hashchange: Select the new near id if it is already rendered.

web/src/hash_util.ts

@@ -276,3 +276,16 @@ export function validate_group_settings_hash(hash: string): string {
     }
     return hash;
 }
+
+export function is_same_narrow(hash1: string, hash2: string): boolean {
+    if (hash1 === hash2) {
+        return true;
+    }
+
+    // Remove elements from hash that don't effect the narrow.
+    // TODO: Expand the regex to include more items we can ignore.
+    hash1 = hash1.replace(/near\/\d+$/, "");
+    hash2 = hash2.replace(/near\/\d+$/, "");
+
+    return hash1 === hash2;
+}

web/src/hashchange.js

@@ -5,13 +5,15 @@ import * as admin from "./admin";
 import * as blueslip from "./blueslip";
 import * as browser_history from "./browser_history";
 import * as drafts_overlay_ui from "./drafts_overlay_ui";
+import {Filter} from "./filter";
 import * as hash_parser from "./hash_parser";
 import * as hash_util from "./hash_util";
 import {$t_html} from "./i18n";
 import * as inbox_ui from "./inbox_ui";
 import * as inbox_util from "./inbox_util";
 import * as info_overlay from "./info_overlay";
 import * as message_fetch from "./message_fetch";
+import * as message_lists from "./message_lists";
 import * as message_viewport from "./message_viewport";
 import * as modals from "./modals";
 import * as narrow from "./narrow";
@@ -126,7 +128,7 @@ function show_home_view() {
 }
 
 // Returns true if this function performed a narrow
-function do_hashchange_normal(from_reload) {
+function do_hashchange_normal(from_reload, old_hash) {
     message_viewport.stop_auto_scrolling();
 
     // NB: In Firefox, window.location.hash is URI-decoded.
@@ -157,6 +159,22 @@ function do_hashchange_normal(from_reload) {
                 show_home_view();
                 return false;
             }
+
+            // Just select the message if the narrow is the same as the current narrow and
+            // we already have the new message we want to select rendered.
+            // TODO: Implement a filter comparison function so that we do it for any two narrows
+            // when calling narrow.activate.
+            if (old_hash && hash_util.is_same_narrow(window.location.hash, old_hash)) {
+                const filter = new Filter(terms);
+                if (filter.has_operator("near")) {
+                    const target_id = Number.parseInt(filter.operands("near")[0], 10);
+                    if (message_lists.current.get(target_id)) {
+                        message_lists.current.select_id(target_id, {then_scroll: true});
+                        return true;
+                    }
+                }
+            }
+
             const narrow_opts = {
                 change_hash: false, // already set
                 trigger: "hash change",
@@ -473,7 +491,7 @@ function hashchanged(from_reload, e) {
     popovers.hide_all();
     modals.close_active_if_any();
     browser_history.state.changing_hash = true;
-    const ret = do_hashchange_normal(from_reload);
+    const ret = do_hashchange_normal(from_reload, old_hash);
     browser_history.state.changing_hash = false;
     return ret;
 }