Introduce post_init() (#1458)

* Introduce post_init()

* Add missing test

* Add missing coverage mark

* Fix typo

aiohttp/abc.py

@@ -11,6 +11,10 @@ class AbstractRouter(ABC):
     def __init__(self):
         self._frozen = False
 
+    @abstractmethod
+    def post_init(self, app):
+        pass  # pragma: no cover
+
     @property
     def frozen(self):
         return self._frozen

aiohttp/web.py

@@ -36,9 +36,11 @@ def __init__(self, *, logger=web_logger, loop=None,
         if loop is None:
             loop = asyncio.get_event_loop()
         if router is None:
-            router = web_urldispatcher.UrlDispatcher(self)
+            router = web_urldispatcher.UrlDispatcher()
         assert isinstance(router, AbstractRouter), router
 
+        router.post_init(self)
+
         if debug is ...:
             debug = loop.get_debug()
 

aiohttp/web_urldispatcher.py

@@ -710,10 +710,14 @@ class UrlDispatcher(AbstractRouter, collections.abc.Mapping):
     ROUTE_RE = re.compile(r'(\{[_a-zA-Z][^{}]*(?:\{[^{}]*\}[^{}]*)*\})')
     NAME_SPLIT_RE = re.compile(r'[.:-]')
 
-    def __init__(self, app):
+    def __init__(self):
         super().__init__()
         self._resources = []
         self._named_resources = {}
+        self._app = None
+
+    def post_init(self, app):
+        assert app is not None
         self._app = app
 
     @asyncio.coroutine
@@ -759,6 +763,9 @@ def _reg_resource(self, resource):
         assert isinstance(resource, AbstractResource), \
             'Instance of AbstractResource class is required, got {!r}'.format(
                 resource)
+        if self._app is None:
+            raise RuntimeError(".post_init() should be called before "
+                               "first resource registering")
         if self.frozen:
             raise RuntimeError("Cannot register a resource into "
                                "frozen router.")

tests/test_urldispatch.py

@@ -13,7 +13,7 @@
 from aiohttp.test_utils import make_mocked_request
 from aiohttp.web import HTTPMethodNotAllowed, HTTPNotFound, Response
 from aiohttp.web_urldispatcher import (AbstractResource, ResourceRoute,
-                                       SystemRoute, View,
+                                       SystemRoute, UrlDispatcher, View,
                                        _defaultExpectHandler)
 
 
@@ -1011,3 +1011,9 @@ def test_convert_empty_path_to_slash_on_freezing(router):
     assert resource.get_info() == {'path': ''}
     router.freeze()
     assert resource.get_info() == {'path': '/'}
+
+
+def test_add_to_non_initialized_router():
+    router = UrlDispatcher()
+    with pytest.raises(RuntimeError):
+        router.add_get('/', make_handler())