add a flag to prevent cookies being restored from a cache hit

aiohttp_client_cache/backends/base.py

@@ -47,6 +47,7 @@ def __init__(
         autoclose: bool = False,
         cache_control: bool = False,
         filter_fn: _FilterFn = lambda r: True,
+        restore_cookies: bool = True,
         **kwargs: Any,
     ):
         """
@@ -64,6 +65,8 @@ def __init__(
             filter_fn: function that takes a :py:class:`aiohttp.ClientResponse` object and
                 returns a boolean indicating whether or not that response should be cached. Will be
                 applied to both new and previously cached responses
+            restore_cookies: Copy cookies from cached responses (and their redirects) into the
+                session's cookie jar on a cache hit
         """
         self.name = cache_name
         self.expire_after = expire_after
@@ -73,6 +76,7 @@ def __init__(
         self.cache_control = cache_control
         self.filter_fn = filter_fn
         self.autoclose = autoclose
+        self.restore_cookies = restore_cookies
         self._disabled = contextvars.ContextVar('_disabled', default=False)
 
         # Allows multiple redirects or other aliased URLs to point to the same cached response

aiohttp_client_cache/session.py

@@ -124,6 +124,8 @@ async def _request(
                 return set_response_defaults(new_response)
 
     def _restore_cookies(self, response: AnyResponse):
+        if not getattr(self.cache, 'restore_cookies', True):
+            return
         self.cookie_jar.update_cookies(response.cookies or {}, response.url)
         for redirect in response.history:
             self.cookie_jar.update_cookies(redirect.cookies or {}, redirect.url)

docs/user_guide.md

@@ -323,6 +323,16 @@ responses (on read). Example:
 >>> cache = SQLiteCache(filter_fn=filter_by_size)
 ```
 
+### Cookies
+
+By default, cookies from a cached response (and any redirects in its history) are copied into the
+session's cookie jar on a cache hit, as if the request had been sent. To keep cached responses from
+modifying the active session's cookies, use `restore_cookies=False`:
+
+```python
+>>> cache = SQLiteCache(restore_cookies=False)
+```
+
 ### Library Compatibility
 
 This library works by extending `aiohttp.ClientSession`, and there are other libraries out there

test/unit/test_session.py

@@ -164,6 +164,27 @@ async def test_session__cookies(mock_request):
     assert cookies['test_cookie'].value == 'value'
 
 
+@patch.object(ClientSession, '_request', return_value=FakeCachedResponse)
+async def test_session__cookies_not_restored(mock_request):
+    cache = MagicMock(spec=CacheBackend)
+    cache.restore_cookies = False
+    redirect = MagicMock(
+        url=URL('https://redirect.com'), cookies=SimpleCookie({'redirect_cookie': 'value'})
+    )
+    response = AsyncMock(
+        is_expired=False,
+        url=URL('https://test.com'),
+        cookies=SimpleCookie({'test_cookie': 'value'}),
+        history=[redirect],
+    )
+    cache.request.return_value = response
+
+    async with CachedSession(cache=cache) as session:
+        session.cookie_jar.clear()
+        await session.get('http://test.url')
+        assert len(session.cookie_jar) == 0
+
+
 @patch.object(ClientSession, '_request', return_value=FakeCachedResponse)
 async def test_session__redirect_cookies(mock_request):
     cache = MagicMock(spec=CacheBackend)