Copy a container

[jstroem]

I have e scenario where I want to reuse the snapshot a container from a given point in time and use it many times over and over again.
One primitive that could be used for this is a Copy method that ensures that both the original and the copied container can be used without interfering with each other.

Is this something that could be built in?

[abhinav]

Hello! We haven't had a chance to fully evaluate the implications of such a
feature, and on first glance would not be strongly opposed to it.

But first, can you describe the use case a bit more? Wanting to re-use a
container many times suggests you might be using it on the request path which
is something we strongly discourage.

[jstroem]

Sure.
In my example I am using the a Dig Container to hold "fixtures" during my go tests.
Some fixtures should be loaded once per go test execution and others once per test.

Let me give you a concrete example:

func setupTestRandomOnce() *rand.Rand {
  return rand.New(rand.NewSource(99))
}

func setupGomockCtrl(t *testing.T, r *rand.Rand) *gomock.Controller {
  return gomock.NewController(t)
}

Here, my setupTestRandomOnce func should only be called once during a go test ./ execution whereas the setupGomockCtrl should be executed on every test.

If I have the possibility to Copy I container, I would be able to setup all the providers that does not relate to *testing.T and then use that as a "Base" to copy every time i run a new test.

I hope that explained my use-case.
Let me know what you think.

[sywhang]

I do realize this is a pretty old thread, but I'd like to revive this feature request. This is a valid use case, and I'll start tracking this work in our todo list for Dig.