The Resurfaced Memory — JavaScript Bug Hunt

Briefing

Inspired by Facebook's Year in Review resurfacing posts people had deleted or locked down. The highlight reel must only ever contain public, non-deleted posts — sorted by likes, best first.

The bug hides in one filter expression in yearReview.js.

Bug report

BUG-2014 · Priority: Critical (trust) · Reported by: comms

• Deleted posts are appearing in Year in Review reels.
• Private posts appear too.
• The "top" post shown is actually the LEAST liked one.

Spec: exclude deleted posts, exclude visibility "private", return the top N by likes, most-liked first.

Logs

[review] included post id=77 deleted=true
[review] first slide likes=2, last slide likes=9540

The code as shipped

src/review/yearReview.js (editable)

// Builds the year-in-review highlight reel.
exports.buildReel = function (posts, topN) {
  var eligible = posts.filter(function (p) {
    return !p.deleted || p.visibility !== "private";
  });
  eligible.sort(function (a, b) {
    return a.likes - b.likes;
  });
  return eligible.slice(0, topN);
};