delete_sub: Do not remove archived stream when deactivated.

Stream is simply marked as `archived: true` instead of removing
the stream from `sub_store` and `stream_info`.

A check in `subscribe_myself` is added before subscribing to a
stream.

web/src/server_events_dispatch.js

@@ -604,6 +604,7 @@ export function dispatch_normal_event(event) {
                         );
                         stream_data.delete_sub(stream.stream_id);
                         stream_settings_ui.remove_stream(stream.stream_id);
+                        message_view_header.maybe_rerender_title_area_for_stream(stream);
                         if (was_subscribed) {
                             stream_list.remove_sidebar_row(stream.stream_id);
                             if (stream.stream_id === compose_state.selected_recipient_id) {
@@ -632,6 +633,7 @@ export function dispatch_normal_event(event) {
                             message_lists.current.update_trailing_bookend(true);
                         }
                     }
+                    message_live_update.rerender_messages_view();
                     stream_list.update_subscribe_to_more_streams_link();
                     break;
                 default:

web/src/stream_data.ts

@@ -143,6 +143,10 @@ export function rename_sub(sub: StreamSubscription, new_name: string): void {
 }
 
 export function subscribe_myself(sub: StreamSubscription): void {
+    if (sub.is_archived) {
+        blueslip.warn("Can't subscribe to an archived stream.");
+        return;
+    }
     const user_id = people.my_current_user_id();
     peer_data.add_subscriber(sub.stream_id, user_id);
     sub.subscribed = true;
@@ -297,12 +301,13 @@ export function slug_to_stream_id(slug: string): number | undefined {
 }
 
 export function delete_sub(stream_id: number): void {
-    if (!stream_info.get(stream_id)) {
+    const sub = get_sub_by_id(stream_id);
+    if (sub === undefined || !stream_info.get(stream_id)) {
         blueslip.warn("Failed to archive stream " + stream_id.toString());
         return;
     }
-    sub_store.delete_sub(stream_id);
-    stream_info.delete(stream_id);
+    sub.is_archived = true;
+    stream_info.set_false(stream_id, sub);
 }
 
 export function get_non_default_stream_names(): {name: string; unique_id: number}[] {

web/tests/dispatch_subs.test.js

@@ -13,6 +13,8 @@ const test_user = events.test_user;
 
 const compose_recipient = mock_esm("../src/compose_recipient");
 const message_lists = mock_esm("../src/message_lists");
+const message_live_update = mock_esm("../src/message_live_update");
+const message_view_header = mock_esm("../src/message_view_header");
 const narrow_state = mock_esm("../src/narrow_state");
 const overlays = mock_esm("../src/overlays");
 const settings_org = mock_esm("../src/settings_org");
@@ -223,6 +225,8 @@ test("stream delete (normal)", ({override}) => {
         removed_sidebar_rows += 1;
     });
     override(stream_list, "update_subscribe_to_more_streams_link", noop);
+    override(message_live_update, "rerender_messages_view", noop);
+    override(message_view_header, "maybe_rerender_title_area_for_stream", noop);
 
     dispatch(event);
 
@@ -239,9 +243,12 @@ test("stream delete (special streams)", ({override}) => {
     const event = event_fixtures.stream__delete;
 
     for (const stream of event.streams) {
+        stream.is_archived = false;
         stream_data.add_sub(stream);
     }
 
+    stream_data.subscribe_myself(event.streams[0]);
+
     // sanity check data
     assert.equal(event.streams.length, 2);
     override(realm, "realm_new_stream_announcements_stream_id", event.streams[0].stream_id);
@@ -254,6 +261,8 @@ test("stream delete (special streams)", ({override}) => {
     override(message_lists.current, "update_trailing_bookend", noop);
     override(stream_list, "remove_sidebar_row", noop);
     override(stream_list, "update_subscribe_to_more_streams_link", noop);
+    override(message_live_update, "rerender_messages_view", noop);
+    override(message_view_header, "maybe_rerender_title_area_for_stream", noop);
 
     dispatch(event);
 
@@ -268,6 +277,7 @@ test("stream delete (stream is selected in compose)", ({override}) => {
     const event = event_fixtures.stream__delete;
 
     for (const stream of event.streams) {
+        stream.is_archived = false;
         stream_data.add_sub(stream);
     }
 
@@ -294,6 +304,8 @@ test("stream delete (stream is selected in compose)", ({override}) => {
         removed_sidebar_rows += 1;
     });
     override(stream_list, "update_subscribe_to_more_streams_link", noop);
+    override(message_live_update, "rerender_messages_view", noop);
+    override(message_view_header, "maybe_rerender_title_area_for_stream", noop);
 
     dispatch(event);
 

web/tests/lib/events.js

@@ -40,6 +40,7 @@ const fake_now = 1596713966;
 
 exports.test_streams = {
     devel: {
+        is_archived: false,
         name: "devel",
         description: ":devel fun:",
         rendered_description: "<b>devel fun</b>",
@@ -56,6 +57,7 @@ exports.test_streams = {
         can_remove_subscribers_group: 2,
     },
     test: {
+        is_archived: false,
         name: "test",
         description: "test desc",
         rendered_description: "test desc",

web/tests/stream_data.test.js

@@ -579,24 +579,32 @@ test("default_stream_names", () => {
 
 test("delete_sub", () => {
     const canada = {
+        is_archived: false,
         stream_id: 101,
         name: "Canada",
         subscribed: true,
     };
 
     stream_data.add_sub(canada);
+    const num_subscribed_subs = stream_data.num_subscribed_subs();
 
     assert.ok(stream_data.is_subscribed(canada.stream_id));
     assert.equal(stream_data.get_sub("Canada").stream_id, canada.stream_id);
     assert.equal(sub_store.get(canada.stream_id).name, "Canada");
+    assert.equal(stream_data.is_stream_archived(canada.stream_id), false);
 
     stream_data.delete_sub(canada.stream_id);
-    assert.ok(!stream_data.is_subscribed(canada.stream_id));
-    assert.ok(!stream_data.get_sub("Canada"));
-    assert.ok(!sub_store.get(canada.stream_id));
+    assert.ok(stream_data.is_stream_archived(canada.stream_id));
+    assert.ok(stream_data.is_subscribed(canada.stream_id));
+    assert.ok(stream_data.get_sub("Canada"));
+    assert.ok(sub_store.get(canada.stream_id));
+    assert.equal(stream_data.num_subscribed_subs(), num_subscribed_subs - 1);
 
     blueslip.expect("warn", "Failed to archive stream 99999");
     stream_data.delete_sub(99999);
+
+    blueslip.expect("warn", "Can't subscribe to an archived stream.");
+    stream_data.subscribe_myself(canada);
 });
 
 test("notifications", ({override}) => {