add semanticNonNullField and make levels an array

nullability/v0.2/nullability-v0.2.graphql

@@ -11,65 +11,87 @@ type User {
 }
 ```
 
-The `field` argument is the name of the field if `@semanticNonNull` is applied to an object type extension:
-
-```graphql
-# extend the base schema to make User.email semantically non-null.
-extend type User @semanticNonNull(field: "email")
-```
-
-`field` is used for client applications that do not control the base schema and must use type extensions.
-When used on a field definition, `field` must be null.
-
-The `level` argument indicates what level is semantically non null in case of lists:
+The `levels` argument indicates what levels are semantically non null in case of lists:
 
 ```graphql
 type User {
     # friends is semantically non null
-    friends: [User] @semanticNonNull # same as @semanticNonNull(level: 0)
+    friends: [User] @semanticNonNull # same as @semanticNonNull(levels: [0])
 
     # every friends[k] is semantically non null
-    friends: [User] @semanticNonNull(level: 1)
+    friends: [User] @semanticNonNull(levels: [1])
 
     # friends as well as every friends[k] is semantically non null
-    friends: [User] @semanticNonNull(level: 0) @semanticNonNull(level: 1)
+    friends: [User] @semanticNonNull(levels: [0, 1])
 }
 ```
 
-`level` is zero indexed.
+`levels` are zero indexed.
+Passing a negative level or a level greater than the list dimension is an error.
+
+"""
+directive @semanticNonNull(levels: [Int] = [0]) on FIELD_DEFINITION
+
+"""
+Indicates that a position is semantically non null: it is only null if there is a matching error in the `errors` array.
+In all other cases, the position is non-null.
+
+`@semanticNonNullField` is the same as `@semanticNonNull` but can be used on type system extensions for services
+that do not own the schema like client services:
+
+```graphql
+# extend the schema to make User.email semantically non-null.
+extend type User @semanticNonNullField(name: "email")
+```
+
+The `levels` argument indicates what levels are semantically non null in case of lists:
+
+```graphql
+# friends is semantically non null
+extend type User @semanticNonNullField(name: "friends")  # same as @semanticNonNullField(name: "friends", levels: [0])
+
+# every friends[k] is semantically non null
+extend type User @semanticNonNullField(name: "friends", levels: [1])
+
+# friends as well as every friends[k] is semantically non null
+extend type User @semanticNonNullField(name: "friends", levels: [0, 1])
+```
+
+`levels` are zero indexed.
 Passing a negative level or a level greater than the list dimension is an error.
 
+See `@semanticNonNull`.
 """
-directive @semanticNonNull(field: String = null, level: Int = 0) repeatable on FIELD_DEFINITION | OBJECT
+directive @semanticNonNullField(name: String!, levels: [Int] = [0]) repeatable on OBJECT | INTERFACE
 
 """
 Indicates how clients should handle errors on a given position.
 
 When used on the schema definition, `@catch` applies to every position that can return an error.
 
-The `level` argument indicates where to catch errors in case of lists:
+The `levels` argument indicates where to catch errors in case of lists:
 
 ```graphql
 {
     user {
         # friends catches errors
-        friends @catch { name } # same as @catch(level:0)
+        friends @catch { name } # same as @catch(levels: [0])
 
         # every friends[k] catches errors
-        friends @catch(level: 0) { name }
+        friends @catch(levels: [0]) { name }
 
         # friends as well as every friends[k] catches errors
-        friends @catch(level: 0) @catch(level: 1) { name }
+        friends @catch(levels: [0, 1]) { name }
     }
 }
 ```
 
-`level` is zero indexed.
+`levels` are zero indexed.
 Passing a negative level or a level greater than the list dimension is an error.
 
 See `CatchTo` for more details.
 """
-directive @catch(to: CatchTo! = RESULT, level: Int = 0) repeatable on FIELD | SCHEMA
+directive @catch(to: CatchTo! = RESULT, levels: [Int] = [0]) on FIELD | SCHEMA
 
 enum CatchTo {
     """