class__( self.app, environ=self.request.environ, request=self.request, session=self.session, ) def match_request(self) -> None: """Can be overridden by a subclass to hook into the matching of the request. """ try: result = self.url_adapter.match(return_rule=True) # type: ignore self.request.url_rule, self.request.view_args = result # type: ignore except HTTPException as e: self.request.routing_exception = e def push(self) -> None: # Before we push the request context we have to ensure that there # is an application context. app_ctx = _cv_app.get(None) if app_ctx is None or app_ctx.app is not self.app: app_ctx = self.app.app_context() app_ctx.push() else: app_ctx = None self._cv_tokens.append((_cv_request.set(self), app_ctx)) # Open the session at the moment that the request context is available. # This allows a custom open_session method to use the request context. # Only open a new session if this is the first time the request was # pushed, otherwise stream_with_context loses the session. if self.session is None: session_interface = self.app.session_interface self.session = session_interface.open_session(self.app, self.request) if self.session is None: self.session = session_interface.make_null_session(self.app) # Match the request URL after loading the session, so that the # session is available in custom URL converters. if self.url_adapter is not None: self.match_request() def pop(self, exc: t.Optional[BaseException] = _sentinel) -> None: # type: ignore """Pops the request context and unbinds it by doing that. This will also trigger the execution of functions registered by the :meth:`~flask.Flask.teardown_request` decorator. .. versionchanged:: 0.9 Added the `exc` argument. """ clear_request = len(self._cv_tokens) == 1 try: if clear_request: if exc is _sentinel: exc = sys.exc_info()[1] self.app.do_teardown_request(exc) request_close = getattr(self.request, "close", None) if request_close is not None: request_close() finally: ctx = _cv_request.get() token, app_ctx = self._cv_tokens.pop() _cv_request.reset(token) # get rid of circular dependencies at the end of the request # so that we don't require the GC to be active. if clear_request: ctx.request.environ["werkzeug.request"] = None if app_ctx is not None: app_ctx.pop(exc) if ctx is not self: raise AssertionError( f"Popped wrong request context. ({ctx!r} instead of {self!r})" ) def __enter__(self) -> "RequestContext": self.push() return self def __exit__( self, exc_type: t.Optional[type], exc_value: t.Optional[BaseException], tb: t.Optional[TracebackType], ) -> None: self.pop(exc_value) def __repr__(self) -> str: return ( f"<{type(self).__name__} {self.request.url!r}" f" [{self.request.method}] of {self.app.name}>" )