45 lines
1.3 KiB
Plaintext
45 lines
1.3 KiB
Plaintext
/**
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* Copyright (c) 2015-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @flow strict
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*/
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import type { ASTValidationContext } from '../ValidationContext';
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import { GraphQLError } from '../../error/GraphQLError';
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import type { OperationDefinitionNode } from '../../language/ast';
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import type { ASTVisitor } from '../../language/visitor';
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export function singleFieldOnlyMessage(name: ?string): string {
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return (
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(name ? `Subscription "${name}" ` : 'Anonymous Subscription ') +
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'must select only one top level field.'
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);
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}
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/**
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* Subscriptions must only include one field.
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*
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* A GraphQL subscription is valid only if it contains a single root field.
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*/
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export function SingleFieldSubscriptions(
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context: ASTValidationContext,
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): ASTVisitor {
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return {
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OperationDefinition(node: OperationDefinitionNode) {
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if (node.operation === 'subscription') {
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if (node.selectionSet.selections.length !== 1) {
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context.reportError(
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new GraphQLError(
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singleFieldOnlyMessage(node.name && node.name.value),
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node.selectionSet.selections.slice(1),
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),
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);
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}
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}
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},
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};
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}
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