Introspection fails when types implement multiple interfaces

[Matt-Kantor-CK]

Despite being valid, types like type FooBar implements IFoo, IBar cause the apollo-codegen introspect-schema command to blow up with a parser error (Unexpected Name). This was observed with apollo-codegen 0.19.1.

I created a small demo here: https://github.com/mkantor/demo-apollo-codegen-bug

[Matt-Kantor-CK]

I just took a closer look at the spec and it turns out that actually & is the official way to indicate that a type implements multiple interfaces.

However I see a lot of code in the wild using commas instead. I'm having trouble tracking down the history here, but would be curious if anyone has links where I can learn more. My guess would be that some tool(s) were based on an unofficial SDL grammar using comma before the official spec landed with &?

Anyway, this might not be a bug if this tool is only meant to support the official SDL grammar (& works as expected with apollo-codegen introspect-schema). Feel free to close this issue if that's the case.