Fragment Name Uniqueness

Formal Specification

• For each fragment definition fragment in the document
• Let fragmentName be the name of fragment .
• Let fragments be all fragment definitions in the document named fragmentName .
• fragments must be a set of one.

Explanatory Text

Fragment definitions are referenced in fragment spreads by name. To avoid ambiguity, each fragment’s name must be unique within a document.

Inline fragments are not considered fragment definitions, and are unaffected by this validation rule.

For example the following document is valid:

{
  dog {
    ...fragmentOne
    ...fragmentTwo
  }
}

fragment fragmentOne on Dog {
  name
}

fragment fragmentTwo on Dog {
  owner {
    name
  }
}

While this document is invalid:

{
  dog {
    ...fragmentOne
  }
}

fragment fragmentOne on Dog {
  name
}

fragment fragmentOne on Dog {
  owner {
    name
  }
}