Fix bug in CookieJar when a cookie would be expired by mistake

Fixes aio-libs#2084

CONTRIBUTORS.txt

@@ -178,6 +178,7 @@ Will McGugan
 Willem de Groot
 Wilson Ong
 Yannick Koechlin
+Yegor Roganov
 Young-Ho Cha
 Yuriy Shatrov
 Yury Selivanov

aiohttp/cookiejar.py

@@ -74,7 +74,7 @@ def _do_expiration(self):
         cookies = self._cookies
         expirations = self._expirations
         for (domain, name), when in expirations.items():
-            if when < now:
+            if when <= now:
                 cookies[domain].pop(name, None)
                 to_del.append((domain, name))
                 self._host_only_cookies.discard((domain, name))

changes/2084.bugfix

@@ -0,0 +1 @@
+Fix issue with CookieJar incorrectly expiring cookies in some edge cases.

tests/test_cookiejar.py

@@ -1,5 +1,6 @@
 import asyncio
 import datetime
+import itertools
 import os
 import tempfile
 import unittest
@@ -577,3 +578,21 @@ def test_invalid_values(self):
 
         cookie = cookies_sent["invalid-expires-cookie"]
         self.assertEqual(cookie["expires"], "")
+
+    def test_cookie_not_expired_when_added_after_removal(self):
+        """Test case for https://github.com/aio-libs/aiohttp/issues/2084"""
+        timestamps = [533588.993, 533588.993, 533588.993,
+                      533588.993, 533589.093, 533589.093]
+
+        loop = mock.Mock()
+        loop.time.side_effect = itertools.chain(
+            timestamps, itertools.cycle([timestamps[-1]]))
+
+        jar = CookieJar(unsafe=True, loop=loop)
+        # Remove `foo` cookie.
+        jar.update_cookies(SimpleCookie('foo=""; Max-Age=0'))
+        # Set `foo` cookie to `bar`.
+        jar.update_cookies(SimpleCookie('foo="bar"'))
+
+        # Assert that there is a cookie.
+        assert len(jar) == 1