Initialisation

Added the packages and files for the backend server

node_modules/graphql/validation/rules/ScalarLeafsRule.mjs

@@ -0,0 +1,46 @@
+import { inspect } from '../../jsutils/inspect.mjs';
+import { GraphQLError } from '../../error/GraphQLError.mjs';
+import { getNamedType, isLeafType } from '../../type/definition.mjs';
+
+/**
+ * Scalar leafs
+ *
+ * A GraphQL document is valid only if all leaf fields (fields without
+ * sub selections) are of scalar or enum types.
+ */
+export function ScalarLeafsRule(context) {
+  return {
+    Field(node) {
+      const type = context.getType();
+      const selectionSet = node.selectionSet;
+
+      if (type) {
+        if (isLeafType(getNamedType(type))) {
+          if (selectionSet) {
+            const fieldName = node.name.value;
+            const typeStr = inspect(type);
+            context.reportError(
+              new GraphQLError(
+                `Field "${fieldName}" must not have a selection since type "${typeStr}" has no subfields.`,
+                {
+                  nodes: selectionSet,
+                },
+              ),
+            );
+          }
+        } else if (!selectionSet) {
+          const fieldName = node.name.value;
+          const typeStr = inspect(type);
+          context.reportError(
+            new GraphQLError(
+              `Field "${fieldName}" of type "${typeStr}" must have a selection of subfields. Did you mean "${fieldName} { ... }"?`,
+              {
+                nodes: node,
+              },
+            ),
+          );
+        }
+      }
+    },
+  };
+}