All operations, including subscription operations, are covered by the execution section of the GraphQL spec

...and executeQueryOrMutationRootFields

to prepare for integration of executeSubscription

this function currently does not throw GraphQLErrors -- it is not within the parallel try block within execute

to executeSubscriptionRootField

...to execution file

to operate only on ExecutionContext

-- In at least a few cases, destructuring assignment from exeContext can improve code readability.
-- Overrides to exeContext can be set using object spread syntax.

Instead of possibly retuning an array of GraphQLErrors, buildExecutionContext can throw a GraphQLAggregateError to report any encountered errors.

only called by buildExecutionContext

This class is exported only to assist people in implementing their own executors without duplicating too much code and should be used only as last resort for cases such as experimental syntax or if certain features could not be contributed upstream.

It is still part of the internal API and is versioned, so any changes to it are never considered breaking changes. If you still need to support multiple versions of the library, please use the `versionInfo` variable for version detection.

...into Executor

ExecutorArgs and ExecutionContext