tree 4f0a6d6abee20a5c4fd86968af2f4618b3147d1d
parent 3d9d43c19b152e1eff006c15f1b5e84ca209adce
author Jonathan Amsterdam <jba@google.com> 1623356260 -0400
committer Jonathan Amsterdam <jba@google.com> 1623433441 +0000

event: Builder.Start returns a builder

Currently, Builder.Start's second return value is a function which,
when called, sends an End event with a copy of the Start event's
builder. This makes the common case

    ctx, end := event.To(ctx).Start(name)
    defer end()

easy to write.

But it's not possible to add additional labels that way; instead a
whole new builder needs to be constructed from scratch.

So in this CL, Start's second return value is a Builder. The simple
case is almost as short:

    ctx, b := event.To(ctx).Start(name)
    defer b.End()

but now it's equally easy to add more information to the end event:

    ctx, b := event.To(ctx).Start(name)
    defer b.With(Result.Of(err)).End()

Change-Id: Ib489a2704ac78479317eeb3f1f3de0f1b38d610c
Reviewed-on: https://go-review.googlesource.com/c/exp/+/326849
Trust: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Cottrell <iancottrell@google.com>