Fix the problem when generating Federation SDL. #283

src/registry/export_sdl.rs

@@ -115,8 +115,14 @@ impl Registry {
                 description,
                 ..
             } => {
-                if name == &self.query_type && self.is_empty_query {
-                    return;
+                if name == &self.query_type {
+                    if federation && fields.len() <= 4 {
+                        // Is empty query root, only __schema, __type, _service, _entities fields
+                        return;
+                    } else if !federation && fields.len() <= 2 {
+                        // Is empty query root, only __schema, __type
+                        return;
+                    }
                 }
 
                 if let Some(subscription_type) = &self.subscription_type {

src/registry/mod.rs

@@ -257,7 +257,6 @@ pub struct Registry {
     pub directives: HashMap<String, MetaDirective>,
     pub implements: HashMap<String, HashSet<String>>,
     pub query_type: String,
-    pub is_empty_query: bool,
     pub mutation_type: Option<String>,
     pub subscription_type: Option<String>,
 }

src/schema.rs

@@ -214,12 +214,11 @@ where
         }
     }
 
-    fn create_registry() -> Registry {
+    pub fn create_registry() -> Registry {
         let mut registry = Registry {
             types: Default::default(),
             directives: Default::default(),
             implements: Default::default(),
-            is_empty_query: Query::is_empty(),
             query_type: Query::type_name().to_string(),
             mutation_type: if Mutation::is_empty() {
                 None