code review 12405043: testing: add Frames method to adjust the logging of the...

testing: add Frames method to adjust the logging of the caller

Fixes issue 4899.

Work in progress
* {T,B}.Frames(n) returns an unexported type, this is considered antisocial.
* In patchset 4, the api tool rejects the change even though B, T never directly exported these methods. Patchset 5 reorganises things to make the api tool happy.

[dave_cheney.net, 2013-08-03 10:40:29]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://code.google.com/p/go

[r, 2013-08-03 13:23:42]

I'm not a fan of this. It's clumsy, unnecessary, and exposes an
implementation-specific detail of the testing package for outside users to
play with.

There are certain testing patterns where it may help but the testing
package doesn't honor all feature requests and there are other ways to
write such tests.

-rob

[r, 2013-08-03 13:35:15]

It wouldn't satisfy all my objections, but a nicer design would be
something like

// Up returns a *T object whose error reports identify the line n callers
up the frame.
func (t *T) Up(n) *t { .... }

Then you could write

   t.Up(1).Error("this would be tagged with the caller's line number")

I believe that can be done behind the scenes without corrupting the API. I
remain unconvinced, though, since it encourages the creation of testing
helpers, which are the devil's handiwork.

-rob