Zod => JSONSchema compilation produces infinitely recursive schemas when using transforms

[airhorns]

Confirm this is a Node library issue and not an underlying OpenAI API issue

• This is an issue with the Node library

Describe the bug

When using a zodFunction with a zod schema that has multiple references to an object with a transformed property, the produced JSON schema is infinitely recursive and invalid. It causes the OpenAI API to 500 when requested.

I believe both of these conditions are necessary to trigger the bug:

• the schema contains an object with one property that has a .transform attached to it
• the schema contains references to that object more than once, so the JSONSchema transformer has to pop it out into the definitions

The produced JSONSchema ends up looking like this:

{
  "definitions": {
     "test_properties_first_properties_baz": {
       "$ref": "#/definitions/test_properties_first_properties_baz",
     }
   }
}

which is self-referential and broken, sad.

To Reproduce

Here's a test that reproduces the error:

// use ajv to validate that the produced json schema is valid
import Ajv from "ajv";
const ajv = new Ajv();

  test("unchanged schemas with referenced inner pieces produce valid JSON schemas", () => {
    const Inner = z.object({
      baz: z.boolean().transform((v) => v ?? true),
    });

    const Outer = z.object({
      first: Inner,
      second: Inner,
    });

    const jsonSchema = zodFunction({ name: "test", parameters: Outer }).function.parameters;

    expect(jsonSchema).toBeDefined();
    expect(jsonSchema).toMatchSnapshot();

    ajv.compile(jsonSchema as any);
  });

Code snippets

Here's what the problematic compiled JSONSchema looks like:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "additionalProperties": false,
  "definitions": {
    "test": {
      "additionalProperties": false,
      "properties": {
        "first": {
          "additionalProperties": false,
          "properties": {
            "baz": {
              "type": "boolean",
            },
          },
          "required": [
            "baz",
          ],
          "type": "object",
        },
        "second": {
          "$ref": "#/definitions/test_properties_first",
        },
      },
      "required": [
        "first",
        "second",
      ],
      "type": "object",
    },
    "test_properties_first": {
      "additionalProperties": false,
      "properties": {
        "baz": {
          "$ref": "#/definitions/test_properties_first_properties_baz",
        },
      },
      "required": [
        "baz",
      ],
      "type": "object",
    },
    "test_properties_first_properties_baz": {
      "$ref": "#/definitions/test_properties_first_properties_baz",
    },
  },
  "properties": {
    "first": {
      "additionalProperties": false,
      "properties": {
        "baz": {
          "type": "boolean",
        },
      },
      "required": [
        "baz",
      ],
      "type": "object",
    },
    "second": {
      "$ref": "#/definitions/test_properties_first",
    },
  },
  "required": [
    "first",
    "second",
  ],
  "type": "object",
}

OS

macOS

Node version

node v22.2.0

Library version

openai v4.56.0

[airhorns]

ping @RobertCraigie sorry to bother just want to make sure you saw this as it seems up your alley!

[RobertCraigie]

Hey @airhorns, thanks for the bump. I can reproduce this issue and will investigate!

[RobertCraigie]

This will be fixed in the next release! :) #1066

[airhorns]

Bless your beautiful heart thank you!