Combine persistent and one-time responses in one handler

[kettanaito]

Scope

Adds a new behavior

Compatibility

• This is a breaking change

Feature description

How should the user describe a request handler where one logical branch returns a consistent response while the other a one-time response?

// From the V1:
rest.get('/resource', (req, res, ctx) => {
  if (a) {
    return res(ctx.text('One'))
  }

  return res.once(ctx.text('Foo'))
})

If the a condition won't be met, the res.once will be returned, terminating this handler. But if the condition is met, a consistent text response will be returned, preserving this handler.

V2 has no alternative to describe this behavior within a single handler since the { once: true } option applies to the entire request handler. You'd have to split this one into two, which is suboptimal.