compose: Allow the user to direct message bots despite of policy.

After the changes in zulip#25572, users were no longer able to start a direct
message with bots if the organization disabled direct messages. However,
we should allow direct messages to bots regardless of the policy because
it's a useful interface for users to interact with various classes of
bots.

user_ids_string_to_ids_array was also modified to prevent cases where
the split function returned an array of [0] rather than [] when dealing
with a empty id string of "".

Fixes: zulip#21896.

web/src/compose_recipient.js

@@ -15,6 +15,7 @@ import * as dropdown_widget from "./dropdown_widget";
 import {$t} from "./i18n";
 import * as narrow_state from "./narrow_state";
 import {page_params} from "./page_params";
+import * as people from "./people";
 import * as settings_config from "./settings_config";
 import * as stream_bar from "./stream_bar";
 import * as stream_data from "./stream_data";
@@ -110,10 +111,8 @@ export function update_on_recipient_change() {
 
 export function get_posting_policy_error_message() {
     if (selected_recipient_id === "direct") {
-        if (
-            page_params.realm_private_message_policy ===
-            settings_config.private_message_policy_values.disabled.code
-        ) {
+        const recipients = compose_pm_pill.get_user_ids_string();
+        if (!people.user_can_direct_message(recipients)) {
             return $t({
                 defaultMessage: "Direct messages are disabled in this organization.",
             });

web/src/people.ts

@@ -295,7 +295,7 @@ export function user_ids_string_to_emails_string(user_ids_string: string): strin
 }
 
 export function user_ids_string_to_ids_array(user_ids_string: string): number[] {
-    const user_ids = user_ids_string.split(",");
+    const user_ids = user_ids_string.length === 0 ? [] : user_ids_string.split(",");
     const ids = user_ids.map(Number);
     return ids;
 }

web/tests/compose_actions.test.js

@@ -27,7 +27,9 @@ const compose_fade = mock_esm("../src/compose_fade", {
     set_focused_recipient: noop,
     update_all: noop,
 });
-const compose_pm_pill = mock_esm("../src/compose_pm_pill");
+const compose_pm_pill = mock_esm("../src/compose_pm_pill", {
+    get_user_ids_string: ()=> ""
+});
 const compose_ui = mock_esm("../src/compose_ui", {
     autosize_textarea: noop,
     is_full_size: () => false,