@graphql-tools/graphql
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Fork of GraphQL.js
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JavaScript
import { GraphQLError } from '../../error/GraphQLError.js';
import { Kind } from '../../language/kinds.js';
import { collectFields } from '../../execution/collectFields.js';
/**
* Subscriptions must only include a non-introspection field.
*
* A GraphQL subscription is valid only if it contains a single root field and
* that root field is not an introspection field.
*
* See https://spec.graphql.org/draft/#sec-Single-root-field
*/
export function SingleFieldSubscriptionsRule(context) {
return {
OperationDefinition(node) {
if (node.operation === 'subscription') {
const schema = context.getSchema();
const subscriptionType = schema.getSubscriptionType();
if (subscriptionType) {
const operationName = node.name ? node.name.value : null;
const variableValues = Object.create(null);
const document = context.getDocument();
const fragments = Object.create(null);
for (const definition of document.definitions) {
if (definition.kind === Kind.FRAGMENT_DEFINITION) {
fragments[definition.name.value] = definition;
}
}
const fields = collectFields(schema, fragments, variableValues, subscriptionType, node.selectionSet);
if (fields.size > 1) {
const fieldSelectionLists = [...fields.values()];
const extraFieldSelectionLists = fieldSelectionLists.slice(1);
const extraFieldSelections = extraFieldSelectionLists.flat();
context.reportError(new GraphQLError(operationName != null
? `Subscription "${operationName}" must select only one top level field.`
: 'Anonymous Subscription must select only one top level field.', { nodes: extraFieldSelections }));
}
for (const fieldNodes of fields.values()) {
const field = fieldNodes[0];
const fieldName = field.name.value;
if (fieldName.startsWith('__')) {
context.reportError(new GraphQLError(operationName != null
? `Subscription "${operationName}" must not select an introspection top level field.`
: 'Anonymous Subscription must not select an introspection top level field.', { nodes: fieldNodes }));
}
}
}
}
},
};
}