Add isOneOf to inspection query in ApolloSchemaDownloader

[glenngijsberts]

In #537 the @oneOf directive was introduced. However, I noticed that the directive was not included in my schema when I did an introspection, and so the additional types were not generated.

I had a look at the source code, and noticed that the isOneOf was missing from the inspection query done in ApolloSchemaDownloader. I've added it, but I wasn't really able to test this, so I was hoping if somebody can point me in the right direction or help me out with this 🙏

[apollo-cla]

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* (developer-tools)/apollo-mcp-server/(latest)/command-reference.mdx
* (developer-tools)/apollo-mcp-server/(latest)/quickstart.mdx
* (developer-tools)/apollo-mcp-server/(latest)/guides/index.mdx
* graphos/routing/(latest)/operations/subscriptions/configuration.mdx
* graphos/routing/(latest)/performance/caching/entity.mdx
* graphos/routing/v1/customization/native-plugins.mdx
* graphos/routing/v1/graphos-reporting.mdx

Build ID: 08d1b63c67a14a0de34272a3

URL: https://www.apollographql.com/docs/deploy-preview/08d1b63c67a14a0de34272a3

[calvincestari]

Thanks for the PR @glenngijsberts - this seems correct but I'm not sure we can merge it yet since the OneOf spec change PR has not been merged yet.

@martinbonnin / @BoD - is this why isOneOf is commented out in the Kotlin introspection query?

[BoD]

Indeed, selecting isOneOf on __Type will result in an error on servers that don't support it yet - breaking introspection.

To work around this, we implemented "2 step introspection":

• the 1st step is a "pre-introspection" query to gather the capabilities of the server
• 2nd step is the actual introspection query, based on info from the 1st step. What we do in Apollo Kotlin is that we use this base query with certain fields commented, that we programmatically rework (add more fields and such) depending on what is supported.

This can be seen here and here

[calvincestari]

@glenngijsberts - we can see from @BoD's reply that there needs to be more thought put into this change. We cannot break schema downloads for servers out there today so we'll need something like the 2-stage approach that Kotlin has in place.

[glenngijsberts]

@calvincestari @BoD makes sense 👍 I'm gonna have another look at this upcoming week, to see if it's possible to do something similar.

How could I test this? I'm having a bit trouble understanding how everything works in the project, so any advice would be helpful!