Feature Request: Transform Nulls to Undefined for Prisma Query

[adarnon]

The CRUD implementation should expose a way to convert null | undefined to undefined. This would be useful especially for situations where we want to directly pass a where query.

For example, let's say I want to implement a custom resolver for a CRUD query. I can write:

t.crud.myModel({
  resolve(root, args, ctx, info) {
    const model = ctx.prisma.myModel.findUnique({ where: args.where });
    // ... Do something with the result...
    return model;
  }
})

Currently, this is not possible because of null | undefined incompatibilities. Both value might be received from GQL, but Prisma only allows undefined for fields we wish to ignore in the where query. TypeScript won't compile in strict mode, and I assume that in runtime that might even cause bugs.

Internally, the plugin's default resolvers use a custom function to convert null | undefined to undefined: https://github.com/graphql-nexus/nexus-plugin-prisma/blob/6c8801c6e1d99bfdb73a7c1c89db9607712b0e01/src/null.ts

At the very least, this function should be easily available for use. Additionally, maybe there should be a flag to have this transform done on inputs before they are pass to our resolver? Another solution would be to allow us to call the original resolver (as a 5th argument to the resolver function), so we can do some pre/post manipulation on the result.

[HendrikJan]

I guess that this is related to #863