Validate new arguments scenario for 1diff

Reviewed By: chikit

Differential Revision: D56655349

fbshipit-source-id: 514ecc4737283bf4c7f35271028d78fd5b6074c4

compiler/crates/schema/src/definitions/interface.rs

@@ -31,6 +31,13 @@ pub struct Interface {
 }
 
 impl Interface {
+    pub fn named_field<S: Schema>(&self, name: StringKey, schema: &S) -> Option<FieldID> {
+        self.fields
+            .iter()
+            .find(|field_id| schema.field(**field_id).name.item == name)
+            .copied()
+    }
+
     /// Return all objects that implement, directly or recursively, a given interface.
     /// The iteration order of the HashSet might depend on the order in which schema files
     /// are processed. It should not be relied upon when generating artifacts.