stream_list_sort: Don't include unsubscribed streams in sort results.

Fixes bug reported here:
https://chat.zulip.org/#narrow/channel/9-issues/topic/exception.20when.20viewing.20world-public.20channel.20as.20a.20guest/near/2240871

web/src/channel_folders.ts

@@ -140,6 +140,7 @@ export function get_stream_ids_in_folder(folder_id: number): number[] {
 
 export function get_channels_in_folders_matching_search_term_in_folder_name(
     search_term: string,
+    all_subscribed_stream_ids: Set<number>,
 ): number[] {
     const channel_folders = get_channel_folders();
     const matching_channel_folders = util.filter_by_word_prefix_match(
@@ -150,7 +151,11 @@ export function get_channels_in_folders_matching_search_term_in_folder_name(
 
     const channel_ids: number[] = [];
     for (const channel_folder of matching_channel_folders) {
-        channel_ids.push(...get_stream_ids_in_folder(channel_folder.id));
+        for (const stream_id of get_stream_ids_in_folder(channel_folder.id)) {
+            if (all_subscribed_stream_ids.has(stream_id)) {
+                channel_ids.push(stream_id);
+            }
+        }
     }
     return channel_ids;
 }

web/src/stream_list_sort.ts

@@ -122,12 +122,15 @@ type StreamListSortResult = {
     sections: StreamListSection[];
 };
 
-export function sort_groups(stream_ids: number[], search_term: string): StreamListSortResult {
+export function sort_groups(
+    all_subscribed_stream_ids: number[],
+    search_term: string,
+): StreamListSortResult {
     const stream_id_to_name = (stream_id: number): string => sub_store.get(stream_id)!.name;
     // Use -, _, : and / as word separators apart from the default space character
     const word_separator_regex = /[\s/:_-]/;
-    stream_ids = util.filter_by_word_prefix_match(
-        stream_ids,
+    let matching_stream_ids = util.filter_by_word_prefix_match(
+        all_subscribed_stream_ids,
         search_term,
         stream_id_to_name,
         word_separator_regex,
@@ -137,24 +140,25 @@ export function sort_groups(stream_ids: number[], search_term: string): StreamLi
     if (
         current_channel_id !== undefined &&
         stream_data.is_subscribed(current_channel_id) &&
-        !stream_ids.includes(current_channel_id) &&
+        !matching_stream_ids.includes(current_channel_id) &&
         // If any of the topics of the channel match the search term, we need to
         // include the channel in the list of streams.
         topic_list_data.get_list_info(current_channel_id, false, (topic_names) =>
             topic_list_data.filter_topics_by_search_term(topic_names, search_term),
         ).items.length > 0
     ) {
-        stream_ids.push(current_channel_id);
+        matching_stream_ids.push(current_channel_id);
     }
 
     // If the channel folder matches the search term, include all channels
     // of that folder.
     if (user_settings.web_left_sidebar_show_channel_folders && search_term) {
-        stream_ids = [
+        matching_stream_ids = [
             ...new Set([
-                ...stream_ids,
+                ...matching_stream_ids,
                 ...channel_folders.get_channels_in_folders_matching_search_term_in_folder_name(
                     search_term,
+                    new Set(all_subscribed_stream_ids),
                 ),
             ]),
         ];
@@ -179,7 +183,7 @@ export function sort_groups(stream_ids: number[], search_term: string): StreamLi
 
     const folder_sections = new Map<number, StreamListSection>();
 
-    for (const stream_id of stream_ids) {
+    for (const stream_id of matching_stream_ids) {
         const sub = sub_store.get(stream_id);
         assert(sub);
         if (sub.is_archived) {

web/tests/channel_folders.test.cjs

@@ -114,22 +114,38 @@ run_test("basics", () => {
     ]);
     assert.deepEqual(channel_folders.get_stream_ids_in_folder(backend_folder.id), []);
 
+    const subscribed_streams = new Set([
+        stream_1.stream_id,
+        stream_2.stream_id,
+        stream_3.stream_id,
+        stream_4.stream_id,
+    ]);
+
     // Tests for get_channels_in_folders_matching_search_term_in_folder_name
     // Should match 'Frontend' folder and return its streams
     assert.deepEqual(
-        channel_folders.get_channels_in_folders_matching_search_term_in_folder_name("Front"),
+        channel_folders.get_channels_in_folders_matching_search_term_in_folder_name(
+            "Front",
+            subscribed_streams,
+        ),
         [stream_2.stream_id, stream_4.stream_id],
     );
 
     // Should match 'Backend' folder and return no streams
     assert.deepEqual(
-        channel_folders.get_channels_in_folders_matching_search_term_in_folder_name("Back"),
+        channel_folders.get_channels_in_folders_matching_search_term_in_folder_name(
+            "Back",
+            subscribed_streams,
+        ),
         [],
     );
 
     // Should match no folder and return empty array
     assert.deepEqual(
-        channel_folders.get_channels_in_folders_matching_search_term_in_folder_name("Nonexistent"),
+        channel_folders.get_channels_in_folders_matching_search_term_in_folder_name(
+            "Nonexistent",
+            subscribed_streams,
+        ),
         [],
     );