The problem

When accessing a GraphQL API, you typically do this:

apolloClient.mutate(gql`
  mutation MyMutation($name: String!, $password: $String!) {
    insert_user(objects: [{name: $name, password: $password}]) {
      returning {
        id
      }
    }
  }`,
  variables: {
    name: 'kevin',
    password: 'xxx'
  }
)

It's verbose, but if you also use TypeScript, a decent amount of manual type declarations are needed for type safety and that makes it even more verbose:

type OperationResult = {
  insert_user: {
    returning: Array<{ id: string }>
  }
}

type OperationVariables = {
  name: string
  password: string
}

apolloClient.mutate<OperationResult, OperationVariables>(gql`
  mutation MyMutation($name: String!, $password: $String!) {
    insert_user(objects: [{name: $name, password: $password}]) {
      returning {
        id
      }
    }
  }`,
  variables: {
    name: 'kevin',
    password: 'xxx'
  }
)

The solution

I wonder if it's possible/practical to generate a JS/TS/Go SDK with built-in types from a random GraphQL endpoint, given that you are able to access its schema file.

So instead of using DSL, you use an actual language instead:

const client = require('./generated-client')

await client.insert_user({
  objects: [{ name: 'kevin', password: 'xxx' }],
  select: {
    returning: {
      id: true
    }
  }
})

And it's type-safe by default.