users: Allow zero-width-joiners in user names.

Partially fixes: #20128.

zerver/lib/users.py

@@ -23,6 +23,7 @@ from zerver.lib.exceptions import (
     OrganizationAdministratorRequiredError,
     OrganizationOwnerRequiredError,
 )
+from zerver.lib.string_validation import check_string_is_printable
 from zerver.lib.timestamp import timestamp_to_datetime
 from zerver.lib.timezone import canonicalize_timezone
 from zerver.lib.types import ProfileDataElementUpdateDict, ProfileDataElementValue, RawUserDict
@@ -59,9 +60,10 @@ def check_full_name(
         raise JsonableError(_("Name too long!"))
     if len(full_name) < UserProfile.MIN_NAME_LENGTH:
         raise JsonableError(_("Name too short!"))
-    for character in full_name:
-        if unicodedata.category(character)[0] == "C" or character in UserProfile.NAME_INVALID_CHARS:
-            raise JsonableError(_("Invalid characters in name!"))
+    if check_string_is_printable(full_name) is not None or any(
+        character in full_name for character in UserProfile.NAME_INVALID_CHARS
+    ):
+        raise JsonableError(_("Invalid characters in name!"))
     # Names ending with e.g. `|15` could be ambiguous for
     # sloppily-written parsers of our Markdown syntax for mentioning
     # users with ambiguous names, and likely have no real use, so we

zerver/tests/test_settings.py

@@ -125,6 +125,14 @@ class ChangeSettingsTest(ZulipTestCase):
     def test_illegal_characters_in_name_changes(self) -> None:
         self.login("hamlet")
 
+        # Make sure unicode works
+        json_result = self.client_patch("/json/settings", dict(full_name="BLÅHAJ"))
+        self.assert_json_success(json_result)
+
+        # Make sure zero-width-joiners work
+        json_result = self.client_patch("/json/settings", dict(full_name="BLÅHAJ 🏳️‍⚧️"))
+        self.assert_json_success(json_result)
+
         # Now try a name with invalid characters
         json_result = self.client_patch("/json/settings", dict(full_name="Opheli*"))
         self.assert_json_error(json_result, "Invalid characters in name!")