v4: a playlist's dump count is of the dumps the viewer may see — it counted every dump in the playlist, so a card said "3 dumps" over a page listing two, and told everyone how many private dumps a playlist held. The lists (/playlists, a profile's playlists and followed ones, the search, a dump's playlists, the add-to-playlist panel) now count by isMemberVisibleTo's rule, in SQL as VISIBLE_DUMP_COUNT (lib/playlist-members.ts): the public dumps, and for the owner their own private ones. GET /api/playlists and /api/users/:key/follow/playlists read the optional sign-in for it. The community page and the digests count the public dumps, their figures being the same for every reader. Live, playlist_created and playlist_updated carry each socket's own count: broadcastChange builds the owner's message and the others' apart. playlist_dumps_updated loses its dumpCount, a client counting the dumps it is sent.

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

api/lib/playlist-members.ts

@@ -1,7 +1,8 @@
 /**
  * Decides which of a playlist's dumps a viewer may see. The playlist service
- * filters its listings with it, and the WebSocket service filters each
+ * filters its listings with it, the WebSocket service filters each client's
- * client's `playlist_dumps_updated` message the same way.
+ * `playlist_dumps_updated` message the same way, and the queries that list
+ * playlists count their dumps by the same rule.
  *
  * @module
  */
@@ -34,3 +35,28 @@ export function isMemberVisibleTo(
   return !member.isPrivate ||
     (member.userId === viewerId && viewerId === playlist.userId);
 }
+
+/**
+ * The `dump_count` column of a query on `playlists p`: how many of the
+ * playlist's dumps the viewer may see, by {@link isMemberVisibleTo}'s rule.
+ * Its `?` takes the viewer's id, or `""` for a signed-out one, and comes
+ * before the query's other parameters, the column being in its select list.
+ */
+export const VISIBLE_DUMP_COUNT = `(SELECT COUNT(*) FROM playlist_dumps pd
+     INNER JOIN dumps d ON d.id = pd.dump_id
+    WHERE pd.playlist_id = p.id
+      AND (d.is_private = 0 OR (d.user_id = p.user_id AND p.user_id = ?))
+   ) as dump_count`;
+
+/**
+ * Returns how many of `members` the viewer may see in `playlist`, the
+ * `dumpCount` the playlist has for them.
+ */
+export function countVisibleTo(
+  members: PlaylistMember[],
+  playlist: Pick<Playlist, "userId">,
+  viewerId: string | null | undefined,
+): number {
+  return members.filter((m) => isMemberVisibleTo(m, playlist, viewerId))
+    .length;
+}

api/routes/playlists.ts

@@ -77,12 +77,18 @@ const router: Router<AuthState> = new Router<AuthState>({
   prefix: "/api/playlists",
 });
 
-router.get("/", (ctx) => {
+router.get("/", async (ctx) => {
+  const requestingUserId = await parseOptionalAuth(ctx);
   const params = ctx.request.url.searchParams;
   const { page, limit } = parsePagination(params);
   const slug = params.get("category");
   const categoryId = slug ? getCategoryBySlug("playlist", slug).id : undefined;
-  const { items, hasMore } = listPublicPlaylists(page, limit, categoryId);
+  const { items, hasMore } = listPublicPlaylists(
+    requestingUserId,
+    page,
+    limit,
+    categoryId,
+  );
   const responseBody: APIResponse<PaginatedData<Playlist>> = {
     success: true,
     data: { items, hasMore },

api/routes/users.ts

@@ -245,10 +245,16 @@ router.get("/:key/follow/users", (ctx) => {
   ctx.response.body = responseBody;
 });
 
-router.get("/:key/follow/playlists", (ctx) => {
+router.get("/:key/follow/playlists", async (ctx) => {
   const user = resolveUserKey(ctx.params.key);
+  const requestingUserId = await parseOptionalAuth(ctx);
   const { page, limit } = parsePagination(ctx.request.url.searchParams);
-  const { items, hasMore } = getFollowedPlaylistsByUser(user.id, page, limit);
+  const { items, hasMore } = getFollowedPlaylistsByUser(
+    user.id,
+    requestingUserId,
+    page,
+    limit,
+  );
   const responseBody: APIResponse<PaginatedData<Playlist>> = {
     success: true,
     data: { items, hasMore },

api/services/follow-service.ts

@@ -23,6 +23,7 @@ import {
 } from "../model/dump.ts";
 import { isFollowRow } from "../model/follow.ts";
 import { isPlaylistRow, playlistRowToApi } from "../model/playlist.ts";
+import { VISIBLE_DUMP_COUNT } from "../lib/playlist-members.ts";
 import { type Page, pageOf } from "../lib/pagination.ts";
 import { attachCategoryIds, categoryJoin } from "./category-service.ts";
 import { sendToUser } from "./ws-service.ts";
@@ -232,12 +233,14 @@ export function getFollowedPlaylistsDumpFeed(
 
 /**
  * Returns a page of the public playlists `userId` follows, most recently
- * followed first, for their profile and playlists pages.
+ * followed first, for their profile and playlists pages. Their dumps are
+ * counted for `requestingUserId`, null being a signed-out viewer.
  *
  * @throws {APIException} 500 when a row doesn't parse as a playlist.
  */
 export function getFollowedPlaylistsByUser(
   userId: string,
+  requestingUserId: string | null,
   page: number,
   limit: number,
 ): Page<Playlist> {
@@ -245,7 +248,7 @@ export function getFollowedPlaylistsByUser(
 
   const rawRows = db.prepare(
     `SELECT p.*, u.username as owner_username,
-       (SELECT COUNT(*) FROM playlist_dumps pd WHERE pd.playlist_id = p.id) as dump_count
+       ${VISIBLE_DUMP_COUNT}
      FROM playlists p
      LEFT JOIN users u ON u.id = p.user_id
      INNER JOIN follows f ON f.followed_playlist_id = p.id
@@ -253,7 +256,7 @@ export function getFollowedPlaylistsByUser(
        AND p.is_public = 1
      ORDER BY f.created_at DESC
      LIMIT ? OFFSET ?;`,
-  ).all(userId, limit + 1, offset);
+  ).all(requestingUserId ?? "", userId, limit + 1, offset);
 
   if (!rawRows.every(isPlaylistRow)) {
     throw new APIException(500, "Malformed playlist data");

api/services/playlist-service.ts

@@ -44,19 +44,28 @@ import {
 import {
   isMemberVisibleTo,
   type PlaylistMember,
+  VISIBLE_DUMP_COUNT,
 } from "../lib/playlist-members.ts";
 import { LIKE, likePattern } from "../lib/like.ts";
 import { parseRows } from "../model/rows.ts";
 
 /**
  * The select list and `FROM` clause of a playlist query, adding the owner's
- * name and the dump count. Callers append the `WHERE`. The dump count includes
+ * name and the count of the dumps the viewer may see. Callers append the
- * dumps the viewer can't see.
+ * `WHERE`, and pass the viewer's id first, as {@link viewerParam} gives it.
  */
 const PLAYLIST_SELECT = `p.*, u.username as owner_username,
-   (SELECT COUNT(*) FROM playlist_dumps pd WHERE pd.playlist_id = p.id) as dump_count
+   ${VISIBLE_DUMP_COUNT}
    FROM playlists p JOIN users u ON u.id = p.user_id`;
 
+/**
+ * Returns what {@link VISIBLE_DUMP_COUNT}'s parameter takes for `viewerId`: a
+ * signed-out viewer matches no user.
+ */
+function viewerParam(viewerId: string | null | undefined): string {
+  return viewerId ?? "";
+}
+
 /**
  * Converts the rows of a {@link PLAYLIST_SELECT} to playlists, their
  * categories filled in.
@@ -69,13 +78,17 @@ function playlistsOf(rows: unknown[]): Playlist[] {
 
 /**
  * Returns playlist `playlistId`, private or not. A caller that shows it to
- * someone must check `isPublic` first, as the OG middleware does.
+ * someone must check `isPublic` first, as the OG middleware does. Its
+ * `dumpCount` is `viewerId`'s, or a signed-out viewer's without one.
  *
  * @throws {APIException} 404 when there is no such playlist.
  */
-export function getPlaylistById(playlistId: string): Playlist {
+export function getPlaylistById(
+  playlistId: string,
+  viewerId: string | null = null,
+): Playlist {
   const row = db.prepare(`SELECT ${PLAYLIST_SELECT} WHERE p.id = ?;`)
-    .get(playlistId);
+    .get(viewerParam(viewerId), playlistId);
   if (!row || !isPlaylistRow(row)) {
     throw new APIException(404, "Playlist not found");
   }
@@ -136,7 +149,7 @@ export function createPlaylist(
     }
     linkAttachments(req.description, "playlist", id);
   }
-  broadcastPlaylistChange(null, playlist);
+  broadcastPlaylistChange(null, playlist, []);
   return playlist;
 }
 
@@ -144,7 +157,8 @@ export function createPlaylist(
  * Returns a playlist with the dumps `requestingUserId` may see in it, in
  * order, for `GET /api/playlists/:playlistId`, and for
  * `GET /api/users/:key/playlists/:slug` once it has found the playlist by its
- * path. A null `requestingUserId` is a signed-out viewer.
+ * path. A null `requestingUserId` is a signed-out viewer. Its `dumpCount` is
+ * the number of those dumps.
  *
  * @throws {APIException} 404 when there is no such playlist, or it is private
  * and not theirs.
@@ -175,7 +189,7 @@ export function getPlaylist(
     isMemberVisibleTo(d, playlist, requestingUserId)
   );
 
-  return { ...playlist, dumps: visibleDumps };
+  return { ...playlist, dumpCount: visibleDumps.length, dumps: visibleDumps };
 }
 
 /**
@@ -198,10 +212,17 @@ export function searchPlaylists(
   const rows = requestingUserId
     ? db.prepare(
       `SELECT ${PLAYLIST_SELECT} ${catJoin} WHERE (p.is_public = 1 OR p.user_id = ?) AND ${searchClause} ORDER BY p.created_at DESC LIMIT ?;`,
-    ).all(...catParams, requestingUserId, pattern, pattern, limit)
+    ).all(
+      requestingUserId,
+      ...catParams,
+      requestingUserId,
+      pattern,
+      pattern,
+      limit,
+    )
     : db.prepare(
       `SELECT ${PLAYLIST_SELECT} ${catJoin} WHERE p.is_public = 1 AND ${searchClause} ORDER BY p.created_at DESC LIMIT ?;`,
-    ).all(...catParams, pattern, pattern, limit);
+    ).all(viewerParam(null), ...catParams, pattern, pattern, limit);
 
   return playlistsOf(rows);
 }
@@ -209,9 +230,11 @@ export function searchPlaylists(
 /**
  * Returns a page of every public playlist, newest first, for
  * `GET /api/playlists`, optionally only those in the playlist category
- * `categoryId`. The client's `/playlists` page lists them.
+ * `categoryId`. The client's `/playlists` page lists them. Their dumps are
+ * counted for `requestingUserId`, null being a signed-out viewer.
  */
 export function listPublicPlaylists(
+  requestingUserId: string | null,
   page: number,
   limit: number,
   categoryId?: string,
@@ -222,21 +245,22 @@ export function listPublicPlaylists(
     `SELECT ${PLAYLIST_SELECT} ${catJoin}
       WHERE p.is_public = 1
       ORDER BY p.created_at DESC LIMIT ? OFFSET ?;`,
-  ).all(...catParams, limit + 1, offset);
+  ).all(viewerParam(requestingUserId), ...catParams, limit + 1, offset);
   return pageOf(playlistsOf(rows), limit);
 }
 
 /**
  * Returns the public playlists created from `from` to `to`, the fullest first
  * and the newer on a tie. The community service gathers them for the
- * `/community` page and the digests.
+ * `/community` page and the digests, which show every reader the same
+ * figures: only their public dumps are counted.
  */
 export function listNewPublicPlaylists(from: Date, to: Date): Playlist[] {
   const rows = db.prepare(
     `SELECT ${PLAYLIST_SELECT}
       WHERE p.is_public = 1 AND p.created_at >= ? AND p.created_at < ?
       ORDER BY dump_count DESC, p.created_at DESC;`,
-  ).all(from.toISOString(), to.toISOString());
+  ).all(viewerParam(null), from.toISOString(), to.toISOString());
   return playlistsOf(rows);
 }
 
@@ -262,7 +286,13 @@ export function listPlaylistsByUser(
     `SELECT ${PLAYLIST_SELECT} ${catJoin}
       WHERE p.user_id = ?${privacyFilter}
       ORDER BY p.created_at DESC LIMIT ? OFFSET ?;`,
-  ).all(...catParams, userId, limit + 1, offset);
+  ).all(
+    viewerParam(requestingUserId),
+    ...catParams,
+    userId,
+    limit + 1,
+    offset,
+  );
   return pageOf(playlistsOf(rows), limit);
 }
 
@@ -287,7 +317,7 @@ export function updatePlaylist(
   requestingUserId: string,
   canModerate: boolean,
 ): Playlist {
-  const playlist = getPlaylistById(playlistId);
+  const playlist = getPlaylistById(playlistId, requestingUserId);
 
   if (playlist.userId !== requestingUserId && !canModerate) {
     throw new APIException(403, "Only its owner or a moderator may do that");
@@ -347,7 +377,7 @@ export function updatePlaylist(
     }
     linkAttachments(newDescription, "playlist", playlist.id);
   }
-  broadcastPlaylistChange(playlist, updated);
+  broadcastPlaylistChange(playlist, updated, getCurrentMembers(playlist.id));
   // Its followers weren't told of the dumps added while it was private.
   if (!playlist.isPublic && newIsPublic) {
     notifyPlaylistFollowersNowPublic({ playlistId: playlist.id });
@@ -374,7 +404,7 @@ export function deletePlaylist(
   }
 
   db.prepare(`DELETE FROM playlists WHERE id = ?;`).run(playlist.id);
-  broadcastPlaylistChange(playlist, null);
+  broadcastPlaylistChange(playlist, null, []);
 }
 
 /**
@@ -390,7 +420,7 @@ export function getEditablePlaylist(
   requestingUserId: string,
   canModerate: boolean,
 ): Playlist {
-  const playlist = getPlaylistById(playlistId);
+  const playlist = getPlaylistById(playlistId, requestingUserId);
   if (playlist.userId !== requestingUserId && !canModerate) {
     throw new APIException(403, "Only its owner or a moderator may do that");
   }
@@ -421,8 +451,8 @@ export function setPlaylistImage(
   db.prepare(
     `UPDATE playlists SET image_mime = ?, updated_at = ? WHERE id = ?;`,
   ).run(imageMime, new Date().toISOString(), playlist.id);
-  const updated = getPlaylistById(playlist.id);
+  const updated = getPlaylistById(playlist.id, requestingUserId);
-  broadcastPlaylistChange(playlist, updated);
+  broadcastPlaylistChange(playlist, updated, getCurrentMembers(playlist.id));
   return updated;
 }
 
@@ -590,13 +620,13 @@ export function getPlaylistMembershipsForDump(
 ): PlaylistMembership[] {
   const rows = db.prepare(
     `SELECT p.*, u.username as owner_username,
-       (SELECT COUNT(*) FROM playlist_dumps x WHERE x.playlist_id = p.id) as dump_count,
+       ${VISIBLE_DUMP_COUNT},
        EXISTS (SELECT 1 FROM playlist_dumps pd
                 WHERE pd.playlist_id = p.id AND pd.dump_id = ?) as has_dump
      FROM playlists p JOIN users u ON u.id = p.user_id
      WHERE p.user_id = ?
      ORDER BY p.created_at DESC;`,
-  ).all(dumpId, userId);
+  ).all(userId, dumpId, userId);
 
   const memberships = rows.map((row) => {
     if (!isPlaylistRow(row)) {
@@ -626,7 +656,7 @@ export function getPlaylistsForDump(
      INNER JOIN playlist_dumps pd ON pd.playlist_id = p.id
      WHERE pd.dump_id = ? AND (p.is_public = 1 OR p.user_id = ?)
      ORDER BY p.created_at DESC LIMIT 20;`,
-  ).all(dumpId, requestingUserId ?? "");
+  ).all(viewerParam(requestingUserId), dumpId, requestingUserId ?? "");
 
   return playlistsOf(rows);
 }
@@ -701,7 +731,7 @@ export function playlistsHolding(dumpId: string): PlaylistHolder[] {
 
 /**
  * Sends each of `holders` its dumps again, after one of them was deleted or
- * changed visibility: the count moved, or what each viewer may see of them.
+ * changed visibility, which changes what each viewer may see of them.
  */
 export function broadcastHoldersDumps(holders: PlaylistHolder[]): void {
   for (const holder of holders) {

api/services/ws-service.ts

@@ -18,6 +18,7 @@ import type { OnlineUser, ServerToClientMessage } from "../../shared/ws.ts";
 import type { Playlist } from "../../shared/playlist.ts";
 import type { PublicUser, Role } from "../../shared/user.ts";
 import {
+  countVisibleTo,
   isMemberVisibleTo,
   type PlaylistMember,
 } from "../lib/playlist-members.ts";
@@ -179,35 +180,43 @@ export function broadcastPresence(): void {
  * `before` is null for a new item, `after` for a deleted one. A private item's
  * changes reach its owner's sockets alone. When it goes private, everyone else
  * is told it was deleted, and gets nothing of the change; when it goes public,
- * they are told it was created, since to them it is new.
+ * they are told it was created, since to them it is new. The owner's sockets
+ * and the others' each get a message of their own, built with `toOwner` set
+ * for the former, for what the two don't see alike.
  */
 function broadcastChange<T extends { userId: string }>(
   before: T | null,
   after: T | null,
   isPrivate: (item: T) => boolean,
   messages: {
-    created: (item: T) => ServerToClientMessage;
+    created: (item: T, toOwner: boolean) => ServerToClientMessage;
-    updated: (item: T) => ServerToClientMessage;
+    updated: (item: T, toOwner: boolean) => ServerToClientMessage;
     deleted: (item: T) => ServerToClientMessage;
   },
 ): void {
   const item = after ?? before;
   if (!item) return;
-  const toOwner = (client: WsClient) => client.userId === item.userId;
+  const wasPublic = !!before && !isPrivate(before);
-  const toOthers = (client: WsClient) => client.userId !== item.userId;
+  const isPublic = !!after && !isPrivate(after);
 
-  if (!after) {
+  broadcast(
-    broadcast(messages.deleted(item), isPrivate(item) ? toOwner : undefined);
+    !after
-  } else if (!before) {
+      ? messages.deleted(item)
-    broadcast(messages.created(after), isPrivate(after) ? toOwner : undefined);
+      : before
-  } else if (isPrivate(after)) {
+      ? messages.updated(after, true)
-    broadcast(messages.updated(after), toOwner);
+      : messages.created(after, true),
-    if (!isPrivate(before)) broadcast(messages.deleted(after), toOthers);
+    (client) => client.userId === item.userId,
-  } else if (isPrivate(before)) {
+  );
-    broadcast(messages.updated(after), toOwner);
+  const toOthers = (client: WsClient) => client.userId !== item.userId;
-    broadcast(messages.created(after), toOthers);
+  if (after && isPublic) {
-  } else {
+    broadcast(
-    broadcast(messages.updated(after));
+      wasPublic
+        ? messages.updated(after, false)
+        : messages.created(after, false),
+      toOthers,
+    );
+  } else if (wasPublic) {
+    broadcast(messages.deleted(item), toOthers);
   }
 }
 
@@ -265,15 +274,32 @@ export function broadcastCommentLikeUpdate(
  * Tells the clients that may see a playlist how it changed, as
  * {@link broadcastChange} says, for the playlist service after every write to
  * its details. A playlist turned private thus leaves the others' views without
- * their learning what it became.
+ * their learning what it became. `members` are the dumps of `after`: each
+ * socket gets the playlist with the count of those its user may see, the
+ * owner's private dumps being theirs alone to count.
  */
 export function broadcastPlaylistChange(
   before: Playlist | null,
   after: Playlist | null,
+  members: PlaylistMember[],
 ): void {
+  const counted = (playlist: Playlist, toOwner: boolean): Playlist => ({
+    ...playlist,
+    dumpCount: countVisibleTo(
+      members,
+      playlist,
+      toOwner ? playlist.userId : null,
+    ),
+  });
   broadcastChange(before, after, (playlist) => !playlist.isPublic, {
-    created: (playlist) => ({ type: "playlist_created", playlist }),
+    created: (playlist, toOwner) => ({
-    updated: (playlist) => ({ type: "playlist_updated", playlist }),
+      type: "playlist_created",
+      playlist: counted(playlist, toOwner),
+    }),
+    updated: (playlist, toOwner) => ({
+      type: "playlist_updated",
+      playlist: counted(playlist, toOwner),
+    }),
     deleted: (p) => ({
       type: "playlist_deleted",
       playlistId: p.id,
@@ -285,7 +311,8 @@ export function broadcastPlaylistChange(
 /**
  * Sends `playlist_dumps_updated` to the playlist's audience, each socket with
  * only the dumps its user may see, as `GET` would list them. The private dumps
- * in a public playlist stay hidden from everyone but their posters.
+ * in a public playlist stay hidden from everyone but their posters, and so
+ * does their number: a client counts the dumps it is sent.
  */
 export function broadcastPlaylistDumpsUpdated(
   playlist: Pick<Playlist, "id" | "isPublic" | "userId">,
@@ -299,7 +326,6 @@ export function broadcastPlaylistDumpsUpdated(
       dumpIds: members
         .filter((m) => isMemberVisibleTo(m, playlist, client.userId))
         .map((m) => m.id),
-      dumpCount: members.length,
     });
   }
 }

api/test/routes/playlists.test.ts

@@ -146,6 +146,72 @@ test("a public playlist hides its private dumps from everyone but their owner",
   );
 });
 
+test("a playlist's dumpCount is of the dumps the viewer may see", async () => {
+  const owner = await createUser();
+  const author = await createUser();
+  const pl = insertPlaylist({ userId: owner.id, title: "Counted banana" });
+  const pub = insertDump({ userId: owner.id });
+  const mine = insertDump({ userId: owner.id, isPrivate: true });
+  // Someone else's, gone private after it was added: its owner no longer
+  // sees it there, and neither does its poster.
+  const theirs = insertDump({ userId: author.id, isPrivate: true });
+  for (const [i, d] of [pub, mine, theirs].entries()) {
+    db.prepare(
+      `INSERT INTO playlist_dumps (playlist_id, dump_id, position, added_at)
+       VALUES (?, ?, ?, ?);`,
+    ).run(pl.id, d.id, i, new Date().toISOString());
+  }
+  await put(`/api/me/follow/playlists/${pl.id}`, { auth: author.auth });
+
+  const lists = [
+    "/api/playlists",
+    `/api/users/@${owner.username}/playlists`,
+    `/api/users/@${author.username}/follow/playlists`,
+  ];
+  for (
+    const [auth, expected] of [
+      [owner.auth, 2],
+      [author.auth, 1],
+      [undefined, 1],
+    ] as const
+  ) {
+    for (const url of lists) {
+      const { items } = (await get<PaginatedData<Playlist>>(url, { auth }))
+        .data;
+      assertEquals(items.map((p) => p.dumpCount), [expected], url);
+    }
+    assertEquals(
+      (await get<{ playlists: Playlist[] }>("/api/search?q=banana", { auth }))
+        .data.playlists.map((p) => p.dumpCount),
+      [expected],
+    );
+    assertEquals(
+      (await get<Playlist[]>(`/api/dumps/${pub.id}/playlists`, { auth })).data
+        .map((p) => p.dumpCount),
+      [expected],
+    );
+    const page = await get<PlaylistWithDumps>(`/api/playlists/${pl.id}`, {
+      auth,
+    });
+    assertEquals(page.data.dumpCount, expected);
+    assertEquals(ids(page).length, expected);
+  }
+  assertEquals(
+    (await get<PlaylistMembership[]>(`/api/me/playlists?contains=${pub.id}`, {
+      auth: owner.auth,
+    })).data.map((m) => [m.hasDump, m.playlist.dumpCount]),
+    [[true, 2]],
+  );
+  // An edit answers with the editor's count.
+  assertEquals(
+    (await put<Playlist>(`/api/playlists/${pl.id}`, {
+      auth: owner.auth,
+      json: { title: "Counted" },
+    })).data.dumpCount,
+    2,
+  );
+});
+
 test("reorder: must name exactly the current members", async () => {
   const owner = await createUser();
   const { id } = insertPlaylist({ userId: owner.id });

api/test/routes/ws.test.ts

@@ -709,8 +709,32 @@ wsTest(
     for (const c of [a, x, anon]) {
       const msg = await c.next("playlist_dumps_updated");
       assertEquals(msg.dumpIds, [added.id, pub.id]);
-      // The count is the playlist's, as its dumpCount gives it to everyone.
+    }
-      assertEquals(msg.dumpCount, 4);
+
+    // A change to its details carries the count of what each may see, too.
+    await put(`/api/playlists/${pl.id}`, {
+      auth: owner.auth,
+      json: { title: "Renamed" },
+    });
+    assertEquals((await o.next("playlist_updated")).playlist.dumpCount, 3);
+    for (const c of [a, x, anon]) {
+      assertEquals((await c.next("playlist_updated")).playlist.dumpCount, 2);
+    }
+    await put(`/api/playlists/${pl.id}`, {
+      auth: owner.auth,
+      json: { isPublic: false },
+    });
+    await put(`/api/playlists/${pl.id}`, {
+      auth: owner.auth,
+      json: { isPublic: true },
+    });
+    assertEquals(
+      (await o.next("playlist_updated", (m) => m.playlist.isPublic)).playlist
+        .dumpCount,
+      3,
+    );
+    for (const c of [a, x, anon]) {
+      assertEquals((await c.next("playlist_created")).playlist.dumpCount, 2);
     }
   },
 );
@@ -817,7 +841,6 @@ wsTest(
     });
     const hidden = await x.next("playlist_dumps_updated");
     assertEquals(hidden.dumpIds, [keep.id, gone.id]);
-    assertEquals(hidden.dumpCount, 3);
     assertEquals(
       (await o.next("playlist_dumps_updated")).dumpIds,
       [keep.id, flip.id, gone.id],
@@ -835,7 +858,7 @@ wsTest(
     await del(`/api/dumps/${gone.id}`, { auth: owner.auth });
     const after = await x.next(
       "playlist_dumps_updated",
-      (m) => m.dumpCount === 2,
+      (m) => m.dumpIds.length === 2,
     );
     assertEquals(after.dumpIds, [keep.id, flip.id]);
 

api/test/services/community-service.test.ts

@@ -43,9 +43,25 @@ test("communityStatsOf: the period's top public dumps, members, public playlists
   insertPlaylist({ userId: ann.id, title: "Small" });
   const full = insertPlaylist({ userId: bob.id, title: "Full" });
   insertPlaylist({ userId: bob.id, title: "Hidden", isPublic: false });
+  // Bob's private dump isn't counted: every reader gets the same figures.
+  const secret = insertDump({
+    userId: bob.id,
+    title: "Secret",
+    isPrivate: true,
+  });
   db.prepare(
-    `INSERT INTO playlist_dumps (playlist_id, dump_id, position, added_at) VALUES (?, ?, 0, ?), (?, ?, 1, ?);`,
+    `INSERT INTO playlist_dumps (playlist_id, dump_id, position, added_at) VALUES (?, ?, 0, ?), (?, ?, 1, ?), (?, ?, 2, ?);`,
-  ).run(full.id, hit.id, ago(0), full.id, tie.id, ago(0));
+  ).run(
+    full.id,
+    hit.id,
+    ago(0),
+    full.id,
+    tie.id,
+    ago(0),
+    full.id,
+    secret.id,
+    ago(0),
+  );
 
   const stats = communityStatsOf(...week());
   assertEquals(stats.top.map((d) => d.title), ["Hit", "Newer", "Tie"]);

shared/playlist.ts

@@ -40,8 +40,8 @@ export interface Playlist {
   /** It is undefined when the playlist has no cover. */
   imageMime?: string;
   /**
-   * It counts the dumps the viewer can't see too. It is undefined when the
+   * It counts the dumps the viewer may see in it, as its page lists them. It
-   * query didn't count them.
+   * is undefined when the query didn't count them.
    */
   dumpCount?: number;
   /** The owner's current name, which the playlist's path starts with. */

shared/ws.ts

@@ -295,7 +295,8 @@ export interface PlaylistCreatedMessage {
 
 /**
  * Sent by the server when a playlist changes, to every socket if it is public,
- * else to its owner's, as when it has just gone private.
+ * else to its owner's, as when it has just gone private. Its `dumpCount` is
+ * the socket's user's, as in `playlist_created`.
  */
 export interface PlaylistUpdatedMessage {
   type: "playlist_updated";
@@ -325,8 +326,6 @@ export interface PlaylistDumpsUpdatedMessage {
    * private dump is left out.
    */
   dumpIds: string[];
-  /** Counts every dump, hidden ones included, as `Playlist.dumpCount` does. */
-  dumpCount: number;
 }
 
 /**

src/contexts/ws/WSContext.ts

@@ -50,8 +50,6 @@ export interface PlaylistEvent {
    * order.
    */
   dumpIds?: string[];
-  /** Set when the dumps changed. It counts private dumps too. */
-  dumpCount?: number;
 }
 
 /**

src/contexts/ws/WSProvider.tsx

@@ -595,12 +595,11 @@ export function WSProvider({ children }: WSProviderProps): React.JSX.Element {
           }
 
           case "playlist_dumps_updated": {
-            const { playlistId, dumpIds, dumpCount } = msg;
+            const { playlistId, dumpIds } = msg;
             events.emit("playlist", {
               type: "dumps_updated",
               playlistId,
               dumpIds,
-              dumpCount,
             });
             break;
           }

src/hooks/playlist/usePlaylistListSync.ts

@@ -85,10 +85,8 @@ export function usePlaylistListSync(
         const idx = prev.findIndex((p) => p.id === ev.playlistId);
         if (idx === -1) return prev;
         const next = [...prev];
-        next[idx] = {
+        // The dumps this user may see, which are those the playlist counts.
-          ...next[idx],
+        next[idx] = { ...next[idx], dumpCount: ev.dumpIds.length };
-          dumpCount: ev.dumpCount ?? ev.dumpIds.length,
-        };
         return next;
       }
 

src/test/contexts/ws/WSProvider.test.tsx

@@ -481,13 +481,11 @@ describe("dumps, playlists, comments, users", () => {
       type: "playlist_dumps_updated",
       playlistId: "p",
       dumpIds: ["x"],
-      dumpCount: 2,
     });
     expect(events().playlist.at(-1)).toEqual({
       type: "dumps_updated",
       playlistId: "p",
       dumpIds: ["x"],
-      dumpCount: 2,
     });
     socket.receive({ type: "playlist_deleted", playlistId: "p", userId: "u" });
     expect(ws().deletedPlaylistIds.has("p")).toBe(true);

src/test/hooks/playlist/usePlaylistListSync.test.tsx

@@ -99,7 +99,7 @@ describe("usePlaylistListSync", () => {
     expect(ids(items())).toEqual(["c"]);
   });
 
-  test("dumps_updated sets the count", () => {
+  test("dumps_updated counts the dumps this viewer may see", () => {
     const { emit, items } = setup([makePlaylist({ id: "a", dumpCount: 1 })]);
     emit("playlist", {
       type: "dumps_updated",
@@ -109,17 +109,6 @@ describe("usePlaylistListSync", () => {
     expect(items()[0].dumpCount).toBe(3);
   });
 
-  test("dumps_updated counts the members this viewer can't see too", () => {
-    const { emit, items } = setup([makePlaylist({ id: "a", dumpCount: 3 })]);
-    emit("playlist", {
-      type: "dumps_updated",
-      playlistId: "a",
-      dumpIds: ["x", "y"],
-      dumpCount: 4,
-    });
-    expect(items()[0].dumpCount).toBe(4);
-  });
-
   test("a renamed owner's playlists take the new name", () => {
     const { emit, items } = setup([
       makePlaylist({ id: "a", userId: "u1", ownerUsername: "old" }),

src/test/pages/Index.test.tsx

@@ -423,7 +423,6 @@ describe("Followed feed", () => {
       type: "playlist_dumps_updated",
       playlistId: "mix",
       dumpIds: ["x"],
-      dumpCount: 1,
     });
     expect(await screen.findByText("Added to the mix")).toBeInTheDocument();
   });

src/test/pages/PlaylistDetail.test.tsx

@@ -452,7 +452,6 @@ describe("PlaylistDetail", () => {
       type: "playlist_dumps_updated",
       playlistId: "p1",
       dumpIds: ["a", "c"],
-      dumpCount: 3,
     });
     expect(titles()).toEqual(["Alpha", "Charlie"]);
     socket.receive({
@@ -463,7 +462,6 @@ describe("PlaylistDetail", () => {
       type: "playlist_dumps_updated",
       playlistId: "p1",
       dumpIds: ["a", "b", "c"],
-      dumpCount: 3,
     });
     expect(await screen.findByText("Bravo")).toBeInTheDocument();
     expect(titles()).toEqual(["Alpha", "Bravo", "Charlie"]);
@@ -522,7 +520,6 @@ describe("PlaylistDetail", () => {
       type: "playlist_dumps_updated",
       playlistId: "p1",
       dumpIds: ["d", "a", "b", "c"],
-      dumpCount: 4,
     });
     expect(await screen.findByText("Delta")).toBeInTheDocument();
     socket.receive({