GraphQL Codegen + Temporal Zod Demo - Demonstrating how to use GraphQL Codegen to generate Zod schemas with Temporal type support in Deno

README.md

GraphQL Codegen + Temporal Zod Demo

A demonstration of using GraphQL Codegen to generate Zod schemas with Temporal type support using Deno and TypeScript.

Running the Code

# Install dev dependencies so we can run codegen
deno install

# Run GraphQL Codegen
deno task codegen

Then run the demo:

deno test

codegen.yml

schema: schema.graphql
generates:
  src/generated/zod.ts:
    plugins:
      - '@use-pico/graphql-codegen-zod'
    config:
      scalars:
        Instant: 'zInstant'
      imports:
        - "import { zInstant } from \"temporal-zod\";"

deno.json

{
  "tasks": {
    "codegen": "deno run -A npm:@graphql-codegen/cli/graphql-codegen"
  },
  "imports": {
    "graphql": "npm:graphql@16.11.0",
    "temporal-polyfill": "npm:temporal-polyfill@0.3.0",
    "temporal-zod": "npm:temporal-zod@0.5.0",
    "zod": "npm:zod@4.1.12",
    "@use-pico/graphql-codegen-zod": "npm:@use-pico/graphql-codegen-zod@4.0.62",
    "@graphql-codegen/cli": "npm:@graphql-codegen/cli@6.0.1"
  }
}

main.test.ts

import { describe, it } from "jsr:@std/testing/bdd";
import { expect } from "jsr:@std/expect";
import { Temporal } from "temporal-polyfill";
import { z } from "zod";
import { EventSchema } from "./src/generated/zod.ts";

type Event = z.infer<typeof EventSchema>;

describe("EventSchema", () => {
  it("should parse event with Temporal.Instant", () => {
    const parsed: Event = EventSchema.parse({
      name: "System Boot",
      timestamp: Temporal.Now.instant(),
    });

    expect(parsed.name).toBe("System Boot");
    expect(parsed.timestamp).toBeInstanceOf(Temporal.Instant);
  });

  it("should parse event with ISO string timestamp", () => {
    const parsed: Event = EventSchema.parse({
      name: "User Login",
      timestamp: "2025-10-24T15:30:00Z",
    });

    expect(parsed.name).toBe("User Login");
    expect(parsed.timestamp).toBeInstanceOf(Temporal.Instant);
    expect(parsed.timestamp.toString()).toBe("2025-10-24T15:30:00Z");
  });
});

schema.graphql

scalar Instant

type Event {
  name: String!
  timestamp: Instant!
}

type Query {
  events: [Event!]!
}

A superset of https://gist.github.com/kevinmichaelchen/2aafe5c9ea63b11595e920f0bf9746ce

Also see https://www.npmjs.com/package/graphql-codegen-typescript-validation-schema and its scalarSchemas option