Add GqlBytes

It reduces the overhead of hex-en/decoding of strings in
field implementations

Author: Junha Yang

graphql-engine/src/lib.rs

@@ -57,8 +57,8 @@ struct MutationRoot {
 
 #[async_graphql::Object]
 impl MutationRoot {
-    async fn send_transaction(&self, tx_type: String, body: String) -> async_graphql::Result<String> {
-        let tx = coordinator::Transaction::new(tx_type, hex::decode(body).map_err(|_| "Failed to parse body")?);
+    async fn send_transaction(&self, tx_type: String, body: GqlBytes) -> async_graphql::Result<String> {
+        let tx = coordinator::Transaction::new(tx_type, body.0);
         // NOTE: Check `queue_own_transaction()` won't cause a deadlock, especially when called by the async runtime.
         Ok(match self.client.queue_own_transaction(tx) {
             Ok(_) => "Done".to_owned(),

graphql-types/src/lib.rs

@@ -80,3 +80,20 @@ impl ScalarType for GqlH256 {
         GqlValue::String(hex::encode(self.0.as_ref()))
     }
 }
+
+pub struct GqlBytes(pub Vec<u8>);
+
+#[Scalar]
+impl ScalarType for GqlBytes {
+    fn parse(value: GqlValue) -> InputValueResult<Self> {
+        if let GqlValue::String(s) = value {
+            Ok(GqlBytes(hex::decode(&s).map_err(|_| InputValueError::custom("Invalid hex-encoded bytes".to_owned()))?))
+        } else {
+            Err(InputValueError::custom("String expected".to_owned()))
+        }
+    }
+
+    fn to_value(&self) -> GqlValue {
+        GqlValue::String(hex::encode(&self.0))
+    }
+}