Method Build

annotated.go:1650–1688

Build builds and returns a constructor based on fx.In/fx.Out params and results wrapping the original constructor passed to fx.Annotate.

()

// Build builds and returns a constructor based on fx.In/fx.Out params and
// results wrapping the original constructor passed to fx.Annotate.
func (ann *annotated) Build() (interface{}, error) {
	ann.container = dig.New()
	ft := reflect.TypeOf(ann.Target)
	if ft.Kind() != reflect.Func {
		return nil, fmt.Errorf("must provide constructor function, got %v (%T)", ann.Target, ann.Target)
	}

	if err := ann.typeCheckOrigFn(); err != nil {
		return nil, fmt.Errorf("invalid annotation function %T: %w", ann.Target, err)
	}

	ann.applyOptionalTag()

	var (
		err        error
		lcHookAnns []*lifecycleHookAnnotation
	)
	for _, annotation := range ann.Annotations {
		if lcHookAnn, ok := annotation.(*lifecycleHookAnnotation); ok {
			lcHookAnns = append(lcHookAnns, lcHookAnn)
			continue
		}
		if ann.Target, err = annotation.build(ann); err != nil {
			return nil, err
		}
	}

	// need to call cleanUpAsResults before applying lifecycle annotations
	// to exclude the original results from the hook's scope if any
	// fx.As annotations were applied
	ann.cleanUpAsResults()

	for _, la := range lcHookAnns {
		if ann.Target, err = la.build(ann); err != nil {
			return nil, err
		}
	}
	return ann.Target, nil
}

// applyOptionalTag checks if function being annotated is variadic
// and applies optional tag to the variadic argument before