set the default in OPTIONS for TOWER_URL_BASE to the request hostname

see: #5470

awx/api/metadata.py

@@ -67,7 +67,10 @@ class Metadata(metadata.SimpleMetadata):
         # Indicate if a field has a default value.
         # FIXME: Still isn't showing all default values?
         try:
-            field_info['default'] = field.get_default()
+            default = field.get_default()
+            if not default and field.field_name == 'TOWER_URL_BASE':
+                default = '{}://{}'.format(self.request.scheme, self.request.get_host())
+            field_info['default'] = default
         except serializers.SkipField:
             pass
 
@@ -167,6 +170,10 @@ class Metadata(metadata.SimpleMetadata):
         return actions
 
     def determine_metadata(self, request, view):
+        # store request on self so we can use it to generate field defaults
+        # (such as TOWER_URL_BASE)
+        self.request = request
+
         metadata = super(Metadata, self).determine_metadata(request, view)
 
         # Add version number in which view was added to Tower.

awx/main/tests/functional/api/test_settings.py

@@ -30,6 +30,7 @@ def test_license_cannot_be_removed_via_system_settings(mock_no_license_file, get
     url = reverse('api:setting_singleton_detail', args=('system',))
     response = get(url, user=admin, expect=200)
     assert not response.data['LICENSE']
+    Setting.objects.create(key='TOWER_URL_BASE', value='https://towerhost')
     Setting.objects.create(key='LICENSE', value=enterprise_license)
     response = get(url, user=admin, expect=200)
     assert response.data['LICENSE']
@@ -44,6 +45,13 @@ def test_license_cannot_be_removed_via_system_settings(mock_no_license_file, get
     assert response.data['LICENSE']
 
 
+@pytest.mark.django_db
+def test_url_base_defaults_to_request(options, admin):
+    # If TOWER_URL_BASE is not set, default to the Tower request hostname
+    resp = options(reverse('api:setting_singleton_detail', args=('system',)), user=admin, expect=200)
+    assert resp.data['actions']['PUT']['TOWER_URL_BASE']['default'] == 'http://testserver'
+
+
 @pytest.mark.django_db
 def test_jobs_settings(get, put, patch, delete, admin):
     url = reverse('api:setting_singleton_detail', args=('jobs',))

awx/settings/defaults.py

@@ -861,7 +861,7 @@ ORG_ADMINS_CAN_SEE_ALL_USERS = True
 TOWER_ADMIN_ALERTS = True
 
 # Note: This setting may be overridden by database settings.
-TOWER_URL_BASE = "https://towerhost"
+TOWER_URL_BASE = ""
 
 TOWER_SETTINGS_MANIFEST = {}