graphql-yoga-disable-introspection/index.js

Disable introspection in graphql-yoga with a validation rule

var graphql = require('graphql');
/**
 * No introspection: __schema and __type are disallowed in the query.
 */
module.exports = function NoIntrospection(context) {
  return {
    Field(node) {
      if (node.name.value === '__schema' || node.name.value === '__type') {
				context.reportError(
          new graphql.GraphQLError(
            'GraphQL introspection is not allowed',
            [node]
          )
        );
			}	
    }
  };
}