Questions about createUnionType with array

[hyunwoona]

Hi,

I'm trying to create a Union type so I can either return an array of RateTypesPayload or ErrorPayload like this:

  @Query(() => RateTypesQueryResponse, {

So I created a Union type as follows

export const RateTypesQueryResponse = createUnionType({
  name: `RateTypesQueryResponse`,
  types: () => [Array<RateTypesPayload>, ErrorPayload] as const,
  resolveType: (value) =>
    (value as ErrorPayload).error === undefined
      ? Array<RateTypesPayload>
      : ErrorPayload,
});

This worked for non-array types, but for arrays, with the code above, the compiler throws the following error:

TypeError: Cannot read properties of undefined (reading 'type')
    at /Users/eric/code/title-rates-api/node_modules/type-graphql/dist/schema/schema-generator.js:72:58
    at Array.map (<anonymous>)
    at typesThunk (/Users/eric/code/title-rates-api/node_modules/type-graphql/dist/schema/schema-generator.js:72:45)
    at resolveThunk (/Users/eric/code/title-rates-api/node_modules/graphql/type/definition.js:480:40)
    at defineTypes (/Users/eric/code/title-rates-api/node_modules/graphql/type/definition.js:944:15)
    at GraphQLUnionType.getTypes (/Users/eric/code/title-rates-api/node_modules/graphql/type/definition.js:900:26)
    at collectReferencedTypes (/Users/eric/code/title-rates-api/node_modules/graphql/type/schema.js:356:59)
    at collectReferencedTypes (/Users/eric/code/title-rates-api/node_modules/graphql/type/schema.js:368:9)
    at new GraphQLSchema (/Users/eric/code/title-rates-api/node_modules/graphql/type/schema.js:153:7)
    at SchemaGenerator.generateFromMetadataSync (/Users/eric/code/title-rates-api/node_modules/type-graphql/dist/schema/schema-generator.js:31:32)

I also tried with Array<typeof RateTypesPayload>, [RateTypesPayload], etc.
How can I make this work with an array?
Thank you!

[MichalLytek]

GraphQL spec does not allow arrays in unions