39 lines
1.1 KiB
Plaintext
39 lines
1.1 KiB
Plaintext
// @flow strict
|
|
|
|
import { GraphQLError } from '../../error/GraphQLError';
|
|
|
|
import { type ASTVisitor } from '../../language/visitor';
|
|
import { type OperationDefinitionNode } from '../../language/ast';
|
|
|
|
import { type ASTValidationContext } from '../ValidationContext';
|
|
|
|
export function singleFieldOnlyMessage(name: ?string): string {
|
|
return name
|
|
? `Subscription "${name}" must select only one top level field.`
|
|
: 'Anonymous Subscription must select only one top level field.';
|
|
}
|
|
|
|
/**
|
|
* Subscriptions must only include one field.
|
|
*
|
|
* A GraphQL subscription is valid only if it contains a single root field.
|
|
*/
|
|
export function SingleFieldSubscriptions(
|
|
context: ASTValidationContext,
|
|
): ASTVisitor {
|
|
return {
|
|
OperationDefinition(node: OperationDefinitionNode) {
|
|
if (node.operation === 'subscription') {
|
|
if (node.selectionSet.selections.length !== 1) {
|
|
context.reportError(
|
|
new GraphQLError(
|
|
singleFieldOnlyMessage(node.name && node.name.value),
|
|
node.selectionSet.selections.slice(1),
|
|
),
|
|
);
|
|
}
|
|
}
|
|
},
|
|
};
|
|
}
|