Schema composition with directives that use complex argument types

Consider the following type definitions that will be used to build an Apollo Federation schema:

directive @something(rules: [Rule!]!) on OBJECT | FIELD_DEFINITION

enum Number {
  one
  two
}

input Rule {
  numbers: [Number!]!
}

type Something {
  id: ID!
}

extend type Query {
  getSomething(id: ID!): Something!
    @something(rules: [{ numbers: [one, two] }])
}

A single directive called @something is declared, that takes in a non-nullable list of GraphQL input object types. This directive can then be used on objects and field definitions to perform some task. An example of a similar directive can be found here: https://docs.amplify.aws/cli/graphql-transformer/auth#auth.

The problem arises during composition of the schema, namely that input type Rule is being registered twice, leading to this error: https://github.com/graphql/graphql-js/blob/00eab30fb269b6e2a4e8e61d097d3e249319420e/src/type/schema.js#L223.

From what it seems, type property name is used to uniquely identify any given type in the schema, as evidenced by: https://github.com/graphql/graphql-js/blob/00eab30fb269b6e2a4e8e61d097d3e249319420e/src/type/schema.js#L216 https://github.com/graphql/graphql-js/blob/00eab30fb269b6e2a4e8e61d097d3e249319420e/src/type/schema.js#L221

During schema composition, all declared types are collected in a set using the following helper function: https://github.com/graphql/graphql-js/blob/00eab30fb269b6e2a4e8e61d097d3e249319420e/src/type/schema.js#L403

Inside that function, there is a check that should prevent duplicate types from being added to the set of all referenced types: https://github.com/graphql/graphql-js/blob/00eab30fb269b6e2a4e8e61d097d3e249319420e/src/type/schema.js#L409

Given this information and understanding the mechanics of Set class in JS, there is a chance that !typeSet.has(namedType)will result in a false positive if two objects have different references. As a consequence, some types may be registered twice, as in the example above with Rule type.

This problem appears to be quite simple to fix. There are two approaches:

• Use Set class from immutable-js, which I would not recommend (see: https://stackoverflow.com/a/56353815)

• Change the following check !typeSet.has(namedType) to something like ![...typeSet].find(({ name }) => name === namedType.name) (see the following line: https://github.com/graphql/graphql-js/blob/00eab30fb269b6e2a4e8e61d097d3e249319420e/src/type/schema.js#L409)

I published an example repository to illustrate the problem: https://github.com/azaxarov/graphql-service-with-complex-directive-parameter

So far, I see no obvious side-effects of implementing a fix using approach nr. 2.

[yaacovCR]

Not sure I agree where the bug is. Seems like similar types with identical names are being created unnecessarily/inappropriately.

[IvanGoncharov]

@azaxarov every time this issue brought up is due to bugs in libraries using graphql-js. The problem here is that we can’t deeply compare non-trivial objects two types can have differences hidden in unexpected places (e.g. extensions or custom class inherited from GraphQLInputObjectType). So our position is to be safe-side instead of silently ignoring such bugs.

That said if you think such checks restricting valid usage scenarios please feel free to open an issue and describe a such scenario.