invite: Add guest visibility note with live-updating user count.

Previously, when the guest role was selected in the Invite modal and
guests were restricted from viewing all other users, there was no
indication of how many users the invited guests would be able to see
once they joined.

This commit resolves that issue by adding a note in the Invite modal
that dynamically informs users of the number of visible users.

Fixes #31159.

web/src/invite.ts

@@ -5,6 +5,7 @@ import assert from "minimalistic-assert";
 import {z} from "zod";
 
 import copy_invite_link from "../templates/copy_invite_link.hbs";
+import render_guest_visible_users_message from "../templates/guest_visible_users_message.hbs";
 import render_invitation_failed_error from "../templates/invitation_failed_error.hbs";
 import render_invite_user_modal from "../templates/invite_user_modal.hbs";
 import render_invite_tips_banner from "../templates/modal_banner/invite_tips_banner.hbs";
@@ -22,6 +23,7 @@ import {$t, $t_html} from "./i18n";
 import * as input_pill from "./input_pill";
 import * as invite_stream_picker_pill from "./invite_stream_picker_pill";
 import {page_params} from "./page_params";
+import * as peer_data from "./peer_data";
 import * as settings_config from "./settings_config";
 import * as settings_data from "./settings_data";
 import {current_user, realm} from "./state_data";
@@ -308,6 +310,31 @@ function set_streams_to_join_list_visibility(): void {
     }
 }
 
+function update_guest_visible_users_count(): void {
+    const invite_as = Number.parseInt(
+        $<HTMLSelectOneElement>("select:not([multiple])#invite_as").val()!,
+        10,
+    );
+
+    assert(!Number.isNaN(invite_as));
+
+    const guest_role_selected = invite_as === settings_config.user_role_values.guest.code;
+    if (!guest_role_selected || settings_data.guests_can_access_all_other_users()) {
+        $("#guest_visible_users_container").hide();
+        return;
+    }
+    const stream_ids = $("#invite_select_default_streams").is(":checked")
+        ? stream_data.get_default_stream_ids()
+        : stream_pill.get_stream_ids(stream_pill_widget);
+    const visible_users_count = peer_data.get_unique_subscriber_count_for_streams(stream_ids);
+
+    const message_html = render_guest_visible_users_message({
+        user_count: visible_users_count,
+    });
+
+    $("#guest_visible_users_container").html(message_html).show();
+}
+
 function generate_invite_tips_data(): Record<string, boolean> {
     const {realm_description, realm_icon_source, custom_profile_fields} = realm;
 
@@ -360,6 +387,11 @@ function open_invite_user_modal(e: JQuery.ClickEvent<Document, undefined>): void
             stream_pill_widget = invite_stream_picker_pill.create($stream_pill_container);
         }
 
+        $("#invite_as, #invite_streams_container .input, #invite_select_default_streams").on(
+            "change",
+            update_guest_visible_users_count,
+        );
+
         $("#invite-user-modal").on("click", ".setup-tips-container .banner_content a", () => {
             dialog_widget.close();
         });

web/src/peer_data.ts

@@ -158,3 +158,18 @@ export function is_user_subscribed(stream_id: number, user_id: number): boolean
     const subscribers = get_user_set(stream_id);
     return subscribers.has(user_id);
 }
+
+export function get_unique_subscriber_count_for_streams(stream_ids: number[]): number {
+    const valid_subscribers = new LazySet([]);
+
+    for (const stream_id of stream_ids) {
+        const subscribers = get_user_set(stream_id);
+
+        for (const user_id of subscribers.keys()) {
+            if (!people.is_valid_bot_user(user_id)) {
+                valid_subscribers.add(user_id);
+            }
+        }
+    }
+    return valid_subscribers.size;
+}

web/src/settings_data.ts

@@ -381,3 +381,10 @@ export function get_request_data_for_stream_privacy(selected_val: string): {
         }
     }
 }
+
+export function guests_can_access_all_other_users(): boolean {
+    const everyone_group = user_groups.get_user_group_from_id(
+        realm.realm_can_access_all_users_group,
+    );
+    return everyone_group.name === "role:everyone";
+}

web/templates/guest_visible_users_message.hbs

@@ -0,0 +1,6 @@
+<p id="guest_visible_users_message">
+    {{t 'Guests will be able to see {user_count} users in their channels when they join.'}}
+    <a id="guest_help_link" class="help_link_widget" href="/help/guest-users#configure-whether-guests-can-see-all-other-users" target="_blank" rel="noopener noreferrer">
+        <i class="fa fa-question-circle-o" aria-hidden="true"></i>
+    </a>
+</p>

web/templates/invite_user_modal.hbs

@@ -91,5 +91,7 @@
             </div>
         </div>
     </div>
+    <div id="guest_visible_users_container" class="input-group" style="display: none;">
+    </div>
     {{/if}}
 </form>

web/tests/peer_data.test.js

@@ -44,6 +44,13 @@ const george = {
     full_name: "George",
     user_id: 103,
 };
+const bot_botson = {
+    email: "botson-bot@example.com",
+    user_id: 35,
+    full_name: "Bot Botson",
+    is_bot: true,
+    role: 300,
+};
 
 function contains_sub(subs, sub) {
     return subs.some((s) => s.name === sub.name);
@@ -292,3 +299,20 @@ test("is_subscriber_subset", () => {
     peer_data.is_subscriber_subset(undefined, sub_a.stream_id);
     blueslip.reset();
 });
+
+test("get_unique_subscriber_count_for_streams", () => {
+    const sub = {name: "Rome", subscribed: true, stream_id: 1001};
+    stream_data.add_sub(sub);
+
+    people.add_active_user(fred);
+    people.add_active_user(gail);
+    people.add_active_user(george);
+    people.add_active_user(bot_botson);
+
+    const stream_id = sub.stream_id;
+    peer_data.set_subscribers(stream_id, [me.user_id, fred.user_id, bot_botson.user_id]);
+
+    const count = peer_data.get_unique_subscriber_count_for_streams([stream_id]);
+
+    assert.equal(count, 2);
+});

web/tests/settings_data.test.js

@@ -946,3 +946,31 @@ run_test("user_can_create_web_public_streams", ({override}) => {
     override(realm, "server_web_public_streams_enabled", false);
     assert.equal(settings_data.user_can_create_web_public_streams(), false);
 });
+
+run_test("guests_can_access_all_other_users", () => {
+    const guest_user_id = 1;
+    const member_user_id = 2;
+
+    const members = {
+        name: "role:members",
+        id: 1,
+        members: new Set([member_user_id]),
+        is_system_group: true,
+        direct_subgroup_ids: new Set([]),
+    };
+    const everyone = {
+        name: "role:everyone",
+        id: 2,
+        members: new Set([guest_user_id]),
+        is_system_group: true,
+        direct_subgroup_ids: new Set([1]),
+    };
+
+    user_groups.initialize({realm_user_groups: [members]});
+    realm.realm_can_access_all_users_group = members.id;
+    assert.ok(!settings_data.guests_can_access_all_other_users());
+
+    user_groups.initialize({realm_user_groups: [members, everyone]});
+    realm.realm_can_access_all_users_group = everyone.id;
+    assert.ok(settings_data.guests_can_access_all_other_users());
+});