/// <summary>
/// For each subscription operation definition subscription in the document
/// Let subscriptionType be the root Subscription type in schema.
/// Let selectionSet be the top level selection set on subscription.
/// Let variableValues be the empty set.
/// Let groupedFieldSet be the result of CollectFields(subscriptionType, selectionSet, variableValues).
/// groupedFieldSet must have exactly one entry.
/// </summary>
public static CombineRule R5231SingleRootField()
{
return((context, rule) =>
{
rule.EnterDocument += document =>
{
var subscriptions = document.Definitions
.OfType <GraphQLOperationDefinition>()
.Where(op => op.Operation == OperationType.Subscription)
.ToList();
if (!subscriptions.Any())
{
return;
}
var schema = context.Schema;
//todo(pekka): should this report error?
if (schema.Subscription == null)
{
return;
}
var subscriptionType = schema.Subscription;
foreach (var subscription in subscriptions)
{
var selectionSet = subscription.SelectionSet;
var variableValues = new Dictionary <string, object>();
var groupedFieldSet = SelectionSets.CollectFields(
schema,
context.Document,
subscriptionType,
selectionSet,
variableValues);
if (groupedFieldSet.Count != 1)
{
context.Error(
ValidationErrorCodes.R5231SingleRootField,
"Subscription operations must have exactly one root field.",
subscription);
}
}
};
});
}
public static async Task <ISubscriberResult> CreateSourceEventStreamAsync(
IExecutorContext context,
OperationDefinition subscription,
IReadOnlyDictionary <string, object?> coercedVariableValues,
object initialValue,
CancellationToken cancellationToken)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (subscription == null)
{
throw new ArgumentNullException(nameof(subscription));
}
if (coercedVariableValues == null)
{
throw new ArgumentNullException(nameof(coercedVariableValues));
}
cancellationToken.ThrowIfCancellationRequested();
var schema = context.Schema;
var subscriptionType = schema.Subscription;
var groupedFieldSet = SelectionSets.CollectFields(
context.Schema,
context.Document,
subscriptionType,
subscription.SelectionSet,
coercedVariableValues
);
var fields = groupedFieldSet.Values.First();
var fieldName = fields.First().Name;
var fieldSelection = fields.First();
var coercedArgumentValues = ArgumentCoercion.CoerceArgumentValues(
schema,
subscriptionType,
fieldSelection,
coercedVariableValues);
var field = schema.GetField(subscriptionType.Name, fieldName);
var path = new NodePath();
var resolveContext = new ResolverContext(
subscriptionType,
initialValue,
field,
fieldSelection,
fields,
coercedArgumentValues,
path,
context);
var subscriber = schema.GetSubscriber(subscriptionType.Name, fieldName);
if (subscriber == null)
{
throw new QueryExecutionException(
$"Could not subscribe. Field '{subscriptionType}:{fieldName}' does not have subscriber",
path);
}
var subscribeResult = await subscriber(resolveContext, cancellationToken)
.ConfigureAwait(false);
return(subscribeResult);
}