mattdrayer/direct-idp-login: Allow tpa_hint to match hidden providers

common/djangoapps/third_party_auth/provider.py

@@ -43,9 +43,23 @@ class Registry(object):
         return sorted(cls._enabled_providers(), key=lambda provider: provider.name)
 
     @classmethod
-    def displayed_for_login(cls):
-        """Returns list of providers that can be used to initiate logins in the UI"""
-        return [provider for provider in cls.enabled() if provider.display_for_login]
+    def displayed_for_login(cls, tpa_hint=None):
+        """
+        Args:
+            tpa_hint (string): An override used in certain third-party authentication
+                scenarios that will cause the specified provider to be included in the
+                set along with any providers matching the 'display_for_login' criteria.
+                Note that 'provider_id' cannot have a value of None according to the
+                current implementation.
+
+        Returns:
+            List of ProviderConfig entities
+        """
+        return [
+            provider
+            for provider in cls.enabled()
+            if provider.display_for_login or provider.provider_id == tpa_hint
+        ]
 
     @classmethod
     def get(cls, provider_id):

common/djangoapps/third_party_auth/tests/test_provider.py

@@ -89,6 +89,45 @@ class RegistryTest(testutil.TestCase):
         self.assertNotIn(no_log_in_provider.provider_id, provider_ids)
         self.assertIn(normal_provider.provider_id, provider_ids)
 
+    def test_tpa_hint_provider_displayed_for_login(self):
+        """
+        Tests to ensure that an enabled-but-not-visible provider is presented
+        for use in the UI when the "tpa_hint" parameter is specified
+        """
+
+        # A hidden provider should be accessible with tpa_hint (this is the main case)
+        hidden_provider = self.configure_google_provider(visible=False, enabled=True)
+        provider_ids = [
+            idp.provider_id
+            for idp in provider.Registry.displayed_for_login(tpa_hint=hidden_provider.provider_id)
+        ]
+        self.assertIn(hidden_provider.provider_id, provider_ids)
+
+        # New providers are hidden (ie, not flagged as 'visible') by default
+        # The tpa_hint parameter should work for these providers as well
+        implicitly_hidden_provider = self.configure_linkedin_provider(enabled=True)
+        provider_ids = [
+            idp.provider_id
+            for idp in provider.Registry.displayed_for_login(tpa_hint=implicitly_hidden_provider.provider_id)
+        ]
+        self.assertIn(implicitly_hidden_provider.provider_id, provider_ids)
+
+        # Disabled providers should not be matched in tpa_hint scenarios
+        disabled_provider = self.configure_twitter_provider(visible=True, enabled=False)
+        provider_ids = [
+            idp.provider_id
+            for idp in provider.Registry.displayed_for_login(tpa_hint=disabled_provider.provider_id)
+        ]
+        self.assertNotIn(disabled_provider.provider_id, provider_ids)
+
+        # Providers not utilized for learner authentication should not match tpa_hint
+        no_log_in_provider = self.configure_lti_provider()
+        provider_ids = [
+            idp.provider_id
+            for idp in provider.Registry.displayed_for_login(tpa_hint=no_log_in_provider.provider_id)
+        ]
+        self.assertNotIn(no_log_in_provider.provider_id, provider_ids)
+
     def test_provider_enabled_for_current_site(self):
         """
         Verify that enabled_for_current_site returns True when the provider matches the current site.