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Diffstat (limited to 'python/flask/ctx.py')
| -rw-r--r-- | python/flask/ctx.py | 457 |
1 files changed, 457 insertions, 0 deletions
diff --git a/python/flask/ctx.py b/python/flask/ctx.py new file mode 100644 index 0000000..ec8e787 --- /dev/null +++ b/python/flask/ctx.py @@ -0,0 +1,457 @@ +# -*- coding: utf-8 -*- +""" + flask.ctx + ~~~~~~~~~ + + Implements the objects required to keep the context. + + :copyright: © 2010 by the Pallets team. + :license: BSD, see LICENSE for more details. +""" + +import sys +from functools import update_wrapper + +from werkzeug.exceptions import HTTPException + +from .globals import _request_ctx_stack, _app_ctx_stack +from .signals import appcontext_pushed, appcontext_popped +from ._compat import BROKEN_PYPY_CTXMGR_EXIT, reraise + + +# a singleton sentinel value for parameter defaults +_sentinel = object() + + +class _AppCtxGlobals(object): + """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 + """ + + def get(self, name, default=None): + """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, default=_sentinel): + """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 raise 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, default=None): + """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): + return item in self.__dict__ + + def __iter__(self): + return iter(self.__dict__) + + def __repr__(self): + top = _app_ctx_stack.top + if top is not None: + return '<flask.g of %r>' % top.app.name + return object.__repr__(self) + + +def after_this_request(f): + """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 + """ + _request_ctx_stack.top._after_request_functions.append(f) + return f + + +def copy_current_request_context(f): + """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. + + 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 like you + # would otherwise in the view function. + ... + gevent.spawn(do_some_work) + return 'Regular response' + + .. versionadded:: 0.10 + """ + top = _request_ctx_stack.top + if top is None: + raise RuntimeError('This decorator can only be used at local scopes ' + 'when a request context is on the stack. For instance within ' + 'view functions.') + reqctx = top.copy() + def wrapper(*args, **kwargs): + with reqctx: + return f(*args, **kwargs) + return update_wrapper(wrapper, f) + + +def has_request_context(): + """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 _request_ctx_stack.top is not None + + +def has_app_context(): + """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 _app_ctx_stack.top is not None + + +class AppContext(object): + """The application context binds an application object implicitly + to the current thread or greenlet, similar to how the + :class:`RequestContext` binds request information. The application + context is also implicitly created if a request context is created + but the application is not on top of the individual application + context. + """ + + def __init__(self, app): + self.app = app + self.url_adapter = app.create_url_adapter(None) + self.g = app.app_ctx_globals_class() + + # Like request context, app contexts can be pushed multiple times + # but there a basic "refcount" is enough to track them. + self._refcnt = 0 + + def push(self): + """Binds the app context to the current context.""" + self._refcnt += 1 + if hasattr(sys, 'exc_clear'): + sys.exc_clear() + _app_ctx_stack.push(self) + appcontext_pushed.send(self.app) + + def pop(self, exc=_sentinel): + """Pops the app context.""" + try: + self._refcnt -= 1 + if self._refcnt <= 0: + if exc is _sentinel: + exc = sys.exc_info()[1] + self.app.do_teardown_appcontext(exc) + finally: + rv = _app_ctx_stack.pop() + assert rv is self, 'Popped wrong app context. (%r instead of %r)' \ + % (rv, self) + appcontext_popped.send(self.app) + + def __enter__(self): + self.push() + return self + + def __exit__(self, exc_type, exc_value, tb): + self.pop(exc_value) + + if BROKEN_PYPY_CTXMGR_EXIT and exc_type is not None: + reraise(exc_type, exc_value, tb) + + +class RequestContext(object): + """The request context contains all request relevant information. It is + created at the beginning of the request and pushed to the + `_request_ctx_stack` and removed at the end of it. 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 + for you. In debug mode the request context is kept around if + exceptions happen so that interactive debuggers have a chance to + introspect the data. With 0.4 this can also be forced for requests + that did not fail and outside of ``DEBUG`` mode. By setting + ``'flask._preserve_context'`` to ``True`` on the WSGI environment the + context will not pop itself at the end of the request. This is used by + the :meth:`~flask.Flask.test_client` for example to implement the + deferred cleanup functionality. + + You might find this helpful for unittests where you need the + information from the context local around for a little longer. Make + sure to properly :meth:`~werkzeug.LocalStack.pop` the stack yourself in + that situation, otherwise your unittests will leak memory. + """ + + def __init__(self, app, environ, request=None): + self.app = app + if request is None: + request = app.request_class(environ) + self.request = request + self.url_adapter = app.create_url_adapter(self.request) + self.flashes = None + self.session = None + + # Request contexts can be pushed multiple times and interleaved with + # other request contexts. Now only if the last level is popped we + # get rid of them. Additionally if an application context is missing + # one is created implicitly so for each level we add this information + self._implicit_app_ctx_stack = [] + + # indicator if the context was preserved. Next time another context + # is pushed the preserved context is popped. + self.preserved = False + + # remembers the exception for pop if there is one in case the context + # preservation kicks in. + self._preserved_exc = None + + # 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 = [] + + self.match_request() + + def _get_g(self): + return _app_ctx_stack.top.g + def _set_g(self, value): + _app_ctx_stack.top.g = value + g = property(_get_g, _set_g) + del _get_g, _set_g + + def copy(self): + """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 + """ + return self.__class__(self.app, + environ=self.request.environ, + request=self.request + ) + + def match_request(self): + """Can be overridden by a subclass to hook into the matching + of the request. + """ + try: + url_rule, self.request.view_args = \ + self.url_adapter.match(return_rule=True) + self.request.url_rule = url_rule + except HTTPException as e: + self.request.routing_exception = e + + def push(self): + """Binds the request context to the current context.""" + # If an exception occurs in debug mode or if context preservation is + # activated under exception situations exactly one context stays + # on the stack. The rationale is that you want to access that + # information under debug situations. However if someone forgets to + # pop that context again we want to make sure that on the next push + # it's invalidated, otherwise we run at risk that something leaks + # memory. This is usually only a problem in test suite since this + # functionality is not active in production environments. + top = _request_ctx_stack.top + if top is not None and top.preserved: + top.pop(top._preserved_exc) + + # Before we push the request context we have to ensure that there + # is an application context. + app_ctx = _app_ctx_stack.top + if app_ctx is None or app_ctx.app != self.app: + app_ctx = self.app.app_context() + app_ctx.push() + self._implicit_app_ctx_stack.append(app_ctx) + else: + self._implicit_app_ctx_stack.append(None) + + if hasattr(sys, 'exc_clear'): + sys.exc_clear() + + _request_ctx_stack.push(self) + + # 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) + + def pop(self, exc=_sentinel): + """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. + """ + app_ctx = self._implicit_app_ctx_stack.pop() + + try: + clear_request = False + if not self._implicit_app_ctx_stack: + self.preserved = False + self._preserved_exc = None + if exc is _sentinel: + exc = sys.exc_info()[1] + self.app.do_teardown_request(exc) + + # If this interpreter supports clearing the exception information + # we do that now. This will only go into effect on Python 2.x, + # on 3.x it disappears automatically at the end of the exception + # stack. + if hasattr(sys, 'exc_clear'): + sys.exc_clear() + + request_close = getattr(self.request, 'close', None) + if request_close is not None: + request_close() + clear_request = True + finally: + rv = _request_ctx_stack.pop() + + # 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: + rv.request.environ['werkzeug.request'] = None + + # Get rid of the app as well if necessary. + if app_ctx is not None: + app_ctx.pop(exc) + + assert rv is self, 'Popped wrong request context. ' \ + '(%r instead of %r)' % (rv, self) + + def auto_pop(self, exc): + if self.request.environ.get('flask._preserve_context') or \ + (exc is not None and self.app.preserve_context_on_exception): + self.preserved = True + self._preserved_exc = exc + else: + self.pop(exc) + + def __enter__(self): + self.push() + return self + + def __exit__(self, exc_type, exc_value, tb): + # do not pop the request stack if we are in debug mode and an + # exception happened. This will allow the debugger to still + # access the request object in the interactive shell. Furthermore + # the context can be force kept alive for the test client. + # See flask.testing for how this works. + self.auto_pop(exc_value) + + if BROKEN_PYPY_CTXMGR_EXIT and exc_type is not None: + reraise(exc_type, exc_value, tb) + + def __repr__(self): + return '<%s \'%s\' [%s] of %s>' % ( + self.__class__.__name__, + self.request.url, + self.request.method, + self.app.name, + ) |