fix: sync removes albums no longer in subsonic, classify non-json responses as api errors

server/test/library.test.ts

@@ -154,4 +154,53 @@ describe('library sync', () => {
     expect(state.albums).toBe(503)
     await app.close()
   })
+
+  it('re-sync removes albums that disappeared from subsonic', async () => {
+    // sync 1 (from settings PUT): 1 album 'Kept Album'
+    // sync 2 (explicit POST): 1 album 'Only Album' — 'Kept Album' must be gone
+    let syncCount = 0
+    const shrinking = (async (input: any) => {
+      const url = new URL(String(input))
+      if (url.pathname.endsWith('/rest/ping')) {
+        return new Response(JSON.stringify({ 'subsonic-response': { status: 'ok' } }), {
+          status: 200,
+          headers: { 'content-type': 'application/json' },
+        })
+      }
+      if (url.pathname.endsWith('/rest/getAlbumList2')) {
+        syncCount++
+        const album =
+          syncCount === 1
+            ? { id: 1, name: 'Kept Album', artist: 'Artist A' }
+            : { id: 9, name: 'Only Album', artist: 'Artist B' }
+        return new Response(
+          JSON.stringify({ 'subsonic-response': { status: 'ok', albumList2: { album: [album] } } }),
+          { status: 200, headers: { 'content-type': 'application/json' } }
+        )
+      }
+      return new Response('nope', { status: 404 })
+    }) as typeof fetch
+    const app = await buildTestApp(shrinking)
+    const cookie = await setupAdmin(app)
+    await app.inject({
+      method: 'PUT',
+      url: '/api/settings',
+      ...auth(cookie),
+      payload: { subsonicUrl: 'http://n.local', subsonicUsername: 'sam', subsonicPassword: 'pass' },
+    })
+
+    const first = await waitForDone(app, cookie)
+    expect(first.albums).toBe(1)
+    expect(await app.inject({ method: 'GET', url: '/api/library/albums?q=Kept', ...auth(cookie) }).then((r) => r.json())).toMatchObject({ albums: [expect.objectContaining({ title: 'Kept Album' })] })
+
+    await app.inject({ method: 'POST', url: '/api/library/sync', ...auth(cookie) })
+    const second = await waitForDone(app, cookie)
+    expect(second.albums).toBe(1)
+
+    const stale = await app.inject({ method: 'GET', url: '/api/library/albums?q=Kept', ...auth(cookie) })
+    expect(stale.json().albums).toHaveLength(0) // stale album removed
+    const kept = await app.inject({ method: 'GET', url: '/api/library/albums?q=Only', ...auth(cookie) })
+    expect(kept.json().albums).toHaveLength(1)
+    await app.close()
+  })
 })