Request config (#2949)

CHANGES/2949.feature

@@ -0,0 +1 @@
+Add ``request.config_dict`` for exposing nested applications data.

aiohttp/helpers.py

@@ -14,6 +14,7 @@
 import time
 import weakref
 from collections import namedtuple
+from collections.abc import Mapping
 from contextlib import suppress
 from math import ceil
 from pathlib import Path
@@ -30,7 +31,7 @@
 from .log import client_logger
 
 
-__all__ = ('BasicAuth',)
+__all__ = ('BasicAuth', 'ChainMapProxy')
 
 PY_36 = sys.version_info >= (3, 6)
 PY_37 = sys.version_info >= (3, 7)
@@ -741,3 +742,46 @@ def set_result(fut, result):
 def set_exception(fut, exc):
     if not fut.done():
         fut.set_exception(exc)
+
+
+class ChainMapProxy(Mapping):
+    __slots__ = ('_maps',)
+
+    def __init__(self, maps):
+        self._maps = tuple(maps)
+
+    def __init_subclass__(cls):
+        raise TypeError("Inheritance class {} from ChainMapProxy "
+                        "is forbidden".format(cls.__name__))
+
+    def __getitem__(self, key):
+        for mapping in self._maps:
+            try:
+                return mapping[key]
+            except KeyError:
+                pass
+        raise KeyError(key)
+
+    def get(self, key, default=None):
+        return self[key] if key in self else default
+
+    def __len__(self):
+        # reuses stored hash values if possible
+        return len(set().union(*self._maps))
+
+    def __iter__(self):
+        d = {}
+        for mapping in reversed(self._maps):
+            # reuses stored hash values if possible
+            d.update(mapping)
+        return iter(d)
+
+    def __contains__(self, key):
+        return any(key in m for m in self._maps)
+
+    def __bool__(self):
+        return any(self._maps)
+
+    def __repr__(self):
+        content = ", ".join(map(repr, self._maps))
+        return 'ChainMapProxy({})'.format(content)

aiohttp/web_request.py

@@ -19,7 +19,7 @@
 from yarl import URL
 
 from . import hdrs, multipart
-from .helpers import DEBUG, HeadersMixin, reify, sentinel
+from .helpers import DEBUG, ChainMapProxy, HeadersMixin, reify, sentinel
 from .streams import EmptyStreamReader
 from .web_exceptions import HTTPRequestEntityTooLarge
 
@@ -664,6 +664,14 @@ def app(self):
         """Application instance."""
         return self._match_info.current_app
 
+    @property
+    def config_dict(self):
+        lst = self._match_info.apps
+        app = self.app
+        idx = lst.index(app)
+        sublist = list(reversed(lst[:idx + 1]))
+        return ChainMapProxy(sublist)
+
     async def _prepare_hook(self, response):
         match_info = self._match_info
         if match_info is None:

docs/structures.rst

@@ -0,0 +1,55 @@
+.. _aiohttp-structures:
+
+
+Common data structures
+======================
+
+.. module:: aiohttp
+
+.. currentmodule:: aiohttp
+
+
+Common data structures used by *aiohttp* internally.
+
+
+FrozenList
+----------
+
+A list-like structure which implements
+:class:`collections.abc.MutableSequence`.
+
+The list is *mutable* unless :meth:`FrozenList.freeze` is called,
+after that the list modification raises :exc:`RuntimeError`.
+
+
+.. class:: FrozenList(items)
+
+   Construct a new *non-frozen* list from *items* iterable.
+
+   The list implements all :class:`collections.abc.MutableSequence`
+   methods plus two additional APIs.
+
+   .. attribute:: frozen
+
+      A read-only property, ``True`` is the list is *frozen*
+      (modifications are forbidden).
+
+   .. method:: freeze()
+
+      Freeze the list. There is no way to *thaw* it back.
+
+
+ChainMapProxy
+-------------
+
+An *immutable* version of :class:`collections.ChainMap`.  Internally
+the proxy is a list of mappings (dictionaries), if the requested key
+is not present in the first mapping the second is looked up and so on.
+
+The class supports :class:`collections.abc.Mapping` interface.
+
+.. class:: ChainMapProxy(maps)
+
+   Create a new chained mapping proxy from a list of mappings (*maps*).
+
+   .. versionadded:: 3.2

docs/utilities.rst

@@ -16,4 +16,5 @@ Miscellaneous API Shared between Client And Server.
    multipart_reference
    streams
    signals
+   structures
    websocket_utilities

docs/web_advanced.rst

@@ -96,7 +96,7 @@ internal data structures and could terminate them gracefully::
    app.router.add_get('/', handler)
 
 All not finished jobs will be terminated on
-:attr:`aiohttp.web.Application.on_cleanup` signal.
+:attr:`Application.on_cleanup` signal.
 
 To prevent cancellation of the whole :term:`web-handler` use
 ``@atomic`` decorator::
@@ -306,7 +306,7 @@ handling every incoming request.
 .. warning::
 
    Parallel reads from websocket are forbidden, there is no
-   possibility to call :meth:`aiohttp.web.WebSocketResponse.receive`
+   possibility to call :meth:`WebSocketResponse.receive`
    from two tasks.
 
    See :ref:`FAQ section <aiohttp_faq_parallel_event_sources>` for
@@ -321,12 +321,18 @@ Data Sharing aka No Singletons Please
 :mod:`aiohttp.web` discourages the use of *global variables*, aka *singletons*.
 Every variable should have its own context that is *not global*.
 
-So, :class:`aiohttp.web.Application` and :class:`aiohttp.web.Request`
+So, :class:`Application` and :class:`Request`
 support a :class:`collections.abc.MutableMapping` interface (i.e. they are
 dict-like objects), allowing them to be used as data stores.
 
+
+.. _aiohttp-web-data-sharing-app-config:
+
+Application's config
+^^^^^^^^^^^^^^^^^^^^
+
 For storing *global-like* variables, feel free to save them in an
-:class:`~.Application` instance::
+:class:`Application` instance::
 
     app['my_private_key'] = data
 
@@ -335,8 +341,24 @@ and get it back in the :term:`web-handler`::
     async def handler(request):
         data = request.app['my_private_key']
 
-Variables that are only needed for the lifetime of a :class:`~.Request`, can be
-stored in a :class:`~.Request`::
+In case of :ref:`nested applications
+<aiohttp-web-nested-applications>` the desired lookup strategy could
+be the following:
+
+1. Search the key in the current nested application.
+2. If the key is not found continue searching in the parent application(s).
+
+For this please use :attr:`Request.config_dict` read-only property::
+
+    async def handler(request):
+        data = request.config_dict['my_private_key']
+
+
+Request's storage
+^^^^^^^^^^^^^^^^^
+
+Variables that are only needed for the lifetime of a :class:`Request`, can be
+stored in a :class:`Request`::
 
     async def handler(request):
       request['my_private_key'] = "data"
@@ -346,7 +368,10 @@ This is mostly useful for :ref:`aiohttp-web-middlewares` and
 :ref:`aiohttp-web-signals` handlers to store data for further processing by the
 next handlers in the chain.
 
-:class:`aiohttp.web.StreamResponse` and :class:`aiohttp.web.Response` objects
+Response's storage
+^^^^^^^^^^^^^^^^^^
+
+:class:`StreamResponse` and :class:`Response` objects
 also support :class:`collections.abc.MutableMapping` interface. This is useful
 when you want to share data with signals and middlewares once all the work in
 the handler is done::
@@ -357,6 +382,9 @@ the handler is done::
       return response
 
 
+Naming hint
+^^^^^^^^^^^
+
 To avoid clashing with other *aiohttp* users and third-party libraries, please
 choose a unique key name for storing data.
 
@@ -392,8 +420,8 @@ response. For example, here's a simple *middleware* which appends
 Every *middleware* should accept two parameters, a :class:`request
 <Request>` instance and a *handler*, and return the response or raise
 an exception. If the exception is not an instance of
-:exc:`aiohttp.web.HTTPException` it is converted to ``500``
-:exc:`aiohttp.web.HTTPInternalServerError` after processing the
+:exc:`HTTPException` it is converted to ``500``
+:exc:`HTTPInternalServerError` after processing the
 middlewares chain.
 
 .. warning::
@@ -507,19 +535,19 @@ has been prepared, they can't customize a :class:`Response` **while** it's
 being prepared. For this :mod:`aiohttp.web` provides *signals*.
 
 For example, a middleware can only change HTTP headers for *unprepared*
-responses (see :meth:`~aiohttp.web.StreamResponse.prepare`), but sometimes we
+responses (see :meth:`StreamResponse.prepare`), but sometimes we
 need a hook for changing HTTP headers for streamed responses and WebSockets.
 This can be accomplished by subscribing to the
-:attr:`~aiohttp.web.Application.on_response_prepare` signal::
+:attr:`Application.on_response_prepare` signal::
 
     async def on_prepare(request, response):
         response.headers['My-Header'] = 'value'
 
     app.on_response_prepare.append(on_prepare)
 
 
-Additionally, the :attr:`~aiohttp.web.Application.on_startup` and
-:attr:`~aiohttp.web.Application.on_cleanup` signals can be subscribed to for
+Additionally, the :attr:`Application.on_startup` and
+:attr:`Application.on_cleanup` signals can be subscribed to for
 application component setup and tear down accordingly.
 
 The following example will properly initialize and dispose an aiopg connection
@@ -621,7 +649,7 @@ toolbar URLs are served by prefix like ``/admin``.
 
 Thus we'll create a totally separate application named ``admin`` and
 connect it to main app with prefix by
-:meth:`~aiohttp.web.Application.add_subapp`::
+:meth:`Application.add_subapp`::
 
    admin = web.Application()
    # setup admin routes, signals and middlewares
@@ -635,13 +663,13 @@ It means that if URL is ``'/admin/something'`` middlewares from
 the call chain.
 
 The same is going for
-:attr:`~aiohttp.web.Application.on_response_prepare` signal -- the
+:attr:`Application.on_response_prepare` signal -- the
 signal is delivered to both top level ``app`` and ``admin`` if
 processing URL is routed to ``admin`` sub-application.
 
-Common signals like :attr:`~aiohttp.web.Application.on_startup`,
-:attr:`~aiohttp.web.Application.on_shutdown` and
-:attr:`~aiohttp.web.Application.on_cleanup` are delivered to all
+Common signals like :attr:`Application.on_startup`,
+:attr:`Application.on_shutdown` and
+:attr:`Application.on_cleanup` are delivered to all
 registered sub-applications. The passed parameter is sub-application
 instance, not top-level application.
 
@@ -895,8 +923,8 @@ As discussed in :ref:`aiohttp-deployment` the preferable way is
 deploying *aiohttp* web server behind a *Reverse Proxy Server* like
 :term:`nginx` for production usage.
 
-In this way properties like :attr:`~BaseRequest.scheme`
-:attr:`~BaseRequest.host` and :attr:`~BaseRequest.remote` are
+In this way properties like :attr:`BaseRequest.scheme`
+:attr:`BaseRequest.host` and :attr:`BaseRequest.remote` are
 incorrect.
 
 Real values should be given from proxy server, usually either
@@ -910,9 +938,9 @@ headers too, pushing non-trusted data values.
 That's why *aiohttp server* should setup *forwarded* headers in custom
 middleware in tight conjunction with *reverse proxy configuration*.
 
-For changing :attr:`~BaseRequest.scheme` :attr:`~BaseRequest.host` and
-:attr:`~BaseRequest.remote` the middleware might use
-:meth:`~BaseRequest.clone`.
+For changing :attr:`BaseRequest.scheme` :attr:`BaseRequest.host` and
+:attr:`BaseRequest.remote` the middleware might use
+:meth:`BaseRequest.clone`.
 
 .. seealso::
 

docs/web_reference.rst

@@ -489,6 +489,16 @@ and :ref:`aiohttp-web-signals` handlers.
       An :class:`Application` instance used to call :ref:`request handler
       <aiohttp-web-handler>`, Read-only property.
 
+   .. attribute:: config_dict
+
+      A :class:`aiohttp.ChainMapProxy` instance for mapping all properties
+      from the current application returned by :attr:`app` property
+      and all its parents.
+
+      .. seealso:: :ref:`aiohttp-web-data-sharing-app-config`
+
+      .. versionadded:: 3.2
+
    .. note::
 
       You should never create the :class:`Request` instance manually
@@ -498,6 +508,7 @@ and :ref:`aiohttp-web-signals` handlers.
 
 
 
+
 .. _aiohttp-web-response: