fix(v3): refresh Songs grid after a Settings rescan / DLC-folder change (#624)

Reported on macOS: on a fresh install, pointing at a DLC folder in Settings and
running a scan showed NO songs until an app restart. The scan itself was fine —
_background_scan re-reads config.json fresh, so it scans the new folder and
populates the library — but the v3 Songs grid never reloaded.

The Settings Rescan / Full Rescan handlers only refreshed the classic (v2)
library via loadLibrary(); the v3 grid (static/v3/songs.js) had no listener for
a scan it didn't initiate (only its own upload path self-refreshes via
watchUploadScan). So its cached, pre-DLC (empty) DOM/snapshot survived a sidebar
return until a full reload (restart).

Fix: the rescan handlers now emit `library:changed` (static/app.js). The v3 grid
listens and reloads if it's the active screen, else sets `_libraryDirty` so the
next onV3SongsScreenEnter does a full re-fetch — a short-circuit placed ahead of
every cached-DOM fast-path so it can't restore the stale grid.

Tests: tests/js/v3_library_refresh.test.js guards the emit + the reload/dirty
wiring (DOM/event glue isn't headlessly unit-testable; end-to-end wants an
in-app run of the reporter's flow: set DLC in Settings → scan → Songs populate
without restart).


Claude-Session: https://claude.ai/code/session_01QbexxfTt8q2tAn436MqGWF

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: byrongamatos <xasiklas@gmail.com>

static/app.js

@@ -4543,6 +4543,9 @@ async function rescanLibrary() {
             _treeStats = null;
             _tuningNames = null;  // re-fetch on next drawer open
             loadLibrary();
+            // Tell the v3 Songs grid the library changed so it reloads instead of
+            // keeping a cached (e.g. pre-DLC, empty) grid until an app restart.
+            if (window.feedBack) window.feedBack.emit('library:changed', { reason: 'rescan' });
         }
     }, 1000);
 }
@@ -4571,6 +4574,9 @@ async function fullRescanLibrary() {
             _treeStats = null;
             _tuningNames = null;  // re-fetch on next drawer open
             loadLibrary();
+            // Tell the v3 Songs grid the library changed so it reloads instead of
+            // keeping a cached (e.g. pre-DLC, empty) grid until an app restart.
+            if (window.feedBack) window.feedBack.emit('library:changed', { reason: 'rescan' });
         }
     }, 1000);
 }

static/v3/songs.js

@@ -338,6 +338,12 @@
     // tracks filenames scored while the library was off-screen, applied on enter.
     const _dirtyScores = new Set();
 
+    // Set when a library scan / DLC-folder change happened while this screen was
+    // off (or showing a stale, e.g. pre-DLC empty, grid). The grid's cached DOM /
+    // snapshot would otherwise survive a sidebar return, so we force a full
+    // re-fetch on the next entry. (feedBack — "No DLC until restart".)
+    let _libraryDirty = false;
+
     function repaintAccuracy(key) {
         const apply = (el, variant) => {
             if (el.getAttribute('data-fn') !== key) return;
@@ -1049,6 +1055,10 @@
     }
 
     async function onV3SongsScreenEnter() {
+        // A library scan / DLC-folder change marked the grid stale — re-fetch
+        // from scratch instead of restoring a cached (possibly empty, pre-DLC)
+        // snapshot. Must win over every fast-path below.
+        if (_libraryDirty) { _libraryDirty = false; await reload(); return; }
         // Pull in any scores recorded while the library was off-screen (the usual
         // play→return flow) before the fast-paths below restore the cached DOM,
         // so the just-played song's badge is current. The full render() path
@@ -1202,5 +1212,16 @@
             const active = document.querySelector('.screen.active');
             if (active && active.id === 'v3-songs') applyScoreRefresh();
         });
+        // A library scan (rescan / full rescan from Settings, or a DLC-folder
+        // change) can add or remove songs while this grid is cached — the
+        // Settings rescan only refreshed the classic library, so the v3 grid
+        // stayed on its pre-scan (e.g. empty, pre-DLC) state until an app
+        // restart. Reload now if we're showing; otherwise mark dirty so the next
+        // entry re-fetches instead of restoring the stale snapshot.
+        sm.on('library:changed', () => {
+            const active = document.querySelector('.screen.active');
+            if (active && active.id === 'v3-songs') { _libraryDirty = false; reload(); }
+            else _libraryDirty = true;
+        });
     }
 })();