Nathan
Boiron

It can sometimes be useful to have optional dependencies in the Fx container.

For example to run some checks when boot the app only when some dependencies are present.

fx.New(
    // ...
    
    fx.Invoke(fx.Annotate(func(foo *Foo) error {
        if foo == nil {
            // The dependency was not provided, we skip the rest
            return nil
        }
        
        // Here we can run checks on foo
        
        return ...
    }, fx.ParamTags(`optional:"true"`))),
)