Unify duplicate handling in Tasks

[duesee]

• Emit warning`
• Take first or last?
  • Append -> Last
  • PostAppendNoOp -> Last (no warning)
  • PostAppendCheck -> Last (no warning)
  • AuthenticateTask -> Take last data (no warning). May take data instead of status.
  • ...

Proposal:

I think we want to tell our users not only that there was a duplicate, but also how we resolved the situation. Maybe something like ...

if let Some(old) = self.output.replace(seq) {
    // Note: `unwrap` can't fail here.
    warn!(?old, new=?self.output.unwrap(), "duplicate data replaced");
}

... ?

[soywod]

Is there any task that should take and keep the first? Seems like it is always the last. Otherwise I really like your proposition!

[duesee]

I think not. It should always be the last.

[duesee]

Hey @soywod! Can you assign me this issue?

[duesee]

Or make me a collaborator so I can do myself, how you prefer :D

[soywod]

Or make me a collaborator so I can do myself

Invitation sent!