Apidays Paris 2023 - Software and APIs for Smart, Sustainable and Sovereign Societies December 6, 7 & 8, 2023 GraphQL Nullability, State of the Union Martin Bonnin, Mobile Engineer at Apollo GraphQL ------ Check out our conferences at https://www.apidays.global/ Do you want to sponsor or talk at one of our conferences? https://apidays.typeform.com/to/ILJeAaV8 Learn more on APIscene, the global media made by the community for the community: https://www.apiscene.io Explore the API ecosystem with the API Landscape: https://apilandscape.apiscene.io/

1. GraphQL nullability
State of the union
apidays 2023

2. Agenda
● Problem
● Solutions

3. Part I: the problem

4. 2016

5. {
"data" {
"video": {
"id": "42",
"title": "GraphQL 101",
"uploadDate": "2023-12-03T22:26:46Z"
}
}
}

6. 2017

8. 2017
Nullable types!

9. ❤

10. But…
Non-Null String String!
Nullable String? String
💪
🤔

11. query GetVideo {
video(id: "42") {
title
description
viewCount
comments(first: 5) {
nodes {
author
text
}
}
}
}
Nullable

12. ??Why is everything nullable????
?????
??

13. https://graphql.org/learn/best-practices/#nullability

15. Error null != Semantic null
{
"errors": [
{
"message": "cannot resolve title",
"path": "video.title"
}
]
"data": {
"video": {
"id": "42",
"title": null
}
}
}

16. Terminology
● Error null
○ Exceptional case
○ Has an error in the errors array
● Semantic null
○ Business case
○ No error in the errors array

17. @Composable
fun VideoItem(video: Video) {
Text(text = video.title!!)
}

18. @Composable
fun VideoItem(response: Response) {
if (response.errors.isNotEmpty()) {
Error()
} else {
Text(text = response.data.video.title!!)
}
}

19. 2 months later

20. Post mortem
● New feature: video upload
● During the upload, a video doesn’t have a title yet
● This was a backward compatible schema
change!

21. @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)
}
}
}

22. Different shades of error handling

23. There is more…

25. @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

26. 10 fields ⇨ 1024 possibilities

27. Guessing game
● Semantic null?
● Error null?
● 🤷

28. GraphQL is missing types
Your favorite
type-safe language
GraphQL
string → String!
string | null → String
string | error → String
string | null | error → String

29. Part II: solutions

30. 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
}

31. Evolving the language

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. 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

34. Asterisk
string → String!
string | null → don’t use
string | error → String*
string | null | error → String
graphql/graphql-spec/pull/1048
Never a semantic
null

35. 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

36. ❤

37. Conclusion
● null is not always what it seems!
● be aware of the tradeoffs
● document nullability
● get involved!

38. Thank you!
graphql/nullability-wg

39. Empty slide

40. Input nullability
string → String!
string | null → String
string | absent → String
string | null | absent → String
graphql/graphql-spec/issues/476

41. Semantic non-null
string → String!
string | null → don’t use
string | error → !String
string | null | error → String
graphql/graphql-spec/pull/1065

42. Interrobang
string → String!
string | null → don’t use
string | error → String!?
string | null | error → String
graphql/graphql-spec/pull/1046

43. string → String!
string | null → don’t use
string | error → String @semanticNonNull
string | null | error → String
@semanticNonNull

44. Problem 2: what default?
● Fail the whole query
○ Easy
○ Fragile
● Handle field errors
○ Hard
○ Robust

45. 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

46. 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

47. 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?
}
}

48. string → String
string | null → String?
string | error → String @throws
string | null | error → String? @throws
Exceptions
graphql/nullability-wg/discussions/39

49. Exceptions
string → don’t use
string | null → don’t use
string | error → String
string | null | error → String?
graphql/nullability-wg/discussions/39

51. Layouts
How do I add a new slide with a preexisting layout?
Layout Guidelines
To add template to a blankslide, click on layout. Click on any template and start editing.

52. Font & Sizes
How do I edit text while keeping the same font style and size?
Layout Guidelines
Right click “Paste without formatting” Or select your text and click “Clear formatting”

53. Add images
How do I add a image container?
Layout Guidelines
Click on the picture icon
to replace image
Double Click to resize or
adjust image placement
Test it out here!

54. Iconography Library 1
Database
CMS
BFF
API
Event Queue
Web
IOS
Android
IoT
AI

55. Iconography Library 2
BFF
BFF
BFF
BFF

56. Illustrations Library 1
Supergraph

57. Illustrations Library 2

58. Illustrations Library 3

59. Illustrations Library 4

60. Typeface Guidelines
DM Sans
Heading 1: 36 - Bold
Heading 2: 24 - Bold

61. Typeface Guidelines
Inter
Body 1: 12 - Regular - Medium - Bold

62. Background colors
Color Guidelines
#15252D
#FFEADB #CFD7D6
Typeface color
Aa Aa
Aa Aa
#FFFFFF

63. Layouts Examples👇

64. Intro cover

65. October, 2023
The value journey with
Apollo GraphOS

66. Exploring what we learned from hundreds of organizations transforming
their business and customer experiences with GraphQL
Insights on the rise of GraphQL
John Doe
Engineer
Katharina Wagner
October 2023 Sunday palace
Engineer

67. Exploring what we learned from hundreds of organizations transforming
their business and customer experiences with GraphQL
Insights on the rise of GraphQL
John Doe
Engineer
Katharina Wagner
Engineer
October 2023 on Sunday Palace

68. Title
Paragraph
Eyebrow

69. Title
Paragraph
Eyebrow

70. Title
Paragraph
Eyebrow

71. Title
Paragraph
Eyebrow

73. Slide cover 1

74. A Data Streaming Platform which
didn’t make the ecosystem
sustainable

75. Slide cover 2

76. “If a monolithic architecture is working
for your company, then don't let us be
the ones to convince you otherwise. If
you are down this microservices road,
then Federation is a really great option.”
Meeng Chee
CEO at Peloton
Email or contact

77. APIs fuel growth.
They are a critical component of every digital initiative in the modern age.
Modernization
initiatives
Developer velocity Omni-channel Mergers and
acquisitions

78. How do the developers that support these initiatives
access all of these APIs?
Products
Images
Deals
Reviews
Inventory
Recommend
ations

79. Three GraphQL Pillars
Option B
Option A Option C

80. ● Self-service
Teams can use them
asynchronously.
● Paved road
A clear, proven path
for teams to follow.
● Time to value
New users get great
results quickly.
● Coherence
Teams can easily find
what they need.
● Cohesion
Features build on each
other.
● Opinionated
A platform cannot be
one-size-fits all.

81. A really long long
subtitle with at least 3
lines of text.
Item title
Build variants of your graph for testing,
staging, and production environments.
Prevent breaking changes
Ensure you can safely deliver changes
across all clients using schema checks.
Communicate cross-functionally
Deliver notifications to systems and
teams using webhooks.
Title

82. Safely ship changes to
the graph with tools
that integrate with your
CI/CD pipeline.
Test with ease
Build variants of your graph for testing,
staging, and production environments.
Prevent breaking changes
Ensure you can safely deliver changes
across all clients using schema checks.
Communicate cross-functionally
Deliver notifications to systems and
teams using webhooks.
DELIVER