graphql: Restrict construction of selection sets

Author: lutter

graphql/src/execution/ast.rs

@@ -14,10 +14,23 @@ pub struct FragmentDefinition {
 
 #[derive(Debug, Clone, PartialEq)]
 pub struct SelectionSet {
-    pub span: (Pos, Pos),
+    span: (Pos, Pos),
     pub items: Vec<Selection>,
 }
 
+impl SelectionSet {
+    pub fn new(span: (Pos, Pos), items: Vec<Selection>) -> Self {
+        SelectionSet { span, items }
+    }
+
+    pub fn empty_from(other: &SelectionSet) -> Self {
+        SelectionSet {
+            span: other.span.clone(),
+            items: Vec::new(),
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq)]
 pub enum Selection {
     Field(Field),

graphql/src/execution/execution.rs

@@ -282,14 +282,8 @@ pub fn execute_root_selection_set_uncached(
 ) -> Result<Object, Vec<QueryExecutionError>> {
     // Split the top-level fields into introspection fields and
     // regular data fields
-    let mut data_set = a::SelectionSet {
-        span: selection_set.span,
-        items: Vec::new(),
-    };
-    let mut intro_set = a::SelectionSet {
-        span: selection_set.span,
-        items: Vec::new(),
-    };
+    let mut data_set = a::SelectionSet::empty_from(selection_set);
+    let mut intro_set = a::SelectionSet::empty_from(selection_set);
     let mut meta_items = Vec::new();
 
     for (_, fields) in collect_fields(ctx, root_type, iter::once(selection_set)) {

graphql/src/execution/query.rs

@@ -295,10 +295,7 @@ impl Query {
 
             let (selection_set, error_policy) = bcs.entry(bc).or_insert_with(|| {
                 (
-                    a::SelectionSet {
-                        span: self.selection_set.span,
-                        items: vec![],
-                    },
+                    a::SelectionSet::empty_from(&self.selection_set),
                     field_error_policy,
                 )
             });
@@ -800,7 +797,7 @@ impl RawQuery {
                     }
                 })
                 .collect::<Result<Vec<_>, _>>()?;
-            Ok(a::SelectionSet { span, items })
+            Ok(a::SelectionSet::new(span, items))
         }
 
         fn expand_directives(