GraphQL_nullability__state_of_the_union.pdf

Transcript

1. GraphQL nullability State of the union apidays 2023
2. Agenda • Problem • Solutions
4. { "data" { "video": { "id": "42", "title": "GraphQL 101", "uploadDate": "2023-12-03T22:26:46Z" } } }
7. 2017 Nullable types!
8. ❤
9. But… Non-Null String String! Nullable String? String 💪 🤔
10. query GetVideo { video(id: "42") { title description viewCount comments(first: 5) { nodes { author text } } } } Nullable
11. ??Why is everything nullable???? ????? ??
12. https://graphql.org/learn/best-practices/#nullability
14. Error null != Semantic null { "errors": [ { "message": "cannot resolve title", "path": "video.title" } ] "data": { "video": { "id": "42", "title": null } } }
15. Terminology • Error null ◦ Exceptional case ◦ Has an error in the errors array • Semantic null ◦ Business case ◦ No error in the errors array
16. @Composable fun VideoItem(video: Video) { Text(text = video.title!!) }
17. @Composable fun VideoItem(response: Response) { if (response.errors.isNotEmpty()) { Error() } else { Text(text = response.data.video.title!!) } }
18. 2 months later
19. Post mortem • New feature: video upload • During the upload, a video doesn’t have a title yet • This was a backward compatible schema change!
20. @Composable fun VideoItem(response: Response) { if (response.errors.isNotEmpty()) { Error() } else { if (response.data.video.title == null) { Text(text = "This video doesn't have a title yet") } else { Text(text = response.data.video.title) } } }
21. Different shades of error handling
22. There is more…
24. @Composable fun VideoItem(response: Response) { if (response.errors.any { it.path == "video.title" }) { Error() // Can't display a video without a title } else { if (response.data.video.title != null) { Text(text = "This video does not have a title yet") } else { Text(text = response.data.video.title!!) } if (response.errors.any { it.path == "video.viewCount" }) { // Skip viewCount } else { Text(text = "${response.data.video.viewCount!!} + views") } } } Partial data
25. 10 fields ⇨ 1024 possibilities
26. Guessing game • Semantic null? • Error null? • 🤷
27. GraphQL is missing types Your favorite type-safe language GraphQL string → String! string | null → String string | error → String string | null | error → String
28. Part II: solutions
29. Documentation type Video { """ The title of the Video null if the video has just been uploaded """ title: String """ Number of times this video has been watched Never null unless there is an error """ viewCount: Int }
30. Evolving the language
31. Nullability working group 2021 Client Controlled Nullability May 2023 sub working group Sep 2023 GraphQL conf True nullability Asterisk Interrobang Oct 2023 semantic-non-null @strictNullability @catch graphql/nullability-wg
32. Nullability working group 2021 Client Controlled Nullability May 2023 sub working group Sep 2023 GraphQL conf True nullability Asterisk Interrobang Oct 2023 semantic-non-null @strictNullability @catch graphql/nullability-wg
33. Asterisk string → String! string | null → don’t use string | error → String* string | null | error → String graphql/graphql-spec/pull/1048 Never a semantic null
34. Strict nullability string → String! string | null → don’t use string | error → String string | null | error → String? graphql/graphql-wg/discussions/1410 schema @strictNullability { query: Query } Never a semantic null
35. ❤
36. Conclusion • null is not always what it seems! • be aware of the tradeoffs • document nullability • get involved!
37. Thank you! graphql/nullability-wg martinbonnin
38. Empty slide
39. Input nullability string → String! string | null → String string | absent → String string | null | absent → String graphql/graphql-spec/issues/476
40. Semantic non-null string → String! string | null → don’t use string | error → !String string | null | error → String graphql/graphql-spec/pull/1065
41. Interrobang string → String! string | null → don’t use string | error → String!? string | null | error → String graphql/graphql-spec/pull/1046
42. string → String! string | null → don’t use string | error → String @semanticNonNull string | null | error → String @semanticNonNull
43. Problem 2: what default? • Fail the whole query ◦ Easy ◦ Fragile • Handle field errors ◦ Hard ◦ Robust
44. Opting in error handling • Start easy • Add error handling progressively fragment VideoDetails on Video { video { title # opt-in error handling viewCount @catch } } facebook/relay/issues/4416
45. Opting in error handling fragment VideoDetails on Video { video { title # opt-in error handling viewCount @catch } } sealed interface Result<T> { class Success(val value: T): Result class Failure(val error: error): Result } Video( val title: String val viewCount: Result<Int> ) apollographql/apollo-kotlin/pull/5405
46. Client Controlled Nullability graphql/graphql-wg/blob/main/rfcs/ClientControlledNullability.md fragment videoDetails on Video { video { # We need title to display a video title! # It's okay to fail viewCount viewCount? } }
47. string → String string | null → String? string | error → String @throws string | null | error → String? @throws Exceptions graphql/nullability-wg/discussions/39
48. Exceptions string → don’t use string | null → don’t use string | error → String string | null | error → String? graphql/nullability-wg/discussions/39