Implement req.clone() (#1361)

* Implement req.clone()

* Update CHANGES

CHANGES.rst

@@ -99,7 +99,7 @@ CHANGES
 
 - Don't flap `tcp_cork` in client code, use TCP_NODELAY mode by default.
 
--
+- Implement `web.Request.clone()` #1361
 
 -
 

aiohttp/web_reqrep.py

@@ -52,7 +52,6 @@ class Request(collections.MutableMapping, HeadersMixin):
     def __init__(self, message, payload, transport, reader, writer,
                  time_service, *,
                  secure_proxy_ssl_header=None):
-        self._app = None
         self._message = message
         self._transport = transport
         self._reader = reader
@@ -74,6 +73,41 @@ def __init__(self, message, payload, transport, reader, writer,
         self._state = {}
         self._cache = {}
 
+    def clone(self, *, method=sentinel, rel_url=sentinel,
+              headers=sentinel):
+        """Clone itself with replacement some attributes.
+
+        Creates and returns a new instance of Request object. If no parameters
+        are given, an exact copy is returned. If a parameter is not passed, it
+        will reuse the one from the current request object.
+
+        """
+
+        if self._read_bytes:
+            raise RuntimeError("Cannot clone request "
+                               "after reading it's content")
+
+        dct = {}
+        if method is not sentinel:
+            dct['method'] = method
+        if rel_url is not sentinel:
+            dct['path'] = str(URL(rel_url))
+        if headers is not sentinel:
+            dct['headers'] = CIMultiDict(headers)
+            dct['raw_headers'] = [(k.encode('utf-8'), v.encode('utf-8'))
+                                  for k, v in headers.items()]
+
+        message = self._message._replace(**dct)
+
+        return Request(
+            message,
+            self._payload,
+            self._transport,
+            self._reader,
+            self._writer,
+            self._time_service,
+            secure_proxy_ssl_header=self._secure_proxy_ssl_header)
+
     # MutableMapping API
 
     def __getitem__(self, key):

docs/web_reference.rst

@@ -277,6 +277,23 @@ like one using :meth:`Request.copy`.
       *If-Modified-Since* header is absent or is not a valid
       HTTP date.
 
+   .. method:: clone(*, method=..., rel_url=..., headers=...)
+
+      Clone itself with replacement some attributes.
+
+      Creates and returns a new instance of Request object. If no parameters
+      are given, an exact copy is returned. If a parameter is not passed, it
+      will reuse the one from the current request object.
+
+      :param str method: http method
+
+      :param rel_url: url to use, :class:`str` or :class:`~yarl.URL`
+
+      :param headers: :class:`~multidict.CIMultidict` or compatible
+                      headers container.
+
+      :return: a cloned :class:`Request` instance.
+
    .. coroutinemethod:: read()
 
       Read request body, returns :class:`bytes` object with body content.

tests/test_web_request.py

@@ -7,6 +7,7 @@
 from yarl import URL
 
 from aiohttp.protocol import HttpVersion
+from aiohttp.streams import StreamReader
 from aiohttp.test_utils import make_mocked_request
 
 
@@ -266,3 +267,54 @@ def test_rel_url(make_request):
 def test_url_url(make_request):
     req = make_request('GET', '/path', headers={'HOST': 'example.com'})
     assert URL('http://example.com/path') == req.url
+
+
+def test_clone():
+    req = make_mocked_request('GET', '/path')
+    req2 = req.clone()
+    assert req2.method == 'GET'
+    assert req2.rel_url == URL('/path')
+
+
+def test_clone_method():
+    req = make_mocked_request('GET', '/path')
+    req2 = req.clone(method='POST')
+    assert req2.method == 'POST'
+    assert req2.rel_url == URL('/path')
+
+
+def test_clone_rel_url():
+    req = make_mocked_request('GET', '/path')
+    req2 = req.clone(rel_url=URL('/path2'))
+    assert req2.rel_url == URL('/path2')
+
+
+def test_clone_rel_url_str():
+    req = make_mocked_request('GET', '/path')
+    req2 = req.clone(rel_url='/path2')
+    assert req2.rel_url == URL('/path2')
+
+
+def test_clone_headers():
+    req = make_mocked_request('GET', '/path', headers={'A': 'B'})
+    req2 = req.clone(headers=CIMultiDict({'B': 'C'}))
+    assert req2.headers == CIMultiDict({'B': 'C'})
+    assert req2.raw_headers == ((b'B', b'C'),)
+
+
+def test_clone_headers_dict():
+    req = make_mocked_request('GET', '/path', headers={'A': 'B'})
+    req2 = req.clone(headers={'B': 'C'})
+    assert req2.headers == CIMultiDict({'B': 'C'})
+    assert req2.raw_headers == ((b'B', b'C'),)
+
+
+@asyncio.coroutine
+def test_cannot_clone_after_read(loop):
+    payload = StreamReader(loop=loop)
+    payload.feed_data(b'data')
+    payload.feed_eof()
+    req = make_mocked_request('GET', '/path', payload=payload)
+    yield from req.read()
+    with pytest.raises(RuntimeError):
+        req.clone()