Putting a Jetpack on your legacy codebase

At Pinterest, we are always working on using the latest technologies when possible in our 10+ year old codebase. Adding architecture components such as Hilt and Navigation without requiring everyone to rewrite their existing features can be quite a challenge. Hear about some of the techniques and challenges the platform team at Pinterest has had to use in order to adopt these new technologies under the hood.

Transcript

1. Putting a Jetpack on your legacy codebase Kurt Nelson (he/him) Android Platform at Pinterest
2. Platform Teams • Mobile-wide issues • Build, framework, testing • Android, iOS, Web
3. Forward- looking big picture Ensuring the stability, security and performance going forward Library choices and upgrades
4. We experiment early with new technologies
5. We pay attention to what is going on in the Android world hi room.
6. Handling Android Changes
7. Handling Android Changes Kotlin
8. Handling Android Changes Jetpack Compose
9. Handling Android Changes Jetpack Compose
10. Knowledge transfer Getting 100+ engineers to hold it right.
11. At a large organization, we need to teach about it, roll out access, review new usage, and handle deprecation.
12. Migration We need to make sure it is safe to swap code out.
13. Secret history lesson time
14. While you were using ALL the Square libraries…
15. Google has Product Areas Android and the Google suite of apps historically only shared the CEO.
16. Google Plus was chunked up and turned into the internal framework.
17. Hilt and Jetpack Datastore came from G+
18. Frameworks even at Google were a fragmented mess.
19. Along Comes Jetpack…
20. Original goal was to decouple app behavior from the OS Hence Jeti f ier.
21. It was a piecemeal migration for the Google suite of apps.
22. Spoiler: We took care of users of the G+ framework
23. Back at Pinterest • The app is from around 2012 • Over 700 unique committers • Most code is O(years) old
24. One app, one repo 100 monthly committers
25. The Birth of ScreenManager Our attempt to f ix fragments
26. Screen API Our innocent looking Fragment replacement. fun bind(screenDescription: ScreenDescription) val isScreenBound: Boolean val wasScreenEverBound: Boolean fun activate() val isScreenActivated: Boolean fun deactivate() fun unbind() fun destroy() fun getView(): View?
27. Appropriate at the time • Our app is full pages • MVPish • Solved fragment transaction crashes
28. The Gotcha interface ScreenDescription : Parcelable { val screenClass: Class<out Screen> val screenTransitionId: Int val arguments: Bundle var instanceState: Bundle? var showBottomNav: Boolean var uniqueId: String val results: MutableMap<String, Bundle> val internalName: String }
29. Re f lection! And basically our own version of a FragmentManager And our own version of Navigation And constructor injection
30. How do we back out? And what do we back out f irst?
31. Prioritization
32. Prioritization Which First? • Jetpack Navigation • Jetpack DataStore • Real Fragments & Lifecycle • Hilt • Compose • ViewPager2
33. Prioritization Tradeoffs • Reliability • Rollout speed • Unknowns in our legacy code • Learning • Normal day to day work
34. Legacy Async Code We made coroutines GA
35. When is the pain worth it? For navigation, we are not sure.
36. Jetpack Libraries are scarier than others as they are crucial to showing anything on screen.
37. Where are we now?
38. Full Hilt Complete
39. Jetpack DataStore In validation
40. Compose Blocked on performance improvements
41. Lifecycle Using normal androidx.Lifecycle patterns
42. Navigation We have a proof of concept
43. Outsourcing from your team What can others do?
44. Outsourcing from your team Java to Kotlin
45. Migration Options
46. Migration Options Only for new code
47. Migration Options Under the hood
48. Migration Options Shim layer
49. Migration Options Central migration
50. Migration Options Distributed self- serve
51. Migration Options Distributed mandate
52. Putting a Jetpack on your legacy codebase Kurt Nelson (he/him) Android Platform at Pinterest Mastodon: kurt@nelson.fun, kurtisnelson on the socials github.com/kurtisnelson/presentations