options

Generator For Funtional Options

Opinionated Code Generators For Functional Options In Golang

Usage

whittle options -type TypeToGenerateOptionsFor

Example

generate functional options for the current directories package

e.g. given package

package worker

//go:generate whittle options -type Worker

type Worker struct {
	times     int    `opts`
	namespace string `opts:"SetNamespace"`
}

func New() *Worker { &Worker }

go generate

will produce:

package worker

type Option func(*Worker)

type Options []Option

func (o Options) Apply(w *Worker) {
	for _, opt := range o {
		opt(w)
	}
}

func WithTimes(times int) Option {
	return func(w *Worker) {
		w.times = times
	}
}

func SetNamespace(namespace string) Option {
	return func(w *Worker) {
		w.namespace = namespace
	}
}

Now to wire in the new options, all you have to do is:

func New(opts ...Option) *Worker {
    worker := &Worker{
        times: 5, // some sensible default
        namespace: "default_namespace" // another sensible default
    }

    Options(opts).Apply(worker)

    return worker
}

Roadmap

• lib/options: initial simple implementation of generating source for functional options
• lib/parse: initial implementation of source code -> fun internals parsing
• cmd/fun: initial implemenation of the executable
• lib/parse: support parsing field tags on target structs
• lib/options: support generation of provided options e.g. generate func WithSomeFieldName(value string) Option
• cmd/fun: update binary to support wiring new options together
• cmd/opt: rename fun to opt as it will now live as a sub-command of whittle
• cmd/whittle/options: renamed (again) to options for clarity