ldap: Continue syncing other fields even if a field is missing.

Earlier the behavior was to raise an exception thereby stopping the
whole sync. Now we log an error message and skip the field. Also
fixes the `query_ldap` command to report missing fields without
error.

Fixes: #11780.

zerver/management/commands/query_ldap.py

@@ -17,9 +17,9 @@ def query_ldap(**options: str) -> None:
                 print("No such user found")
             else:
                 for django_field, ldap_field in settings.AUTH_LDAP_USER_ATTR_MAP.items():
-                    value = ldap_attrs[ldap_field]
+                    value = ldap_attrs.get(ldap_field, ["LDAP field not present", ])[0]
                     if django_field == "avatar":
-                        if isinstance(value[0], bytes):
+                        if isinstance(value, bytes):
                             value = "(An avatar image file)"
                     print("%s: %s" % (django_field, value))
                 if settings.LDAP_EMAIL_ATTR is not None:

zerver/tests/test_auth_backends.py

@@ -2897,6 +2897,23 @@ class TestZulipLDAPUserPopulator(ZulipLDAPTestCase):
                 self.perform_ldap_sync(self.example_user('hamlet'))
                 f.assert_called_once_with(*expected_call_args)
 
+    def test_update_custom_profile_field_not_present_in_ldap(self) -> None:
+        self.mock_ldap.directory = {
+            'uid=hamlet,ou=users,dc=zulip,dc=com': {
+                'cn': ['King Hamlet', ],
+            }
+        }
+        hamlet = self.example_user('hamlet')
+        no_op_field = CustomProfileField.objects.get(realm=hamlet.realm, name='Birthday')
+        expected_value = CustomProfileFieldValue.objects.get(user_profile=hamlet, field=no_op_field).value
+
+        with self.settings(AUTH_LDAP_USER_ATTR_MAP={'full_name': 'cn',
+                                                    'custom_profile_field__birthday': 'birthDate'}):
+            self.perform_ldap_sync(self.example_user('hamlet'))
+
+        actual_value = CustomProfileFieldValue.objects.get(user_profile=hamlet, field=no_op_field).value
+        self.assertEqual(actual_value, expected_value)
+
 class TestZulipAuthMixin(ZulipTestCase):
     def test_get_user(self) -> None:
         backend = ZulipAuthMixin()

zproject/backends.py

@@ -347,7 +347,13 @@ class ZulipLDAPAuthBackendBase(ZulipAuthMixin, LDAPBackend):
             if not attr.startswith('custom_profile_field__'):
                 continue
             var_name = attr.split('custom_profile_field__')[1]
-            value = ldap_user.attrs[ldap_attr][0]
+            try:
+                value = ldap_user.attrs[ldap_attr][0]
+            except KeyError:
+                # If this user doesn't have this field set then ignore this
+                # field and continue syncing other fields. `django-auth-ldap`
+                # automatically logs error about missing field.
+                continue
             values_by_var_name[var_name] = value
 
         fields_by_var_name = {}   # type: Dict[str, CustomProfileField]