fix: __typename do not work at root level (#2840)

Co-authored-by: Tushar Mathur <[email protected]>

src/core/jit/builder.rs

@@ -354,6 +354,7 @@ impl Builder {
         });
 
         let plan = OperationPlan::new(
+            name,
             fields,
             operation.ty,
             self.index.clone(),

src/core/jit/input_resolver.rs

@@ -82,6 +82,7 @@ where
             .collect::<Result<Vec<_>, _>>()?;
 
         Ok(OperationPlan::new(
+            self.plan.root_name(),
             new_fields,
             self.plan.operation_type(),
             self.plan.index.clone(),

src/core/jit/model.rs

@@ -345,6 +345,7 @@ pub struct Nested<Input>(Vec<Field<Nested<Input>, Input>>);
 
 #[derive(Clone)]
 pub struct OperationPlan<Input> {
+    root_name: String,
     flat: Vec<Field<Flat, Input>>,
     operation_type: OperationType,
     nested: Vec<Field<Nested<Input>, Input>>,
@@ -379,6 +380,7 @@ impl<Input> OperationPlan<Input> {
         }
 
         Ok(OperationPlan {
+            root_name: self.root_name,
             flat,
             operation_type: self.operation_type,
             nested,
@@ -389,7 +391,9 @@ impl<Input> OperationPlan<Input> {
 }
 
 impl<Input> OperationPlan<Input> {
+    #[allow(clippy::too_many_arguments)]
     pub fn new(
+        root_name: &str,
         fields: Vec<Field<Flat, Input>>,
         operation_type: OperationType,
         index: Arc<Index>,
@@ -406,6 +410,7 @@ impl<Input> OperationPlan<Input> {
             .collect::<Vec<_>>();
 
         Self {
+            root_name: root_name.to_string(),
             flat: fields,
             nested,
             operation_type,
@@ -414,6 +419,11 @@ impl<Input> OperationPlan<Input> {
         }
     }
 
+    /// Returns the name of the root type
+    pub fn root_name(&self) -> &str {
+        &self.root_name
+    }
+
     /// Returns a graphQL operation type
     pub fn operation_type(&self) -> OperationType {
         self.operation_type