Create function to check for long names in devices (#8364)

* Create a new function to verify that the length of a device name is
under a certain threshold.
* Refactor old code and tests to use said function.
* Verify device name length during registration of device
* Add a test for the above

Signed-off-by: Dionysis Grigoropoulos <dgrig@erethon.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/tests/handlers/test_device.py b/tests/handlers/test_device.py
index 6aa322bf3a..969d44c787 100644
--- a/tests/handlers/test_device.py
+++ b/tests/handlers/test_device.py
@@ -35,6 +35,17 @@ class DeviceTestCase(unittest.HomeserverTestCase):
         # These tests assume that it starts 1000 seconds in.
         self.reactor.advance(1000)
 
+    def test_device_is_created_with_invalid_name(self):
+        self.get_failure(
+            self.handler.check_device_registered(
+                user_id="@boris:foo",
+                device_id="foo",
+                initial_device_display_name="a"
+                * (synapse.handlers.device.MAX_DEVICE_DISPLAY_NAME_LEN + 1),
+            ),
+            synapse.api.errors.SynapseError,
+        )
+
     def test_device_is_created_if_doesnt_exist(self):
         res = self.get_success(
             self.handler.check_device_registered(