Add Typescript typings about graphql

[jneurock]

Thanks for the idea! Can you share some pain points where adding TypeScript would have helped you with this library?

[kdembler]

It's not that painful since the functionality offered by the library isn't that complex and there's only a handful of functions but it's still nice to have. With typings:

• when working with TS, a developer wouldn't need to provide module declaration, i.e. declare module '@miragejs/graphql'
• automatic imports by IDE would be supported
• developers would get better IntelliSense experience
• TS would check for correct function call arguments

Like I've said, these aren't very outstanding issues, but it's pretty standard nowadays to offer TS support

[jneurock]

Checking in now that #23 was merged to see if this issue can be closed or if there's more work to do. Thanks!!

[kdembler]

#23 is certainly a good start but I'd say there's still more work to be done to close this issue. #23 provides basic types that tsc can infer on its own, but for many cases that may not be good enough. For example, let's look at the generated typings for createGraphQLHandler:

export function createGraphQLHandler(graphQLSchema: any | string, mirageSchema: any, { context, resolvers, root }?: {
    context: any;
    resolvers: any;
    root: any;
}): graphQLHandler;

While its certainly much better than nothing, the typings could be improved. In general, any any (:wink:) instance is a place for improvement because any pretty much disables any type checking. graphQLSchema excepts either string or an AST schema - types for this exists inside graphql package. Same with resolvers - those could be typed as well.

There's also one issue I see introduced with this PR, when I try to provide custom resolvers to the handler, I now also need to pass context and root because those aren't marked as optional, so this example from the README won't work in TS-enabled environment:

const graphQLHandler = createGraphQLHandler(graphQLSchema, this.schema, {
  resolvers: {
    Mutation: {
      // Coerce the record returned from the default resolver to a Boolean
      deletePerson: (obj, args, context, info) =>
        !!mirageGraphQLFieldResolver(...arguments)
    }
  }
})

[jneurock]

Thanks for the feedback!

[jneurock]

It has taken years to find the time to work on a TypeScript version of this library but I finally got around to it. I have released version 0.2.0-alpha.1 to npm. This version is based on the typescript branch. If anyone wants to give it a try, it would be great to see if there are any issues.

There should be not breaking changes when it comes to creating a request handler (the main functionality) but there are some breaking changes to a few functions that I would be surprised to see anyone use.

Thanks in advance for any feedback!