Annotated Invokes

[fionera]

Hi,

currently we need to call fx.Invoke with a custom Type with fx.In and the parameters. How about implementing support for fx.Annotated in fx.Invoke calls?

[abhinav]

Hey, we considered that but the problem is that constructors usually have
multiple parameters. A name or group specified with fx.Annotated would
apply to all parameters, which is not what you usually want.

For example, if you have,

func New(ro *sql.DB, rw *sql.DB) Repository

There's no easy way to annotate the names for individual parameters.
We're open to suggestions that address this concern.

[abhinav]

This feature is now available in v1.15.0 in the following form:

fx.Invoke(
  fx.Annotate(
    func(foo Thing) {
        // ...
    },
    fx.ParamTags(`name:"a"`),
  ),
)

Which is roughly equivalent to,

type invokeParams struct {
    fx.In
    
    Foo Thing `name:"a"`
}

fx.Invoke(
    func(p invokeParams) {
        foo := p.Foo

        // ...
    },
)