[extractor] Add _perform_login function (#2943)

* Adds new functions `_initialize_pre_login` and `_perform_login` as part of the extractor API
* Adds `ie.supports_login` to the public API

test/test_iqiyi_sdk_interpreter.py

@@ -12,11 +12,6 @@ from test.helper import FakeYDL, is_download_test
 from yt_dlp.extractor import IqiyiIE
 
 
-class IqiyiIEWithCredentials(IqiyiIE):
-    def _get_login_info(self):
-        return 'foo', 'bar'
-
-
 class WarningLogger(object):
     def __init__(self):
         self.messages = []
@@ -40,8 +35,8 @@ class TestIqiyiSDKInterpreter(unittest.TestCase):
         If `sign` is incorrect, /validate call throws an HTTP 556 error
         '''
         logger = WarningLogger()
-        ie = IqiyiIEWithCredentials(FakeYDL({'logger': logger}))
-        ie._login()
+        ie = IqiyiIE(FakeYDL({'logger': logger}))
+        ie._perform_login('foo', 'bar')
         self.assertTrue('unable to log in:' in logger.messages[0])
 
 

test/test_netrc.py

@@ -7,18 +7,19 @@ import unittest
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
 
-from yt_dlp.extractor import (
-    gen_extractors,
-)
+from yt_dlp.extractor import gen_extractor_classes
+from yt_dlp.extractor.common import InfoExtractor
+
+NO_LOGIN = InfoExtractor._perform_login
 
 
 class TestNetRc(unittest.TestCase):
     def test_netrc_present(self):
-        for ie in gen_extractors():
-            if not hasattr(ie, '_login'):
+        for ie in gen_extractor_classes():
+            if ie._perform_login is NO_LOGIN:
                 continue
             self.assertTrue(
-                hasattr(ie, '_NETRC_MACHINE'),
+                ie._NETRC_MACHINE,
                 'Extractor %s supports login, but is missing a _NETRC_MACHINE property' % ie.IE_NAME)