v4: toJSONSchema `.default()` `.catch()` input values considered non optional

[samchungy]

Something tricky to deal with in my library when generating JSON Schema from Zod Types was figuring out whether to generate an input (request) type or a output (response) type. I assume that was the intention of the pipes parameter.

The current required implementation only considers the output type.

https://github.com/colinhacks/zod/blob/2ade678ffc5fbe609d92537f3910f91f15d77725/packages/core/src/util.ts#L538

I considered changing optional

https://github.com/colinhacks/zod/blob/2ade678ffc5fbe609d92537f3910f91f15d77725/packages/core/src/schemas.ts#L1480

to a function instead of a getter which takes an optional output defaulted pipes value but that lead me down a rabbit hole... Keen to help you implement this but I understand that this might require quite a bit of tinkering.

console.log(
  JSON.stringify(
    z.toJSONSchema(
      z.object({
        jobId: z.string().default("foo"), // or .catch()
      }),
      {
        reused: "ref",
        pipes: "output",
      }
    ),
    null,
    2
  )
);

{
  "type": "object",
  "properties": {
    "jobId": {
      "type": "string",
      "default": "foo"
    }
  },
  "required": [
    "jobId"
  ]
}

In this scenario jobId should not be marked as required.