resolvers-composition: do not mutate resolvers

Currently, composeResolvers mutates the resolvers argument. I am requesting that this behaviour be changed in a future major version, or add a setting so it can be set to not mutate.

[ardatan]

I am not sure I understand your issue because we cannot compose resolvers without mutating them. If you have any idea about doing that differently, feel free to create a PR.

I am trying to use the composeResolvers function as a replacement for graphql-middleware's applyMiddleware function.

Modifying the example from that package's README, I would have expected something like this to work:

const typeDefs = `
type Query {
  hello(name: String): String
  bye(name: String): String
}
`
const resolvers = {
  Query: {
    hello: (root, args, context, info) => {
      console.log(`3. resolver: hello`)
      return `Hello ${args.name ? args.name : 'world'}!`
    },
    bye: (root, args, context, info) => {
      console.log(`3. resolver: bye`)
      return `Bye ${args.name ? args.name : 'world'}!`
    },
  },
}

const logInput = (next) => async (root, args, context, info) => {
  console.log(`1. logInput: ${JSON.stringify(args)}`)
  const result = await next(root, args, context, info)
  console.log(`5. logInput`)
  return result
}

const logResult = (next) => async (root, args, context, info) => {
  console.log(`2. logResult`)
  const result = await next(root, args, context, info)
  console.log(`4. logResult: ${JSON.stringify(result)}`)
  return result
}

const resolversWithMiddleware = composeResolvers(resolvers, {
  '*.*': [logInput, logResult],
});

const serverWithMiddleware = new ApolloServer({
  schema: makeExecutableSchema({ typeDefs, resolvers: resolversWithMiddleware }),
})

const serverWithoutMiddleware = new ApolloServer({
  schema: makeExecutableSchema({ typeDefs, resolvers })
})

But the serverWithoutMiddleware server has the middleware applied, because composeResolvers mutated resolvers.

[ardatan]

Feel free to create a PR to fix this.