Errors when dealing with discriminated union types

[ctriley]

I have a typescript type that looks like this:

export type CyclingOptimizationInput =
  /** Define optimization by weighing three criteria. */
  { triangle: TriangleCyclingFactorsInput; type?: never; }
  |  /** Use one of the predefined optimization types. */
  { triangle?: never; type: CyclingOptimizationType; };

When I generate the graphql code without this plugin, it works fine. However, when trying to generate code with this plugin, I get a mismatch between the generated zod schema and the typescript type. I'm not sure how to resolve this.

I believe the type above should lead to a discriminated union zod type, something like:

export function CyclingOptimizationInputSchema(): z.ZodType<CyclingOptimizationInput> {
  return z.union([
    z.object({
      triangle: z.lazy(() => TriangleCyclingFactorsInputSchema()),
      type: z.undefined()
    }),
    z.object({
      triangle: z.undefined(),
      type: CyclingOptimizationTypeSchema
    })
  ]);
}

However, I get

export function CyclingOptimizationInputSchema(): z.ZodObject<Properties<CyclingOptimizationInput>> {
  return z.object({
    triangle: z.lazy(() => TriangleCyclingFactorsInputSchema().nullish()),
    type: CyclingOptimizationTypeSchema.nullish()
  })
}

This leads to the error

The types of 'optimization._type' are incompatible between these types.
Type '{ type: CyclingOptimizationType | undefined; triangle: TriangleCyclingFactorsInput | undefined; } | { type: CyclingOptimizationType | undefined; triangle: TriangleCyclingFactorsInput | undefined; } | null | undefined' is not assignable to type 'InputMaybe | undefined'.

which refers to

export function BicyclePreferencesInputSchema(): z.ZodObject<Properties<BicyclePreferencesInput>> {
  return z.object({
    boardCost: z.number().nullish(),
    optimization: z.lazy(() => CyclingOptimizationInputSchema().nullish()),
    parking: z.lazy(() => BicycleParkingPreferencesInputSchema().nullish()),
    reluctance: z.number().nullish(),
    rental: z.lazy(() => BicycleRentalPreferencesInputSchema().nullish()),
    speed: z.number().nullish(),
    walk: z.lazy(() => BicycleWalkPreferencesInputSchema().nullish())
  })
}

All of these types are from the open trip planner project found here: https://github.com/opentripplanner/OpenTripPlanner

My codegen.ts is:

import type { CodegenConfig } from "@graphql-codegen/cli";

const config: CodegenConfig = {
  schema:
    "https://raw.githubusercontent.com/opentripplanner/OpenTripPlanner/v2.6.0/src/main/resources/org/opentripplanner/apis/gtfs/schema.graphqls",
  generates: {
    "src/__generated__/graphql-types.ts": {
      documents: ["../otp/src/**/*.ts"],
      plugins: ["typescript", "typescript-validation-schema"],
      config: {
        scalars: {
          Duration: "string",
          GeoJson: "GeoJSON.FeatureCollection",
          Polyline: "string",
          Grams: "number",
          Long: "number",
          CoordinateValue: "number",
          Cost: "number",
          LocalDate: "string",
          Locale: "string",
          OffsetDateTime: "string",
          Ratio: "number",
          Reluctance: "number",
          Speed: "number",
          ID: "string",
        },
        strictScalars: true,
        schema: "zod",
      },
    },
  },
};

export default config;