[Bug]: GraphQL Aliased Field Queries Cause Duplicate Dictionary Key Error for Same Entity

[JerryNixon]

Discussed in #2785

^{Originally posted by ascii1010 July 24, 2025}

brochure: books(
  filter: { type: { eq: "brochure" } }
) {
  items {
    id
    description
  }
}

magazine: books(
  filter: { type: { eq: "magazine" } }
) {
  items {
    id
    description
  }
}

The above generates error:

An item with the same key has already been added. Key: books

Theory

The issue is not GraphQL itself. It is the resolver implementation using the entity name as the dictionary key instead of the alias or a unique field identifier. Two selections of books are valid GraphQL, but the server code is deduplicating by entity name and therefore treating them as a duplicate dictionary key.