Directives Are Unique Per Location

Formal Specification

• For every location in the document for which Directives can apply:
  • Let directives be the set of Directives which apply to location .
  • For each directive in directives :
    • Let directiveName be the name of directive .
    • Let namedDirectives be the set of all Directives named directiveName in directives .
    • namedDirectives must be a set of one.

Explanatory Text

Directives are used to describe some metadata or behavioral change on the definition they apply to. When more than one directive of the same name is used, the expected metadata or behavior becomes ambiguous, therefore only one of each directive is allowed per location.

For example, the following query will not pass validation because@skiphas been used twice for the same field:

query ($foo: Boolean = true, $bar: Boolean = false) {
  field @skip(if: $foo) @skip(if: $bar)
}

However the following example is valid because@skiphas been used only once per location, despite being used twice in the query and on the same named field:

query ($foo: Boolean = true, $bar: Boolean = false) {
  field @skip(if: $foo) {
    subfieldA
  }
  field @skip(if: $bar) {
    subfieldB
  }
}