graphql-yoga/esm/validations/stream-directive-on-list-field.js

import { isListType, isWrappingType, GraphQLError, } from 'graphql';
import { GraphQLStreamDirective } from '../directives/stream.js';
/**
 * Stream directive on list field
 *
 * A GraphQL document is only valid if stream directives are used on list fields.
 */
export function StreamDirectiveOnListFieldRule(context) {
    return {
        Directive(node) {
            const fieldDef = context.getFieldDef();
            const parentType = context.getParentType();
            if (fieldDef &&
                parentType &&
                node.name.value === GraphQLStreamDirective.name &&
                !(isListType(fieldDef.type) ||
                    (isWrappingType(fieldDef.type) && isListType(fieldDef.type.ofType)))) {
                context.reportError(new GraphQLError(`Stream directive cannot be used on non-list field "${fieldDef.name}" on type "${parentType.name}".`, { nodes: node }));
            }
        },
    };
}