We should probably trim() received displaynames rather than preserving trailing/leading whitespace (SYN-647)

[matrixbot]

Submitted by @​matthew:matrix.org

(Imported from https://matrix.org/jira/browse/SYN-647)

[DMRobertson]

To do this:

• replace displayname_to_set with displayname_to_set.strip() if it is not None

  synapse/synapse/handlers/profile.py

  Lines 168 to 183 in 1f54734

  	displayname_to_set: Optional[str] = new_displayname
  	if new_displayname == "":
  	displayname_to_set = None
  	# If the admin changes the display name of a user, the requesting user cannot send
  	# the join event to update the displayname in the rooms.
  	# This must be done by the target user himself.
  	if by_admin:
  	requester = create_requester(
  	target_user,
  	authenticated_entity=requester.authenticated_entity,
  	)
  	await self.store.set_profile_displayname(
  	target_user.localpart, displayname_to_set
  	)

• add a test under in this suite

  synapse/tests/rest/client/test_profile.py

  Line 32 in 9bb2eac

  class ProfileTestCase(unittest.HomeserverTestCase):

  which demonstrates that the new logic works.

[mohit-rathee]

Well replacing displayname_to_set with displayname_to_set.strip() if it is not None may do something unintentional as if user send something like new_displayname=" " then code will save displayname_to_set="".
So let's directly trim new_displayname and then perform checks.