test: parity with prettier on github schema

cynic-parser/tests/actual_schemas.rs

@@ -14,6 +14,16 @@ macro_rules! schema_tests {
                 insta::assert_snapshot!(parsed.to_sdl_pretty());
             }
 
+            #[test]
+            fn roundtrip() {
+                let parsed = cynic_parser::parse_type_system_document(SCHEMA)
+                    .map_err(|error| error.to_report(SCHEMA))
+                    .unwrap();
+                let sdl = parsed.to_sdl();
+
+                assert_eq!(SCHEMA, sdl);
+            }
+
             #[test]
             fn double_roundtrip() {
                 let parsed = cynic_parser::parse_type_system_document(SCHEMA)

cynic-parser/tests/snapshots/actual_schemas__books__snapshot.snap

@@ -8,6 +8,9 @@ schema {
   subscription: SubscriptionRoot
 }
 
+"""
+Directs the executor to query only when the field exists.
+"""
 directive @ifdef on FIELD
 
 type Book {

schemas/books.graphql

@@ -4,7 +4,9 @@ schema {
   subscription: SubscriptionRoot
 }
 
-# Directs the executor to query only when the field exists.
+"""
+Directs the executor to query only when the field exists.
+"""
 directive @ifdef on FIELD
 
 type Book {