Implement is_session_init_request()

docs/usage/session.rst

@@ -338,6 +338,12 @@ To define a different session config for a given URL pattern, install
 
 .. autofunction:: scrapy_zyte_api.session_config
 
+If in a session config implementation or in any other Scrapy component you need
+to tell whether a request is a :ref:`session initialization request
+<session-init>` or not, use :func:`~scrapy_zyte_api.is_session_init_request`:
+
+.. autofunction:: scrapy_zyte_api.is_session_init_request
+
 Classes decorated with :func:`~scrapy_zyte_api.session_config` are registered
 into :data:`~scrapy_zyte_api.session_config_registry`:
 

scrapy_zyte_api/__init__.py

@@ -19,6 +19,7 @@
 from ._session import (
     ScrapyZyteAPISessionDownloaderMiddleware,
     SessionConfig,
+    is_session_init_request,
     session_config,
 )
 from ._session import session_config_registry as _session_config_registry

scrapy_zyte_api/_session.py

@@ -37,6 +37,12 @@
 ZYTE_API_META_KEYS = ("zyte_api", "zyte_api_automap", "zyte_api_provider")
 
 
+def is_session_init_request(request):
+    """Return ``True`` if the request is a :ref:`session initialization request
+    <session-init>` or ``False`` otherwise."""
+    return request.meta.get(SESSION_INIT_META_KEY, False) is True
+
+
 class SessionRetryFactory(RetryFactory):
     temporary_download_error_stop = stop_after_attempt(1)
 
@@ -362,6 +368,10 @@ def check(self, response: Response, request: Request) -> bool:
 
         The default implementation checks the outcome of the ``setLocation``
         action if a location was defined, as described in :ref:`session-check`.
+
+        If you need to tell whether *request* is a :ref:`session initialization
+        request <session-init>` or not, use
+        :func:`~scrapy_zyte_api.is_session_init_request`.
         """
         if self._checker:
             return self._checker.check(response, request)