Apollo Plugin willResolveField event is not fired

[lkrzyzanek]

I'm cross-posting question from envelop: n1ru4l/envelop#1523

We use envelop (as part of graphql-mesh) with Apollo as custom server.

Apollo plugins implementing execute phase works correctly. Events like requestDidStart or willSendResponse are fired without any issue. (https://www.apollographql.com/docs/apollo-server/integrations/plugins/)

The problem is that willResolveField is not fired at all. The executionDidStart which is just before it is executed.
This breaks plugins which use this event e.g. ApolloServerPluginCacheControl. (https://github.com/apollographql/apollo-server/blob/main/packages/apollo-server-core/src/plugin/cacheControl/index.ts#L133)

Is there any reason/limitation that causes this issue?

Thanks.
Libor

[ardatan]

Not sure about your configuration but if a source has its own executor that doesn't use resolvers, willResolveField won't work.
For example GraphQL handler has an executor instead of graphql-js's execute that calls resolvers and so on, so there are no resolvers.
In that case, you don't get willResolveField triggered.
That's an expected behavior.

[lkrzyzanek]

Thanks for reply.
We follow docs how to provide custom server: https://www.the-guild.dev/graphql/mesh/docs/getting-started/customize-mesh-server#provide-a-standalone-server-implementation so the main executor is as described in docs (with envelope etc).

We use GraphQL & Open API handlers where some GraphQL handlers are local JS implementations (by using makeExecutableSchema) and another external subgraphs.
My thought was that if GraphQL datasource is created by using local JS with typeDefs & resolves then willResolveField could be executed but it isn't.

Does it mean that it's expected that willResolveField is not executed and then Apollo Plugins are just partially supported? Or is it more related to envelop itself?

[lkrzyzanek]

Reading docs and I see that envelop has own event that seems to be equivalent to willResolveField.
It's onResolverCalled - https://www.envelop.dev/docs/plugins/lifecycle#onresolvercalledapi

If this is true then Apollo Plugin using willResolveField could be re-implemented to Envelop plugin by using onResolverCalled.
WDYT?