对象类型验证

Object types have the potential to be invalid if incorrectly defined. This set of rules must be adhered to by every Object type in a GraphQL schema.

1. An Object type must define one or more fields.
2. The fields of an Object type must have unique names within that Object type; no two fields may share the same name.
3. Each field of an Object type must not have a name which begins with the characters "__" (two underscores).
4. An object type must be a super‐set of all interfaces it implements:
   1. The object type must include a field of the same name for every field defined in an interface.
      1. The object field must be of a type which is equal to or a sub‐type of the interface field (covariant).
         1. An object field type is a valid sub‐type if it is equal to (the same type as) the interface field type.
         2. An object field type is a valid sub‐type if it is an Object type and the interface field type is either an Interface type or a Union type and the object field type is a possible type of the interface field type.
         3. An object field type is a valid sub‐type if it is a List type and the interface field type is also a List type and the list‐item type of the object field type is a valid sub‐type of the list‐item type of the interface field type.
         4. An object field type is a valid sub‐type if it is a Non‐Null variant of a valid sub‐type of the interface field type.
      2. The object field must include an argument of the same name for every argument defined in the interface field.
         1. The object field argument must accept the same type (invariant) as the interface field argument.
      3. The object field may include additional arguments not defined in the interface field, but any additional argument must not be required.