Undo Send Never Works — JavaScript Bug Hunt

Briefing

Inspired by Gmail's Undo Send — and by the unit-mismatch bugs that break features like it. The undo window is 5 seconds, but the button is dead the instant an email leaves.

One comparison in undoSend.js mixes milliseconds with seconds.

Bug report

BUG-CTRL-Z · Priority: High · Reported by: dogfood

canUndo(sentAtMs, nowMs) with a 5-second window:

• 2s after sending -> must be true
• 6s after sending -> must be false
• exactly 5.000s -> still true (inclusive)

Observed: false even 50ms after sending.

Logs

[undo] sentAt=1700000000000 now=1700000000050 canUndo=false (?!)

The code as shipped

src/mail/undoSend.js (editable)

// The undo-send grace window.
var WINDOW_SECONDS = 5;

exports.canUndo = function (sentAtMs, nowMs) {
  return nowMs - sentAtMs <= WINDOW_SECONDS;
};