user-settings: Make default `None` for name, email and password changes.

Updates `json_change_settings` so that the default value for the `email`,
`full_name`, `new_password` and `old_password` parameters is `None` instead
of an empty string, which also makes the type annotation `Optional[str]`.

Also, updates tests for email and full name changes to include an empty
string as one of the tested invalid values.

zerver/tests/test_email_change.py

@@ -244,7 +244,9 @@ class EmailChangeTestCase(ZulipTestCase):
         )
 
     def test_post_invalid_email(self) -> None:
-        data = {"email": "hamlet-new"}
+        invalid_emails = ["", "hamlet-new"]
+        for email in invalid_emails:
+            data = {"email": email}
             self.login("hamlet")
             url = "/json/settings"
             result = self.client_patch(url, data)

zerver/tests/test_settings.py

@@ -121,8 +121,10 @@ class ChangeSettingsTest(ZulipTestCase):
         json_result = self.client_patch("/json/settings", dict(full_name="x" * 1000))
         self.assert_json_error(json_result, "Name too long!")
 
-        # Now try a too-short name
-        json_result = self.client_patch("/json/settings", dict(full_name="x"))
+        # Now try too-short names
+        short_names = ["", "x"]
+        for name in short_names:
+            json_result = self.client_patch("/json/settings", dict(full_name=name))
             self.assert_json_error(json_result, "Name too short!")
 
     def test_illegal_characters_in_name_changes(self) -> None:

zerver/views/user_settings.py

@@ -147,10 +147,10 @@ def check_settings_values(
 def json_change_settings(
     request: HttpRequest,
     user_profile: UserProfile,
-    full_name: str = REQ(default=""),
-    email: str = REQ(default=""),
-    old_password: str = REQ(default=""),
-    new_password: str = REQ(default=""),
+    full_name: Optional[str] = REQ(default=None),
+    email: Optional[str] = REQ(default=None),
+    old_password: Optional[str] = REQ(default=None),
+    new_password: Optional[str] = REQ(default=None),
     twenty_four_hour_time: Optional[bool] = REQ(json_validator=check_bool, default=None),
     dense_mode: Optional[bool] = REQ(json_validator=check_bool, default=None),
     starred_message_counts: Optional[bool] = REQ(json_validator=check_bool, default=None),
@@ -227,7 +227,7 @@ def json_change_settings(
             notification_sound, email_notifications_batching_period_seconds, default_language
         )
 
-    if new_password != "":
+    if new_password is not None:
         return_data: Dict[str, Any] = {}
         if email_belongs_to_ldap(user_profile.realm, user_profile.delivery_email):
             raise JsonableError(_("Your Zulip password is managed in LDAP"))
@@ -270,8 +270,10 @@ def json_change_settings(
         request.session.save()
 
     result: Dict[str, Any] = {}
+
+    if email is not None:
         new_email = email.strip()
-    if user_profile.delivery_email != new_email and new_email != "":
+        if user_profile.delivery_email != new_email:
             if user_profile.realm.email_changes_disabled and not user_profile.is_realm_admin:
                 raise JsonableError(_("Email address changes are disabled in this organization."))
 
@@ -299,7 +301,7 @@ def json_change_settings(
 
             do_start_email_change_process(user_profile, new_email)
 
-    if user_profile.full_name != full_name and full_name.strip() != "":
+    if full_name is not None and user_profile.full_name != full_name:
         if name_changes_disabled(user_profile.realm) and not user_profile.is_realm_admin:
             # Failingly silently is fine -- they can't do it through the UI, so
             # they'd have to be trying to break the rules.