Keep packages backwards compatible

FOSDEM 2017 talk on keeping Go packages backwards compatible

Transcript

1. keep packages backwards compatible
2. some tips
3. Small APIs commit to everything you export
4. Export fewer interfaces
5. package example type Service interface { Process() } func New() Service { return &service{} }
6. package example type Service interface { Process() NewMethod() // ⚡ } func New() Service { return &service{} }
7. Receive interfaces Return structs
8. package example type Service struct { // ... } func New() *Service { return &Service{} }
9. Export your input interfaces
10. package example func Process(in input) error { // ... } // ⚠ type input interface { // ... }
12. // Input exported for documentation type Input interface { // ... } func Process(in Input) error { // ... }
13. Keeping interfaces to yourself
14. package testing type TB interface { Error(args ...interface{}) Fail() // ... // contains filtered or unexported methods }
15. package testing type TB interface { Error(args ...interface{}) Fail() // ... // A private method to prevent users implementing // interface and so future additions to it will // violate Go 1 compatibility. private() }
16. Nice optional params
17. cr, _ := crawler.New() cr.Crawl("http://godoc.org", process)
18. cr, _ := crawler.New( crawler.WithAllowedHosts("godoc.org"), ) cr.Crawl("http://godoc.org", process)
19. cr, _ := crawler.New( crawler.WithAllowedHosts("godoc.org"), crawler.WithMaxDepth(4), ) cr.Crawl("http://godoc.org", process)
20. func New(opts ...Option) (*Simple, error) type Option func(*options) error type options struct
21. // WithMaxDepth sets the max depth of the crawl func WithMaxDepth(depth int) Option { return func(opts *options) error { if depth < 0 { return fmt.Errorf("invalid depth: %d", depth) } opts.maxDepth = depth return nil } }
23. Be backwards compatible!
24. twitter.com/ernesto_jimenez ernesto@slackline.io