Subscription Context

[lucapinelli]

Hi,
I'm running a server implemented using the recipe: "ws server usage with Express GraphQL". During the onConnect I'm doing the user authentication. Is there a way to inject the user info (or any other info) in the GraphQL subscription context? If during the onConnect it is not possible, in which stage it is possible to modify the context that will be available during the GraphQL subscriptions?

[enisdenjo]

Yap, you can use the context server option (there is also a "ws server usage with custom context value" recipe). You can either provide it with a static context or a function which returns a context.

This value is then used as the GraphQL execution arguments contextValue:

graphql-ws/src/server.ts

Lines 718 to 723 in 79bd429

	// if `onSubscribe` didn't specify a context, inject one
	if (!('contextValue' in execArgs))
	execArgs.contextValue =
	typeof context === 'function'
	? await context(ctx, message, execArgs)
	: context;

[lucapinelli]

thank you! This works perfectly 👍

[bnussman]

I'm so confused. I want to set the context onConnect. The accepted answer does not tell you how to set it only onConnect. I don't want my auth checking to happen for "each operation".

[enisdenjo]

@bnussman you cannot set the GraphQL context in onConnect, only in context and onSubscribe.

If you don't want the re-create the context for each operation; you can create one in onConnect, set it on the connection context extra and then just forward it down inside context. Roughly:

import { authenticateUser } from './my-auth';

useServer(
  {
    // authenticate the user and set it on the connection context
    onConnect: async (ctx) => {
      const user = await authenticateUser(ctx);
      if (!user) {
        return false;
      }
      ctx.extra.user = user;
    },
    // pass down the user from the connection context down to the GraphQL context
    context: (ctx) => ({
      user: ctx.extra.user,
    }),
  },
);

[bnussman]

Thank you so much. I totally neglected to see the extra field. Appreciate you @enisdenjo!