Add Typescript typings

[kdembler]

As the title says, it'd be great to have typings for this library. Seeing Typescript on the rise and in use in many projects (including one I'm working on), it'd make developer experience better.

[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!