Allow applyMiddlewareToField to spread extra properties or add specific key for extra metadata

Currently applyMiddlewareToField only spreads the properties it wants to:

https://github.com/prisma/graphql-middleware/blob/500925ade884a025cb6eb2ba99672c4f4a52b13c/src/applicator.ts#L41-L84

It would be really useful if extra properties were also added to the final field definition, that way we could declare some custom properties that could be used directly in the middlewares.

For instance, we could have a middleware added to all mutations, but that only does something to mutations that have a specific flag.

// ...
const resolvers = {
  // ...
  Mutation: {
    // ...
    DoSomething: {
      flags: [FLAGS.SPECIFIC_FLAG],
      resolve: async (root, args, context, info)=> {
        // ...
      },
    }
  },
}

then on the middleware:

const customValidation = {
  async Mutation(resolve, root, args, context, info) {
    // use info to get the _typeConfig of the mutation being executed
    const mutationConfig = ...;
    if (mutationConfig.flags && mutationConfig.flags.includes(FLAGS.SPECIFIC_FLAG)) {
      // Do something
    }
  }
}

I’m asking for that because I’m migrating some code that uses graphql-add-middleware to use graphql-middleware instead.

I’m going to write a post about validations with graphql-middleware, but for it to work I need this “feature”.

Thoughts?

I can get some time to work on that if it’s acceptable.

addResolveFunctionsToSchema from graphql-tools does spreads all other properties, so it’s not a problem.

See related code there: https://github.com/apollographql/graphql-tools/blob/3b77c2071e4b2328b1a4c4471c61d4ad93a6ae57/src/generate/addResolveFunctionsToSchema.ts#L121

https://github.com/apollographql/graphql-tools/blob/3b77c2071e4b2328b1a4c4471c61d4ad93a6ae57/src/generate/addResolveFunctionsToSchema.ts#L140-L147

[JCMais]

@maticzav btw, I just published the post I mentioned above: https://medium.com/@jonathancardoso/graphql-mutation-arguments-validation-with-yup-using-graphql-middleware-645822fb748

[JCMais]

@marktani I’ve just opened a PR for this: https://github.com/prisma/graphql-middleware/pull/26