What happens when a defer-generated cb() is called back one than once?

[maxtaco]

Should maybe make it impotent after the first call, and or have the Deferrals object complain if its counter drops below 0.

[craigyk]

Are you trying to figure out how to handle callbacks that are passed for things like progress updates (so they're legitimately called more than once)? Or are there circumstances where the iced implementation might be buggy and you want to catch them?

[maxtaco]

I was worried about this case:

loop
  await fs.watchFile "/path/to/some/changing/file.txt", {}, defer curr, prev
  console.log "it changed!"

This is an issue because fs.watchFile will call back repeatedly, every time the file is changed (unless you give { persistent : 0} as options). You'll wind up with n^2 log lines, for n changes. Probably not what you wanted.... In this case, I would say just use hand-rolled cbs, but the iced runtime should warn you.