v4: a dump or playlist going public notifies its followers — a private dump notified no one when posted, and nothing told its followers when it was made public: the poster's followers never learnt of it, nor did the followers of the public playlists holding it. Likewise, the dumps added to a playlist while it was private were never notified to its followers. updateDump and replaceFileDump now call notifyIfWentPublic, which notifies the poster's followers (user_dump_posted) and, through the new notifyPlaylistFollowersNowPublic, the followers of each public playlist holding the dump (playlist_dump_added). updatePlaylist calls the same function when a playlist goes public, for each public dump in it, from the bottom up. A follower hears of a dump once both it and the playlist are public; the source keys stop a dump made private and public again from notifying twice. 256 backend tests pass, and deno check, deno fmt and doc:lint are clean.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

api/test/routes/playlists.test.ts

@@ -320,6 +320,33 @@ test("adding to a followed public playlist notifies followers, private dumps exc
   });
 });
 
+test("a playlist going public notifies its followers of the public dumps added meanwhile", async () => {
+  const owner = await createUser();
+  const follower = await createUser();
+  const { id } = insertPlaylist({ userId: owner.id, title: "Mix" });
+  await put(`/api/me/follow/playlists/${id}`, { auth: follower.auth });
+  const before = insertDump({ userId: owner.id, title: "Before" });
+  await post(`/api/playlists/${id}/dumps/${before.id}`, { auth: owner.auth });
+  db.prepare(`DELETE FROM notifications WHERE user_id = ?;`).run(owner.id);
+  const setPublic = (isPublic: boolean) =>
+    put(`/api/playlists/${id}`, { auth: owner.auth, json: { isPublic } });
+
+  await setPublic(false);
+  const during = insertDump({ userId: owner.id, title: "During" });
+  const priv = insertDump({ userId: owner.id, isPrivate: true });
+  for (const d of [during, priv]) {
+    await post(`/api/playlists/${id}/dumps/${d.id}`, { auth: owner.auth });
+  }
+  assertEquals(count(`SELECT COUNT(*) as n FROM notifications;`), 1);
+  await setPublic(true);
+  const titles = (db.prepare(
+    `SELECT data FROM notifications WHERE user_id = ? ORDER BY created_at;`,
+  ).all(follower.id) as { data: string }[]).map((n) =>
+    JSON.parse(n.data).dumpTitle
+  );
+  assertEquals(titles, ["Before", "During"]);
+});
+
 test("playlist covers: upload and serve", async () => {
   const owner = await createUser();
   const other = await createUser();