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457 lines
16 KiB
457 lines
16 KiB
# -*- coding: utf-8 -*-
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"""
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flask.ctx
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~~~~~~~~~
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Implements the objects required to keep the context.
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:copyright: © 2010 by the Pallets team.
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:license: BSD, see LICENSE for more details.
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"""
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import sys
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from functools import update_wrapper
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from werkzeug.exceptions import HTTPException
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from .globals import _request_ctx_stack, _app_ctx_stack
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from .signals import appcontext_pushed, appcontext_popped
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from ._compat import BROKEN_PYPY_CTXMGR_EXIT, reraise
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# a singleton sentinel value for parameter defaults
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_sentinel = object()
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class _AppCtxGlobals(object):
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"""A plain object. Used as a namespace for storing data during an
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application context.
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Creating an app context automatically creates this object, which is
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made available as the :data:`g` proxy.
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.. describe:: 'key' in g
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Check whether an attribute is present.
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.. versionadded:: 0.10
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.. describe:: iter(g)
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Return an iterator over the attribute names.
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.. versionadded:: 0.10
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"""
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def get(self, name, default=None):
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"""Get an attribute by name, or a default value. Like
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:meth:`dict.get`.
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:param name: Name of attribute to get.
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:param default: Value to return if the attribute is not present.
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.. versionadded:: 0.10
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"""
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return self.__dict__.get(name, default)
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def pop(self, name, default=_sentinel):
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"""Get and remove an attribute by name. Like :meth:`dict.pop`.
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:param name: Name of attribute to pop.
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:param default: Value to return if the attribute is not present,
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instead of raise a ``KeyError``.
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.. versionadded:: 0.11
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"""
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if default is _sentinel:
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return self.__dict__.pop(name)
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else:
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return self.__dict__.pop(name, default)
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def setdefault(self, name, default=None):
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"""Get the value of an attribute if it is present, otherwise
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set and return a default value. Like :meth:`dict.setdefault`.
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:param name: Name of attribute to get.
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:param: default: Value to set and return if the attribute is not
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present.
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.. versionadded:: 0.11
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"""
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return self.__dict__.setdefault(name, default)
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def __contains__(self, item):
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return item in self.__dict__
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def __iter__(self):
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return iter(self.__dict__)
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def __repr__(self):
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top = _app_ctx_stack.top
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if top is not None:
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return '<flask.g of %r>' % top.app.name
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return object.__repr__(self)
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def after_this_request(f):
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"""Executes a function after this request. This is useful to modify
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response objects. The function is passed the response object and has
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to return the same or a new one.
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Example::
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@app.route('/')
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def index():
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@after_this_request
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def add_header(response):
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response.headers['X-Foo'] = 'Parachute'
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return response
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return 'Hello World!'
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This is more useful if a function other than the view function wants to
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modify a response. For instance think of a decorator that wants to add
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some headers without converting the return value into a response object.
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.. versionadded:: 0.9
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"""
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_request_ctx_stack.top._after_request_functions.append(f)
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return f
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def copy_current_request_context(f):
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"""A helper function that decorates a function to retain the current
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request context. This is useful when working with greenlets. The moment
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the function is decorated a copy of the request context is created and
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then pushed when the function is called.
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Example::
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import gevent
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from flask import copy_current_request_context
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@app.route('/')
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def index():
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@copy_current_request_context
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def do_some_work():
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# do some work here, it can access flask.request like you
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# would otherwise in the view function.
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...
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gevent.spawn(do_some_work)
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return 'Regular response'
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.. versionadded:: 0.10
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"""
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top = _request_ctx_stack.top
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if top is None:
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raise RuntimeError('This decorator can only be used at local scopes '
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'when a request context is on the stack. For instance within '
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'view functions.')
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reqctx = top.copy()
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def wrapper(*args, **kwargs):
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with reqctx:
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return f(*args, **kwargs)
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return update_wrapper(wrapper, f)
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def has_request_context():
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"""If you have code that wants to test if a request context is there or
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not this function can be used. For instance, you may want to take advantage
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of request information if the request object is available, but fail
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silently if it is unavailable.
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::
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class User(db.Model):
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def __init__(self, username, remote_addr=None):
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self.username = username
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if remote_addr is None and has_request_context():
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remote_addr = request.remote_addr
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self.remote_addr = remote_addr
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Alternatively you can also just test any of the context bound objects
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(such as :class:`request` or :class:`g` for truthness)::
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class User(db.Model):
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def __init__(self, username, remote_addr=None):
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self.username = username
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if remote_addr is None and request:
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remote_addr = request.remote_addr
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self.remote_addr = remote_addr
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.. versionadded:: 0.7
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"""
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return _request_ctx_stack.top is not None
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def has_app_context():
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"""Works like :func:`has_request_context` but for the application
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context. You can also just do a boolean check on the
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:data:`current_app` object instead.
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.. versionadded:: 0.9
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"""
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return _app_ctx_stack.top is not None
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class AppContext(object):
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"""The application context binds an application object implicitly
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to the current thread or greenlet, similar to how the
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:class:`RequestContext` binds request information. The application
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context is also implicitly created if a request context is created
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but the application is not on top of the individual application
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context.
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"""
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def __init__(self, app):
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self.app = app
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self.url_adapter = app.create_url_adapter(None)
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self.g = app.app_ctx_globals_class()
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# Like request context, app contexts can be pushed multiple times
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# but there a basic "refcount" is enough to track them.
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self._refcnt = 0
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def push(self):
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"""Binds the app context to the current context."""
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self._refcnt += 1
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if hasattr(sys, 'exc_clear'):
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sys.exc_clear()
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_app_ctx_stack.push(self)
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appcontext_pushed.send(self.app)
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def pop(self, exc=_sentinel):
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"""Pops the app context."""
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try:
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self._refcnt -= 1
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if self._refcnt <= 0:
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if exc is _sentinel:
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exc = sys.exc_info()[1]
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self.app.do_teardown_appcontext(exc)
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finally:
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rv = _app_ctx_stack.pop()
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assert rv is self, 'Popped wrong app context. (%r instead of %r)' \
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% (rv, self)
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appcontext_popped.send(self.app)
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def __enter__(self):
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self.push()
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return self
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def __exit__(self, exc_type, exc_value, tb):
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self.pop(exc_value)
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if BROKEN_PYPY_CTXMGR_EXIT and exc_type is not None:
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reraise(exc_type, exc_value, tb)
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class RequestContext(object):
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"""The request context contains all request relevant information. It is
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created at the beginning of the request and pushed to the
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`_request_ctx_stack` and removed at the end of it. It will create the
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URL adapter and request object for the WSGI environment provided.
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Do not attempt to use this class directly, instead use
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:meth:`~flask.Flask.test_request_context` and
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:meth:`~flask.Flask.request_context` to create this object.
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When the request context is popped, it will evaluate all the
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functions registered on the application for teardown execution
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(:meth:`~flask.Flask.teardown_request`).
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The request context is automatically popped at the end of the request
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for you. In debug mode the request context is kept around if
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exceptions happen so that interactive debuggers have a chance to
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introspect the data. With 0.4 this can also be forced for requests
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that did not fail and outside of ``DEBUG`` mode. By setting
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``'flask._preserve_context'`` to ``True`` on the WSGI environment the
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context will not pop itself at the end of the request. This is used by
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the :meth:`~flask.Flask.test_client` for example to implement the
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deferred cleanup functionality.
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You might find this helpful for unittests where you need the
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information from the context local around for a little longer. Make
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sure to properly :meth:`~werkzeug.LocalStack.pop` the stack yourself in
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that situation, otherwise your unittests will leak memory.
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"""
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def __init__(self, app, environ, request=None):
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self.app = app
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if request is None:
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request = app.request_class(environ)
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self.request = request
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self.url_adapter = app.create_url_adapter(self.request)
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self.flashes = None
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self.session = None
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# Request contexts can be pushed multiple times and interleaved with
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# other request contexts. Now only if the last level is popped we
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# get rid of them. Additionally if an application context is missing
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# one is created implicitly so for each level we add this information
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self._implicit_app_ctx_stack = []
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# indicator if the context was preserved. Next time another context
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# is pushed the preserved context is popped.
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self.preserved = False
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# remembers the exception for pop if there is one in case the context
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# preservation kicks in.
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self._preserved_exc = None
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# Functions that should be executed after the request on the response
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# object. These will be called before the regular "after_request"
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# functions.
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self._after_request_functions = []
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self.match_request()
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def _get_g(self):
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return _app_ctx_stack.top.g
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def _set_g(self, value):
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_app_ctx_stack.top.g = value
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g = property(_get_g, _set_g)
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del _get_g, _set_g
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def copy(self):
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"""Creates a copy of this request context with the same request object.
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This can be used to move a request context to a different greenlet.
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Because the actual request object is the same this cannot be used to
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move a request context to a different thread unless access to the
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request object is locked.
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.. versionadded:: 0.10
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"""
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return self.__class__(self.app,
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environ=self.request.environ,
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request=self.request
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)
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def match_request(self):
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"""Can be overridden by a subclass to hook into the matching
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of the request.
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"""
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try:
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url_rule, self.request.view_args = \
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self.url_adapter.match(return_rule=True)
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self.request.url_rule = url_rule
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except HTTPException as e:
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self.request.routing_exception = e
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def push(self):
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"""Binds the request context to the current context."""
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# If an exception occurs in debug mode or if context preservation is
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# activated under exception situations exactly one context stays
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# on the stack. The rationale is that you want to access that
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# information under debug situations. However if someone forgets to
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# pop that context again we want to make sure that on the next push
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# it's invalidated, otherwise we run at risk that something leaks
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# memory. This is usually only a problem in test suite since this
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# functionality is not active in production environments.
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top = _request_ctx_stack.top
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if top is not None and top.preserved:
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top.pop(top._preserved_exc)
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# Before we push the request context we have to ensure that there
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# is an application context.
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app_ctx = _app_ctx_stack.top
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if app_ctx is None or app_ctx.app != self.app:
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app_ctx = self.app.app_context()
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app_ctx.push()
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self._implicit_app_ctx_stack.append(app_ctx)
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else:
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self._implicit_app_ctx_stack.append(None)
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if hasattr(sys, 'exc_clear'):
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sys.exc_clear()
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_request_ctx_stack.push(self)
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# Open the session at the moment that the request context is available.
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# This allows a custom open_session method to use the request context.
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# Only open a new session if this is the first time the request was
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# pushed, otherwise stream_with_context loses the session.
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if self.session is None:
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session_interface = self.app.session_interface
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self.session = session_interface.open_session(
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self.app, self.request
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)
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if self.session is None:
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self.session = session_interface.make_null_session(self.app)
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def pop(self, exc=_sentinel):
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"""Pops the request context and unbinds it by doing that. This will
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also trigger the execution of functions registered by the
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:meth:`~flask.Flask.teardown_request` decorator.
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.. versionchanged:: 0.9
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Added the `exc` argument.
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"""
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app_ctx = self._implicit_app_ctx_stack.pop()
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try:
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clear_request = False
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if not self._implicit_app_ctx_stack:
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self.preserved = False
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self._preserved_exc = None
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if exc is _sentinel:
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exc = sys.exc_info()[1]
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self.app.do_teardown_request(exc)
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# If this interpreter supports clearing the exception information
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# we do that now. This will only go into effect on Python 2.x,
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# on 3.x it disappears automatically at the end of the exception
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# stack.
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if hasattr(sys, 'exc_clear'):
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sys.exc_clear()
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request_close = getattr(self.request, 'close', None)
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if request_close is not None:
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request_close()
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clear_request = True
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finally:
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rv = _request_ctx_stack.pop()
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# get rid of circular dependencies at the end of the request
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# so that we don't require the GC to be active.
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if clear_request:
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rv.request.environ['werkzeug.request'] = None
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# Get rid of the app as well if necessary.
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if app_ctx is not None:
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app_ctx.pop(exc)
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assert rv is self, 'Popped wrong request context. ' \
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'(%r instead of %r)' % (rv, self)
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def auto_pop(self, exc):
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if self.request.environ.get('flask._preserve_context') or \
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(exc is not None and self.app.preserve_context_on_exception):
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self.preserved = True
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self._preserved_exc = exc
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else:
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self.pop(exc)
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def __enter__(self):
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self.push()
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return self
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def __exit__(self, exc_type, exc_value, tb):
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# do not pop the request stack if we are in debug mode and an
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# exception happened. This will allow the debugger to still
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# access the request object in the interactive shell. Furthermore
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# the context can be force kept alive for the test client.
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# See flask.testing for how this works.
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self.auto_pop(exc_value)
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if BROKEN_PYPY_CTXMGR_EXIT and exc_type is not None:
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reraise(exc_type, exc_value, tb)
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def __repr__(self):
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return '<%s \'%s\' [%s] of %s>' % (
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self.__class__.__name__,
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self.request.url,
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self.request.method,
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self.app.name,
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)
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