Work as expected with a warning on request meta copy (#116)

scrapy_zyte_smartproxy/middleware.py

@@ -3,6 +3,10 @@
 import warnings
 from base64 import urlsafe_b64decode
 from collections import defaultdict
+try:
+    from urllib.request import _parse_proxy
+except ImportError:
+    from urllib2 import _parse_proxy
 
 from six.moves.urllib.parse import urlparse, urlunparse
 from w3lib.http import basic_auth_header
@@ -17,6 +21,11 @@
 logger = logging.getLogger(__name__)
 
 
+def _remove_auth(auth_proxy_url):
+    proxy_type, user, password, hostport = _parse_proxy(auth_proxy_url)
+    return urlunparse((proxy_type, hostport, "", "", "", ""))
+
+
 class ZyteSmartProxyMiddleware(object):
 
     url = 'http://proxy.zyte.com:8011'
@@ -108,6 +117,7 @@ def open_spider(self, spider):
             return
 
         self._auth_url = self._make_auth_url(spider)
+        self._authless_url = _remove_auth(self._auth_url)
 
         logger.info(
             "Using Zyte Smart Proxy Manager at %s (apikey: %s)" % (
@@ -214,6 +224,19 @@ def process_request(self, request, spider):
         if self._is_enabled_for_request(request):
             if 'proxy' not in request.meta:
                 request.meta['proxy'] = self._auth_url
+            elif (
+                request.meta['proxy'] == self._authless_url
+                and b"Proxy-Authorization" not in request.headers
+            ):
+                logger.warning(
+                    "The value of the 'proxy' meta key of request {request} "
+                    "has no API key. You seem to have copied the value of "
+                    "the 'proxy' request meta key from a response or from a "
+                    "different request. Copying request meta keys set by "
+                    "middlewares from one request to another is a bad "
+                    "practice that can cause issues.".format(request=request)
+                )
+                request.meta['proxy'] = self._auth_url
             targets_zyte_api = self._targets_zyte_api(request)
             self._set_zyte_smartproxy_default_headers(request)
             request.meta['download_timeout'] = self.download_timeout