Add ARGUMENT in DirectiveLocation

[dugenkui03]

I think it will be great if ARGUMENT will be allowed in DirectiveLocation, and ARGUMENT means that user can user directive on argument in query.

That is the scene: we want to divide list argument into groups by size, and get the field value respectively, then merge the result into result list.

1. schema type definition:

Type Query{
     itemList(itemIds: [Int]): [Item]
}

Type Item{
      id: ID
      price: Int
}

2. ARGUMENT definition:

directive @partition(size: Int) on ARGUMENT

3. use @partition in query:

query getTooManyItemByIds(itemIds:[Int]){
      itemList(itemIds:$itemIds @partition(size:5)){
             id
             price
      }
} 

[rivantsov]

+1 for the idea; but sample case is not good IMHO

[SpencerMacKinnon]

Adding the ability to specify a directive on an input-object field (within the query document, not the input object field definition) would be useful as well.