Optional & nullable not output together on optional union type property with null value

[tvillaren]

Bug description

When an optional property references a union type with null, the result is not using the optional() modifier

Input

export interface A {
  a?: number | null;
}

Expected output

export const aSchema = z.object({
  a: z.number().optional().nullable()
});

Actual output

export const aSchema = z.object({
  a: z.number().nullable()
});

Potential fix

Did some fiddling on a fork, and found that the isOptional flag was not passed down in case of an union type traversal.

Versions

• Typescript: v4.5.2
• Zod: v1.7.0

[tvillaren]

Actually, my PR doesn't fix all cases, only the "simple" one.

Union with multiple primitive types and null fails as well:

it("should allow nullable on union properties", () => {
    const source = `export interface A {
      a: number | string | null;
    }
    `;

    expect(generate(source)).toMatchInlineSnapshot(`
      "export const aSchema = z.object({
          a: z.union([z.number(), z.string()]).nullable()
      });"
    `);
  });

I proposed a fix in my PR as well.

[fabien0102]

Part of 1.8.0 release 😀