Implement BaseRequest.get_extra_info() (#4196)

* Add get_extra_info for BaseRequest

`BaseRequest.get_extra_info()` provides a shortcut for accessing extra
information from the underlying protocols' transport

* Add get_extra_info default value test

* Add return type annotation to BaseRequest.get_extra_info()

* Remove async from BaseRequest.get_extra_info()

* Rewrite get_extra_info test, cover all branches

* Add news entry to CHANGES for #4189

* Add Raphael Bialon to CONTRIBUTORS.txt

* Add documentation for BaseRequest.get_extra_info()

* Update web_reference.rst

Add versionadded to get_extra_info() documentation

CHANGES/4189.feature

@@ -0,0 +1 @@
+Implement BaseRequest.get_extra_info() to access a protocol transports' extra info.

CONTRIBUTORS.txt

@@ -206,6 +206,7 @@ Pepe Osca
 Philipp A.
 Pieter van Beek
 Rafael Viotti
+Raphael Bialon
 Raúl Cumplido
 Required Field
 Robert Lu

aiohttp/web_request.py

@@ -673,6 +673,18 @@ async def post(self) -> 'MultiDictProxy[Union[str, bytes, FileField]]':
         self._post = MultiDictProxy(out)
         return self._post
 
+    def get_extra_info(self, name: str, default: Any = None) -> Any:
+        """Extra info from protocol transport"""
+        protocol = self._protocol
+        if protocol is None:
+            return default
+
+        transport = protocol.transport
+        if transport is None:
+            return default
+
+        return transport.get_extra_info(name, default)
+
     def __repr__(self) -> str:
         ascii_encodable_path = self.path.encode('ascii', 'backslashreplace') \
             .decode('ascii')

docs/web_reference.rst

@@ -346,6 +346,18 @@ and :ref:`aiohttp-web-signals` handlers.
 
       :return: a cloned :class:`Request` instance.
 
+   .. method:: get_extra_info(name, default=None)
+
+      Reads extra information from the protocol's transport.
+      If no value associated with ``name`` is found, ``default`` is returned.
+
+      :param str name: The key to look up in the transport extra information.
+
+      :param default: Default value to be used when no value for ``name`` is
+                      found (default is ``None``).
+
+      .. versionadded:: 3.7
+
    .. comethod:: read()
 
       Read request body, returns :class:`bytes` object with body content.

tests/test_web_request.py

@@ -1,6 +1,7 @@
 import asyncio
 import socket
 from collections.abc import MutableMapping
+from typing import Any
 from unittest import mock
 
 import pytest
@@ -694,6 +695,31 @@ def test_url_https_with_closed_transport() -> None:
     assert str(req.url).startswith('https://')
 
 
+async def test_get_extra_info() -> None:
+    valid_key = 'test'
+    valid_value = 'existent'
+    default_value = 'default'
+
+    def get_extra_info(name: str, default: Any = None):
+        return {valid_key: valid_value}.get(name, default)
+    transp = mock.Mock()
+    transp.get_extra_info.side_effect = get_extra_info
+    req = make_mocked_request('GET', '/', transport=transp)
+
+    req_extra_info = req.get_extra_info(valid_key, default_value)
+    transp_extra_info = req._protocol.transport.get_extra_info(valid_key,
+                                                               default_value)
+    assert req_extra_info == transp_extra_info
+
+    req._protocol.transport = None
+    extra_info = req.get_extra_info(valid_key, default_value)
+    assert extra_info == default_value
+
+    req._protocol = None
+    extra_info = req.get_extra_info(valid_key, default_value)
+    assert extra_info == default_value
+
+
 def test_eq() -> None:
     req1 = make_mocked_request('GET', '/path/to?a=1&b=2')
     req2 = make_mocked_request('GET', '/path/to?a=1&b=2')