wire: replace wire.Value with wire.Zero about wire HOT 7 CLOSED

I like Value. It feels like time.Time{}, big.Int{}, etc to me. But, I'm not hugely opinionated - both seem pretty readable imo.

from wire.

@enocom, @tbpg, @jadekler any thoughts?

from wire.

I'm worried about the following edge cases in wire.Value as it exists now:

1. Referring to a package variable that changes. The declaration makes it seem like it would take on the value from initialization time, but it's actually evaluated when the injector is called (mildly surprising).
2. There's no way to write an interface-nil expression in a way that could be preserved at runtime. This limits Wire provider sets to being compile-time only.

from wire.

#1 is a bummer, I agree. Could you elaborate on #2? I don't fully grok.

from wire.

Consider an implementation of Wire that does not do code generation, but instead relies on reflection. (There are no plans to do so, but it would be nice to allow this to permit interoperability with other DI libraries.) If you write goose.Value(MyInterface(nil)) to satisfy a dependency on MyInterface, it will work in the gowire code gen tool, but the type information is lost at runtime (this is a subtle point, see Francesc's Understanding Nil for a refresher).

from wire.

Do we not have the same problem regardless of the name? I'm in fairly-unfamiliar and barely-grokking territory though so I may not be the best reviewer heh.

from wire.

I discussed this with @rsc and he came up with a better idea to preserve wire.Value while fixing the more confusing semantics. I've captured this in #104; I'm closing this issue out in favor of that one.

from wire.