Extract possibleTypes for interface types in buildClientSchema

[IanChen83]

The IntrospectionInterfaceType includes the possibleTypes field, but when we call buildClientSchema with the introspection result provided, the possibleType is not used

graphql-js/src/utilities/buildClientSchema.ts

Lines 246 to 255 in 1bf71ee

	function buildInterfaceDef(
	interfaceIntrospection: IntrospectionInterfaceType,
	): GraphQLInterfaceType {
	return new GraphQLInterfaceType({
	name: interfaceIntrospection.name,
	description: interfaceIntrospection.description,
	interfaces: () => buildImplementationsList(interfaceIntrospection),
	fields: () => buildFieldDefMap(interfaceIntrospection),
	});
	}

.

This information, however, is useful for static analysis that doesn't require an executable schema. Does it make sense to provide isTypeOf during buildClientSchema for interface types ?

[yaacovCR]

The introspection result contains bidirectional data, ie interfaces report which concrete types implement them and object types report which interfaces they implement. But when creating a schema, only the latter is required, and the rest is calculated.

On that, we appear to be agreed! But I am afraid I do not yet understand what you are suggesting should be different! Perhaps you are suggesting that some of this (re)calculation can be avoided when creating a schema directly from an introspection result, speeding up the process?

That might be an interesting optimization. Is that tho what you are suggesting?

Sorry for the late comment!