On specifying ordered vs unordered enum definitions

[cdaringe]

Problem

There is no specification on whether EnumTypeDefinition are sorted by Name, and it causes friction for GQL clients who presume there is order.

Context

• EnumTypeDefinition makes no indication of ordering
• Ordering very is significant to clients who convert the stringly-GQL DSL to typed client SDKs
  • example 1 (typescript): Allow sorting in enums to be disabled dotansimha/graphql-code-generator#6935 (comment)
  • example 2 (ios/apollo gen):
    • given an enum enum { Xx Zz Yy }
      • enum => union: union Foo = Xx | Zz | Yy
      • struct: public struct AsXxOrZzOrYy: GraphQLSelectionSet {

As observed from the above, ordering matters during codegen to GQL consumers. If a schema maintainer changed the enum to enum { Yy Xx Zz }, some clients would see this as a breaking change in the status quo.

Discussion

• To help consumers/clients of GQL succeed, the spec should disambiguate ordering on EnumTypeDefinition.

Personal recommendation: enums and tagged unions alike are Sets, thus intrinsically unordered. We should state as much. Equipped with this assertion, client libraries whom seek to do type generation should apply stable sorting.

[benjie]

Good catch. In my opinion, like fields, they should be in the order in which they were defined, which effectively means tools are free to make their own decisions. Either way, the order should be stable in my opinion:

1. introspect a GraphQL schema
2. build a schema from these introspection results
3. introspect this new schema using the same introspection query

The results of 1 and 3 should be identical.

[cdaringe]

@benjie! long time, no-GitHub-see :)

Either way, the order should be stable in my opinion ...

Just to clarify, are you asserting that you think, in the spec, EnumTypeDefinition should specify that entries are ordered?

[martinbonnin]

We've been occasionaly hit by such sorting issues in Apollo Kotlin and the more I think about it the more I think the "good" order for tools is the schema order. Everything else is surprising and error prone.

Sorting codegen by name is dangerous because the schema author doesn't control the sorting anymore so adding an enum starting with "a" offsets all the subsequent ones. All in all, my favorite solution is to keep things as is and have tools that analyze schema changes output a warning for such order changes.

[benjie]

@cdaringe 👋 😁

Just to clarify, are you asserting that you think, in the spec, EnumTypeDefinition should specify that entries are ordered?

Yes; I was writing a reply here but figured more valuable to just make the changes I want to see... so please see explanation in #1063

[cdaringe]

Sounds good. Let’s move subsequent convo over there