feat: hook into onExecuteSubscriptionEvent and useContextPerSubscriptionEvent

[n1ru4l]

This is the first attempt of trying to solve #80

Example Usage:

import { envelop } from "@envelop/core";

const getEnveloped = envelop({
  plugins: [
    useContextPerSubscriptionEvent(async () => ({
      contextValue: { someValue: 1 },
      onEnd: () => cleanupResources()
    }))
  ]
});

const { subscribe } = getEnveloped();

There are several things that are currently not optimal

1. subscribe override

I created a copy of subscribe from graphql-js (which is surprisingly lightweight) and adjusted it so a custom execute function can be used for the ExecuteSubscriptionEvent phase.

I assume that the reason why it is not possible to provide a custom execute to the original subscribe from graphql-js is that the usage of execute is considered an implementation detail.

There is a pull request that attempts to allow overriding the execute passed to subscribe but no update from the graphql-js maintainers has been made recently. (graphql/graphql-js#2485) I also created graphql/graphql-js#3071

The plugin hard overrides the subscribe function. I cannot imagine any use-cases right now where you would want to compose subscribe functions (but I for example compose execute functions within graphql-live-query, so there might be a niche for that also with subscribe).

Ideally, I would like to avoid having a copy of subscribe, but I see no other option right now.

2. Context composition hook compatibility

This does currently not work with context composition, as we use a custom factory for creating the context. It would be interesting to get more insight on this from different people. I usually use the same context factory function for all operation types (mutation, subscription, or query). So maybe instead of having a custom createContext factory function, we should instead construct the context the same way as for execute (or subscribe). Probably the useContextPerSubscriptionValue createContext argument should be optional and instead, the implementation should use the default composition way of creating the context if the argument is not provided. Right now you would have to do sth like this:

import { envelop } from "@envelop/core";

let contextFactor = null;
const getEnveloped = envelop({
  plugins: [
    useContextPerSubscriptionEvent(async () => ({
      contextValue: await contextFactory()
    }))
  ]
});

const { subscribe, _contextFactory } = getEnveloped();
contextFactory = _contextFactory;

[changeset-bot]

🦋 Changeset detected

Latest commit: 3bb8394

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
@envelop/core	Patch
@envelop/types	Patch
@envelop/execute-subscription-event	Patch

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[theguild-bot]

The latest changes of this PR are available as alpha in npm (based on the declared changesets):

@envelop/[email protected]
@envelop/[email protected]
@envelop/[email protected]

[dotansimha]

@n1ru4l maybe we should append this context to the general one?
I think it might be an issue that we have separate context created here, and not having the original one as well, since resolvers might depend on the context.

[dotansimha]

Update this ;)

[dotansimha]

Some plugins might use setExecuteFn during onExecute with the assumption that they override this function.
Does it mean that these plugins need somehow to override this function here ?

[dotansimha]

Looking good. just some minor changes :) (and we need a rebase :P )