user_groups: Allow setting and changing can_leave_group setting.

Fixes #31951.

web/src/settings_components.ts

@@ -920,6 +920,7 @@ export function check_group_property_changed(elem: HTMLElement, group: UserGroup
     switch (property_name) {
         case "can_add_members_group":
         case "can_join_group":
+        case "can_leave_group":
         case "can_manage_group": {
             const pill_widget = get_group_setting_widget(property_name);
             assert(pill_widget !== null);
@@ -1409,6 +1410,7 @@ export function initialize_disable_btn_hint_popover(
 export const group_setting_widget_map = new Map<string, GroupSettingPillContainer | null>([
     ["can_add_members_group", null],
     ["can_join_group", null],
+    ["can_leave_group", null],
     ["can_manage_group", null],
 ]);
 
@@ -1450,7 +1452,11 @@ export function set_group_setting_widget_value(
     }
 }
 
-type group_setting_name = "can_manage_group" | "can_join_group" | "can_add_members_group";
+type group_setting_name =
+    | "can_add_members_group"
+    | "can_join_group"
+    | "can_leave_group"
+    | "can_manage_group";
 
 export function create_group_setting_widget({
     $pill_container,

web/src/user_group_create.ts

@@ -29,8 +29,9 @@ export function get_name(): string | undefined {
 }
 
 let can_add_members_group_widget: GroupSettingPillContainer | undefined;
-let can_manage_group_widget: GroupSettingPillContainer | undefined;
 let can_join_group_widget: GroupSettingPillContainer | undefined;
+let can_leave_group_widget: GroupSettingPillContainer | undefined;
+let can_manage_group_widget: GroupSettingPillContainer | undefined;
 
 class UserGroupMembershipError {
     report_no_members_to_user_group(): void {
@@ -168,6 +169,10 @@ function create_user_group(): void {
     const can_join_group =
         settings_components.get_group_setting_widget_value(can_join_group_widget);
 
+    assert(can_leave_group_widget !== undefined);
+    const can_leave_group =
+        settings_components.get_group_setting_widget_value(can_leave_group_widget);
+
     assert(settings_components.new_group_can_mention_group_widget !== null);
     const can_mention_group_value = settings_components.new_group_can_mention_group_widget.value();
     assert(can_mention_group_value !== undefined);
@@ -182,6 +187,7 @@ function create_user_group(): void {
         members: JSON.stringify(user_ids),
         can_add_members_group: JSON.stringify(can_add_members_group),
         can_join_group: JSON.stringify(can_join_group),
+        can_leave_group: JSON.stringify(can_leave_group),
         can_mention_group,
         can_manage_group: JSON.stringify(can_manage_group),
     };
@@ -274,5 +280,11 @@ export function set_up_handlers(): void {
         setting_type: "group",
     });
 
+    can_leave_group_widget = settings_components.create_group_setting_widget({
+        $pill_container: $container.find(".can-leave-group-container .pill-container"),
+        setting_name: "can_leave_group",
+        setting_type: "group",
+    });
+
     user_group_components.setup_permissions_dropdown("can_mention_group", undefined, true);
 }

web/src/user_group_edit.js

@@ -190,6 +190,13 @@ function show_general_settings(group) {
         setting_type: "group",
         group,
     });
+
+    settings_components.create_group_setting_widget({
+        $pill_container: $edit_container.find(".can-leave-group-container .pill-container"),
+        setting_name: "can_leave_group",
+        setting_type: "group",
+        group,
+    });
     update_general_panel_ui(group);
 
     if (!page_params.development_environment) {

web/templates/user_group_settings/group_permissions.hbs

@@ -23,6 +23,16 @@
     </div>
 </div>
 
+<div class="input-group can-leave-group-container">
+    <label>{{t "Who can leave this group" }}</label>
+    <div class="pill-container person_picker prop-element" id="id_{{can_leave_group_widget_name}}" data-setting-widget-type="group-setting-type">
+        <div class="input" contenteditable="true"
+          data-placeholder="{{t 'Add roles, groups or users' }}">
+            {{~! Squash whitespace so that placeholder is displayed when empty. ~}}
+        </div>
+    </div>
+</div>
+
 <div class="input-group can-add-members-group-container">
     <label>{{t "Who can add members to this group" }}</label>
     <div class="pill-container person_picker prop-element" id="id_{{can_add_members_group_widget_name}}" data-setting-widget-type="group-setting-type">

web/templates/user_group_settings/user_group_creation_form.hbs

@@ -31,7 +31,9 @@
                             {{> group_permissions
                               can_add_members_group_widget_name="new_group_can_add_members_group"
                               can_join_group_widget_name="new_group_can_join_group"
-                              can_mention_group_widget_name="new_group_can_mention_group" can_manage_group_widget_name="new_group_can_manage_group"
+                              can_leave_group_widget_name="new_group_can_leave_group"
+                              can_mention_group_widget_name="new_group_can_mention_group"
+                              can_manage_group_widget_name="new_group_can_manage_group"
                               }}
                         </div>
                     </section>

web/templates/user_group_settings/user_group_settings.hbs

@@ -41,7 +41,13 @@
                     {{> ../settings/settings_save_discard_widget section_name="group-permissions" }}
                 </div>
 
-                {{> group_permissions can_add_members_group_widget_name="can_add_members_group" can_join_group_widget_name="can_join_group" can_mention_group_widget_name="can_mention_group" can_manage_group_widget_name="can_manage_group"}}
+                {{> group_permissions
+                  can_add_members_group_widget_name="can_add_members_group"
+                  can_join_group_widget_name="can_join_group"
+                  can_leave_group_widget_name="can_leave_group"
+                  can_mention_group_widget_name="can_mention_group"
+                  can_manage_group_widget_name="can_manage_group"
+                  }}
             </div>
 
             <div class="group_detail_box">